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Randomised trial of CPAP vs bilevel support in the treatment of obesity hypoventilation syndrome without severe nocturnal desaturation
  1. A J Piper1,2,3,
  2. D Wang1,2,
  3. B J Yee1,2,3,
  4. D J Barnes1,
  5. R R Grunstein1,2,3
  1. 1
    Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Camperdown, Sydney, Australia
  2. 2
    Sleep and Circadian Group, Woolcock Institute of Medical Research, Sydney, Australia
  3. 3
    NHMRC Centre for Respiratory and Sleep Medicine, University of Sydney, Camperdown, Sydney, Australia
  1. Dr A J Piper, Respiratory Failure Service, Royal Prince Alfred Hospital, Missenden Rd, Camperdown, Sydney, NSW 2050, Australia; ajp{at}


Background: Untreated, obesity hypoventilation is associated with significant use of health care resources and high mortality. It remains unclear whether continuous positive airway pressure (CPAP) or bilevel ventilatory support (BVS) 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: A prospective randomised study was performed in patients with obesity hypoventilation referred with respiratory failure. After exclusion of patients with persisting severe nocturnal hypoxaemia (Spo2 <80% for >10 min) or carbon dioxide retention (>10 mm Hg) despite optimal CPAP, the remaining patients were randomly assigned to receive either CPAP or BVS over a 3-month period. The primary outcome was change in daytime carbon dioxide level. Secondary outcome measures included daytime sleepiness, quality of life, compliance with treatment and psychomotor vigilance testing.

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

Conclusions: Both CPAP and BVS appear to be equally effective in improving daytime hypercapnia in a subgroup of patients with obesity hypoventilation syndrome without severe nocturnal hypoxaemia.

Trial registration number: Australian Clinical Trials Registry ACTRN01205000096651.

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  • The positive pressure devices used in this study were supplied by Air Liquide, Alexandria, Australia and Mayo Healthcare, Rosebery Australia. These companies were not involved in the design, data collection or interpretation of the findings of this study. AJP has received travel support and lecture fees from Weinmann, Germany. RRG has received travel and equipment support from Respironics, USA. These authors’ sleep laboratory has also received an industry-sponsored project grant from ResMed, Australia.

  • AJP was supported by a NHMRC (Australia) Health Professional Research Fellowship and RRG by a NHMRC (Australia) Practitioner Fellowship and the NHMRC CCRE for Respiratory and Sleep Medicine.

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