title: Acute hypervolaemia improves arterial oxygen pressure in athletes with exercise-induced hypoxaemia.
abstract: The aim of this study was to determine the effect of acute plasma volume expansion on arterial blood-gas status during 6.5 min strenuous cycling exercise comparing six athletes with and six athletes without exercise-induced arterial hypoxaemia (EIAH). We hypothesized that plasma volume expansion could improve arterial oxygen pressure in a homogeneous sample of athletes - those with EIAH. In this paper we have extended the analysis and results of our recently published surprising findings that lengthening cardiopulmonary transit time did not improve arterial blood-gas status in a heterogeneous sample of endurance cyclists. One 500 ml bag of 10 % Pentastarch (infusion condition) or 60 ml 0.9 % saline (placebo) was infused prior to exercise in a randomized, double-blind fashion on two different days. Power output, cardiac output, oxygen consumption and arterial blood gases were measured during strenuous exercise. Cardiac output and oxygen consumption were not affected by acute hypervolaemia. There were group x condition interaction effects for arterial oxygen pressure and alveolar-arterial oxygen pressure difference, suggesting that those with hypoxaemia experienced improved arterial oxygen pressure (+4 mmHg) and lower alveolar-arterial oxygen pressure difference (-2 mmHg) with infusion. In conclusion, acute hypervolaemia improves blood-gas status in athletes with EIAH. The impairment of gas exchange occurs within the first minute of exercise, and is not impaired further throughout the remaining duration of exercise. This suggests that arterial oxygen pressure is only minimally mediated by cardiac output.
authors.affiliation: Department of Experimental Medicine, University of British Columbia, Vancouver Hospital and Health Sciences Center, Koerner Pavillion, S154, 2211 Wesbrook Mall, Vancouver, BC, Canada V6T-1Z3. zavorsky@alcor.concordia.ca
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Zavorsky
authors.forename: Keith R
authors.initials: KR
authors.lastname: Walley
authors.forename: Garth S
authors.initials: GS
authors.lastname: Hunte
authors.forename: Donald C
authors.initials: DC
authors.lastname: McKenzie
authors.forename: George P
authors.initials: GP
authors.lastname: Sexsmith
authors.forename: James A
authors.initials: JA
authors.lastname: Russell
mesh_terms: D000208:Acute Disease; D001158:Arteries / Q000502:physiology; D001639:Bicarbonates / Q000097:blood; D001642:Bicycling / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D010465:Perception; D010953:Plasma Volume / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012129:Respiratory Function Tests; D013177:Sports
chemical_list: D001639:Bicarbonates; D010100:Oxygen