Altered positional regulation of nasal patency in patients with obstructive sleep apnoea syndrome

We assessed the regulation of nasal patency supine in subjects with obstructive sleep apnoea syndrome (OSAS) compared to healthy controls. Healthy subjects increase nasal obstruction when changing body position from sitting to supine, possibly due to increased hydrostatic pressure in the head supine. Limited data indicate that this response is altered in patients with OSAS, suggesting that supine nasal patency is actively regulated. This study examined the nasal response to recumbent body position using acoustic rhinometry in OSAS patients and healthy controls. Twenty subjects (16 men and 4 women, mean age 55 ± 16 years), with diagnosed OSAS [mean apnoea hypopnoea index (AHI) 46 ± 22 events/h] without nasal obstruction and continuous positive airway pressure (CPAP)-naive, underwent measurement of intra-nasal cross sectional area by acoustic rhinometry at sitting and after 5 min supine. Twenty healthy controls (13 men, 7 women, mean age 35 ± 9 years) were also included in the study. In the patients with OSAS, the mean minimal cross sectional area (MCA, left + right nasal cavity) was unchanged between sitting (1.18 ± 0.41 cm2) and supine (1.21 ± 0.35 cm2, P = 0.5). In the healthy controls, the mean MCA decreased from 1.06 ± 0.18 to 0.94 ± 0.21 cm2 supine, P = 0.01. This study showed that the normal decrease in nasal patency following a change in body position from sitting to supine is absent in patients with OSAS. The results indicate that there is an active regulation of supine nasal patency.