Treatment Effects on Carbon Dioxide Retention in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome

Objectives This study was designed to examine respiratory control in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS), with or without CO 2 retention. Methods We recruited 10 body mass index-matched, apnea-hypopnea index-matched, age-matched, and lung function-matched OSAHS patients, according to their awake Paco 2 . Five patients were hypercapnic (Paco 2 , ≥ 45 mm Hg), and five patients were eucapnic. Hypoxic responses (the ratio of the change in minute ventilation [Δ V ˙ e] to the change in arterial oxygen saturation[ΔSao 2 ] and the ratio of the change in mouth occlusion pressure over the first 100 ms of inspiration against an occluded airway [ΔP 0.1 ] to Δ Sao 2 ) and hypercapnic responses (Δ V ˙ e/ΔPco 2 ratio andΔP 0.1 /ΔPco 2 ratio) were testedduring wakefulness before treatment in all 10 patients, and before and during treatment (at 2, 4, and 6 weeks) with pressure support in the hypercapnic group. Results Hypercapnic patients had lower mean (± SD)Δ V ˙ e/Δ Sao 2 ratio than eucapnic patients (−0.17 ± 0.04 vs −0.34 ± 0.04 L /min/% Sao 2 , respectively), lower meanΔP 0.1 /Δ Sao 2 ratio(−0.04 ± 0.02 vs −0.14 ± 0.03 cm H 2 O/% Sao 2 , respectively), and lower ΔP 0.1 /ΔPco 2 ratio(0.23 ± 0.1 vs 0.49 ± 0.1 cm H 2 O/mm Hg, respectively)[p 2 had fallen to Conclusions Depressed chemoresponsiveness plays a role that is independent of obesity in the development of CO 2 retention in some OSAHS patients, and it may be a response to sleep-disordered breathing.