Nasal airflow in inspiration and expiration.

Inspiratory and expiratory airflow rates were measured in 30 subjects during quiet respiration (at a pressure gradient of 150 Pa) and at peak flow rates. For low flow rates airflow rate was greater for inspiration than for expiration. Conversely at peak flow rates flow was greatest during expiration. Thus there was a reversal in the phase relationship between inspiration and expiration as flow rate increased. It was also found that peak inspiratory flow rate correlated better with values for nasal resistance than did peak expiratory flow rate. Flow rate measured by rhinomanometry during quiet respiration was more sensitive to physiologically induced changes in nasal resistance than was peak flow rate. The findings are discussed with reference to previous work on the physiology of nasal airflow.