Response of nasal airway resistance to hypercapnia and hypoxia in man

The response of nasal airway resistance (Rn) to various degrees of hypoxia and hypercapnia was measured in six subjects using active posterior mask rhinomanometry. All resistances were computed during expiration at the flow rate of 0.5 liter/sec. Hypercapnia, induced by breathing gas mixtures of various contents of carbon dioxide, significantly decreased Rn (P less than 0.05, Wilcoxon signed rank test). The reduction in Rn was proportional to the inspired partial pressure of carbon dioxide over a range of 0 to 50 torr. Breathing gas mixtures of high and low contents of oxygen produced no significant change in Rn (P less than 0.05, Wilcoxon signed rank test). These results indicate that the nasal airway is actively involved in the respiratory response to hypercapnia but not to moderate hypoxia.