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 exerciseinduced 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 w 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. Experimental Physiology (2003) 88.4, 555-564.

Acute hypervolemia does not improve arterial oxygenation in maximally exercising thoroughbred horses

“…1, 2, 3, 4) mirrored data reported previously reported (Manohar et al 2001a(Manohar et al , b, 2002a(Manohar et al , b, 2003(Manohar et al , 2004. The present study was carried out to determine whether, similar to observations in human athletes (Zavorsky et al 2003), preexercise induction of acute hypervolemia would improve arterial oxygenation in thoroughbred horses performing maximal exercise. In this context, our data revealed that acute pre-exercise expansion of plasma volume did not offer an advantage in significantly modifying the development and/or severity of arterial hypoxemia and desaturation of hemoglobin ( Fig.…”

“…This is in contrast with findings in hyperhydrated horses, wherein arterial oxygen tension during exertion either decreased significantly (Sosa-Leon et al 2002) or remained unaffected (Manohar et al 2003). Although the reasons for divergent findings regarding the effects of hypervolemia on the exercise-induced arterial hypoxemia in human athletes (Zavorsky et al 2003) versus horses (Sosa-Leon et al 2002;Manohar et al 2003) are unclear, it is plausible that the divergent methodologies used for the induction of hypervolemia may have played a role. In this context, whereas hyperhydration in the equine studies (Sosa-Leon et al 2002;Manohar et al 2003) was induced gradually over several hours following nasogastric administration of salt/fluids-which may have allowed H 2 O equilibration across various compartments-hypervolemia in the human athletes was induced rather acutely upon rapid osmotic absorption of water from tissues into the vascular compartment following intravenous (IV) administration of 10% pentastarch (Zavorsky et al 2003).…”

“…In the latter scenario, Sosa-Leon et al (2002) suggested exercise-induced pulmonary edema to be likely intensified. Thus, in view of the interesting findings of Zavorsky et al (2003), it was hypothesized that arterial oxygenation in maximally exercising horses may be improved by limiting the exercise-induced increase in thickness of the bloodgas barrier via pre-exercise osmotic removal of fluid from the pulmonary tissues. Therefore, our objective in the present study was to determine whether rapid pre-exercise induction of hypervolemia in thoroughbred horses in a manner analogous to that in human studies (Zavorsky et al 2003) may similarly improve arterial oxygen tension, and in turn, hemoglobin-oxygen saturation, during high-intensity short-term exercise.…”

“…Recently, it was reported that pre-exercise acute hypervolemia caused a significant improvement in the arterial oxygen tension of human athletes known to experience exercise-induced arterial hypoxemia (Zavorsky et al 2003), although the mechanism(s) involved remained unclear. This is in contrast with findings in hyperhydrated horses, wherein arterial oxygen tension during exertion either decreased significantly (Sosa-Leon et al 2002) or remained unaffected (Manohar et al 2003).…”

“…In this context, whereas hyperhydration in the equine studies (Sosa-Leon et al 2002;Manohar et al 2003) was induced gradually over several hours following nasogastric administration of salt/fluids-which may have allowed H 2 O equilibration across various compartments-hypervolemia in the human athletes was induced rather acutely upon rapid osmotic absorption of water from tissues into the vascular compartment following intravenous (IV) administration of 10% pentastarch (Zavorsky et al 2003). In this study (Zavorsky et al 2003), pre-exercise significant osmotic removal of fluid from the pulmonary tissues caused upon IV pentastarch administration, may have limited the exercise-induced increase in thickness of the blood-gas barrier [note: interstitial pulmonary edema has been demonstrated in healthy exercising pigs (Schaffartzik et al 1993) and horses (West et al 1993)], thereby affecting the pulmonary gas exchange and resulting in the observed improvement in arterial oxygen tension (Zavorsky et al 2003). However, this is unlikely when hypervolemia is induced over several hours following nasogastric administration of NaCl (Manohar et al 2003).…”