Influence of Treatment with Continuous Positive Airway Pressure on Respiratory Muscle Function and Physical Fitness in Patients with Obstructive Sleep Apnoea and Overlap Syndrome

Introduction: The aim of this study was to evaluate the effect of CPAP treatment on respiratory muscle strength and exercise tolerance in patients with obstructive sleep apnoea (OSA) and overlap syndrome (OS). Material and methods: 9 patients with OSA and 9 patients with OS were studied. Respiratory muscle assessment, 6 minute walking distance (6MWD) and cycloergometry exercise test were performed before and after six month period of CPAP treatment. Results: In OSA group exercise tolerance did not change after the treatment. Mean 6MWD was 571.8 ± 76.6 m before and 554.0 ± 125.5 m after treatment, mean W_max was 142 ± 41 W before and 139 ± 38 W after treatment. PI_max in OSA group did not change significantly, 140.4 ± 32.0 cm H₂O before and 155.9 ± 31.5 after treatment (p = 0.14). PE_max improved from 170.5 ± 49.2 cm H₂O, to 199.9 ± 27.6 cm H₂O (p = 0.067). Handgrip force in OSA group improved from 50.5 ± 16.5 kg to 61.0 ± 17.0 kg (left hand) (p = 0.05) and from 53.3 ± 14.2 to 58.9 ± 15.9 (right hand) (p < 0.05). In OS group exercise tolerance improved by 17% after CPAP treatment from W_max = 81 ± 33 W before to 95 ± 38 W after. Mean 6MWD was at the same level before (504 ± 144 m) and after treatment (492 ± 108 m). PI_max in OS group improved from 89.2 ± 35.7 cm H₂O to 106.3 ± 31.4 cm H₂O (p < 0.05). PE_max in OS group did not change significantly, 159.9 ± 45.8 cm H₂O before and 184.2 ± 45.0 cm H₂O after treatment (NS). Handgrip force in OS group improved from 38.1 ± 15.9 kg to 46.9 ± 11.1 kg (left hand) (p < 0.05) and did not change in right hand (44.5 ± 17.7 kg vs. 47.9 ± 10.4 kg) (NS). Data analysis of the whole group (18 pts) showed clear tendency to improve strength of respiratory muscles in patients treated with CPAP. Mean PI_max improved from 123 to 133 cm H₂O (p = 0.006) and PE_max improved from 168.1 to 192 cm H₂O (p = 0.02). Conclusions: CPAP treatment improved strentgh of respiratory and skeletal muscles in patients with OSA and OS and improved exercise tolerance in patients with OS.