Abstract

Background: Untreated, obesity hypoventilation is associated with significant use of health care resources and high mortality. It remains unclear whether CPAP or bilevel ventilatory support should be used as initial management. The aim of this study was to determine if one form of positive pressure is superior to the other in improving daytime respiratory failure.

Methods: Prospective, randomised study of patients with obesity hypoventilation referred with respiratory failure. After exclusion of persisting severe nocturnal hypoxaemia (SpO2<80% for >10 minutes) or carbon dioxide retention (>10mmHg) despite optimal CPAP, patients were randomly assigned to receive either CPAP or bilevel support over a 3-month period. Primary outcome was change in daytime carbon dioxide. Secondary outcome measures included daytime sleepiness, quality of life, compliance with therapy and psychomotor vigilance testing.

Results: Thirty-six patients were randomized to either home CPAP (n=18) or bilevel support (n=18). The two groups did not differ significantly at baseline with regard to physiological or clinical characteristics. Following 3 months of therapy, daytime carbon dioxide levels decreased in both groups (CPAP 6+8 mmHg; bilevel 7+7 mmHg) with no between group differences. There was no difference in compliance between the two therapies (CPAP: 5.8+2.4hrs/night vs bilevel support: 6.1+ 2.1hrs/night). Although both groups reported improvement in daytime sleepiness, subjective sleep quality and psychomotor vigilance performance were better with bilevel support.

Conclusions: Both CPAP and bilevel support appear to be equally effective in improving daytime hypercapnia in the subgroup of OHS patients without severe nocturnal hypoxaemia. The study was registered with the Australian Clinical Trials Registry (ACTRN01205000096651).