Staging of hypoventilation in obesity
| 0 | At risk | BMI >30 kg·m−2 | No hypercapnia |
| 1 | Obesity-associated sleep hypoventilation | BMI >30 kg·m−2 | Intermittent nocturnal hypercapnia; serum bicarbonate <27 mmol·L−1 |
| 2 | Obesity-associated sleep hypoventilation | BMI >30 kg·m−2 | Intermittent nocturnal hypercapnia; serum daytime bicarbonate ≥27 mmol·L−1 |
| 3 | Obesity hypoventilation | BMI >30 kg·m−2 | Sustained daytime hypercapnia (PaCO2 >45 mmHg) |
| 4 | Obesity hypoventilation syndrome | BMI >30 kg·m−2 | Sustained daytime hypercapnia with cardiometabolic abnormalities |
Reproduced and modified from [20] with permission.