the decline in respiratory function of stroke patients is caused by reduced physical 
 activity .
the decline in cardiopulmonary function is related to reduced oxygen transport 
 ability caused by extended bed rest after hospitalization1 .
this condition can cause stroke patients who require intensive 
 rehabilitation to tire easily during aerobic activities requiring endurance , thereby 
 restricting their performance of daily living activities .
consequently , the success rate of 
 rehabilitation drops because functional recovery is hindered2 . in a study conducted by khedr et al.3
the results of analysis 
 of lung function show only 50% of the values expected of normal adults4 , 5 . among the 
 different types of training used to improve respiratory functions , inspiratory muscle 
 training ( imt )
improves inspiratory muscle strength and endurance , regardless of damage to 
 the inspiratory muscles , by applying loads to the diaphragm and the accessory muscles of the 
 inspiratory muscles6 .
it was reported that 
 imt performed by subacute stroke patients for six months improved lung function , maximal 
 inspiratory pressure ( mip ) , exercise tolerance , and pulmonary function indexes7 . in a study conducted by britto et al.8 of chronic stroke patients , imt for eight 
 weeks improved mip and inspiratory muscular endurance ( ime ) .
gollee et al.9 reported that 
 neuromuscular stimulation of the abdominal muscles supported respiration and the application 
 of simple surface stimulation to major paralyzed expiratory muscles induced even muscle 
 contraction , thus helping to improve cough and forced expiration .
it was reported that 
 abdominal muscle stimulation improved respiratory functions during expiration , because the 
 contraction of the abdominal muscles caused by stimulation induces increased coughing and 
 directly increases mip to improve expiratory flow9 .
gollee et al.9 
 also reported that abdominal muscle stimulation could improve conditions in which 
 respiratory rates increase because of decreased lung volume .
abdominal muscle stimulation 
 also improved lung function of paretic patients with decreased functional residual capacity 
 ( frc ) and elastic recoil during inspiration9 .
previous studies have shown that among the methods used to improve the respiratory function 
 of stroke patients , imt is an excellent intervention for improving inspiratory muscle 
 strength and endurance7 .
in addition , abdominal muscle 
 stimulation induced improvement in forced expiration of patients with nervous system 
 disorders , showing decline in respiratory function caused by respiratory air passage 
 obstruction or decreased forced expiration . the present study aimed to verity more efficient imt method , the imt used in clinics with 
 abdominal muscle stimulation , and identify the effects of the new imt method on the 
 improvement of the respiratory function of chronic stroke patients .
the participants were eighteen stroke patients ( 11 males , 7 females ) who voluntarily 
 consented to participate in the study .
they were randomly and equally divided into two groups : an 
 experimental group and a control group .
the experimental group received abdominal 
 stimulation while performing inspiratory muscle training , and the control group only 
 performed inspiratory muscle training .
both groups performed the training 3 times per week , 
 non - consecutively , for 4 weeks .
the 
 average age , height , weight , and body mass index ( bmi ) of the experimental group were 
 54.44  years , 159.86  cm , 63.68  kg , and 24.82  kg / m , respectively , and the average time since 
 stroke onset was 40.55 months .
the average age , height , weight , and body mass index ( bmi ) of 
 the control group were 55.88  years , 158.7  cm , 62.32  kg , and 24.71  kg / m , 
 respectively , and the average time since stroke onset was 46.22 months .
the subjects of the present study were patients who had been diagnosed with stroke using 
 computed tomography and had hemiplegia as a sequela of partial damage of the cerebral 
 hemisphere .
the following exclusion criteria were stroke patients who had had the disease 
 for at least six month or were receiving physical therapy in hospital but not receiving any 
 particular treatment for rehabilitation . lung - function was measured with a spirometer ( chestgraph hi 101 , chest m.i .
lung function was examined three times , and the results of reliability were chosen for the 
 analysis .
the subjects maintained an upright sitting position , and the measurement values 
 included fvc , fev1 , the pef , and fef2575 .
changes in the diaphragm thickness were analyzed using ultrasonography ( logiq 7 , ge co. , 
 usa ) .
for all subjects , the mid axillary lines between ribs 8 and 9 on both sides were 
 checked in a standing posture , then the chest wall was perpendicularly illuminated by a 
 linear transducer ( 5.014.0  mhz ) in an upright sitting position to observe the region 
 between rib 8 and rib 9 in 2d images .
the diaphragm thickness was measured as the distance 
 between two parallel lines that appear bright in the middle of the pleura and in the middle 
 peritoneum .
the distance was measured three times , and the average value was calculated10 . the diaphragm thickness ratio ( tr )
the formula of enright et al.10 formula was used to obtain standardized 
 diaphragm thickness ratios ( tr ) .
tr= ( diaphragm thickness during mip maneuver of frc / mean 
 thickness while relaxing at frc ) .
abdominal stimulation was applied when the subject was sitting with 90 hip flexion . a 
 functional electrical stimulator ( microstim , medel gmbh , germany )
the adhesive 
 surface electrodes ( protens electrodes 48  48  mm , biopro - tech inc , korea ) were attached to 
 the abdominal muscles ( rectus abdominis muscle , lateral abdominal muscle)11 , 12 .
the electricity used had symmetric biphasic rectangular waveforms , a 
 pulse duration of 250  s , a frequency of 40  hz , a maximum output of 90 ma , and a stimulation 
 intensity ranging from 10 to 30 ma .
stimulation time per session was 20 minutes ( current flowing time 5 seconds , no 
 current flowing time 5 seconds , and gradient variation 2.5 seconds ) . using a threshold imt device ( threshold inspiratory muscle trainer , respironics health 
 scan , inc .
, usa ) during an expiration after one inspiration , the patient pressed the current 
 flowing switch with his / her hand on the non - paretic side to induce expiration while 
 stimulation was applied to the abdominal region9 . the therapist helped if a patient had difficulty pressing the 
 switch because of a coordination disorder . for both othe groups ,
imt was identically 
 performed with 30% of the maximal inspiratory pressure ( mip ) for 20 minutes per session , 
 three times per week for four weeks , a total of 12 times .
data obtained from the two groups of subjects were analyzed using spss 18.0 ( spss inc .
because of the small 
 size of the study sample , non - parametric tests were used , and between - group comparisons were 
 performed using the mann 
changes in lung function found after the four - week intervention are shown in table 1table 1 .
the values of the variables measured before and after the intervention 
 ( n=18)grouppre - testpost - testchangetr ( paretic side)experimental1.740.272.160.29 * 0.420.28control1.720.332.000.24 * 0.280.25tr ( non - paretic side)experimental1.750.281.990.280.230.33control1.820.302.050.370.220.27fvc ( % predicted)experimental59.0321.8365.4415.096.419.77control62.6819.2962.6315.720.0517.21fev1 ( % predicted)experimental59.1519.7474.8117.91 * 15.6514.74*control72.2322.0173.1717.770.9418.16pef ( % predicted)experimental41.7219.1967.5015.97 * 25.7726.47*control52.9514.1750.8215.732.138.14fef2575 ( % predicted)experimental71.5832.4092.9828.88 * 25.5429.62control97.1318.9695.0621.232.0719.20*statistical significance , p0.05 .
tr= diaphragm thickening ratio , fvc = forced vital 
 capacity , fev1=forced expiratory volume in one second , pef = peak expiratory 
 flow , fef2575= forced expiratory flow between 25% and 75% of vital 
 capacity .
the comparison of comparing the number of changes between before and after the 
 intervention in the experimental group and the control group revealed significant 
 differences in fev1 and pef ( p < 0.05 ) . * statistical significance , p0.05 .
tr= diaphragm thickening ratio , fvc = forced vital 
 capacity , fev1=forced expiratory volume in one second , pef = peak expiratory 
 flow , fef2575= forced expiratory flow between 25% and 75% of vital 
 capacity after implementing abdominal stimulation during inspiratory muscle training in the 
 experimental group and the control group , tr significantly increased on the paretic side ( p 
 < 0.05 ) , but not on the non - paretic side .
the comparison of changes between before and 
 after the intervention in the experimental group and the control group revealed no 
 significant difference on either the paretic side or the non - paretic side ( table 1 ) .
kim13 reported that increase in the 
 residual capacity or decrease in the lung volume of stroke patients causes weakening of the 
 inspiratory muscle and the expiratory muscle .
the muscles necessary for maintaining posture 
 and the muscles that act during breathing are closely related .
the difficulties of stroke 
 patients in maintaining posture and their deteriorated trunk stability cause the weakening 
 of the expiratory muscles that maintain posture13 . because these expiratory muscles are weak , patients with abdominal 
 muscle paresis , including stroke , experience inability to clean the air passage and are 
 prone to respiratory infections14 . 
 therefore , gollee et al.9 suggested 
 applying neuromuscular stimulation to the abdominal muscles to help the contraction of the 
 major expiratory muscles and to increase expiratory flows and tidal volumes , in order to 
 improve respiration function .
the present study examined a method designed to combine imt with abdominal muscle 
 stimulation to improve forced expiration . in order to examine the effects of the new imt 
 method ,
the new method was performed by the experimental group , whereas only imt was 
 performed by the control group .
moreover , the abdominal stimulation was applied in order to 
 strengthen the expiratory muscle in order to try to improve the cost and time efficiency of 
 using imt devices with other types of devices , as well as to avoid interrupting subject s 
 breathing patterm .
enright et al.10 reported that when the 
 effects of imt were checked in healthy adults , diaphragm thicknesses and tr at maximal 
 inspiration showed significant increases after exercises lasting for eight weeks .
a previous 
 study that conducted imt for cystic fibrosis patients reported that diaphragm thicknesses 
 and tr at maximal inspiration showed significant increases15 . in the present study ,
the tr of the diaphragm on the paretic side 
 showed significant increases in both the experimental group and the control group , 
 consistent with the results of previous studies .
the values of tr also increased on the 
 non - paretic side although this increase was not statistically significant .
sutbeyaz et al.7 divided subacute stroke 
 patients into an imt group , a breathing retraining group , and a control group .
they 
 conducted interventions six times per week for six weeks and compared lung function among 
 the groups .
their results showed significant increases in fvc , fev1 , 
 fef2575 , and maximal inspiratory pressure ( mip ) , but no increase in pef in the 
 inspiratory muscle - training group . in a study conducted by britto et al.8 , mip and ime ( inspiratory muscular 
 endurance )
were measured after imt , and showed significant increases . in a study conducted 
 by enright et al.15 , a group which 
 performed imt showed significant increases in tlc ( total lung capacity ) and vc ( vital 
 capacity ) , but not in fvc and fev1 . moreover , in a study conducted by fregonezi 
 et al.16 , the imt group showed no 
 significant changes in fvc , fev1 , or tlc . interpreting the results of these previous studies ,
although imt shows clear effects on tr , 
 and mip , the effects of imt on lung function are inconsistent .
in particular , we identified 
 that the effects of imt are not strong enough to improve forced expiration . therefore , in 
 the present study , in order to improve forced expiration , abdominal stimulation was applied 
 during imt .
our results show significant increases in fev1 , pef , and fef2575 and the 
 changes in fev1 and pef showed significant differences between the two groups . 

these results were similar to the results of a study conducted by cheng et al.17 , who reported significant increases in 
 fvc , fev1 , and pef after applying abdominal stimulation for four weeks .
in a 
 study conducted by lee et al.18 , 
 stimulation was applied to the anterior and posterolateral regions of the abdomen .
their 
 results showed significant increases in fvc , fev1 , and pef , which is consistent 
 with the results of the present study .
therefore , abdominal stimulation reeducates the 
 expiratory muscles , improves muscle strength and endurance , and induces powerful contraction 
 of the expiratory muscles through repetitive afferent stimulation of the abdominal muscles , 
 thereby increasing intra - abdominal pressure , facilitating upward movement of the diaphragm 
 and decreasing pleural pressure and lung volume , thereby improving expiratory and sputum 
 discharge abilities17 .
if imt were performed by stroke patients with pulmonary function problems resulting from 
 damage to the respiratory muscles caused by stroke and reduced exercise capacity , abdominal 
 muscle stimulation would improve respiratory function . however , we admit this study had some 
 limitations .
the researchers conducted a four - week experiment , and due to the short period 
 of experiment , it was difficult to examine the positive effects on lung function ( fvc ) of 
 the experimental and control groups .
for this reason , it will be necessary to conduct long 
 term experiments that include a more comprehensive analysis of the impact of abdominal 
 stimulation during imt intervention on chronic stroke patients .
   [ purpose ] the purpose of the present study was to verify a new method for improving 
 respiratory functions by applying both abdominal stimulation and inspiratory muscle 
 training ( imt ) to train the inspiratory muscle and the expiratory muscle simultaneously , 
 to improve the efficiency of imt of chronic stroke patients . 
 [ subjects ] eighteen stroke 
 patients were randomly assigned to an experimental group ( n = 9 ) and a control group ( n = 
 9 ) . 
 [ methods ] the experimental group was administered imt with abdominal stimulation , and 
 the control group was administered only imt . during the intervention period , the 
 experimental group and control group received training 20  min / day , 3 times / wk , for 4 
 weeks . to examine the lung functions of the subjects , fvc , fev1 , pef , and 
 fef2575 were measured using an electronic spirometer . 
 the diaphragm 
 thickness ratio was calculated from measurements made with a 7.5-mhz linear probe 
 ultrasonic imaging system . 
 [ result ] the experimental group and the control group showed 
 significant increases in diaphragm thickness ratio on the paretic side , but not on the 
 non - paretic side . 
 with regard to lung function , the experimental group showed significant 
 increases in fev1 , pef , and fef2575 . 
 the changes between before and 
 after the intervention in the two groups were compared with each other , and the results 
 showed significant differences in fev1 and pef . 
 [ conclusion ] the present study 
 identified that imt accompanied by abdominal stimulation improved the pulmonary function 
 of chronic stroke patients . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION