QUANTITATIVE MEASUREMENT OF NASAL PRODUCTION OF NITRIC-OXIDE IN AWAKEHUMANS

The aim of this study was to determine, quantitiatively, the productio n of nitric oxide (NO) in the nose and nasopharynx. Subjects were inst ructed to perform a Valsalva manoeuvre with their mouth open as gas wa s aspirated from a closely fitting nasal CPAP mask by a chemiluminesce nce analyser (Sievers 270B, Sievers Instrument Corp. Boulder, Colorado , U.S.A.). Room air was free to flow in through the mouth and out thro ugh the nose and hence to the analyser. The manoeuvre was continued un til a smooth plateau of at least 20 seconds in duration was achieved o n a chart recorder. The mean plateau concentrations were 176 (+/- 39.6 ) parts per billion (ppb) for males and 135.8 (+/- 24.4) ppb for femal es. The mean male production of NO was 15.8 nanomol/min which was sign ificantly different from that of females of 12.5 nanomol/min (Mann-Whi tney U Test, P<0.01). By measuring the concentration of NO in gas aspi rated from the nose during Valsalva manoeuvre, we excluded the respira tory tract below the glottis from our sampling and as such results rep resent the portion of NO produced in the nose and nasopharynx. These f indings suggest that nasally produced NO is produced in sufficient qua ntities to act as a continuous pulmonary vasodilator, being inspired p referentially into areas of greatest ventilation, thus perhaps acting to continually match ventilation to perfusion.