Influence of inhaled nitric oxide on gas exchange during normoxic and hypoxic exercise in highly trained cyclists.
This study tested the effects of inhaled nitric oxide [NO; 20 parts per million (ppm)] during normoxic and hypoxic (fraction of inspired O(2) = 14%) exercise on gas exchange in athletes with exercise-induced hypoxemia. Trained male cyclists (n = 7) performed two cycle tests to exhaustion to determine maximal O(2) consumption (VO(2 max)) and arterial oxyhemoglobin saturation (Sa(O(2)), Ohmeda Biox ear oximeter) under normoxic (VO(2 max) = 4.88 +/- 0.43 l/min and Sa(O(2)) = 90.2 +/- 0.9, means +/- SD) and hypoxic (VO(2 max) = 4.24 +/- 0.49 l/min and Sa(O(2)) = 75.5 +/- 4.5) conditions. On a third occasion, subjects performed four 5-min cycle tests, each separated by 1 h at their respective VO(2 max), under randomly assigned conditions: normoxia (N), normoxia + NO (N/NO), hypoxia (H), and hypoxia + NO (H/NO). Gas exchange, heart rate, and metabolic parameters were determined during each condition. Arterial blood was drawn at rest and at each minute of the 5-min test. Arterial PO(2) (Pa(O(2))), arterial PCO(2), and Sa(O(2)) were determined, and the alveolar-arterial difference for PO(2) (A-aDO(2)) was calculated. Measurements of Pa(O(2)) and Sa(O(2)) were significantly lower and A-aDO(2) was widened during exercise compared with rest for all conditions (P < 0.05). No significant differences were detected between N and N/NO or between H and H/NO for Pa(O(2)), Sa(O(2)) and A-aDO(2) (P > 0.05). We conclude that inhalation of 20 ppm NO during normoxic and hypoxic exercise has no effect on gas exchange in highly trained cyclists.
Sheel
A W
AW
Allan McGavin Sports Medicine Center and School of Human Kinetics, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
Edwards
M R
MR
Hunte
G S
GS
McKenzie
D C
DC
D000280:Administration, Inhalation; D000328:Adult; D001639:Bicarbonates / Q000097:blood; D001642:Bicycling / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D010108:Oxyhemoglobins / Q000378:metabolism; D010313:Partial Pressure; D012016:Reference Values; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000187:drug effects*; D012146:Rest
D001639:Bicarbonates; D010108:Oxyhemoglobins; D002245:Carbon Dioxide; D009569:Nitric Oxide; D010100:Oxygen