APStracts 6:0283A, 1999.

Simultaneous measurement of nitric oxide production by conducting and alveolar airways of man. Pietropaoli, Anthony P., Irene B. Perillo, Alfonso Torres, Peter T. Perkins, Lauren M. Frasier, Mark J. Utell, Mark W. Frampton and Richard W. Hyde. Departments of Medicine1 and Environmental Medicine2, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 -8692

APStracts 6:0283A, 1999.

Human airways produce nitric oxide (NO) and exhaled NO increases as expiratory flow rates fall. We show that mixing during exhalation between the nitric oxide produced by the lower, alveolar airways () and the upper conducting airways () explains this phenomenon and permits measurement of,, and the NO diffusing capacity of the conducting airways (DUNO). After breathholding for 10-15 seconds the partial pressure of alveolar NO (PALV) becomes constant and during a subsequent exhalation at a constant expiratory flow rate (), the alveoli will deliver a stable amount of NO to the conducting airways. The conducting airways secrete NO into the lumen () that mixes with PALV during exhalation resulting in the observed expiratory concentration of NO (PEX). At fast exhalations PALV makes a large contribution to PEX and at slow exhalations NO from the conducting airways predominates. Simple equations describing this mixing combined with measurements of PEX at several different expiratory flow rates () permit calculation of PALV, UNO, and DUNO. Alveolar airway NO production () is the product of PALV and the alveolar airway diffusion capacity for NO (DLNO). In seven normal subjects, PALV= 1.6 +/- 0.7(10-6 mmHg (S.D.) and _= 0.19+/-0.07 _l/min. Conducting airway NO production () = 0.08 +/-_0.05 _l/min, and DUNO = 0.4 +/- 0.4 ml/min(mmHg. These quantitative measurements of NO production by the alveolar and conducting airways are suitable for exploring alterations in NO production at these sites by diseases and physiological stresses.

Received 12 January 1999; accepted in final form 14 June 1999.
APS Manuscript Number A025-9.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 25 June 1999