Inspiratory muscle training during treatment with corticosteroids in humans

In a previous study performed by us, functional alterations in the inspiratory muscles were evaluated in patients receiving corticosteroids for diseases other than respiratory. We have shown that patients who received high-dose steroids for several weeks developed inspiratory muscle weakness that was reversible following withdrawal of the drug treatment. The present study was designed to evaluate the ability of specific inspiratory muscle training (SIMT) to prevent the effects of a therapeutic dosage of corticosteroids on inspiratory muscle function in patients receiving the drug for diseases other than pulmonary, with no underlying respiratory or muscular disease. Twelve patients, 5 men and 7 women, with ages ranging from 19 to 41 years, who received corticosteroids for diseases other than respiratory were recruited into two groups: 6 patients were assigned to the control group and got sham training and 6 patients received SIMT while receiving corticosteroids in a single-blind group-comparative trial. In both groups, there was no difference between the post-treatment and pretreatment values as regard to the FEV1/FVC relationship. However, in the control group but not in the training group, there was a small but significant decrease, from 99.2 +/- 3.0 to 94.3 +/- 2.8 (mean +/- SEM, p < 0.01) in FEV1 (percent of predicted normal values) and from 103.5 +/- 4.0 to 88.7 +/- 3.1 (p < 0.001) in the FVC, following treatment. All subjects had normal inspiratory muscle strength, as expressed by the maximal inspiratory mouth pressure (PImax) at residual volume, and inspiratory muscle endurance as expressed by the relationship between peak pressure and the PImax before treatment. Following administration of corticosteroids, there was a gradual decrease in both inspiratory muscle strength (from 117.5 +/- 9.4 to 80.5 +/- 3.3 cm H2O, p < 0.005) and endurance (from 82.7 +/- 2.6 to 40.2 +/- 1.7%, p < 0.001) in the control group. On the contrary, despite corticosteroid therapy, there were no significant changes in the inspiratory muscle function in the patients whose inspiratory muscles were specifically trained. We conclude that corticosteroids have a significant deteriorating effect on respiratory muscle function in humans. This weakness is preventable by using SIMT during corticosteroid treatment.