**1. Introduction**

Recent demand on mobility and accessibility of devices is pushing the development of wireless technology to new levels. There are good solutions for data transfer such as WiFi and Bluetooth, whereas, power is still delivered by either batteries or cable, the main bottleneck in the strive for cutting all the wires and limiting the mobility of devices.

For daily-life applications, inductive wireless power transmission has drawn increasing attention from researchers as it offers the highest power transfer efficiency (PTE) among other alternatives such as capacitive, microwave, laser, and acoustic [1,2]. Various products such as electric toothbrushes and mobile chargers using this technique are already commercially available. This technique provides two advantages compared to others: transfer of high power and low-frequency operation, making it less hazardous to the human body [3]. The main issue with this type of inductive wireless power transfer (WPT) is the mobility as the sender and receiver need to be close to each other, less than a few centimetres. Magnetic resonant (MR) WPT, an inductive technique based on highly coupled high-Q resonators, addresses this issue and offers a reasonable distance of power transfer (up to 2 m) [4]. However, a considerable challenge of MR-WPT is to maintain high power transfer throughout a range of distances between resonators and for variations in load value, as these will cause a mismatch between the source and input impedances [5].

In order to solve this challenge, different types of impedance matching techniques have been developed in the last decades. The simplest and most popular ones use capacitive or inductive impedance matching networks (IMNs). The capacitive method uses variable capacitors to tune the transmitter to the resonant frequency or a predefined capacitor sequence for different distances [6,7]. There is a variety of adaptive frequency tuning systems where *L*, *T* and Π-type impedance matching networks contain capacitors [7,8]. Matching can potentially also provide power to multiple device WPT by using only a single transmitter [9].

The four-coil MR-WPT system presented by the MIT group in 2007 [4] has become a recognized solution [10–14] for highly resonant WPT systems for medium distances. The system consists of two or more high-Q resonating coils which are driven by a low-Q coil connected to the power source. The load is also connected to a low-Q coil. The coupling between resonator and the driver coils (or the load coil) can be considered as parts of a matching network, where tuning of the impedance can be achieved by changing the coupling between them. In our study, this method is referred to as inductive matching. In a previous work, we showed that these two matching techniques, i.e., the capacitive and inductive matching could potentially achieve a similar level of matching in certain cases [15]. Among the many different capacitive compensation circuitries, we chose the parallel-series compensation according to reference [8] for comparison to the inductive method. This network offers sufficient degrees of freedom to match perfectly if there is no loss and no restriction on parameter ranges, hence it is sufficient to give an insight into the effect of these limitations. The presented comparison method can also be used to identify matchable regions of other compensation structures.

The aforementioned matching techniques, i.e., capacitive and inductive can be applied to any mismatches in a WPT system to improve the power transfer efficiency [16]. However, there is a challenge in the direct comparison of their matching performances because they have different circuit topologies. The paper describes a method that makes a systematic comparison of their performance possible. The proposed method is based on comparison of the conjugate impedance of the matchable load, displayed in the Smith chart. The conjugate matching method has been analysed in [17], where all concepts of conservation and amplification of power by two port network was defined. This method is used by [18,19] to describe efficiency of the WPT system with inductive IMN. Our work presents a comparison of the matchable loads offered by the inductive and capacitive matching networks over a full range of realistic parameter ranges for three different applications distinguished by their operating frequency and power level [20–22]. The operating frequencies are within the allowed Industrial, Scientific and Medical (ISM) bands [9], which also limits the frequency range in the analysis. For the ease of simulation and calculations we choose to keep the distance constant and match the different load values. We assume the coil sizes are such that the systems operate in near field and the inductances of sender and receiver coils are equal, as in the [18–22].

This paper is organized as follows. In Section 2, impedances are analysed by derivation of reflection coefficients. We intentionally exclude the parasitic components in the system in order to have a clear comparison between these matching techniques in the ideal case. Subsequently, Section 3 visualizes the matchable reflection coefficients in the Smith chart, which graphically illustrates all of the possible complex impedances that are obtained by sweeping matching parameters. Therefore, it demonstrates which method offers the wider area of impedances that can be matched. Furthermore, the impact of parasitic loss to the matchable region is analyzed and optimized power simulation is given in the Section 4 and Section 5 discusses the outcome of the comparison.

#### **2. Reflection Coefficients**

In order to map and compare the tunable impedances of WPT systems, suitable circuit models and corresponding impedance expressions should be established. A generic WPT system with impedance matching networks can be represented as shown in Figure 1. The driving source consists of an ideal voltage source ( *VS*) and a series resistance *RS*. The two-port network consists of resonators, and here we will consider capacitive and inductive impedance matching circuits. The network is terminated by load impedance *ZL* at the output. Here, *iS* and *iL* are currents through *RS* and *ZL*, respectively.

Matching networks are necessary to obtain a match between input impedance *Z*in and source impedance *RS*. They affect the Power Transfer Efficiency (PTE), defined as ratio between power delivered to the load and input power of the two-port network [18]. This research focuses on the comparison of the matchable loads offered by the capacitive and inductive IMNs. Therefore, the two-port network is redrawn as in Figure 2 to get value of an effective impedance *Z*out at the output, which is a complex conjugate *Z*∗*L*form of load impedance that can be perfectly matched.

**Figure 1.** Two-port network representation of a highly resonant WPT system.

**Figure 2.** Two-port network representation when source is terminated.

#### *2.1. Capacitive Matching Network*

A lossless model of the inductive resonant WPT system with capacitive impedance matching is shown in Figure 3. The circuit elements are ideal, i.e., inductors and capacitors do not have parasitics. Matching networks consist of series-parallel connection of capacitors *Cts*, *Ctp* and *Crp*, *Crs* at the transmitter (Tx) and receiver (Rx) sides. The source impedance is considered as resistance *RS*.

**Figure 3.** Equivalent circuit of a WPT system with capacitive impedance matching network.

Applying Kirchhoff's voltage law (KVL) to the circuit in Figure 3, the voltage-current relations can be written in an impedance matrix form

$$
\begin{bmatrix} V\_{out} \\ 0 \\ 0 \\ 0 \end{bmatrix} = \begin{bmatrix} Z\_{11} & Z\_{12} & 0 & 0 \\ Z\_{21} & Z\_{22} & Z\_{23} & 0 \\ 0 & Z\_{32} & Z\_{33} & Z\_{34} \\ 0 & 0 & Z\_{43} & Z\_{44} \end{bmatrix} \begin{bmatrix} i\_L \\ i\_r \\ i\_t \\ i\_S \end{bmatrix} \tag{1}
$$

where

$$Z\_{11} = \frac{1}{j\omega \mathcal{C}\_{rs}} + \frac{1}{j\omega \mathcal{C}\_{rp}},\ Z\_{12} = -\frac{1}{j\omega \mathcal{C}\_{rp}},\tag{2}$$

$$Z\_{21} = -\frac{1}{j\omega \mathcal{C}\_{rp}}, \; Z\_{22} = j\omega L\_r + \frac{1}{j\omega \mathcal{C}\_{rp}}, \; Z\_{23} = j\omega M\_{12\prime} \tag{3}$$

$$Z\_{32} = j\omega M\_{tr}, Z\_{33} = j\omega L\_t + \frac{1}{j\omega \mathbb{C}\_{tp}}, Z\_{34} = -\frac{1}{j\omega \mathbb{C}\_{tp}},\tag{4}$$

$$Z\_{43} = -\frac{1}{j\omega \mathcal{C}\_{tp}} \; , \; Z\_{44} = R\_S + \frac{1}{j\omega \mathcal{C}\_{ts}} + \frac{1}{j\omega \mathcal{C}\_{tp}} \, . \tag{5}$$

Here,

$$M\_{tr} = k\_{tr} \sqrt{L\_t L\_r}, \quad 0 \le k\_{tr} \le 1 \tag{6}$$

is the mutual inductance between inductors *Lt* and *Lr*. The coefficient *ktr* represents the coupling between them and its value is inversely proportional to the cube of their distance [15]. The distance change and variation of load impedance can be controlled by adjusting the capacitances *Cts*, *Ctp* and *Crs*, *Crp* in the matching networks.

The effective impedance *Z*out at the output of two-port network is

$$\mathbf{Z\_{out}} = j\mathbf{X\_{I}} + \frac{\mathbf{Z\_{12}^{2}}(\mathbf{Z\_{34}^{2}} - \mathbf{Z\_{33}}\mathbf{Z\_{44}})}{(\mathbf{Z\_{22}}\mathbf{Z\_{33}} - \mathbf{Z\_{32}^{2}})\mathbf{Z\_{44}} - \mathbf{Z\_{34}^{2}}\mathbf{Z\_{22}}},\tag{7}$$

where

$$X\_I = -\frac{1}{\omega \mathcal{C}\_{rs}} - \frac{1}{\omega \mathcal{C}\_{rp}}.\tag{8}$$

The real and imaginary parts of the impedance are

$$\text{Re}\{Z\_{\text{out}}\} = \Delta R\_S,\\ \text{Im}\{Z\_{\text{out}}\} = \Delta A - \frac{1}{\omega \mathcal{C}\_{rs}} - \frac{1}{\omega \mathcal{C}\_{rp}},\tag{9}$$

where

$$
\Delta = \frac{\omega^2 M\_{tr}^2 Z\_{12}^2 Z\_{34}^2}{B^2 R\_S^2 + (X\_t B - Z\_{34}^2 Z\_{22})^2},
\tag{10}
$$

$$\mathbf{B} = \mathbf{Z}\_{22}\mathbf{Z}\_{33} - \mathbf{Z}\_{32}^2,\\ \mathbf{X}\_t = -\frac{1}{\omega \mathbf{C}\_{ts}} - \frac{1}{\omega \mathbf{C}\_{tp}},\tag{11}$$

$$A = \frac{(Z\_{22}Z\_{34}^2 - X\_l\omega^2M\_{tr}^2)Z\_{34}^2 - Z\_{33}B(X\_l^2 + R\_S^2)}{\omega^2M\_{tr}^2Z\_{34}^2}. \tag{12}$$

The impedance *Zout* can be seen at the output of the two-port network, which is complex conjugate form of load impedance *ZL*. This impedance is used to derive the reflection coefficient (Γ), which can be seen from the load side

$$
\Gamma = (Z\_{\rm out} - Z\_0) / (Z\_{\rm out} + Z\_0) \tag{13}
$$

where *Z*0 is reference impedance equal to *RS*.

Equation (13) is used to draw Γ in the Smith chart to visualize graphically and estimate the values of load impedance that can be perfectly matched. Furthermore, a derivation of the reflection coefficient expression for the inductive matching is discussed in next section, and numerical results are given in Section 3.

#### *2.2. Inductive Matching Network*

Inductive coupling is another method widely exploited to match the input impedance for different distances between resonators or load variation. This system uses additional magnetically coupled

coils at the transmitter or receiver, or both, to enhance the PTE. These coils do not need as high Q as the resonator coils. The most popular one is a four-coils system with source coil *LS*, high-Q transmitter coil *Lt*, high-Q receiver coil *Lr*, and load coil *LL* [4,15]. The matching can be controlled by varying couplings between the source/load coils and high-Q coils—*kS*, *kL*. The equivalent lossless model of such a system is shown in Figure 4. The high-Q coils are connected to series external capacitors to form resonators.

**Figure 4.** Equivalent circuit of WPT system with inductance matching network.

For such a circuit, the same voltage-current relations can be used as in Equation (1), where impedances are

$$Z\_{11} = j\omega L\_{L\prime} \; Z\_{12} = -j\omega M\_{L\prime} \tag{14}$$

$$Z\_{21} = -j\omega M\_{\rm L}, Z\_{22} = j\omega L\_t + \frac{1}{j\omega \mathcal{C}\_{\rm t}}, Z\_{23} = j\omega M\_{\rm tr\prime} \tag{15}$$

$$\mathbf{Z}\_{32} = j\omega M\_{\text{tr}}, \mathbf{Z}\_{33} = j\omega \mathbf{L}\_r + \frac{1}{j\omega \mathbf{C}\_r}, \mathbf{Z}\_{34} = -j\omega M\_{\text{S}\_r} \tag{16}$$

$$Z\_{43} = -j\omega M\_{\rm S},\ Z\_{44} = R\_{\rm S} + j\omega L\_{\rm S} \tag{17}$$

and by neglecting cross-coupling:

$$Z\_{13} = Z\_{14} = Z\_{24} = Z\_{31} = Z\_{41} = Z\_{42} = 0. \tag{18}$$

Here, *MS*/*L* is a mutual inductance between source/load coil (*LS*/*L*) and high-Q coil (*Lt*/*r*)

$$M\_{\mathcal{S}/L} = k\_{\mathcal{S}/L} \sqrt{L\_{\mathcal{S}/L} L\_{t/r'}} \ \ 0 \le k\_{\mathcal{S}/L} \le 1. \tag{19}$$

and *Mtr* is the mutual inductance between resonator coils

$$M\_{tr} = k\_{tr} \sqrt{L\_t L\_r}, \quad 0 \le k\_{tr} \le 1. \tag{20}$$

If we assume that the two resonators have same resonance frequency *ω* = 1/ *Lt*/*rCt*/*r*, then

$$Z\_{22} = Z\_{33} = 0.\tag{21}$$

From impedance Equations (14)–(18) the real and imaginary parts of output impedance *Z*out become

$$\text{Re}\{Z\_{\text{out}}\} = \Delta R\_{\text{S}} \text{ } \text{Im}\{Z\_{\text{out}}\} = \omega (L\_L - \Delta L\_{\text{S}}),\tag{22}$$

where

$$
\Delta = \frac{\omega^2 M\_S^2 M\_L^2}{M\_{tr}^2 \left(R\_S^2 + \omega^2 L\_S^2\right)}.\tag{23}
$$

Furthermore, Equations (13), (22) and (23) are used to calculate the reflection coefficient in the following section. These results conclude the theoretical analysis that is required to compare the two techniques.

#### **3. Matchable Regions of Lossless Model**

This section presents graphs of reflection coefficients in the Smith Chart, based on the equations derived in the previous section for both capacitive and inductive matching. These graphs help us to estimate the matchable loads and to select the proper matching network at the transmitter and receiver side. In the capacitive method the input impedance is controlled via capacitances *Cts*, *Ctp*, *Crs*, *Crp*, whereas in the inductive matching it is controlled by coupling coefficients *kS*, *kL* between the source/load coils and high-Q coils.

In this section, the parasitic components of the system are intentionally excluded to have a clear and ideal case comparison between these two matching techniques. Reflection coefficients were examined for three specific applications, and parameter values used for the cases given in Table 1. The presented cases have been chosen so that they cover a wide range of WPT applications with different specifications for power level and operating frequency [20–22].

**Table 1.** Applications and parameters.

Figures 5–10 show the realizable reflection coefficient values in the Smith Chart. The matchable regions are indicated by bold black borders. Each figure consists of three impedance regions, where each region corresponds to different resulting impedances in the circuit: *Ztx*—impedance at the transmitter, *Ztr*—impedance after transmission, *Zout*—impedance at the output. They are obtained by sweeping the impedance matching network parameters over the realistic range of values, which are given in Table 2. Chosen constraint for the inductive IMN is based on an assumption that the driving and load loops have an inductance equal or smaller than the resonator inductances [4]. The bottom limit for the capacitance variance in the capacitive IMN is the lowest value of capacitance in the market, which is approximately 500 fF (ignoring the possibilities of series connection), whereas the upper limit was chosen sufficient for the application choice. As we can see further from the results the upper limit in the inductive method and lower limit in the capacitive method decides the final shape in the Smith chart. The circuits are equivalent models of an inductive WPT, which consists of source resistance *RS*, matching networks (capacitive or inductive), and lossless coils for transmission and reception.

Case A application in Table 1 is an Electric Vehicle (EV) charging station for transmission of high power. It is designed for low-frequency operation, in our case at 85 kHz frequency, and designed for coils around *Lt* = *Lr* = 60 μH. Figure 5a shows the impedance at the transmitter. This impedance region agrees well with known results for L-type networks in [23]. It is controlled by varying the capacitances *Cts* and *Ctp* within the range given in Table 2. Since the L-type capacitive matching network at the transmitter (Tx) cannot match all impedances, a matching network is required for the receiver part as well. Second stage, in Figure 5b, illustrates reflection graph after the resonator coils *Lt* and *Lr*, which are coupled at *ktr* = 0.01. The inductances change the region into a circle—smaller than Smith chart, which means there is still a limitation in the matchable area. Finally, in Figure 5c, third stage gives impedances that can be matched by the complete network consisting of matching networks at the Tx ( *Cts* and *Ctp*) and Rx ( *Crs* and *Crp*) sides. All the capacitances in this example are varied from 0.1 pF to 200 pF (Table 2). The impedance matching network at the Rx side greatly improves the matchable area, which now practically fills the Smith chart. It means that for case A without losses any load is matchable by the capacitive matching method at *ktr* = 0.01, but it does not mean that this still holds for other coupling coefficient values.

The result of following a similar procedure for case A with the inductive impedance matching network is shown in Figure 6. In this case, matching works by adjusting source/load inductances *LS*/*LL* and coupling coefficients between these and resonator coils (*kS*, *kL*). Inductance and coupling constant ranges are given in Table 2. In Figure 6a, we can notice that the inductive method gives an extremely limited region of impedances that can be matched, hence, matching at the receiver becomes crucial. One thing that can be noticed from Figure 6b impedance range of *Ztr* after the coupling (*ktr* = 0.01) between resonators *Lt*, *Lr* is even smaller, and it shows that three-coil system is not suitable for applications where load values are diverse. However, the resulting matchable impedance of the complete system with four coils, where impedance can be matched at both sides (Tx and Rx), fills around 80% of the Smith chart and is shown in Figure 6c. According to the figure, for case A without losses there is roughly 20% of the impedances that cannot be perfectly matched by the inductive approach.

**Figure 5.** Reflection coefficient graphs show impedances that can be obtained by capacitive matching networks placed into WPT system in case A: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Figure 6.** Reflection coefficient graphs show impedances that can be obtained by inductive coupling in four coiled WPT system in case A: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Figure 7.** Reflection coefficient graphs show impedances that can be obtained by capacitive matching networks placed into WPT system in case B: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Figure 8.** Reflection coefficient graphs show impedances that can be obtained by inductive coupling in four coiled WPT system in case B: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Figure 9.** Reflection coefficient graphs show impedances that can be obtained by capacitive matching networks placed into WPT system in case C: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Figure 10.** Reflection coefficient graphs show impedances that can be obtained by inductive coupling in four coiled WPT system in case C: (**a**) *Ztx*—impedance at the transmitter, (**b**) *Ztr*—impedance after transmission, (**c**) *Zout*—impedance at the output.

**Table 2.** Matching network parameters.

Case B is a low power and high-frequency system, a mobile phone charging device from Airfuel Alliance, which has standard parameters as 6.78 MHz operational frequency and around *Lt* = *Lr* = 6 μH coils for Tx and Rx [21]. Results are given in Figures 7 and 8. Here, the inductive method again shows low performance for a three-coil system since the matchable area fills only about 10% of the Smith chart. However, both methods are able to match all loads with the complete network.

Finally, we consider application case C, which is a high-frequency device with *Lt* = *Lr* = 2.5 μH for Rx and Tx coils. The inductive matching network has larger matchable region than the capacitive method, see Figures 9 and 10. In a complete network, around 90% of the load impedances are matchable by the inductive method, whereas the capacitive approach can match only around 30% of the loads. One thing to note is that the matchable region for the capacitive network has a hole, which appears because of the minimum constraint 0.5 pF in the parameter range. Consequently, the capacitive matching network with these constraints is less versatile in this type of application.

#### **4. Performance of Lossy System**

In this section, system performance is examined in the presence of loss. Therefore, the lossless inductors *Lt* and *Lr* in the previous circuits is replaced by a model of a non-ideal inductor shown in Figure 11. The model consists of an ideal inductor with a series parasitic resistance and a parallel capacitance. We only consider the effect of the parasitic resistance since the parasitic capacitance can be taken care of by compensation circuits. The parasitic resistance is a combination of ohmic and radiative losses of the coil. Other circuit parameters are kept the same as in the previous section for calculation of reflection coefficients. The realizable reflection coefficients over the chosen range of parameters are shown in Figures 12–14.

The inductances of the coils in case A are larger than for the other two cases, so the parasitic resistance *R* = 1 Ω of each coil is higher than for case B and comparable to case C where the skin effect matters. R is estimated assuming a copper coil made from a 30-m long wire of diameter 0.8 mm [20]. The result for case A is shown in Figure 12, where Figure 12a presents realizable reflection coefficients

for capacitive IMN of Figures 3 and 12b presents the results for inductive IMN of Figure 4. Solid lines show borders of matchable regions for lossles networks determined in the previous section, whereas dashed lines bound matchable regions for lossy networks.

**Figure 11.** Model of non-ideal inductor.

**Figure 12.** Matchable regions in lossless and lossy model for case A.

**Figure 13.** Matchable regions in lossless and lossy model for case B.

**Figure 14.** Matchable regions in lossless and lossy model for case C.

The matchable area has been dramatically reduced from 100% to approximately 40% of the Smith chart for capacitive and from 80% to 20% for the inductive technique. It shows that range of matchable impedances is sensitive to loss for both methods and that the inductive method is slightly sensitive to the loss than the capacitive method.

The comparison of matchable regions, after the introduction of parasitic resistance *R* = 0.55 Ω ([21]) in the coils for case B, is shown in Figure 13. The reflection coefficient graphs of capacitive and inductive methods are shown in Figure 13a,b, respectively. The change in the matchable region is again more dramatic for the inductive method since it has about 55% reduction from the ideal case compared to the capacitive method's 20%.

Matchable regions for case C are given in Figure 14. Since the resonator coils operate at the highest frequency in the comparison, we considered skin effect as well. Therefore, ohmic loss at the coils is

chosen as a combination of parasitic resistance and skin effect loss, which is *R* = 1 Ω. R is estimated assuming a copper coil made from a 75-cm long wire of diameter 0.8 mm [22]. As a peculiarity in Figure 14a, we note that the matchable region for the lossless capacitive network has a hole in it and that this vanishes when losses are introduced. The overall numbers are 2% reduction in area for the capacitive and 15% for the inductive approach. While the inductive method in this case still has a matchable region more sensitive to loss than capacitive IMN, the inductive method covers a larger area of matchable impedances both with and without loss.

As mentioned before in Section 2, we considered regions of matchable impedances. It can also be interesting to see how well the network performs for any given load impedance. Here we consider this question by calculating the delivered power to load impedances sampled form the entire Smith chart. It can be obtained in several ways, but we used SPICE AC analysis here. We focused on cases A and B because their matchable regions are most affected by the introduction of ohmic loss. The results are shown in Figures 15 and 16 and demonstrate that capacitive and inductive IMNs can be comparable in matching various load impedances, when the networks are optimized for each particular impedance. Device in case A has more power loss than in case B. Overall, power level is distributed between −4.2 dBm and −4.8 dBm for case A, and −3.5 dBm and −4 dBm for case B.

**Figure 15.** Comparison of optimal power delivered to the various loads for case A.

**Figure 16.** Comparison of optimal power delivered to the various loads for case B.

## **5. Discussion**

Section 3 presented three impedance areas obtained for different stages of ideal circuits (Figures 5–10), which is summarized in Figure 17. In this figure, each trace represents specific application (case A, B, C) and matching network. The impedances at the different stage of circuits, in Figures 5–10, are given in *x*-axis, whereas *y*-axis shows a share of Smith chart in percentage. All the areas have been estimated from the graphs. According to the figure, *Zout* fills a larger area than *Ztr* for all cases, which shows that the impedance matching network at the Rx side is crucial in obtaining large tunable area of load impedance. There is a degradation from 100 to 30% in the area of output impedance *Zout* by the capacitive method from case A to C. An improvement from 10 to 75% in the area of impedance at the transmitter side *Ztx* can be seen for the inductive technique from case A to C. This is due to difference in the operation frequency of the specific applications since for capacitive IMN *XC* ∝ 1/ *f* , while for inductive IMN *XL* ∝ *f* . Therefore, the region of inductive method shrinks in case C (85 kHz—low frequency) and widens in case A (100 MHz—high frequency), and it is vice versa for capacitive matching. At low operation frequencies, the available range of the capacitance values is enough to match most of the load impedances, whereas at high frequency, the matching is limited by the smallest capacitance value in the parameter range, which is 0.5 pF. In the inductive approach, the ranges of load and source inductance values are the same as for the resonator coils. For case C, covering most of the Smith chart can be achieved with a reasonable inductance range, whereas for case A, the inductance range is not large enough to match all the load impedances.

The limitation discussed above also gives a better understanding of the parasitic effects in the lossy WPT systems. For capacitive method, it is crucial to avoid parasitic capacitances of resonator coils at high frequencies since they are comparable with 0.5 pF, whereas for low frequency applications they can be ignored.

The matchable areas of the lossless model and the circuit with parasitics are compared in Figure 18. Here, blue/yellow colors correspond to matching network type and solid/hatched patterns of charts represent ideal and lossy scenarios of examination. The figure shows that the circuit with inductive IMN is more sensitive to the loss than capacitive IMN. In case A, the reductions in matchable areas of inductive and capacitive IMNs are comparable. In case B and case C, the reduction is higher for inductive IMN than for capacitive IMN. Case C is least affected by the parasitics due to high operation frequency. It should be noted that a larger parasitic resistance shrinks the matchable region, whereas a smaller parasitic resistance increases it closer to the ideal case.

It is clear that matching networks provide quite different areas of perfectly matchable impedances. However, the comparison in Figures 15 and 16 showed that the methods have comparable power transfer when the networks are optimized for each load.

**Figure 17.** Matchable area comparison for different stages of the circuit in the ideal case.

**Figure 18.** Area of matchable loads before and after introducing the parasitics.

## **6. Conclusions**

In this paper, we compare areas of matchable loads for capacitive and inductive impedance matching networks (IMNs), which are the common matching techniques in the magnetic resonant wireless power transfer system. Graphical visualization of the impedances by Smith Chart is used for effortless comparison of the IMNs performances. An analytic expression for effective output impedance is derived and used to display the conjugate-image impedance of the load. Without any limitations in the parameter values and frequency range, it is always possible to match any load, i.e., any point in the Smith chart. Therefore, three different applications were considered with constraints: case A—car charging operating at 85 kHz, case B—mobile phone charging at 6.78 MHz, and case C— a high-frequency charging device at 100 MHz.

For the lossless system, the capacitive circuit's matchable area fills the Smith chart for case A, whereas around 20% of the chart that cannot be matched by the inductive IMN. For case B both methods could match any load impedance. On the other hand, the inductive IMN has shown about 60% larger area than the capacitive IMN for case C. The matching network at the receiver improves the area in all cases.

Finally, the impact of parasitic resistance of the resonator coils to the matchable area has been examined. In case A, the reduction of matchable area is 60 percentage points for both methods. The matchable area by the inductive IMN is more sensitive to the parasitic resistance than capacitive IMN for cases B and C. However, simulation of power transfer has shown that both matching networks can be equally effective in matching different load values.

**Author Contributions:** All authors contributed to problem formulation, conceptualization and choice of methods. Y.Z. performed all calculations, simulations and original draft preparation. All authors contributed to interpretation of results, and to editing into the final manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** Y.Z. benefits from a PhD scholarship from University of South-Eastern Norway funded by the Norwegian Ministry of Education and Research. Article processing charge (APC) was funded by the University of South-Eastern Norway.

**Acknowledgments:** The Research Council of Norway is acknowledged for the support to the Norwegian Ph.D. Network on Nanotechnology for Microsystems, Nano-Network (221860/F40).

**Conflicts of Interest:** The authors declare no conflict of interest.


**2. Acquisition of Flatness Calculation Datum**

To establish a detection system for the surface flatness of the initial support of the tunnel based on the three-dimensional laser scanning technology, the acquisition of the flatness calculation datum is very important. The point cloud of the tunnel after preprocessing (Figure 4) is very smooth, which is conducive to the reconstruction of the tunnel model. The reconstruction of the tunnel point cloud model is essentially the surface fitting of the point cloud, and the discrete point cloud is fitted to a curved surface that approximates the surface of the target object. The accuracy of the fitted surface also directly affects the calculation of the flatness of the initial support surface of the tunnel result. The flatness calculation datum surface is essentially a fitting surface suitable for flatness calculation obtained by the point cloud data through the fitting method and optimization processing. To obtain the flatness calculation reference surface, selecting a suitable fitting method can effectively improve the degree of fitting optimization.

**Figure 4.** The point cloud of the tunnel after preprocessing.


*Article* **Regional Strain Pattern Index—A Novel Technique to Predict CRT Response**

**Michał Orszulak 1,\* ,† , Artur Filipecki 1,†, Wojciech Wróbel 1 , Adrianna Berger-Kucza 1 , Witold Orszulak 1 , Dagmara Urba ´nczyk-Swi´c 1 , Wojciech Kwa´sniewski 1 , Edyta Pło ´nska-Go´sciniak 2 and Katarzyna Mizia-Stec 1**

† Both authors contributed equally to this manuscript.

**Abstract:** Background: Cardiac resynchronization therapy (CRT) improves outcome in patients with heart failure (HF) however approximately 30% of patients still remain non-responsive. We propose a novel index—Regional Strain Pattern Index (RSPI)—to prospectively evaluate response to CRT. Methods: Echocardiography was performed in 49 patients with HF (66.5 ± 10 years, LVEF 24.9 ± 6.4%, QRS width 173.1 ± 19.1 ms) two times: before CRT implantation and 15 ± 7 months after. At baseline, dyssynchrony was assessed including RSPI and strain pattern. RSPI was calculated from all three apical views across 12 segments as the sum of dyssynchronous components. From every apical view, presence of four components were assessed: (1) contraction of the early-activated wall; (2) prestretching of the late activated wall; (3) contraction of the early-activated wall in the first 70% of the systolic ejection phase; (4) peak contraction of the late-activated wall after aortic valve closure. Each component scored 1 point, thus the maximum was 12 points. Results: Responders reached higher mean RSPI values than non-responders (5.86 ± 2.9 vs. 4.08 ± 2.4; *p* = 0.044). In logistic regression analysis value of RSPI ≥ 7 points was a predictor of favorable CRT effect (OR: 12; 95% CI = 1.33–108.17; *p* = 0.004). Conclusions: RSPI could be a valuable predictor of positive outcome in HF patients treated with CRT.

**Keywords:** cardiac resynchronization therapy; dyssynchrony; strain pattern; heart failure; RSPI

#### **1. Introduction**

Cardiac resynchronization therapy (CRT) improves the outcome and reduces symptoms in advanced Heart Failure with a Reduced Ejection Fraction (HFrEF) patients with a prolonged duration of QRS complex, especially with Left Bundle Branch Block (LBBB) [1,2]. Pooled data from six selected studies showed that CRT reduced all-cause mortality by 28% and new hospitalizations for worsening HF by 37% [3]. In the CARE-HF and COMPAN-ION trials, it has been shown that CRT reduces heart failure symptoms by one NYHA class and improves quality of life by 5–6% [1,4]. The main purpose of CRT is to reduce dyssynchrony and to restore physiological activation of the left ventricle (LV) myocardium [5]. A thorough, reliable evaluation of dyssynchrony seems to be crucial in the selection of CRT recipients [6]. The precise measurement of intraventricular dyssynchrony must take into account its two main components—electrical dyssynchrony and mechanical dyssynchrony, which are complementary because the final effect of resynchronization therapy depends on the presence of both [7]. If one of these is missing, CRT is unlikely to benefit the patient. The patterns of the LV deformation strain curves allows a complex assessment of both the timing and contractility [8].

Previous studies have demonstrated that identifying the LBBB-related strain pattern highly predicts the LV reverse remodelling [9]. We believe that a generalized appraisal

**Citation:** Orszulak, M.; Filipecki, A.; Wróbel, W.; Berger-Kucza, A.; Orszulak, W.; Urba ´nczyk-Swi´c, D.; Kwa´sniewski, W.; Pło ´nska-Go´sciniak, E.; Mizia-Stec, K. Regional Strain Pattern Index—A Novel Technique to Predict CRT Response. *Int. J. Environ. Res. Public Health* **2021**, *18*, 926. https://doi.org/10.3390/ ijerph18030926

Received: 9 November 2020 Accepted: 16 January 2021 Published: 21 January 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

**\*** Correspondence<EMAIL_ADDRESS>
of dyssynchrony including the analysis of the strain curves from all of the apical views might be a more precise measure to predict the CRT effect. Therefore, we propose a new method, called the Regional Strain Pattern Index (RSPI), which merges information about the dyssynchrony of the strain curves from all three apical views. The objective of this study was to verify RSPI in predicting response to CRT.

#### **2. Materials and Methods**

#### *2.1. Population*

The prospective study included 49 subjects (84% male, 66.5 ± 10 years, 34.7%/63.3% in New York Heart Association class II/III) with symptomatic heart failure qualified for CRT implantation in class I/IIa according to the 2013 ESC Guidelines [10]. Firstly, 71 consecutive patients were recruited but twenty-two patients were lost during the follow-up (six patients due to poor echocardiographic window, four patients because of suboptimal pace delivery (BiV < 90%), four patients were lost during the follow-up, four patients declined participate in the study, two had dysfunction of CRT (dislocation of LV lead) and two patients died). The remaining 49 patients constituted the study group. Twenty (40.8%) patients had already had a cardiac implantable electronic device (CIED) and were receiving an upgrade to a resynchronization system, while the others (29 patients, 59.2%) received a CRT de novo. All of the patients had received optimal pharmacological therapy before CRT including renin-angiotensin antagonists (42 patients; 85.7%), β-blockers (48 patients; 98%), loop diuretic (46 patients; 93.9 %), mineralocorticoid receptor antagonist (46 patients, 93.9%). The exclusion criteria included acute coronary syndrome for three months, inadequate CRT delivery after the follow-up (BiV pacing rate < 90%) or a poor image quality of the echocardiography. All study patients had transthoracic echocardiography and NYHA functional class assessment before CRT implantation and after 15 ± 7 months follow-up period. All of the patients were informed and signed a written consent. The study protocol was approved by the local bioethical committee.

#### *2.2. Echocardiography—General Data*

A full standard echocardiography was performed using a cardiovascular ultrasound system (Vivid 7, GE Medical Systems, Horten, Norway) before and 15 ± 7 months after CRT implantation. LV end-systolic volume (LVESV), end-diastolic volume (LVEDV) and LVEF were measured using the biplane Simpson method. Left Ventricle Global Longitudinal Strain (LVGLS) measurements were performed to assess global left ventricular function. The response to CRT was defined as a ≥15% LVESV reduction after the follow-up period.

The echocardiographic examination included standard gray-scale and color-coded tissue Doppler imaging (TDI) in all of the apical views (4-chamber, 2-chamber and 3 chamber) with six basal and six-midsegmental models of the myocardial velocity curves. Time to peak myocardial velocity during the ejection phase was measured in relation to the beginning of the QRS complex [9].

In addition to the TDI-derived parameters, gray-scale imagining that was optimized for longitudinal strain (with high frame rates; >35 frames/s) and subsequent strain pattern analysis was performed. Two-dimensional longitudinal strain data were processed using a speckle-tracking examination from the apical views and the reference point was the beginning of the QRS complex. The endocardial border was traced in end-systole. Segmentation of the region of interest for a 18-segment model was performed. Segmentation was automatically proposed by the analysis software with visual verification and a manual correction if needed [10].

The ejection phase was defined as the time from the beginning of QRS to aortic valve closure (AVC). AVC was defined using a pulsed-wave Doppler ultrasound in the LV outflow tract from an apical 5-chamber view. The AVC timing was appropriately noted on the tissue velocity and strain waveforms. Three cardiac cycles were taken to average measurements. Echocardiographic images were analyzed offline with a customized software package (EchoPac, General Electric (GE) Healthcare, Boston, MA, USA).

Atrioventricular (defined as the left ventricular diastolic filling time/RR time, LVDFT/ RR), interventricular (defined as the difference between the aortic and pulmonary preejection time- interventricular mechanical delay, IVMD) and intraventricular dyssynchrony parameters were evaluated.

The following intraventricular dyssynchrony parameters were calculated:

#### *2.3. Echocardiography—Strain Pattern Analysis*

Strain pattern analysis was performed according to the model proposed by Risum et al. [9]. The pattern of the strain curve in patients with LBBB (so-called "classical pattern") reflects an abnormal, dyssynchronous activation of the LV walls. The classical pattern is characterized by an early peak contraction in the early-activated wall, whereas the opposing late-activated wall is prestretched and shows a late contraction [11].

All three criteria must be fulfilled to identify a strain pattern as "classical" (LBBB-related):

Strain pattern analysis was performed using all three apical views. If all three criteria were fulfilled in at least one view, then the strain pattern was recognized as being "classical". A pattern that did not fulfill the criteria of a classical pattern was considered to be a "heterogeneous pattern".

#### *2.4. Echocardiography—Regional Strain Pattern Index*

Our innovative scoring system is based on the methodology of strain pattern analysis that was proposed by Risum et al. [9]. By definition, the classical pattern includes three criteria, but it comprises four components, actually: (1) the early contraction of the earlyactivated wall, (2) the prestretching of the opposing, late-activated wall, (3) the contraction of the early-activated wall occurs in the first 70% of the systolic ejection phase and (4) the peak contraction of the late-activated wall occurs after aortic valve closure. Illustration of the four components of RSPI is shown on Figure 1.

"classical". A pattern that did not fulfill the criteria of a classical pattern was considered

Our innovative scoring system is based on the methodology of strain pattern analysis that was proposed by Risum et al [9]. By definition, the classical pattern includes three criteria, but it comprises four components, actually: 1) the early contraction of the early-activated wall, 2) the prestretching of the opposing, late-activated wall, 3) the con-

and 4) the peak contraction of the late-activated wall occurs after aortic valve closure. Il-

to be a "heterogeneous pattern".

*2.4. Echocardiography—Regional Strain Pattern Index*

lustration of the four components of RSPI is shown on Figure 1.

**Figure 1.** Components of Regional Strain Pattern Index (RSPI). Illustration of the four components of RSPI based on an analysis of the 4-chamber apical view strain curves: 1) the early contraction of the early-activated wall (light blue line; light blue arrow); 2) the prestretching of the opposing, late-activated wall (blue line, yellow arrow); 3) the contraction of the early-activated wall occurs in the first 70% of the systolic ejection phase and 4) the peak contraction of the late-activated wall occurs after aortic valve closure (red line, red arrow). AVC indicates aortic valve closure. **Figure 1.** Components of Regional Strain Pattern Index (RSPI). Illustration of the four components of RSPI based on an analysis of the 4-chamber apical view strain curves: (1) the early contraction of the early-activated wall (light blue line; light blue arrow); (2) the prestretching of the opposing, late-activated wall (blue line, yellow arrow); (3) the contraction of the early-activated wall occurs in the first 70% of the systolic ejection phase and (4) the peak contraction of the late-activated wall occurs after aortic valve closure (red line, red arrow). AVC indicates aortic valve closure.

The component "contraction of the early-activated wall within the first 70% of the systolic ejection phase" was verified based on the timing measurements (time to peak systolic strain of the early activated wall with regard to the ejection phase time). The remaining three components were based on a visual assessment and were referred to as peak strain curve. The presence of RSPI component was recognized if there was an evident positive/negative peak strain curve. Evaluation of echo strain measurements was The component "contraction of the early-activated wall within the first 70% of the systolic ejection phase" was verified based on the timing measurements (time to peak systolic strain of the early activated wall with regard to the ejection phase time). The remaining three components were based on a visual assessment and were referred to as peak strain curve. The presence of RSPI component was recognized if there was an evident positive/negative peak strain curve. Evaluation of echo strain measurements was performed by one observer. In 20 randomly selected strain studies the inter- and intra-observer variabilities for the longitudinal strain were 7 and 5%, respectively.

RSPI calculation is based on strain curves analysis from apical 4-, 2-, and 3-chamber views. RSPI was calculated as the sum of dyssynchronous components from all three apical views. One point was attributed to the presence of each component, thus a maximum of 12 points could be achieved (four points in each view). Presence of dyssynchronous components was analyzed among basal or midventricular segments. RSPI has no relation to the type of strain pattern (classical or heterogeneous). An example how to calculate RSPI is shown in Figures 2–4.

The study population was divided into two groups according to the RSPI score: ≥7 points (19 patients, 38.8% of the population) and <7 points (30 patients, 61.2% of the population).

population).

performed by one observer. In 20 randomly selected strain studies the inter- and intra-observer variabilities for the longitudinal strain were 7 and 5%, respectively.

points (19 patients, 38.8% of the population) and <7 points (30 patients, 61.2% of the

RSPI calculation is based on strain curves analysis from apical 4-, 2-, and 3-chamber views. RSPI was calculated as the sum of dyssynchronous components from all three apical views. One point was attributed to the presence of each component, thus a maximum of 12 points could be achieved (four points in each view). Presence of dyssynchronous components was analyzed among basal or midventricular segments. RSPI has no relation to the type of strain pattern (classical or heterogeneous). An example how to

**Figure 2.** RSPI calculation: 4-chamber view. In 4-chamber view patient reached 3 points: early contraction of the midventricular segment (light blue line; light blue arrow) in the interventricular septum [1 point] but peak contraction slightly exceeds 70% of the systolic ejection phase [0 point]; early prestretching of the basal segment (red line; yellow arrow) in the lateral wall [1 point] with the peak contraction (red arrow) after aortic valve closure [1 point]. **Figure 2.** RSPI calculation: 4-chamber view. In 4-chamber view patient reached 3 points: early contraction of the midventricular segment (light blue line; light blue arrow) in the interventricular septum [1 point] but peak contraction slightly exceeds 70% of the systolic ejection phase [0 point]; early prestretching of the basal segment (red line; yellow arrow) in the lateral wall [1 point] with the peak contraction (red arrow) after aortic valve closure [1 point]. *Int. J. Environ. Res. Public Health* **2021**, *18*, x FOR PEER REVIEW 6 of 14

**Figure 3**. RSPI calculation: 2-chamber view. In 2-chamber view patient reached 2 point: the basal segment in the anterior wall exhibits contraction movement (red line; light blue arrow) [1 point], but it does not fulfill criterion of early 70% of the ejection phase [0 point]. The basal segment in the inferior wall (yellow line) does not show early stretching [0 point] but peak contraction occurs after aortic valve closure (red arrow) [1 point]. **Figure 3.** RSPI calculation: 2-chamber view. In 2-chamber view patient reached 2 point: the basal segment in the anterior wall exhibits contraction movement (red line; light blue arrow) [1 point], but it does not fulfill criterion of early 70% of the ejection phase [0 point]. The basal segment in the inferior wall (yellow line) does not show early stretching [0 point] but peak contraction occurs after aortic valve closure (red arrow) [1 point].

*Int. J. Environ. Res. Public Health* **2021**, *18*, x FOR PEER REVIEW 7 of 14

**Figure 4.** RSPI calculation: 3-chamber view. In 3-chamber view patient reached 3 points: early contraction of the basal segment (red line; light blue arrow) in the anteroseptal wall [1 point] but peak contraction exceeds 70% of the systolic ejection phase [0 point]; early prestretching of the basal segment (yellow line; yellow arrow) in the posterior wall [1 point] with the peak contraction (red arrow) after aortic valve closure [1 point]. **Figure 4.** RSPI calculation: 3-chamber view. In 3-chamber view patient reached 3 points: early contraction of the basal segment (red line; light blue arrow) in the anteroseptal wall [1 point] but peak contraction exceeds 70% of the systolic ejection phase [0 point]; early prestretching of the basal segment (yellow line; yellow arrow) in the posterior wall [1 point] with the peak contraction (red arrow) after aortic valve closure [1 point].

#### *2.5. Statistical Analysis*  The statistical analysis was performed using Statistica 10 Software. The distribution *2.5. Statistical Analysis*

was verified using a Shapiro-Wilk test. Continuous variables were compared using Kolmogorov-Smirnov test or Wilcoxon test when appropriate. The comparison of RSPI score between groups was performed by Mann-Whitney U test. Categorical variables (reported as numbers with percentages) were tested using χ2 statistics and the McNemar test when appropriate. Spearman rank coefficients tests were used to determine the relationships between the variables. Univariate regression analysis with dyssynchrony indexes as the independent variables was also performed. The receiver operating characteristics (ROC) was analyzed for RSPI. Reproducibility was assessed for the strain measurements. *P* value <0.05 was considered to be statistically significant. The statistical analysis was performed using Statistica 10 Software. The distribution was verified using a Shapiro-Wilk test. Continuous variables were compared using Kolmogorov-Smirnov test or Wilcoxon test when appropriate. The comparison of RSPI score between groups was performed by Mann-Whitney U test. Categorical variables (reported as numbers with percentages) were tested using χ 2 statistics and the McNemar test when appropriate. Spearman rank coefficients tests were used to determine the relationships between the variables. Univariate regression analysis with dyssynchrony indexes as the independent variables was also performed. The receiver operating characteristics (ROC) was analyzed for RSPI. Reproducibility was assessed for the strain measurements. *p* value < 0.05 was considered to be statistically significant.

#### **3. Results 3. Results**

#### *3.1. Baseline Characteristics 3.1. Baseline Characteristics*

The study included 49 patients (84% male, 66.5 ± 10 years, NYHA II/III/IV: 34.7%/63.3%/2%; 57.1% ischemic etiology of HF), who underwent CRT implantation. The mean QRS duration was 173.1 ± 19.1 ms. Thirty-five (71.4%) patients had a native LBBB according to the ESC 2013 criteria. Seven (14.3%) patients had a dominant right ventricular pacing rhythm (pacemaker-dependent patients, and therefore native rhythm could not be defined) and seven patients had a non-LBBB morphology. Twenty (40.8%) patients had CIED (three pacemakers (PM) and 17 ICD) and underwent an upgrade to a resynchronization system. Among the three patients with a previously implanted PM, two had a dominant right ventricular pacing rhythm and one had LBBB. Among the 17 The study included 49 patients (84% male, 66.5 ± 10 years, NYHA II/III/IV: 34.7%/ 63.3%/2%; 57.1% ischemic etiology of HF), who underwent CRT implantation. The mean QRS duration was 173.1 ± 19.1 ms. Thirty-five (71.4%) patients had a native LBBB according to the ESC 2013 criteria. Seven (14.3%) patients had a dominant right ventricular pacing rhythm (pacemaker-dependent patients, and therefore native rhythm could not be defined) and seven patients had a non-LBBB morphology. Twenty (40.8%) patients had CIED (three pacemakers (PM) and 17 ICD) and underwent an upgrade to a resynchronization system. Among the three patients with a previously implanted PM, two had a dominant right ventricular pacing rhythm and one had LBBB. Among the 17 patients with ICD, five of

them had a dominant right ventricular pacing rhythm, 10 had LBBB and two had non-LBBB. Thirty-two (65.3%) patients had a contraction pattern (classical pattern) that was typical for LBBB and 17 (34.7%) patients had a heterogeneous pattern according to Risum's method. The baseline characteristics are presented in Table 1. Thirty-six (73.5%) patients responded positively to CRT. No significant differences between responders and non-responders were observed regarding baseline demographics, clinical or echocardiographic parameters. However, non-responders compared with responders were more likely to have CIED before CRT implantation and they underwent "up-grade to CRT" (not de novo implantation).

**Table 1.** Baseline characteristics of general population, responders and non-responders.

Note: NYHA: New York Heart Association; HF: Heart Failure; QRS = QRS width; LBBB—Left Bundle Branch Block; AF: Atrial Fibrillation; CIED: Cardiac Implantable Electronic Device; CRT: Cardiac Resynchronization Therapy; LVESV: Left Ventricular Ventricular End Systolic Volume; LVEF: Left Ventricular Ejection Fraction; \* *p* < 0.05 responders vs non-responders.

#### *3.2. Follow-Up*

The mean follow-up was 14.9 ± 7 months. For the entire study group, a significant decrease in NYHA class was observed (from 2.75 ± 0.52 to 1.9 ± 0.7; *p* < 0.001). There were no important differences in the clinical response between the responders and nonresponders (Table 2). During the follow-up, almost all of the echocardiographic parameters improved. The LVEDV and LVESV volumes were reduced. The LVEF increased from 24.9 ± 6.4% to 31.9 ± 6.9%; *p* < 0.001. LVGLS) for the entire population increased from −6.94 ± 2.16 to −7.95 ± 2.68%; *p* = 0.039.

#### *3.3. Effect of CRT on the Dyssynchrony Parameters*

Table 2 shows the changes in dyssynchrony indexes after CRT. All of the fields of dyssynchrony improved after CRT implantation. The incidence of the septal flash and the typical LBBB contraction pattern decreased (from 31.1% to 11.1%, *p* = 0.039 and from 65.3% to 12.2%, *p* < 0.001, respectively). Similarly, tissue velocity—derived dyssynchrony indexes changed significantly after CRT. A significant reduction of dyssynchrony was observed in the responders but not in the non-responder group.

#### *3.4. Regional Strain Pattern Index*

The RSPI was higher in the responders than in the non-responders (5.86 ± 2.92 vs. 4.08 ± 2.4; *p* = 0.044). The RSPI was independent of gender (male: 5.15 ± 2.93; female: 6.63 ± 2.34; *p* = 0.21), HF etiology (ischemic vs. non-ischemic: 5.18 ± 2.83 vs. 5.67 ± 2.99, respectively; *p* = 0.72) or the presence of LBBB (LBBB: 5.83 ± 2.68; non-LBBB 4.29 ± 3.15; *p* = 0.15). No correlation was found between the RSPI and the echocardiography parameters, dyssynchrony indexes, QRS duration or NYHA class.

**Table 2.** Dyssynchrony indexes and NYHA class before and after CRT in responders and non-responders.

Note: LVEF: Left Ventricular Ejection Fraction; LVESV: Left Ventricular Ventricular End Systolic Volume; LVEDV: Left Ventricular Ventricular End Diastolic Volume; LVDFT/RR: Left Ventricular Diastolic Filling Time/RR ratio: SPWMD Septal-To-Posterior Wall Motion Delay; RSPI: Regional Strain Pattern Index; NYHA: New York Heart Association; CRT: Cardiac Resynchronization Therapy.

> ROC curve analysis was performed for the RSPI (Figure 5). The optimal cut-off value to predict CRT response was at 7 points. RSPI ≥ 7 had a 50% sensitivity, a 92% specificity and a 64.7% positive and 40% negative predictive value in predicting the CRT response (area under curve, AUC = 0.691, *p* = 0.014).

> In the RSPI ≥ 7 points group, reverse remodelling (defined as a reduction of LVESV ≥ 15%) was observed in 18/19 patients (94.7%). Among the non-responders, only one patient (1/13; 7.7%) had RSPI of more than seven points and the other 12 patients (92.3%) were in the RSPI < 7 points group (*p* < 0.01).

#### *3.5. Prediction of the Response to CRT*

At the 15-month follow-up, the mean LVESV reduction was 23.2 ± 19.8 % (range −22% to 72.3%). None of the baseline dyssynchrony indices correlated with the LVESV reduction. For the entire population, the RSPI did not show a relationship with the reverse remodelling (rho = 0.079; *p* = 0.59). In the univariate logistic regression analysis (Table 3) among all of the dyssynchrony indexes, only the RSPI ≥ 7 points predicted a positive response to CRT (OR: 12; 95% CI = 1.33–108.17; *p* = 0.027).

**Figure 5.** Receiver operating characteristic curves for Regional Strain Pattern Index (RSPI) in prediction of Cardiac Resynchronization Therapy (CRT) response (AUC = area under the curve) **Figure 5.** Receiver operating characteristic curves for Regional Strain Pattern Index (RSPI) in prediction of Cardiac Resynchronization Therapy (CRT) response (AUC = area under the curve).

Note: RSPI: Regional Strain Pattern Index.

#### **4. Discussion**

Numerous approaches have been proposed to quantify dyssynchrony and to improve patient's selection for CRT implantation [12,13]. In this study, we have presented our innovative proposal for the prediction of CRT response. We have introduced and verified the clinical use of RSPI. Our modified analysis of the contraction strain curve pattern was aimed at minimizing and overcoming the limitations of the previously employed echocardiographic indices of LV dyssynchrony.

RSPI is based on the assumption that dyssynchrony is a quantitative rather than qualitative process and RSPI reflects the severity of the disease. RSPI is expected to be effective also in a scarred myocardium. In the segments with an impaired contractility, the lack of a strain curve makes it impossible to define the strain pattern. However, in such a case, the features of intraventricular dyssynchrony may be present in other segments/views. Theoretically, this remaining portion of dyssynchrony in the viable segments may be revealed by RSPI and is believed to be a potential indicator for a positive response to CRT. Therefore, it is expected that a high RSPI score will identify responders even in case of patients with scarred segments and abnormal regional contractility.

Four important issues are listed below along with an explanation of why RSPI appears to be better than other methods for predicting the beneficial effects of CRT.

Firstly, it is a quantitative approach to dyssynchrony. Some of the classical, aforementioned parameters are based on rigid cut-off values or on the presence of specific signs such as a septal flash. We assumed that dyssynchrony (and the CRT response as well) is a "continuous" value and that it cannot be treated solely in terms of "presence" or "absence".

Secondly, it is a composite appraisal of dyssynchrony. The advantage of RSPI is that it takes into account dyssynchrony in 12 regions (three apical views with four segments in each view). Previous investigators have shown that the cumulative score of dyssynchrony increases the responsiveness to CRT [14,15]. In the classical parameters, the diminished contractility of one wall may lead to incorrect results. In RSPI, even in the case of impaired myocardial viability in one region, features of dyssynchrony may be present in the remaining regions. Therefore, the final RSPI could remain high, thus reflecting an existing dyssynchrony. Moreover, RSPI reflects changes during the entire cardiac cycle, not just in the ejection period.

Thirdly, the contractility. Patients without preserved contractility are unlikely to have a positive response to CRT. Abnormal contractility modifies the strain-derived pattern of LBBB [16]. Decreased contractility and scarring may predict a poor response to CRT regardless of the pathogenesis of cardiomyopathy [17,18]. Our innovative parameter indirectly assesses the contractility. The absence of contraction makes it impossible to assess the strain curves. Therefore, RSPI would not be scored in these regions (which actually means a "0" point).

Fourthly, the feasibility and simplicity. Many of the proposed dyssynchrony parameters require either specialized software or complex calculations [19]. To calculate RSPI, there is no need for extra tooling or to transfer the images to another system for the final processing of the results. RSPI calculation is possible ad hoc while performing a basic echocardiography examination.

Measurements of various dyssynchrony parameters were performed (Table 3). Among all of the indexes, only RSPI ≥ 7 points showed a significant relation with the CRT response in the univariate model (OR: 12; 95% CI 1.33–108.17; *p* = 0.027), whereas the general RSPI reached a borderline statistical significance (OR: 1.26; 95% CI 0.98–1.61; *p* = 0.068). Therefore, maybe the innovative quantitative methods based on strain analysis would be useful in improving the identification of CRT responders. Recently, Gorcsan et al. [20] proposed Systolic Stretch Index (SSI)—similar to our methodology based on strain analysis. SSI was strongly associated with favorable clinical outcomes including in the important patient subgroup with QRS width 120 to 149 ms or non-LBBB.

In our study, we intended to prove the usefulness of RSPI in case of all the patients who met the CRT criteria. Our group reflects the real-life, potential CRT recipients. In daily

clinical practice, it is not only LBBB but also patients with non-LBBB and patients with CIED that undergo an up-grade procedure. Overall, the positive and negative predictive values of RSPI are quite modest but we must keep in mind that the study population was heterogeneous with different baseline conditions. Within the whole perspective, among the patients with different kinds of CRT indications, RSPI was positively verified with a specificity at satisfactory level of 92.3%.

The arguments presented in the discussion show that the evaluation of dyssynchrony is a composite, multifaceted problem. The Regional Strain Pattern Index is our new approach and has the potential to become a simple and practical tool for everyday use.

#### **5. Limitations**

Some limitations to our study should be addressed:

#### **6. Conclusions**

RSPI constitutes an innovative, valuable predictor for a CRT response. RSPI value of ≥7 points is an independent predictor of CRT response. RSPI appears to be better than the previously used dyssynchrony indexes for selecting patients for CRT and for efficiently identifying long-term responders.

**Author Contributions:** Conceptualization K.M.-S. and M.O.; methodology K.M.-S., W.O.; software W.W. and M.O.; validation K.M.-S., E.P.-G.; formal analysis W.W., A.B.-K.; investigation W.O., A.F., D.U.-S., W.K.; writing—original draft preparation M.O.; writing—review and editing, M.O.; visualization M.O.; supervision K.M.-S., A.F.; project administration A.F.; funding acquisition K.M.-S. All authors have read and agreed to the published version of the manuscript.

**Funding:** Grant for scientific research in the field of CRT efficacy funded by Medical University of Silesia.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by Ethics Committee of Medical University of Silesia. Resolution with a positive opinion of Committee: Nr KNW/0022/KB1/123/13, dated 03.12.2013.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **References**

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**4. The valorization of new technologies for agricultural product conservation in Burkina Faso**

This section presents the concept of valorization and analyzes the national environment through existing valorization structures and actions.

#### **4.1 The concept of valorization**

The valorization of the results of the research is a polysemic and multidimensional concept whose content varies according to the implied actors, their expectations, and their interests. [17] distinguishes six different categories from the concept of valorization in Burkina Faso: academic or professional, scientific, technological, economic, social, and political valorizations. Of course, these different categories are not mutually exclusive. Academic valorization involves the incorporation of recent research results into the training modules for updating the

**55**

*Local Techniques for Crop Conservation in Burkina Faso: Analysis of the Valorization Status…*

content of the courses offered to students or professionals engaged in the process of improving their professional knowledge and skills. Scientific valorization is mainly the activity of researchers. For these authors, the valorization of the results of research means the diffusion and the exchange of knowledge. The valorization is concerned in this case with the dissemination in the form of scientific publications in specialized journals, communications at conferences and seminars, posters, data

The social valorization of a research or an innovation aims to demonstrate the social utility of research or innovation in particular for the company to provide public funding. Economic valorization emphasizes the economic utility of innovation including its contribution to economic growth, increased productivity, and the creation of jobs and incomes for people. Regarding political valorization it aims to take into account innovations in the formulation execution, evaluation of public

The national referential of the interventions of the government of Burkina Faso and its partners over the period 2016-2020, which is the National Economic and Social Development Plan (PNDES), gives importance to the valorization seeking to increase the number of research results and innovations valued in favor of the structural transformation of the economy. This is justified by the fact that most

In Burkina Faso, scientific research and invention and innovation activities have generated many results that can contribute to the endogenous development of populations in many sectors of economic activity. Indeed the support provided to research and innovation since the 1990s by institutions such as the World Bank bilateral and multilateral cooperation agencies as well as international research institutions has enabled the country to have access to scientific and technological knowledge that can bring added value to the direct beneficiaries and to the State

However, it is clear that many of these research and innovation results are less known to potential users, less used, and of little value. However, research activities are expensive, and the low value of research results is thus a poor allocation of resources as is the case in many developing countries [14]. In response to this, policy-makers are committed to enhancing the value of scientific research results, innovations, and inventions by institutionalizing the National Forum for Scientific Research and Technological Innovations (FRSIT) in 1995. The Ministry of Higher Education, Scientific Research, and Innovation (MESRSI) through the general direction of the National Agency for the Valorization of Research Results (DG ANVAR) organizes every 2 years the "FRSIT." This forum allows all actors (decision-makers, researchers, inventors and innovators, promoters, development partners, users, and the public) to become familiar with the research, its results, and the inventions and technological innovations realized in Burkina Faso but also outside the country. It is in this national environment favorable to the valorization of the results of research and innovation that the technologies Tilgr-Baore and Klimax Z were created by local innovators. What is the importance of intellectual property rights in the valorization of innovations?

Intellectual property rights are mechanisms for the recognition and protection of intellectual materialization through invention and innovation which entitle their authors to use the fruit resulting from the valorization of their creation. Protection

*DOI: http://dx.doi.org/10.5772/intechopen.85179*

policies, and decision-making in general.

innovations are poorly known by potential users.

**4.2 Analysis of the national environment**

and thus reduce poverty in the country.

**4.3 The intellectual property rights**

sheets, photo, and video.

#### *Local Techniques for Crop Conservation in Burkina Faso: Analysis of the Valorization Status… DOI: http://dx.doi.org/10.5772/intechopen.85179*

content of the courses offered to students or professionals engaged in the process of improving their professional knowledge and skills. Scientific valorization is mainly the activity of researchers. For these authors, the valorization of the results of research means the diffusion and the exchange of knowledge. The valorization is concerned in this case with the dissemination in the form of scientific publications in specialized journals, communications at conferences and seminars, posters, data sheets, photo, and video.

The social valorization of a research or an innovation aims to demonstrate the social utility of research or innovation in particular for the company to provide public funding. Economic valorization emphasizes the economic utility of innovation including its contribution to economic growth, increased productivity, and the creation of jobs and incomes for people. Regarding political valorization it aims to take into account innovations in the formulation execution, evaluation of public policies, and decision-making in general.

The national referential of the interventions of the government of Burkina Faso and its partners over the period 2016-2020, which is the National Economic and Social Development Plan (PNDES), gives importance to the valorization seeking to increase the number of research results and innovations valued in favor of the structural transformation of the economy. This is justified by the fact that most innovations are poorly known by potential users.

#### **4.2 Analysis of the national environment**

In Burkina Faso, scientific research and invention and innovation activities have generated many results that can contribute to the endogenous development of populations in many sectors of economic activity. Indeed the support provided to research and innovation since the 1990s by institutions such as the World Bank bilateral and multilateral cooperation agencies as well as international research institutions has enabled the country to have access to scientific and technological knowledge that can bring added value to the direct beneficiaries and to the State and thus reduce poverty in the country.

However, it is clear that many of these research and innovation results are less known to potential users, less used, and of little value. However, research activities are expensive, and the low value of research results is thus a poor allocation of resources as is the case in many developing countries [14]. In response to this, policy-makers are committed to enhancing the value of scientific research results, innovations, and inventions by institutionalizing the National Forum for Scientific Research and Technological Innovations (FRSIT) in 1995. The Ministry of Higher Education, Scientific Research, and Innovation (MESRSI) through the general direction of the National Agency for the Valorization of Research Results (DG ANVAR) organizes every 2 years the "FRSIT." This forum allows all actors (decision-makers, researchers, inventors and innovators, promoters, development partners, users, and the public) to become familiar with the research, its results, and the inventions and technological innovations realized in Burkina Faso but also outside the country. It is in this national environment favorable to the valorization of the results of research and innovation that the technologies Tilgr-Baore and Klimax Z were created by local innovators. What is the importance of intellectual property rights in the valorization of innovations?

#### **4.3 The intellectual property rights**

Intellectual property rights are mechanisms for the recognition and protection of intellectual materialization through invention and innovation which entitle their authors to use the fruit resulting from the valorization of their creation. Protection

*Agricultural Economics - Current Issues*

producers in rural areas. It keeps up to 98% of production. The cost of making this innovation amounts to 1 million CFA francs. Given this cost, the exploitation in association or in a group of both producers and sellers is recommended [14].

This section presents the concept of valorization and analyzes the national

The valorization of the results of the research is a polysemic and multidimensional concept whose content varies according to the implied actors, their expectations, and their interests. [17] distinguishes six different categories from the concept of valorization in Burkina Faso: academic or professional, scientific, technological, economic, social, and political valorizations. Of course, these different categories are not mutually exclusive. Academic valorization involves the incorporation of recent research results into the training modules for updating the

**4. The valorization of new technologies for agricultural product**

environment through existing valorization structures and actions.

**conservation in Burkina Faso**

*Presentation of Tilgr-Baore. Source: The promoter, 2018.*

**4.1 The concept of valorization**

**54**

**Figure 3.**

reassures innovators that products are not being pirated or spoofed. It puts innovators in trust with the use of their products with recognition because many innovators are reluctant to give information about the "processes" that are used in their innovation.

There are several systems of protection of an invention/innovation among which patents are the most known and most commonly used in Burkina Faso. The benefits of patent protection are multiple. In particular, the protection allows the work to be well scientifically documented, protects potential users, and provides substantial remuneration to the inventor or research institute concerned. Patents help to strengthen the country's brand image because the more the number of patents increases, the more the level and credibility of the research or innovation that produces them are enhanced [18].

Burkina Faso is a member of the African Intellectual Property Organization and the World Intellectual Property Organization. These institutions are responsible for the management of patents and other intellectual property rights. There is also a National Intellectual Property Office (DNPI) in the country which is the public institution charged with protecting the intellectual property rights of innovators and raising awareness and giving advice on the need for property ownership. However, the partnership of innovators with intellectual property organizations is weak in the agricultural sectors of Burkina Faso.

### **4.4 Valorization statements and constraint of valorization of Tilgr-Baore technology**

The Tilgr-Baore technology was presented at the National Forum for Scientific Research and Technological Innovation (FRSIT) in 2016, where it was selected among the best innovations and awards. FRSIT has also included it on the national list of innovations. The steps for the patenting of Tilgr-Baore are in progress. The innovator with the support of FRSIT and DG ANVAR filed his patent application with the African Intellectual Property Organization. He holds from this organization for the moment just the acts which prove that he has introduced to OAPI his patent application for Tilgr-Baore.

Because of its importance for the conservation of agricultural products, the Tilgr-Baore is increasingly popularized by programs that work in the rural world. These projects include the Support Program for the Modernization of Agro-Pastoral Family Farms (PAMEFA program) whose objective is to promote modern family farming, the Agricultural Sector Support Project (PROFIL program) that involves installing 500 boxes of Tilgr-Baore types in four regions of the Burkina Faso, and an action research program of INSS, whose objective is to facilitate the access of Tilgr-Baore innovation to producers organized into associations and unions of associations.

Despite these promotional actions of Tilgr-Baore, there are constraints to the diffusion of innovation. The promoter of the innovation expresses itself in these terms: "There is the PROFIL program which has installed 5OO boxes in 4 regions of Burkina Faso, but has not been completed. There was no follow-up or training for the operators of the box so that these beneficiaries could use the technology" (Ouedraogo Lassane, Ouagadougou, November 2018).

Considering the example of the PROFIL project, the developer estimates at 35% the completion rate of the construction of the 500 Tilgr-Baore box. Lack of training of beneficiaries remains the main obstacle to exploiting innovation. These remarks raise the difficulty of training beneficiaries on the various facets of technology. From the maintenance of the environment where Tilgr-Baore is installed, to the box itself and then to the stored products, a whole procedure of maintenance must be taught to the beneficiaries of the box for its judicious exploitation.

**57**

*Local Techniques for Crop Conservation in Burkina Faso: Analysis of the Valorization Status…*

The Tilgr-Baore technology benefits from the support of various ministerial departments including the Department of Scientific Research and the Department of the Environment, Agriculture, Trade, and Crafts. This is an asset for promoting innovation, but it is difficult to bring together these different actors around a table to coordinate interventions. In this regard, the initiator of Tilgr-Baore said: "The fact that our technology brings together several ministerial departments, lead to difficulties to bring them together to work. This is a problem for us because we do not know how to bring all these authorities together to coordinate the actions of valorization of the technology" (Ouedraogo Lassane, Ouagadougou, November 2018). So, there is a need for a revitalization of the partnership between the ministerial departments, concerned with the promotion of innovation, and innovators. Based on survey data from rural producers, the following section analyzes the

Perception of innovation is very important in the adoption process. It indicates the user's view of a technology. Individual innovation decisions are based on the individual's perceptions of the innovation. According to [19], rejection, discontinuance, and re-invention frequently occur during the diffusion of an innovation, and such behavior may be rational and appropriate from the individual's point of view, if only the diffusion scholar could adequately understand the individual's perceptions of the innovation and of his or her own situation, problems, and needs. We are therefore analyzing the farmers' perception of Tilgr-Baore, in order to guide

This section presents the model used to analyze the perception of Tilgr-Baore, the source of the data, the descriptive statistics of the sample, and the econometric

The perception of Tilgr-Baore is analyzed using a probit model. The dependent variable is a binary variable. In most practical cases, one can choose indifferently between the models probit and logit, to analyze the perception of the innovation or adoption of innovation. We choose a probit model to analyze the perception of

the latent variable that is unobservable, whose value depends on a

*Xi* + ε*i* (1)

is the farmers' perceptions of Tilgr-Baoré

the sociodemographic and institutional characteristics that can

*Xi* + ε*i* > 0 (2)

*DOI: http://dx.doi.org/10.5772/intechopen.85179*

perception of Tilgr-Baoré technology by rural people.

policies aimed at better dissemination of this innovation.

**5.1 Model specification and definition of model variables**

series of explanatory variables Xi. We have the following equation:

*Yi* = 1 *if Y*∗ > 0 that is to sayβ′

∗ = β′

The dichotomous variable *Y*, observed, is linked to the latent variable *Y\** by the

results of the estimation.

Tilgr-Baore technology.

*Yi*

where the dependent variable *Yi*

*5.1.1 Probit model*

Consider Y\*

following relation:

= 0 *ifnot*.

technology and *Xi*

**5. Perception of farmers toward Tilgr-Baore technology**

*Local Techniques for Crop Conservation in Burkina Faso: Analysis of the Valorization Status… DOI: http://dx.doi.org/10.5772/intechopen.85179*

The Tilgr-Baore technology benefits from the support of various ministerial departments including the Department of Scientific Research and the Department of the Environment, Agriculture, Trade, and Crafts. This is an asset for promoting innovation, but it is difficult to bring together these different actors around a table to coordinate interventions. In this regard, the initiator of Tilgr-Baore said: "The fact that our technology brings together several ministerial departments, lead to difficulties to bring them together to work. This is a problem for us because we do not know how to bring all these authorities together to coordinate the actions of valorization of the technology" (Ouedraogo Lassane, Ouagadougou, November 2018). So, there is a need for a revitalization of the partnership between the ministerial departments, concerned with the promotion of innovation, and innovators.

Based on survey data from rural producers, the following section analyzes the perception of Tilgr-Baoré technology by rural people.

## **5. Perception of farmers toward Tilgr-Baore technology**

Perception of innovation is very important in the adoption process. It indicates the user's view of a technology. Individual innovation decisions are based on the individual's perceptions of the innovation. According to [19], rejection, discontinuance, and re-invention frequently occur during the diffusion of an innovation, and such behavior may be rational and appropriate from the individual's point of view, if only the diffusion scholar could adequately understand the individual's perceptions of the innovation and of his or her own situation, problems, and needs. We are therefore analyzing the farmers' perception of Tilgr-Baore, in order to guide policies aimed at better dissemination of this innovation.

This section presents the model used to analyze the perception of Tilgr-Baore, the source of the data, the descriptive statistics of the sample, and the econometric results of the estimation.

#### **5.1 Model specification and definition of model variables**

The perception of Tilgr-Baore is analyzed using a probit model. The dependent variable is a binary variable. In most practical cases, one can choose indifferently between the models probit and logit, to analyze the perception of the innovation or adoption of innovation. We choose a probit model to analyze the perception of Tilgr-Baore technology.

#### *5.1.1 Probit model*

*Agricultural Economics - Current Issues*

that produces them are enhanced [18].

**technology**

associations.

patent application for Tilgr-Baore.

weak in the agricultural sectors of Burkina Faso.

reassures innovators that products are not being pirated or spoofed. It puts innovators in trust with the use of their products with recognition because many innovators are reluctant to give information about the "processes" that are used in their innovation. There are several systems of protection of an invention/innovation among which patents are the most known and most commonly used in Burkina Faso. The benefits of patent protection are multiple. In particular, the protection allows the work to be well scientifically documented, protects potential users, and provides substantial remuneration to the inventor or research institute concerned. Patents help to strengthen the country's brand image because the more the number of patents increases, the more the level and credibility of the research or innovation

Burkina Faso is a member of the African Intellectual Property Organization and the World Intellectual Property Organization. These institutions are responsible for the management of patents and other intellectual property rights. There is also a National Intellectual Property Office (DNPI) in the country which is the public institution charged with protecting the intellectual property rights of innovators and raising awareness and giving advice on the need for property ownership. However, the partnership of innovators with intellectual property organizations is

**4.4 Valorization statements and constraint of valorization of Tilgr-Baore**

The Tilgr-Baore technology was presented at the National Forum for Scientific Research and Technological Innovation (FRSIT) in 2016, where it was selected among the best innovations and awards. FRSIT has also included it on the national list of innovations. The steps for the patenting of Tilgr-Baore are in progress. The innovator with the support of FRSIT and DG ANVAR filed his patent application with the African Intellectual Property Organization. He holds from this organization for the moment just the acts which prove that he has introduced to OAPI his

Because of its importance for the conservation of agricultural products, the Tilgr-Baore is increasingly popularized by programs that work in the rural world. These projects include the Support Program for the Modernization of Agro-Pastoral Family Farms (PAMEFA program) whose objective is to promote modern family farming, the Agricultural Sector Support Project (PROFIL program) that involves installing 500 boxes of Tilgr-Baore types in four regions of the Burkina Faso, and an action research program of INSS, whose objective is to facilitate the access of Tilgr-Baore innovation to producers organized into associations and unions of

Despite these promotional actions of Tilgr-Baore, there are constraints to the diffusion of innovation. The promoter of the innovation expresses itself in these terms: "There is the PROFIL program which has installed 5OO boxes in 4 regions of Burkina Faso, but has not been completed. There was no follow-up or training for the operators of the box so that these beneficiaries could use the

Considering the example of the PROFIL project, the developer estimates at 35% the completion rate of the construction of the 500 Tilgr-Baore box. Lack of training of beneficiaries remains the main obstacle to exploiting innovation. These remarks raise the difficulty of training beneficiaries on the various facets of technology. From the maintenance of the environment where Tilgr-Baore is installed, to the box itself and then to the stored products, a whole procedure of maintenance must be

technology" (Ouedraogo Lassane, Ouagadougou, November 2018).

taught to the beneficiaries of the box for its judicious exploitation.

**56**

Consider Y\* the latent variable that is unobservable, whose value depends on a series of explanatory variables Xi. We have the following equation:

$$\mathbf{Y}\_i^\* = \boldsymbol{\mathfrak{f}}^\prime \mathbf{X}\_i + \mathbf{e}\_i \tag{1}$$

The dichotomous variable *Y*, observed, is linked to the latent variable *Y\** by the following relation:

$$Y\_i = \mathbf{1} \quad \text{if } Y^\* > \mathbf{0} \text{ that is to say} \\ \text{g}' \\ X\_i + \mathbf{e}\_i > \mathbf{0} \tag{2}$$

= 0 *ifnot*.

where the dependent variable *Yi* is the farmers' perceptions of Tilgr-Baoré technology and *Xi* the sociodemographic and institutional characteristics that can influence the perception of innovation. β being the coefficients, ε*i* is the error term. We assume the error term is distributed normally with mean zero and variance one. *i* = 1, 2……n. *n* is the number of observations.

If β′ *Xi* + ε*i* > 0, the farmer has a very good perception of the Tilgr-Baore, which tcould give him enough incentives to adopt the technology, and the dichotomous variable takes the value 1. The error term is due to the effects not considered.


**13.7 Dangers in the habitat**

Life within the habitat structures is also full of health and safety threats. Simple survival requirements also present significant challenges that include providing water for humans and crops, creating an ongoing supply of oxygen, growing food in Martian soil and/or hydroponically, interacting with others on a prolonged basis within an confined and enclosed space, keeping Martian dust out of the habitat, dealing with circadian rhythm issues, adjusting to time differences (the Martian day is 40 minutes longer than Earth's), and dealing with delayed communications with Earth. Accumulating challenges could produce problematic behavioral and abnormal psychological patterns for some individuals.

Bringing Martian microbes into the laboratories within the habitat can present contamination worries. It can result in microbes escaping quarantines or otherwise infecting astrobiologists. An epidemic could arise if the microbes are harmful to humans.

**163**

*Astrosociology on Mars*

members of society.

geriatric physicians.

**13.9 A few final questions and thoughts**

more importantly, monitored once the settlement is active.

*DOI: http://dx.doi.org/10.5772/intechopen.93309*

**13.8 Aging and space gerontology**

to the biomedical changes that will challenge them.

Physical epidemiologists and social epidemiologists would have to work together to track the spread of disease and the structure and procedures employed to combat its spread. There are other issues that can result in health-related problems generated in the outside environment that have both medical and sociocultural implications.

Another issue is less theoretical and actually inevitable. Space medicine will be difficult enough without the added complications of advanced aging. Many settlers will necessarily be older based on the need for them to put their expertise and training into effect. In any case, they will age. Therefore, gerontology, defined as the scientific study of old age, the process of aging, and the particular problems of old people, will become important as everyone ages under a never-before set of medical conditions exacerbated by the Martian environment. It will involve medical astrosociology in terms of how individuals handle growing old on Mars in addition

*Space gerontology* has been recognized by NASA and others for quite some time, in fact since 1978 or earlier. The advent of the Space Shuttle program with its first flight of Columbia in 1981 and the recognition that older astronauts would be traveling into near Earth orbit in microgravity, it became worrisome that little was known about the long-term effects of space travel as people age [69]. Nearing the end of the human life cycle in space ecosystems will produce changes, many of which will have never been experienced on Earth. Will ageism be a problem if, for example, not enough medical supplies exist for the younger

How will settlers handle death? What will cemeteries on Mars look like and what types of religious ceremonies will be held? What meanings will be attached to the deaths of the new Martians? It is quite possible that the ways that deaths are treated will evolve into one or more uniquely Martian versions of Earth observances. This type of sociocultural change is important for astrosociologists to study and understand. Very importantly, the added complications affecting human beings in a harsh Martian environment that will inevitably impact significantly on the internal ecosystem will make implementing healthcare extraordinarily unique and difficult. What was learned regarding living in microgravity will not apply exactly the same way in a one-third gravity field. Gerontologists who also possess social science training will prove to be invaluable members of the Martian society, just as will

What new syndromes or health complications will arise on Mars? How will living on Mars affect men compared to women? Will health issues affect ethnic groups differently? Will life expectancy change? These types of questions must be anticipated by both physicians and medical astrosociologists before arriving at Mars; and

While space medicine physicians focus mostly on the biomedical issues, medical astrosociologists concentrate on the social and cultural elements that interact with the biomedical aspects that can easily add further complications beyond the strictly medical concerns. This complicates how those reacting to the patient should handle any particular case. For example, are there religious factors that do not allow certain medical procedures or drugs? How do physicians and social scientists work together to treat patients, avoid discriminatory practices, and monitor the population to minimize epidemic potentials in such enclosed ecosystems? Medical astrosociology

*Mars Exploration - A Step Forward*

to seek other options.

**Figure 6.**

**13.6 Genetics and lava tubes**

*Terraforming Mars/image credit: NASA.*

clearly provided authorization.

**13.7 Dangers in the habitat**

mal psychological patterns for some individuals.

locations on the planet in order to thicken the atmosphere and make it breathable. Such a herculean effort would take hundreds if not thousands of years. The resource expenditures and length of the process have led proponents of Martian settlement

Genetic enhancements may better adapt humans to living on Mars physically speaking, but what will it do to the human psyche? How will it affect behavior? Is it even ethical? What about the history of eugenics? The Nazi regime in Germany instituted various forms of eugenics, which led to unethical experiments and genocide against Jews and other perceived unworthy categories of people. While altering the human body to better tolerate solar radiation, for example, may seem like a logical idea, the human experience in this area is highly problematic. Ethical questions abound such as to whether or not those who receive enhancements have

Other proposals include living inside lava tubes, as mentioned, utilizing 3D printing to construct habitat components, and creating human made subterranean habitats. While the external environment that impacts the surface is harmful to human life that currently exist, the places where humans actually live—that is, the ecosystems in the habitat structures—present potentially equally dangerous conditions as well.

Life within the habitat structures is also full of health and safety threats. Simple survival requirements also present significant challenges that include providing water for humans and crops, creating an ongoing supply of oxygen, growing food in Martian soil and/or hydroponically, interacting with others on a prolonged basis within an confined and enclosed space, keeping Martian dust out of the habitat, dealing with circadian rhythm issues, adjusting to time differences (the Martian day is 40 minutes longer than Earth's), and dealing with delayed communications with Earth. Accumulating challenges could produce problematic behavioral and abnor-

Bringing Martian microbes into the laboratories within the habitat can present contamination worries. It can result in microbes escaping quarantines or otherwise infecting astrobiologists. An epidemic could arise if the microbes are harmful to humans.

**162**

Physical epidemiologists and social epidemiologists would have to work together to track the spread of disease and the structure and procedures employed to combat its spread. There are other issues that can result in health-related problems generated in the outside environment that have both medical and sociocultural implications.