Oxygen cost of ventilation in the resting horse

Abstract The purpose of this study was to develop a technique to measure the oxygen cost of ventilation and the values of ventilatory parameters in seven normal horses rebreathing carbon dioxide (CO 2 ). All the horses responded to increased inspiratory levels of CO 2 by increasing their tidal volume (V T ) and frequency of breathing (V f ). The mean ( se ) oxygen cost litre −1 of ventilation, measured at rates of ventilation greater than 200 litres min −1 was 1·7 (0·04) ml litre −l , similar to that of normal human subjects ventilating submaximally. It was concluded that the CO 2 rebreathing test is a practical, non-invasive means of measuring the oxygen cost of breathing and the ventilatory response to CO 2 in horses.