OXYGEN COST OF VENTILATION IN THE RESTING HORSE

The purpose of this study was to develop a technique to measure the ox ygen cost of ventilation and the values of ventilatory parameters in s even normal horses rebreathing carbon dioxide (CO2). All the horses re sponded to increased inspiratory levels of CO2 by increasing their tid al volume (V-T) and frequency of breathing (V-f). The mean (Se) oxygen cost litre(-1) of ventilation, measured at rates of ventilation great er than 200 litres min(-1) was 1.7 (0.04) ml litre(-1), similar to tha t of normal human subjects ventilating submaximally. It was concluded that the CO2 rebreathing test is a practical, non-invasive means of me asuring the oxygen cost of breathing and the ventilatory response to C O2 in horses.