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Front Physiol. 2014 Nov 10;5:433. doi: 10.3389/fphys.2014.00433. eCollection 2014.

Inflation and deflation pressure-volume loops in anesthetized pinnipeds confirms compliant chest and lungs.

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Life Sciences, Texas A&M University-Corpus Christi Corpus Christi, TX, USA.
Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center Boston, MA, USA.
The Marine Mammal Center Sausalito, CA, USA.
Vancouver Aquarium Vancouver, BC, Canada.
Marine Mammal Research Unit, Fisheries Centre, University of British Columbia Vancouver, BC, Canada.
The Marine Mammal Center Sausalito, CA, USA ; A. Watson Armour III Center for Animal Health and Welfare, Shedd Aquarium Chicago, IL, USA.


We examined structural properties of the marine mammal respiratory system, and tested Scholander's hypothesis that the chest is highly compliant by measuring the mechanical properties of the respiratory system in five species of pinniped under anesthesia (Pacific harbor seal, Phoca vitulina; northern elephant seal, Mirounga angustirostris; northern fur seal Callorhinus ursinus; California sea lion, Zalophus californianus; and Steller sea lion, Eumetopias jubatus). We found that the chest wall compliance (CCW) of all five species was greater than lung compliance (airways and alveoli, CL) as predicted by Scholander, which suggests that the chest provides little protection against alveolar collapse or lung squeeze. We also found that specific respiratory compliance was significantly greater in wild animals than in animals raised in an aquatic facility. While differences in ages between the two groups may affect this incidental finding, it is also possible that lung conditioning in free-living animals may increase pulmonary compliance and reduce the risk of lung squeeze during diving. Overall, our data indicate that compliance of excised pinniped lungs provide a good estimate of total respiratory compliance.


diving physiology; excised lung; lung mechanics; minimum air volume; total lung capacity

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