Continuous positive airway pressure (CPAP) may be a preferred alternative to noninvasive ventilation (NIV) as first-line therapy in stable ambulatory patients with obesity hypoventilation syndrome (OHS) and concurrent severe obstructive sleep apnea (OSA), as suggested by study results published in the Annals of the American Thoracic Society. Despite the conclusions of this study, the investigators indicated that NIV and CPAP exhibit comparable efficacy profiles in this patient population.

The study was a literature review conducted to inform an international panel of experts on the development of an OHS clinical practice guideline funded by the American Thoracic Society. Research studies published between January 1946 and March 2019 that compared NIV and CPAP in patients with OHS were included in the review.

Treatments were compared with regard to the incidence of the following outcomes: mortality, resolution of daytime sleepiness and hypercapnia, quality of life, hospitalization, hospital length of stay, emergency room visits, motor vehicle accidents, cardiovascular events, changes in gas exchange and sleep, exercise capacity, and the need for supplemental oxygen.

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A total of 5 full-text articles, including 3 randomized trials and one observational study, were selected for inclusion in the review. Included trials had populations that ranged from 36 to 225 patients. Overall, no differences were found between patients who received NIV or CPAP with OHS in terms of mortality, cardiovascular events, and healthcare resource utilization.

In a study with a 5.5-year follow-up, there was no difference between NIV or CPAP in mortality (11% vs 14.9%, respectively; risk ratio [RR], 0.82; 95% CI, 0.36-1.87). In an observational study, there was also no difference between NIV or CPAP in the mortality outcome (5% vs 4.8%, respectively; RR, 1.04; 95% CI, 0.31-3.46). Other studies found no difference between NIV and CPAP with regard to hypercapnia resolution at 3 months (46.6% vs 36.3%, respectively; RR, 1.29, 95% CI, 0.94-1.77) or 3 years (51.9% vs 40.7%, respectively; RR, 1.28; 95% CI, 0.91-1.79). No differences were found in healthcare utilization in NIV and CPAP groups at 3 months (9.7% vs 10.3%, respectively; RR, 0.94; 95% CI, 0.20-4.27) or 5.5 years (52.6% vs 44.9%, respectively; RR, 1.17; 95% CI, 0.88-1.55).

All randomized trials and the observational study reported improvements in quality of life with both treatments. The researchers suggested that CPAP may be a preferable to NIV for initial treatment of stable ambulatory adult patients with OHS and severe OSA (apnea hypopnea index ≥30 events/h) who also present with chronic stable respiratory failure, mainly due to the higher costs and number of resources associated with NIV.

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Limitations of the review included the quality of evidence, the small sample sizes of some of the included trials, and the lack of a pooled analysis of all the reviewed data.

“Although the current data does not favor one form of PAP therapy over another in people with stable chronic OHS,” the investigators wrote, “the panel remarked that further studies are needed to confirm this position.”


Soghier I, Brożek JL, Afshar M, et al. Noninvasive ventilation versus CPAP as initial treatment of obesity hypoventilation syndrome: a systematic review. A systematic review that informed the ATS Guideline on Obesity Hypoventilation Syndrome [published online July 31, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201905-380OC