Obesity hypoventilation syndrome is high carbon dioxide while awake (PaCO2 above 45 mmHg) in a person with a BMI of 30 or more, when no other cause explains it. Most patients also have obstructive sleep apnea, and without treatment it can lead to heart failure and respiratory failure.
Key symptoms
- Daytime sleepiness and fatigue
- Morning headaches
- Loud snoring and pauses in breathing at night
- Shortness of breath
- Leg swelling
What you find on exam
- BMI and neck circumference
- Low oxygen saturation while awake
- Leg edema and raised jugular venous pressure
- Sleepiness or slowed thinking
Tests
- Arterial blood gas: PaCO2 above 45 mmHg while awake
- Serum bicarbonate (27 mmol/L or more suggests it)
- Sleep study (polysomnography)
- Echocardiogram, spirometry and thyroid tests
Treatment basics
- CPAP at night, or bilevel PAP if carbon dioxide stays high
- Weight loss through diet, medicines or bariatric surgery
- Avoid sedatives, opioids and alcohol
- Careful oxygen; too much can raise carbon dioxide further
- Treat heart failure and fluid overload
Red flags
- Confusion or extreme sleepiness (rising carbon dioxide)
- Acidosis on the blood gas: pH below 7.35
- Severe low oxygen or signs of right heart failure
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.