The Obesity-Hypoventilation Syndrome (OHS) may occur in severely obese patients. It may be related to the increased work of breathing associated with displacing a large mass of fat.


Synonym: Pickwickian syndrome (after Samuel Pickwick from the Pickwick Papers by Charles Dickens)


Clinical features:

(1) obesity, typically morbid obesity

(2) chronic fatigue

(3) hypersomnolence

(4) dyspnea on simple exertion

(5) morning headaches


Laboratory findings:

(1) hypercapnia while awake (PaCO2 > 45 mm Hg)

(2) increase in PaCO2 by > 10 mm Hg when asleep

(3) hypoxemia (SaO2 < 90%) while awake

(4) hypoxemia (SaO2 < 90%) while asleep

(5) respiratory acidosis while asleep (pH < 7.3)

(6) oximetry while asleep shows persistent desaturation of oxyhemoglobin


Common concurrent conditions:

(1) obstructive sleep apnea



(1) cor pulmonale and right heart failure

(2) polycythemia


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