Obesity hypoventilation syndrome

**Definition:** Obesity hypoventilation syndrome is characterised by obesity (in adults, Body-Mass-Index > 30 kg/m²) and daytime hypercapnia indicated by arterial partial pressure of carbon dioxide (PaCO2) > 45 mm Hg that cannot be fully attributed to an underlying cardiopulmonary or neurologic disease. Hypercapnia worsens during sleep and is often associated with severe arterial oxygen desaturation. Obstructive sleep apnoea is also present in the majority of cases and should be diagnosed in addition to obesity hypoventilation.

Note: A definitive diagnosis requires demonstration of daytime hypercapnia and objective evidence based on polysomnography, with carbon dioxide (CO2) monitoring (by arterial, end-tidal or transcutaneous measures).

**Inclusions:** - Pickwickian syndrome