Respiratory Function in Voluntary Participating Patagonia Sea Lions (Otaria flavescens) in Sternal Recumbency

We measured esophageal pressures (n = 4), respiratory flow rates (n = 5), and expired O(2) and CO(2) (n = 4) in five adult Patagonia sea lions (Otaria flavescens, body mass range 94.3–286.0 kg) during voluntary breaths while laying down out of water. The data were used to estimate the dynamic specific lung compliance (sCL), the O(2) consumption rate ([Formula: see text] O(2)) and CO(2) production rates ([Formula: see text] CO(2)) during rest. Our results indicate that the resting tidal volume in Patagonia sea lions is approximately 47–73% of the estimated total lung capacity. The esophageal pressures indicated that expiration is passive during voluntary breaths. The average sCL of sea lions was 0.41 ± 0.11 cmH(2)O(−1), which is similar to those measured in anesthetized sea lions and awake cetaceans, and significantly higher as compared to humans (0.08 cmH(2)O(−1)). The average estimated [Formula: see text] O(2) and [Formula: see text] CO(2) using breath-by-breath respirometry were 1.023 ± 0.327 L O(2) min(−1) (range: 0.695–1.514 L O(2) min(−1)) and 0.777 ± 0.318 L CO(2) min(−1), (range: 0.510–1.235 L CO(2) min(−1)), respectively, which is similar to previously published metabolic measurements from California and Steller sea lions using conventional flow-through respirometry. Our data provide end-tidal gas composition and offer novel data for respiratory physiology in pinnipeds, which may be important for clinical medicine and conservation efforts.