Effect of hyperoxia on oxygen consumption in exercising ponies

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Abstract
Published reports of O2 consumption (.ovrhdot.VO2) during exercise in hyperoxia were equivocal. When measured at the lung using respiratory gas equations, .ovrhdot.VO2 was elevated in hyperoxia and, when measured at the blood-tissue level using the cardiovascular Fick (CVF) equation, it was unchanged. Through the use of both equations, simultaneous determinations of .ovrhdot.VO2 during hyperoxia in exercising ponies were made. In normoxia, during treadmill exercise (115 m/min, 10% grade) of 7 ponies, there was no difference in exercise .ovrhdot.VO2, whether measured by the Haldane transformation (HT) or CVF equations (P > 0.05). In hyperoxia, the exercise .ovrhdot.VO2 was significantly increased from the normoxia condition (P < 0.05) when measured by the HT equation but not when measured by the CVF equation (P > 0.05). Using the CVF equation as the method of choice for .ovrhdot.VO2 determinations in hyperoxia, no change in exercise .ovrhdot.VO2 in the hyperoxic condition was shown.