COMMENTARY

Obesity Hypoventilation Syndrome: Oxygen Isn't Enough

Matthew F. Watto, MD; Paul N. Williams, MD

Disclosures

June 30, 2021

This transcript has been edited for clarity.

Matthew F. Watto, MD: Welcome back to The Curbsiders. I'm Dr Matthew Watto here with my good friend, Dr Paul Nelson Williams. Tonight we're going to be talking about obesity hypoventilation syndrome (OHS), telling you about our favorite pearls from a recent discussion with Dr Aneesa Das, who is a pulmonologist and an expert on OHS. I was always very confused about this topic, but I feel better now. What did you learn, Paul?

Paul N. Williams, MD: A lot. It's a topic that I found a bit nebulous at times before this conversation. Part of that confusion — for me, at least — was the significant overlap between OHS and obstructive sleep apnea (OSA). You made the point that when you're doing polysomnography, the higher the apnea–hypoxia index, the more likely it is to be OHS, which intuitively makes sense, but I never actually heard it out loud. So, just sort of prick your ears to that possibility.

To make the diagnosis of OHS, you need obesity and hypopnea, and you need to rule out everything else. It's something that I think more about now that we've talked to Dr Das at length. The conversation that really resonated with me as a primary care doctor is what I can do about this. We had a nice discussion about talking openly with the patient about the need for weight loss. The American Thoracic Society recommends losing 25%-30% of body weight.

Watto: It's a crazy amount. Essentially, the only way to get that is with bariatric surgery, which Das said is an underused option. In reality, if your patient has 10% weight loss, it's high-fives all around. That's a huge win.

Williams: Which means it's an important discussion to have and reinforce and reiterate in the framework of this other disease process.

Watto: I was really interested in the pathophysiology of OHS, which helped me understand it a little bit better. She mentioned three things:

  • Leptin resistance: Leptin is important in ventilator drive. Without leptin, the respiratory stimulation is just not there.

  • Chest wall restriction: The excess weight that they're carrying puts pressure on the thoracic muscles, impairing ventilation further.

  • Overlap with OSA: 70%-90% will also have OSA.

For treatment, I thought everybody with OHS would automatically need BiPAP [bilevel positive airway pressure]. But when you actually read about it, they don't. Most patients are okay with just CPAP [continuous positive airway pressure] because it treats a big part of the pathophysiology — the obstructive portion.

Williams: Dr Das raised an important point. The management of OHS is supporting the ventilation issues. She reiterated that we shouldn't use oxygen alone to treat OHS. You need positive airway pressure. That's the critical part, plus or minus oxygen. Oxygen is not an appropriate monotherapy for OHS. You can harm patients that way.

Watto: As much as patients like it. It's often thrown out there as a potentially benign therapy. Oxygen is not a benign therapy. Patients ask, "Can't I just wear oxygen overnight?" and I've run into a fair number of people who are doing that. But that is not recommended for this condition.

We got very deep on this topic with Dr Das. We talked about musical instruments that might help people tone their oropharynx and lose tongue fat. If that is just the most tantalizing morsel, then you have to listen to our full discussion: Obesity Hypoventilation Syndrome (OHS) and the Didgeridoo with Dr Aneesa Das. And hopefully you will enjoy it as much as we did.

The Curbsiders are a national network of students, residents, and clinician educators from across the country, representing 15 different institutions. They "curbside" experts to deconstruct various topics in the world of medicine to provide listeners with clinical pearls, practice-changing knowledge, and bad puns. Learn more about their contributors and follow them on Twitter.

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