Posture and the nasal cycle.

The experiments reported in this communication show that the spontaneous nasal cycle of airflow resistances, which alternates between cavities of seated subjects, persists in healthy young adults standing, supine, and laterally recumbent. In addition, persistence of the cycle was recorded throughout 24-hour periods of unrestricted light activity, rest, and recumbency. Recumbency was found to augment amplitude of the cycle, yet resistance of the combined nasal cavities showed little change to accompany daytime activity or nocturnal sleeping postures. In subjects with normal noses, resistance remained similar to that of upright subjects in the range of 2 to 3 cm of H2O/L/s. By contrast, noses with fixed unilateral obstruction showed high cyclical resistances of the combined nasal cavities. The importance of the cycle in rhinoscopic assessment, nasal airway obstruction, and breathing disorders of sleep is discussed.