The effects of threshold inspiratory muscle training in patients with obstructive sleep apnea: a randomized experimental study

Objectives: Patients with obstructive sleep apnea (OSA) (an obstructed airway and intermittent hypoxia) negatively affect their respiratory muscles. We evaluated the effects of a 12-week threshold inspiratory muscle training (TIMT) program on OSA severity, daytime sleepiness, and pulmonary function in newly diagnosed OSA. Methods: Sixteen patients with moderate-to-severe OSA were randomly assigned to a TIMT group and 6 to a control group. The home-based TIMT program was 30–45 min/day, 5 days/week, for 12 weeks using a TIMT training device. Their apnea-hypopnea index (AHI), Epworth sleepiness scale (ESS), and forced vital capacity (FVC) scores were evaluated pre- and post-treatment. Polysomnographic (PSG) analysis showed that 9 TIMT-group patients had positively responded (TIMT-responder group: post-treatment AHI < pre-treatment) and that 7 had not (TIMT non-responder group: post-treatment AHI > pre-treatment). Results: Post-treatment AHI and ESS scores were significantly (both P < 0.05) lower 6% and 20.2%, respectively. A baseline AHI ≤ 29.0/h predicted TIMT-responder group patients (sensitivity 77.8%; specificity 85.7%). FVC was also significantly (P < 0.05) higher 7.2%. Baseline AHI and FEV_6.0 were significant predictors of successful TIMT-responder group intervention. OSA severity and daytime sleepiness were also significantly attenuated. Conclusions: Home-based TIMT training is simple, efficacious, and cost-effective.