Document Detail

Assessment of nitric oxide formation during exercise.
MedLine Citation:
PMID:  10194156     Owner:  NLM     Status:  MEDLINE    
We measured the end-tidal plateau in exhaled NO concentration (CETNO) by chemiluminescence and calculated the product of V E and CETNO (V NO) in nine healthy subjects at rest and during three intensities of cycling exercise (30%, 60%, and 90% V O2max), two levels of hyperventilation (V E = 42.8 +/- 9.1 L/min and 84.2 +/- 6. 6 L/min), and during breathing of hypoxic gas mixtures (five subjects, FIO2 = 14%) at rest and during exercise at 90% V O2max. Immediately after each trial we also measured exhaled [NO] at constant expiratory flow rates ([NO]CF) of 46 ml/s and 950 ml/s, utilizing added expiratory resistance to increase mouth pressure and close the velum (Silkoff and colleagues, Am. J. Respir. Crit. Care Med. 1997;155:260). CETNO decreased and V NO increased above resting levels with increasing exercise intensity during hyperventilation and during hypoxic exercise (p < 0.05). [NO]CF, measured at either 46 ml/s or 950 ml/s, did not increase under any of the conditions investigated (exercise, hyperventilation, or hypoxia). Venous blood from seven of the subjects was sampled for the measurement of plasma [NO3-]. Resting plasma [NO3-] averaged 42.5 +/- 14.7 micromol/L, with no change during exercise, hyperventilation, or hypoxia. On the basis of these results we conclude that reported increases in V NO do not reflect an exercise-induced augmentation of systemic and/or airway NO production. Rather, the increases in V NO during exercise or hyperventilation are a function of high airflow rates, which reduce the luminal [NO]. This decreases the concentration gradient for NO between the alveolar space and pulmonary capillary blood, which results in a decrease in the fraction of NO taken up by the blood and an increase in the volume of NO recovered in the exhaled air (V NO).
C M St Croix; T J Wetter; D F Pegelow; K C Meyer; J A Dempsey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of respiratory and critical care medicine     Volume:  159     ISSN:  1073-449X     ISO Abbreviation:  Am. J. Respir. Crit. Care Med.     Publication Date:  1999 Apr 
Date Detail:
Created Date:  1999-05-17     Completed Date:  1999-05-17     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9421642     Medline TA:  Am J Respir Crit Care Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1125-33     Citation Subset:  AIM; IM    
Department of Preventive Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
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MeSH Terms
Anoxia / metabolism
Breath Tests*
Hyperventilation / metabolism
Middle Aged
Nitrates / blood
Nitric Oxide / biosynthesis*
Nitrites / blood
Physical Exertion*
Pulmonary Ventilation
Grant Support
R01-15469//PHS HHS
Reg. No./Substance:
0/Nitrates; 0/Nitrites; 10102-43-9/Nitric Oxide

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