Nasal nitric oxide is independent of nasal cavity volume

This study was performed to evaluate the relationship between nasal nitric oxide (NO) and changes in nasal cavity volume resulting from the topical ap plication of xylometazoline and saline and between upright and supine postu re. Nasal NO was measured using a fixed high flow technique that avoids con tamination with lower airways NO. in nine healthy subjects nasal NO concent ration was measured by a rapid response chemiluminescent analyzer. A tapere d tube was inserted in one nostril, into which room air was insufflated to produce a constant flow of 100 mL/second; another tube was inserted into th e opposite nostril for NO sampling (air exit side). Subjects were instructe d to keep the vellum closed while NO was sampled through a sideport connect ed to the analyzer. Nasal cavity volume was measured by acoustic rhinometry from a segment of the acoustic pathway, 2 to 5 cm from the nostril. Nasal cavity volume and NO measurements were made at baseline, 15 minutes, and 60 minutes after intervention (administration of saline 0.9%, xylometazoline or posture changes on 3 consecutive days). Xylometazoline produced a signif icant increase in nasal cavity volume, together with a significant reductio n in NO level at 15 and 60 minutes after intervention. In addition, the cha nge from seated to supine position decreased the total nasal volume signifi cantly, but without changes in nasal NO. No correlation was found between t he magnitudes of changes in nasal NO and the changes in nasal volume. Topic al application of xylomethazoline resulted in increased nasal cavity volume and reduced NO output. In contrast to previous published reports, a techni que using high flow rate insufflation demonstrated an abscence of correlati on between the magnitudes of changes in nasal NO and nasal cavity volume br ought about by decongestant, saline, or posture.