Expiratory and inspiratory muscle functions in obstructive sleep apnea syndrome

Objective: Obstructive sleep apnea syndrome (OSAS) patients are thought to experience increased resistive load due to both anatomical and functional changes. This can possibly contribute to respiratory muscle dysfunction. We aimed to measure daytime maximal inspiratory and expiratory pressures, in order to find out respiratory muscle functions in OSAS. Materials and Methods: Patients admitted to our sleep laboratory for one-year period were prospectively analysed. All the cases had undergone overnight polysomnography. All cases had pulmonary function tests performed by the same experienced technician in the morning following sleep study. The study population consisted of 51 (37.8%) female and 84 (62.2%) male patients, with a mean age of 47. Results: Apnea hypopnea index (AHI) was found to be correlated with forced expiratory volume in one second (FEV1) and forced volume vital capacity (FVC) values and FVC%. FEV1/FVC, maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) values did not seem to be correlated with AHI. FVC (L), FVC%, FEV1, FEV1%, MIP, MIP% and MEP were similar in patients with and without OSAS. OSAS patients had significantly lower MEP% values. FVC, FEV1 and MEP% showed significant differences in different stages of the disease. Other parameters were similar in all groups. Conclusion: In this study we demonstrated that maximal expiratory muscle strength of awake OSAS patients was lower, whereas inspiratory muscle strength was similar in subjects with and without OSAS.