[Study of appropriate expiratory velocity when measuring exhaled nitric oxide (NO) concentration]

We studied the appropriate expiratory velocity when measuring exhaled NO concentration by constant expiratory flow maneuver in relation to height and the required time for measurement, and obtained the following results. 1) There was a significant positive correlation between height and the required time. 2) There was a significant negative correlation between expiratory velocity and the required time. 3) Percent ratios of children who reached the plateau of exhaled NO concentration were significantly higher when expiratory velocity was over 2000 ml/minute. These findings suggest that expiratory velocity of over 2000 ml/minute may be appropriate when measuring exhaled NO concentration.