CPAP vs. BiPAP for Morbidly Obese Patients with Hypoventilation

Diagnosis and Classification of OHS

The American Thoracic Society defines obesity hypoventilation syndrome (OHS) by the combination of obesity (BMI > 30 kg/m²), sleep-disordered breathing, and awake daytime hypercapnia (elevated blood carbon dioxide levels), after excluding other causes for hypoventilation 1, 4
Screening for OHS in obese patients with sleep-disordered breathing can be done using serum bicarbonate levels, with levels < 27 mmol/L making the diagnosis of OHS very unlikely 2, 3
Arterial blood gas analysis should be performed in patients with serum bicarbonate > 27 mmol/L to confirm or rule out the diagnosis 3

For stable ambulatory patients with OHS and severe obstructive sleep apnea (AHI > 30 events/h), the American College of Chest Physicians recommends CPAP as first-line treatment rather than BiPAP (NIV) 1, 2, 3
The American Academy of Sleep Medicine suggests that CPAP has similar effectiveness to BiPAP but is less costly and requires fewer resources for approximately 70% of OHS patients who have concomitant severe OSA 2, 3
For patients with OHS without severe OSA, the American Thoracic Society considers BiPAP (NIV) as first-line therapy 3

The American Heart Association recommends weight loss interventions for all patients with OHS 6
Sustained weight loss of 25-30% of body weight is likely required to achieve resolution of hypoventilation, according to the American College of Cardiology 6
Bariatric surgery may be considered for patients who cannot achieve sufficient weight loss through lifestyle interventions, as suggested by the American Society for Metabolic and Bariatric Surgery 6, 4

The American Thoracic Society recommends monitoring treatment effectiveness through arterial blood gas measurements 3
Consider switching from CPAP to BiPAP if patient shows suboptimal oximetry results or persistent hypercapnia despite adequate CPAP adherence 4

Do not rely solely on oxygen saturation during wakefulness to decide when to measure blood carbon dioxide levels in patients suspected of having OHS, as recommended by the American College of Physicians 2, 3
Discharging hospitalized patients without arranging prompt outpatient sleep study and PAP titration should be avoided, according to the American Academy of Sleep Medicine 5, 4