Short- and long-term effects of CPAP on upper airway anatomy and collapsibility in OSAH

Rationale and aim  In obstructive sleep apnea hypopnea (OSAH) patients, an increase of upper airway (UA) collapsibility has been described together with a reduced UA caliber due to inflammation, edema, and fat accumulation in pharyngeal walls. CPAP is the main treatment of OSAH and acts mechanically by increasing pressure inside UA. The aim of this study was to assess the short- and long-term effects of CPAP on UA caliber and collapsibility in severe OSAH patients. Patients and methods  Ten obese patients (nine male, age 55± 9 yr, BMI 35.1 ± 6.1, Epworth sleepiness scale 12.3 ± 3.6 point, AHI 58.8 ± 27.1) had measurements of oropharingeal junction area (OPJ), mean pharyngeal area (APmean), maximal pharyngeal area (APmax) by acoustic pharyngometry and determination of expired volume in the first 0.5 s after the application at the mouth of −5 cmH₂O negative expiratory pressure (V,NEP_0.5) during wakefulness in the supine position under basal conditions (baseline) and after 1 week and 6 months of CPAP treatment. Results  OPJ was 0.74 ± 0.28 cm² at baseline, 0.90 ± 0.24 cm² after 1 week and 1.05 ± 0.31 cm² after 6 months (1 week and 6 months vs baseline p < 0.05). APmax was 2.28 ± 0.74 cm² at baseline, 2.79 ± 0.90 cm² after 1 week and 2.94 ± 0.33 cm² after 6 months (1 week and 6 months vs baseline p < 0.05). APmean was 1.43 ± 0.46 cm² at baseline, 1.82 ± 0.45 cm² after 1 week and 1.94 ± 0.35 cm² after 6 months (1 week vs baseline p < 0.01; 6 months vs baseline; p < 0.05). V,NEP_0.5 was 290 ± 73 mL at baseline, 291 ± 65 mL after 1 week and 338 ± 67 mL after 6 months (6 months vs baseline p < 0.05; 1 week vs 6 months p < 0.01). Conclusions  Our data suggest that CPAP treatment might be effective in OSAH patients not only by causing a mechanical splint of UA but also by inducing an improvement on anatomical (early) and functional (later on) aspects of UA that can be observed during wakefulness.