Updates in Obesity Hypoventilation Syndrome Diagnosis, with Atul Malhotra, MD

Atul Malhotra, MD, a sleep medicine specialist at UC San Diego Health, presented “Obesity Hypoventilation Syndrome - Updates in Diagnosis, PAP, and Weight Management” at SLEEP 2025, the 39th annual meeting of the Associated Professional Sleep Societies in Seattle.

HCPLive sat down with Malhotra at the meeting to discuss these new updates and what they mean for obesity hypoventilation syndrome (OHS) care. He talked about the most important updates in the diagnostic criteria or clinical approach to identify OHS in 2025 and what’s new in the management of OHS with positive airway pressure (PAP) therapy.

“We don't check as many arterial blood gases as we used to, and I think there's increasing awareness that obesity hypoventilation syndrome is a common problem, particularly [in] the sleep clinic,” Malhotra said. “Body Mass Index is 40, about a 30% prevalence of obesity. [With] obesity hypoventilation syndrome, if your body mass index is 50, it's about a 50% prevalence of obesity. Looking at the serum bicarbonate can be quite helpful, and high clinical suspicion can be quite helpful as well.”

He explained that when the bicarbonate level is elevated, obstructive sleep apnea (OSA) and OHS often coexist. OHS worsens the prognosis of OSA, leading to poor outcomes.

“[Assessing] blood gas during the daytime can be quite helpful because it's elevated in patients with obesity hypoventilation syndrome and typically not elevated in obstructive sleep,” Malhorta said.

Capnometry via an app can also be helpful. In clinical settings, experts have used polysomnography to measure carbon dioxide levels transcutaneously, but now patients have begun at-home capnometry through apps.

When bicarbonate rises, Malhorta said hypercapnia could be a cause, but also other influences such as steroids and diuretics. Glucocorticoids or thiazide diuretics can elevate bicarbonates via metabolic alkalosis.

“it's really not diagnostic of hypercapnia if you have a high bicarbonate, but should raise your clinical suspicion,” Malhorta said. “Especially if a bicarbonate is normal, it's less likely to be hypoventilation.”

When it comes to PAP, many patients have high adherence to this treatment, but do not feel any better.

“See, the usual things that we do in terms of PAP troubleshooting…You need to lose about 25 or 30% of your body weight to resolve hypoventilation syndrome,” Malhorta said. “Let's resolve the hypercapnia.”

Relevant disclosures for Malhotra include Eli Lilly and Company, LivaNova, Itamar, ZOLL Respicardia, Impulse Dynamics, Jazz Pharmaceuticals, and Eisai Inc.

References

Nowalk N, Malhotra A, Mokhlesi B, et al. Obesity Hypoventilation Syndrome - Updates in Diagnosis, PAP, and Weight Management. Presented at SLEEP 2025, the 39th annual meeting of the Associated Professional Sleep Societies, on Tuesday, June 10 in Seattle.