BMI | Lung function | ↑Paco2 nocturnal(mm Hg) | ↑Paco2diurnal | |
Normal | 18–25 | Normal | 2–3 | No |
OSA | >18 | Normal | >5 | No |
Overlap | >27 | Obstructive | >10 | Yes |
OHS | >30 | Restrictive | >15 | Yes |
BMI, body mass index; OHS, obesity hypoventilation syndrome; OSA, obstructive sleep apnoea; Paco2, arterial carbon dioxide tension.