Influence of inhaled nitric oxide on gas exchange during normoxic and hypoxic exercise in highly trained cyclists

J Appl Physiol (1985). 2001 Mar;90(3):926-32. doi: 10.1152/jappl.2001.90.3.926.


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.

MeSH terms

  • Administration, Inhalation
  • Adult
  • Bicarbonates / blood
  • Bicycling / physiology*
  • Carbon Dioxide / blood*
  • Exercise / physiology*
  • Heart Rate / drug effects
  • Humans
  • Hydrogen-Ion Concentration
  • Hypoxia / physiopathology*
  • Male
  • Nitric Oxide / administration & dosage
  • Nitric Oxide / pharmacology*
  • Oxygen / blood*
  • Oxygen Consumption / drug effects
  • Oxygen Consumption / physiology*
  • Oxyhemoglobins / metabolism
  • Partial Pressure
  • Reference Values
  • Respiratory Function Tests
  • Respiratory Mechanics / drug effects*
  • Rest


  • Bicarbonates
  • Oxyhemoglobins
  • Carbon Dioxide
  • Nitric Oxide
  • Oxygen