Specific inspiratory muscle training in patients with mild asthma with high consumption of inhaled beta(2)-agonists. The relationship among inspiratory muscle strength, the perception of dyspnea and inhaled beta2-agonist use in patients with asthma. Inspiratory muscle training in patients with bronchial asthma. Influence of gender and inspiratory muscle training on the perception of dyspnea in patients with asthma.
It has been known for many years that there are variations between asthmatic patients in terms of their perception of breathlessness during airway obstruction.
                To investigate the relationship between beta(2)-agonist consumption and the score of perception of dyspnea, in mild asthmatics, and the relationship between the effect of specific inspiratory muscle training (SIMT) on the score of perception of dyspnea and beta(2)-agonist consumption in "high perceivers."
                Daily beta(2)-agonist consumption was assessed during a 4-week run-in period in 82 patients with mild asthma. Patients with a mean beta(2)-agonist consumption of > 1 puff/d ("high consumers") then were randomized into two groups: one group of patients received SIMT for 3 months; the other group of patients was assigned as a control group and received sham training. Inspiratory muscle strength and perception of dyspnea were assessed before patients entered the study, following the 4-week run-in period, and after completing the training period.
                Following the 4-week run-in period, 23 high-consumer patients (mean [+/- SEM] beta(2)-agonist consumption, 2.7 +/- 0.4 puffs/d) were detected. The mean Borg score during breathing against resistance was significantly higher (p < 0.05) in the patients with high beta(2)-agonist consumption than in the subjects with low mean beta(2)-agonist consumption. Following SIMT, the mean maximal inspiratory pressure increased significantly from 94.1 +/- 5.1 to 109.7 +/- 5.2 cm H(2)O (p < 0.005) in the training group. The increase in inspiratory muscle strength was associated with a statistically significant decrease in the mean Borg score during breathing against resistance (p < 0.05) as well as in the mean daily beta(2)-agonist consumption.
                We have shown that patients with mild asthma, who have a high beta(2)-agonist consumption, have a higher perception of dyspnea than those with normal consumption. In addition, SIMT was associated with a decrease in perception of dyspnea and a decrease in beta(2)-agonist consumption. It is well documented that the perception of dyspnea (POD), subjectively reported by patients, is related to the activity and strength of the inspiratory muscles, and influences the use of 'as needed' beta2-agonists.
                To investigate the relationship among the increase in inspiratory muscle strength after specific inspiratory muscle training, beta2-agonist consumption and the POD in patients with persistent, mild to moderate asthma.
                Inspiratory muscle strength, daily beta2-agonist consumption and the POD were measured in 30 patients with mild to moderate asthma. Patients were then randomly assigned to two groups: one group received specific inspiratory muscle training until an increase of more than 20 cm H2O was reached, and one group was a control group and received sham training. Inspiratory muscle strength, the POD and daily beta2-agonist consumption were assessed during and after the training period.
                There was no good correlation between the baseline maximal inspiratory pressure and the POD, or between the baseline maximal inspiratory pressure and the mean daily beta2-agonist consumption. However, there was a significant correlation between the POD and the mean daily beta2-agonist consumption. The increase in inspiratory muscle strength after the inspiratory muscle training was closely correlated with the decrease in the POD (P<0.001) and the decrease in beta2-agonist consumption (P<0.001).
                The present study shows that, in patients with mild to moderate, persistent asthma, there is a correlation between the POD and the mean daily beta2-agonist consumption. When the inspiratory muscles are strengthened, there is a significant decrease in the POD and in beta2-agonist consumption. In patients with asthma, the respiratory muscles have to overcome the increased resistance while they become progressively disadvantaged by hyperinflation. We hypothesized that increasing respiratory muscle strength and endurance with specific inspiratory muscle training (SIMT) would result in improvement in asthma symptoms in patients with asthma. Thirty patients with moderate to severe asthma were recruited into 2 groups; 15 patients received SIMT (group A) and 15 patients were assigned to the control group (group B) and got sham training in a double-blind group-comparative trial. The training was performed using a threshold inspiratory muscle trainer. Subjects of both groups trained five times a week, each session consisted of 1/2-h training, for six months. Inspiratory muscle strength, as expressed by the PImax at RV, increased significantly, from 84.0 +/- 4.3 to 107.0 +/- 4.8 cm H2O (p < 0.0001) and the respiratory muscle endurance, as expressed by the relationship between Pmpeak and PImax from 67.5 +/- 3.1 percent to 93.1 +/- 1.2 percent (p < 0.0001), in patients of group A, but not in patients of group B. This improvement was associated with significant improvements compared with baseline for asthma symptoms (nighttime asthma, p < 0.05; morning tightness, p < 0.05; daytime asthma, p < 0.01; cough, p < 0.005), inhaled B2 usage (p < 0.05), and the number of hospital (p < 0.05) and sick-leave (p < 0.05) days due to asthma. Five patients were able to stop taking oral/IM corticosteroids while on training and one in the placebo group. We conclude that SIMT, for six months, improves the inspiratory muscle strength and endurance, and results in improvement in asthma symptoms, hospitalizations for asthma, emergency department contact, absence from school or work, and medication consumption in patients with asthma. Men and women respond differently to asthma.
                Maximal inspiratory mouth pressure (P(Imax)), beta(2)-agonist consumption, and perception of dyspnea (POD) were measured in 22 women and 22 men with mild persistent-to-moderate asthma. Next, the women were randomized into two groups: those who received inspiratory muscle training and those who received sham training. The training ended when the P(Imax) of the training group was equal to that of the male subjects. POD was then measured once again.
                Baseline P(Imax) was significantly lower (p < 0.01) while POD and mean daily beta(2)-agonist consumption were significantly higher in the female subjects. P(Imax) reached the level of the male subjects at the end of the 20th week of training. The increase in the P(Imax) was associated with a statistically significant decrease in mean daily beta(2)-agonist use and in POD to a similar level as in male subjects.
                POD and mean daily beta(2)-agonist consumption in asthmatic women are significantly higher, and the P(Imax) significantly lower, than that of their male counterparts. When the P(Imax) of female subjects following training is equal to that in male subjects, the differences in POD and mean daily beta(2)-agonist consumption disappear.
Currently there is insufficient evidence to suggest that inspiratory muscle training provides any clinical benefit to patients with asthma. Due to the limited availability of studies in this area there is a need for further trials evaluating the efficacy of inspiratory muscle training devices in patients with asthma. These studies should investigate asthmatics with a range of severity. They should investigate clinically relevant outcomes such as lung function, symptoms, exacerbation rate and concomitant medications.