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1. A 45-year-old man presents with excessive daytime
sleepiness, loud snoring, and witnessed apneas. He has a
body mass index of 32 kg/m2 and a neck circumference of
17 inches. He undergoes a polysomnography, which
shows an apnea-hypopnea index of 25 events per hour,
with oxygen desaturation to 85%. What is the most likely
diagnosis?
A) Obstructive sleep apnea
B) Central sleep apnea
C) Narcolepsy
D) Idiopathic hypersomnia
*E) Obesity hypoventilation syndrome
Rationale: Obesity hypoventilation syndrome (OHS) is a
condition characterized by chronic daytime hypercapnia,
sleep-disordered breathing, and obesity. OHS is diagnosed
when the arterial carbon dioxide pressure (PaCO2) is
greater than 45 mmHg during wakefulness. OHS patients
typically have severe obstructive sleep apnea (OSA), but
OSA alone does not cause daytime hypercapnia. Central
sleep apnea, narcolepsy, and idiopathic hypersomnia are
not associated with obesity or hypercapnia.
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