The naso-oral index: a more valid measure than peak flow rate?

Using a modified respiratory spirometer, we set out to determine whether the nasal peak flow rate, or a new parameter the naso-oral 1 second index (the ratio between the nasal forced inspiratory '1 second' volume and the oral forced inspiratory '1 second' volume) correlated with anterior rhinomanometry and visual analogue scores. Ten patients undergoing nasal surgery for nasal obstruction were recruited into the study. The naso-oral 1 second index consistently correlated better than the nasal peak flow rate with anterior rhinomanometry. The naso-oral index also correlated better than nasal peak flow with visual analogue scores. Correlation was best demonstrated when assessing the benefit gained by patients from surgery. The naso-oral index is a potentially useful clinical parameter, and correlates acceptably well both with visual analogue scores and anterior rhinomanometry.