Investigation of the effect of expiratory muscle strength training applied at different intensities on systemic inflammation and oxidative stress in patients with obstructive sleep apnea syndrome

Repeated nightly cycles of hypoxia and reoxygenation increase oxidative stress and systemic inflammationin patients with obstructive sleep apnea syndrome (OSAS). There is no study in the literature examining the effect of expiratory muscle strength training (EMST) on oxidative stress and systemic inflammation in patients with moderate OSAS. The study was planned as a double-blind, prospective randomized controlled study in order to investigate the effects of high and low intensity EMST on disease severity, systemic inflammation and oxidative stress, sleep stages, disease-related symptoms, respiratory muscle strength, exercise capacity, daytime sleepiness, sleep quality, and fatigue severity and to compare the effects of the low and high-intensity groups in male patients with moderate OSAS. A total of 31 male patients diagnosed with moderate OSAS were included in the study. The patients were randomly divided into two groups as high-intensity training (n=16) and low-intensity training (n=15). EMST treatment was given at 60% of maximum expiratory pressure (MEP) for the high-intensity training group, at 30% of MEP for the low-intensity training group, 25 breaths once a day, 5 breaths/set for a total of 5 sets, 7 days/week for 12 weeks. Disease severity (apnea/hypopnea index-AHI), respiratory sleep events and sleep stagesby polysomnography, systemic inflammation [C-reactive protein (CRP), Tumor Necrosis Factor-alpha (TNF-α), Interleukin-6 (IL-6), Interleukin-10 (IL-10)] by taking serum blood samples), oxidative stress[(Total Oxidant Level (TOS), Total Antioxidant Level (TAS), Oxidative Stress Index (OSI)], respiratory muscle strengthusing a mouth pressure device, functional capacity using the 6-minute walking test (6MWT), daytime sleepiness using the Epworth SleepinessScale (ESS), fatigue severity using the Fatigue Severity Scale (FSS), and sleep quality using the Pitssburg Sleep Quality Index (PSQI) were evaluated before and after the treatment. Disease-related symptoms were questioned as present/absent. After treatment, increase in inspiratory and expiratory muscle strength, and decrease in TOS, OSI, TNF-α and IL-6 levels were similar in both groups (p>0.05). AHI % changes after treatment were 53.94% in the high-intensity training group and 27% in the low-intensity training group. The percent AHI change value of the high-intensity training group was higher than the low-intensity training group (p<0.05). In the high-intensity training group, AHI, supine AHI, non-supine AHI, AI, HI, REMAHI and NREMAHI, duration of desaturation and sleep efficiency were statistically significantly decreased compared to the low-intensity training group (p<0.05). 6MWT walking distance increased similarly in both groups after treatment (p>0.05). The decrease in dyspnea, general fatigue and perception of leg fatigue was similar in both groups after 6MWT after treatment (p>0.05). The rate of reduction in disease-related symptoms was higher in the high-intensity training group than in the low-intensity training group (p<0.05).ESS, FSS, PSQI subjective sleep quality and total scores decreased similarly in both groups (p>0.05). In conclusion, the effects of high and low intensity EMST on respiratory muscle strength, functional capacity, fatigue severity, daytime sleepiness, sleep quality, systemic inflammation and oxidative stress are similar. High-intensity EMST is more effective than low-intensity EMST training for reducing AHI level and disease-related symptoms. EMST is an effective treatment option and can be added to the pulmonary rehabilitation program of patientswith moderate OSAS. Keywords: Obstructive sleep apnea syndrome, respiratory muscle strength training, inflammation, oxidative stress.