Establishing norms for nasal spirometry

There is no simple and accurate method for this assessment. Since the nose-nasopharynx region is not a tube and has a wider diameter than the trachea, it does not offer resistance as envisaged by the Poiseuille's equation. Since normal values for nasal spirometry do not exist, we have performed oronasal and nasal spirometry in 600 healthy subjects in three age groups. In oronasal spirometry, the subject breathes through the nose and mouth, while in conventional spirometry, breathing is through the mouth only. Since the oral pathway is used in both, and additionally, nasal pathway is used in oronasal spirometry, one feels that there should be no difference between the two sets of results. Within similar groups, our oronasal values are seen to be similar to published oral values. Since we have measured both oronasal and nasal parameters in each subject, it provides us with a unique opportunity to eliminate the problem of large normal range in one stroke.