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Res. 1989 Sep;16(5):363-73.  Arterial gas tensions and
hemoglobin concentrations of the freely diving Weddell seal.
Massachusetts General Hospital, Department of Anesthesia, Boston
02114.   Heart rate, body temperature, arterial blood gas
tensions, pHa and hemoglobin concentrations were measured during
and after free diving of the Weddell seal (Leptonychotes
weddelli), beneath the fast ice of McMurdo Sound, Antarctica. To
examine arterial nitrogen tensions (PaN2), 47 samples of
arterial blood were obtained from 4 seals diving up to 23 min to
depths of 230 m. Peak arterial nitrogen tensions between 2000
and 2500 mmHg were recorded at depths of 40-80 m during descent,
indicating that the seal's lung collapses by 25-50 m. Then
arterial blood nitrogen tensions slowly decreased to about 1500
mmHg near surfacing. Thus during diving alveolar collapse and
redistribution of blood nitrogen allow the seal to avoid
nitrogen narcosis and decompression sick