Obesity Hypoventilation Syndrome: Clinical Guideline by American Thoracic Society

The American Thoracic Society has published an official clinical guideline on the evaluation and management of obesity hypoventilation syndrome in American Journal of Respiratory and Critical Care Medicine.

Obesity hypoventilation syndrome (OHS) is a breathing disorder that affects some people who are obese, causing them to have too much carbon dioxide and too little oxygen in their blood. Medically, OHS is defined by the combination of obesity (body mass index ≥30 kg/m2), sleep-disordered breathing and awake daytime hypercapnia (awake resting partial pressure of arterial CO2 or PaCO2 ≥45 mmHg at sea level), after excluding other causes for hypoventilation.

Studies have estimated that 8-20 per cent of obese patients with sleep apnea have this potentially life-threatening condition. According to the authors of the guideline, most patients with OHS are undiagnosed or misdiagnosed, jeopardizing their health and resulting in increased health care costs.

“The purpose of the guideline is to improve early recognition of obesity hypoventilation syndrome and advise clinicians concerning the management of OHS, with the goal of reducing variability in clinical practice and optimizing the evaluation and management of patients with OHS,” said guideline panel chair Babak Mokhlesi, MD, MSc, a pulmonologist and a sleep specialist who is a professor of medicine and director of the Sleep Disorders Center and the Sleep Medicine Fellowship training program at the University of Chicago. “The panel believes that early recognition and effective treatment of OHS are important in improving morbidity and mortality.”

The panel of 18 experts who produced the guideline included pulmonologists with expertise in sleep-disordered breathing, sleep specialists, a respiratory therapist, a critical care physician, a pulmonary hypertension specialist, an expert in weight reduction and a patient. The group reviewed the results of a systematic search of clinically relevant questions and focused on patient-centred outcomes, such as improving quality of life and quality of sleep, daytime sleepiness, gas exchange, need for supplemental oxygen, hospital resource utilization and death.

Using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework, the panel made five recommendations:

1) That clinicians use a serum bicarbonate level <27 mmol/l to exclude the diagnosis of OHS in obese patients with sleep-disordered breathing when suspicion for OHS is not very high but to measure arterial blood gases in patients strongly suspected of having OHS;

2) That stable ambulatory patients with OHS receive positive airway pressure (PAP);

3) That continuous positive airway pressure (CPAP) rather than noninvasive ventilation (NIV) be offered as the first line treatment to stable ambulatory patients with OHS and co-existent severe obstructive sleep apnea;

4) That patient hospitalized with respiratory failure and suspected of having OHS be discharged with NIV until they undergo outpatient diagnostic procedures and PAP titration in the sleep laboratory (ideally within 2-3 months); and

5) That patients with OHS use weight-loss interventions that produced a sustained weight loss of 25-30 per cent of body weight (more likely to be obtained with bariatric surgery) to achieve resolution of OHS.

All the recommendations were deemed “conditional” by the panel because of the “very low level of certainty in the evidence.”

The authors of the guideline noted several opportunities for research that they believe would benefit patients with OHS. Randomized trials, they wrote, are needed to determine which is better for screening obese patients with sleep-disordered breathing for OHS: measuring bicarbonate levels or oxygen saturation.

Studies are also needed to evaluate the impact of various PAP modes in OHS patients who do not have severe obstructive sleep apnea, whether patients suspected of OHS but discharged from the hospital without a diagnosis should continue on PAP treatment until an outpatient study confirms or rules out OHS and which bariatric weight-loss interventions are most effective in patients with OHS.

The panel emphasized that clinicians caring for these patients should consider severe obesity a major, modifiable factor in the development and severity of OHS. Clinicians need to educate their patients and engage in shared decision making about the best strategy for their patients to sustain weight loss of at least 25-30 percent, which the authors said is needed to resolve OHS.

In making its recommendations, the panel aimed for guidelines that could be used internationally. The authors recognize, however, that local resources may guide decisions within the framework on the panel’s recommendation.

The authors emphasized that each patient is different, medically and personally. “No recommendation can take into account all of the variable and often compelling circumstances that might affect the potential benefits, harms and burdens of intervention in specific cases and contexts,” they wrote. Therefore, the guidelines should not be applied “in a blanket fashion.”