Pulmonary Shunts in Harbor Seals and Sea Lions during Simulated Dives to Depth
Abstract
Pulmonary shunts in seals and sea lions were determined before and during dives to simulated depths up to 100 m. Five young harbor seals weighing 36-50 kg and two young sea lions weighing 21-40 kg were dived in a compression chamber. Before and during the dives, blood samples were obtained from the aorta and usually the pulmonary artery. Arterial O₂, and CO₂ tensions, hemoglobin concentration, and venous O₂ contents were determined. From these data the physiological pulmonary shunt of the lung could be calculated. These shunts ranged from 8.4% at the surface to a pulmonary shunt due to compression of over 70% during a dive to 100 m. As discussed, structure of the terminal airways might be expected to affect the rate that alveoli would compress and develop shunts. However, we conclude that at pressures of less than 8 atm (equivalent to 70-m depth) there is not a marked difference in the degree of compression shunt between sea lions and harbor seals even though there are striking differences in terminal airway anatomy.
