Pulmonary gas exchange in freely diving weddell seals Leptonychotes weddelli

Abstract

Composition of end-tidal samples collected from the first expiration after resting apneusis and after deep or prolonged dives was determined in voluntarily diving adult Weddell seals whose average weight was 425 kg. Also determined was respiratory exchange ratio (R) and oxygen consumption (o2). After an average resting apneusis of 4.5 min the end-tidal 0, tension (paO2) averaged 59 mm Hg and CO2 tension (PaCO2) averaged 50 mm Hg. After deep dives of an average submersion of 11.5 min the PAO2 = 70mmHg and PaCO2=27 mm Hg. The exploratory dives, which ranged from 25-47 min, averaged PaO2=40 mm Hg and PaCO2 = 36 mm Hg. It is concluded that the marked difference in the end-tidal composition of the deep dives is a result of hyperventilation preparatory for the dive and subsequent lung collapse and little gas exchange during the dive. Resting R was 0.69, but after dives R was highly variable. It began low and usually rose above 1.0 and subsequently fell to near 0.70. Mean resting O2 was 309 ml × kg-1× hr-1 whereas O2 after dives was initially as high as 2.4 L × kg-1× hr-1 but fell precipitously during the ventilation period. Mean overall o2 which included both the ventilation and the submersion period was 254 ml × kg-1× hr-1. The reasons for diving o2 being lower than resting O2 are discussed and it is concluded that the cost of diving is not great. © 1973.