Pulmonary function in freely diving Weddell seals, Leptonychotes weddelli

Minute volume, tidal volume, dead space volume (E, VT, VD), and diving lung volume were measured in adult, unrestrained Weddell seals, Leptonychotes weddelli, whose mean weight was 425 kg. The effects of oxygen ventilation on dive duration were observed in four adult seals. E ranged from 19.5 L/min while resting to 224 L/min after a dive, VT was 5.4 L to 15.2 L, the average VD for two animals was 1.6 L, and lung volumes ranged from 5 L during a dive to 21 L after inspiration. Dive durations of 66 min and probably 87 min were observed after oxygen ventilation. The results indicate that the ability to increase ventilation rate above the resting value, is less than that in terrestrial mammals. Diving lung volumes are large enough that blood and tissue inert gas tensions could increase to several atmospheres during deep dives if small airways closed at low pressures and most of the gases were trapped in the lungs. Blood oxygen tensions may play a primary role in influencing the length of the dive.