In:
Journal of Applied Physiology, American Physiological Society, Vol. 87, No. 4 ( 1999-10-01), p. 1532-1542
Abstract:
Human airways produce nitric oxide (NO), and exhaled NO increases as expiratory flow rates fall. We show that mixing during exhalation between the NO produced by the lower, alveolar airways (V˙l NO ) and the upper conducting airways (V˙u NO ) explains this phenomenon and permits measurement ofV˙l NO ,V˙u NO , and the NO diffusing capacity of the conducting airways (Du NO ). After breath holding for 10–15 s the partial pressure of alveolar NO (Pa) 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 (V˙u NO ), which mixes with Pa during exhalation, resulting in the observed expiratory concentration of NO (Pe). At fast exhalations, Pa makes a large contribution to Pe, and, at slow exhalations, NO from the conducting airways predominates. Simple equations describing this mixing, combined with measurements of Pe at several different expiratory flow rates, permit calculation of Pa,V˙u NO , and Du NO .V˙l NO is the product of Pa and the alveolar airway diffusion capacity for NO. In seven normal subjects, Pa = 1.6 ± 0.7 × 10 −6 (SD) Torr,V˙l NO = 0.19 ± 0.07 μl/min,V˙u NO = 0.08 ± 0.05 μl/min, and Du NO = 0.4 ± 0.4 ml ⋅ min −1 ⋅ Torr −1 . These quantitative measurements ofV˙l NO andV˙u NO are suitable for exploring alterations in NO production at these sites by diseases and physiological stresses.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/jappl.1999.87.4.1532
Language:
English
Publisher:
American Physiological Society
Publication Date:
1999
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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