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Despite no evidence, the ATS issues a guideline on managing obesity hypoventilation syndrome
Clinical Question
What is the optimal approach to managing patients with obesity hypoventilation syndrome?
Bottom line
Because of the "overall very low quality of the evidence," the American Thoracic Society (ATS) makes no strong recommendations, but conditionally recommends the use of serum bicarbonate levels to establish a diagnosis when the clinical suspicion of obesity hypoventilation syndrome (OHS) is less than 20% and the use of blood gas results when the suspicion is high. The ATS also conditionally recommends using positive airway pressure, preferably continuous positive airway pressure, for treatment. Additionally, the ATS conditionally recommends that patients hospitalized for respiratory failure be discharged with noninvasive ventilation until formal testing is completed. Finally, the ATS conditionally recommends sustained 25% to 30% weight loss and acknowledges that this is unlikely to be achieved without bariatric surgery. 5
Reference
Study design: Practice guideline
Funding: Unknown/not stated
Setting: Various (guideline)
Synopsis
The ATS convened a multidisciplinary panel devoid of any primary care presence to develop a guideline for managing patients with OHS: a combination of body mass index greater than 30 kg/m^2, sleep-disordered breathing, and awake daytime hypercapnia (PaCO2 45 mm Hg or higher at sea level). The authors report that at least 50% of the chairs and panel members were free from financial or intellectual conflict of interest. The team conducted systematic reviews to guide their recommendations. In general, they found that the existing research is of poor quality and the data are heterogeneous. To establish the diagnosis, the panel recommends arterial blood gas testing plus a sleep study to determine the presence of sleep-disordered breathing. Recognizing that the arterial blood gas test is painful and inconvenient, the panel suggests that this can be skipped in patients with less than a 20% likelihood of having OHS: a serum bicarbonate level of less than 27 mmol/L effectively rules out hypercapnia. Of 32 papers on managing patients with OHS, only 3 reported randomized trials and they had only a handful of patients. These studies showed positive airway pressure (PAP) improved control of sleep-disordered breathing, daytime hypercapnia, and sleep quality. Based on 10 observational studies of hospitalized patients without a prior diagnosis of OHS, the panel "agreed that the desirable effects of PAP outweigh its trivial, undesirable effects." They recommend that these patients still warrant formal evaluation as outpatients, but that interim treatment is warranted given the high short-term mortality associated with these patients. The panel also identified 2 randomized trials and 7 case series of weight loss in patients with OHS. The panel's best guess was that, based on these reports, sustained weight loss of 25% to 30% of actual body weight is associated with the resolution or a clinically meaningful reduction of hypoventilation. They were pessimistic that anything other than bariatric surgery would deliver this. Finally, for every one of the areas reviewed, the panel identified key areas needing further research.
Reviewer
Henry C. Barry, MD, MS
Professor
Michigan State University
East Lansing, MI
Comments
Weight bias
"They were pessimistic that anything other than bariatric surgery would deliver [sustained weight loss of 25% to 30% of actual body weight]." This is not a pessimistic statement; it is an evidence-based statement. Typical result with a real-word behavioral intervention is 3 - 5%; with the intensive weight loss intervention in Look AHEAD, average weight loss was 6.0% at 9.6 years, but such interventions are scarcely available. With obesity medications (liraglutide or naltrexone-bupropion), weight loss is 5 - 10%. With bariatric surgery (sleeve gastrectomy or roux-en-Y gastric bypass), 30 - 40% weight loss is achieved. Patients with OHS should be offered referral to a bariatric surgery centre.