Nasal patency and the effectiveness of nasal continuous positive air pressure in obstructive sleep apnea

Nasal airway obstruction may exacerbate sleep apnea and is difficult to quantify on clinical examination. In this study, we examined the relationship among nasal patency, the frequency of sleep apnea events, and effective nasal continuous positive air pressures. Acoustic rhinometry was used as an objective measurement of nasal cross-sectional areas in 76 patients without nasal symptoms who underwent study with diagnostic polysomnography because of obstructive sleep apnea. Patients with persistent obstructive sleep apnea were titrated to nasal continuous positive air pressure in a split night study. All subjects had a mean apnea/hypopnea index of 28, and those with obstructive sleep apnea had a mean apnea/hypopnea index of 43. Mean cross-sectional areas 1 to 4 cm into the nose were 1.7, 1.1, 2.1, and 2.8 cm(2), respectively (F = 39, p < 0.001). However, there was no correlation between the apnea/hypopnea index and the cross-sectional area at the four distances (r = 0.03, 0.06, 0.02, and 0.02, respectively, p = not significant), Correlations between nasal continuous positive air pressures and cross-sectional areas did not reveal a significant relationship at any of the four sites (r = 0.09, 0.07, -0.03, 0.00, respectively). Findings in patients with apnea were also compared with those in patients without apnea and significant differences were not found (F = 0.019, p = not significant). Although it would seem intuitive that increased nasal obstruction is associated with the severity of obstructive sleep apnea and difficulty with the use of nasal continuous positive air pressure, this study shows that nasal patency, as measured by acoustic rhinometry, does not correlate with the severity of obstructive sleep apnea, as determined by the apnea/hypopnea index or the effective nasal continuous positive air pressure.