High Mallampati score and nasal obstruction are associated risk factors for obstructive sleep apnoea

Induced nasal obstruction can cause obstructive apnoeas in healthy subjects during sleep, but the relationship between nasal resistance measured during wakefulness and obstructive sleep apnoea syndrome (OSAS) is weak. It was postulated that if the subjects could not breathe through the nose, the oral airway must be used, but if this airway is narrowed as well, then it could precipitate sleep-disordered breathing (SDB). Nasal patency, Mallampati score (MS), neck circumference and body mass index were measured in 202 subjects referred to the authors' hospital to undergo a full-night polysomnography for suspicion of SDB. A significant correlation was found between the MS and apnoea/hypopnoea index measured during sleep. However, the relationship between these parameters was only significant in patients with nasal obstruction. The relative risk of having OSAS with a MS of III or IV was 1.95 for the whole group and 2.45 in patients with nasal obstruction. In conclusion, a high Mallampati score represents a predisposing factor for obstructive sleep apnoea syndrome, especially if it is associated with nasal obstruction. These patients merit special attention from both the sleep physician and the anaesthetist.