Ventilation and diaphragm activity during sustained hypoxia in awake canines

•Mammals show a biphasic ventilatory response to sustained hypoxia, although this has not been found in canines.•We examined isocapnic hypoxia (SpO2 80%) sustained for 20min in awake canines.•Ventilation during hypoxia increased by 239%, then declined 50% to a sustained plateau.•Costal diaphragm EMG showed a concurrent decline during sustained hypoxia.•The biphasic ventilatory response to sustained hypoxia, “roll off”, in canines is similar to other large mammals, although magnitude and timing differ from humans.