Effect of acetazolamide on pulmonary and muscle gas exchange during normoxic and hypoxic exercise.
Acetazolamide (ACZ) is used to prevent acute mountain sickness at altitude. Because it could affect O2 transport in several different and potentially conflicting ways, we examined its effects on pulmonary and muscle gas exchange and acid-base status during cycle exercise at approximately 30, 50 and 90% VO2max in normoxia (F(IO2) = 0.2093) and acute hypoxia (F(IO2) = 0.125). In a double-blind, order-balanced, crossover design, six healthy, trained men (normoxic VO2max= 59 ml kg(-1) min(-1)) exercised at both F(IO2) values after ACZ (3 doses of 250 mg, 8 h apart) and placebo. One week later this protocol was repeated using the other drug (placebo or ACZ). We measured cardiac output (QT), leg blood flow (LBF), and muscle and pulmonary gas exchange, the latter using the multiple inert gas elimination technique. ACZ did not significantly affect VO2, QT, LBF or muscle gas exchange. As expected, ACZ led to lower arterial and venous blood [HCO3-], pH and lactate levels (P < 0.05), and increased ventilation (P < 0.05). In both normoxia and hypoxia, ACZ resulted in higher arterial P(O2) and saturation and a lower alveolar-arterial P(O2) difference (AaD(O2)) due to both less VA/Q mismatch and less diffusion limitation (P < 0.05). In summary, ACZ improved arterial oxygenation during exercise, due to both greater ventilation and more efficient pulmonary gas exchange. However, muscle gas exchange was unaffected.
Jonk
Amy M
AM
Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0623, USA.
van den Berg
Irene P
IP
Olfert
I Mark
IM
Wray
D Walter
DW
Arai
Tatsuya
T
Hopkins
Susan R
SR
Wagner
Peter D
PD
D000086:Acetazolamide / Q000008:administration & dosage*; D000136:Acid-Base Equilibrium / Q000187:drug effects; D000328:Adult; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage*; D002302:Cardiac Output / Q000187:drug effects; D018592:Cross-Over Studies; D006801:Humans; D000860:Hypoxia / Q000188:drug therapy* / Q000503:physiopathology; D007866:Leg / Q000098:blood supply; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D015656:Respiratory Mechanics / Q000187:drug effects
D002257:Carbonic Anhydrase Inhibitors; D000086:Acetazolamide; D010100:Oxygen