Kooyman and Sinnett (1982) measured pulmonary shunts in
harbour seals and California sea lions in a pressure chamber, in
an attempt to define the degree of alveolar collapse with pressure.
Pulmonary shunt is a measure of incomplete gas exchange
with a pulmonary shunt of 100% equivalent to complete alveolar
collapse. Kooyman and Sinnett (1982) found that pulmonary
shunt increased with compression and predicted that alveolar collapsewould
occur at approximately 1700 kPa in both species, much
deeper than suggested in freely diving Weddell seals (Falke et
al., 1985) and bottlenose dolphins (Ridgway and Howard, 1979).
Furthermore, the data presented by Kooyman and Sinnett (1982)
suggested that the pulmonary shunt occurs gradually as theorized
by Scholander (1940).