Meeting Abstract

88.4  Monday, Jan. 6 14:15  Lung mechanics in live cetaceans FAHLMAN, A*; BRODSKY, M; ROCHO-LEVIN, J; LEVINE, G; LORING, S/H; KLEINHENZ, D; AUSTIN, T; Texas A&M Univ. Corpus Christi; V.M.D. Consulting; Dolphin Quest Oahu; Dolphin Quest Oahu; Beth Israel Deaconess Medical Center; Texas A&M Univ. Corpus Christi; Paxarms Inc. andreas.fahlman@tamucc.edu

For breath-hold diving mammals time underwater needs to be maximized to enhance foraging efficiency. However, O₂ stores are finite, so the animal eventually must return to the surface to renew this resource. Functional anatomic adaptations, like compliant lungs and stiff conducting airways in comparison to their terrestrial counterparts is a major principal in our current understanding of their respiratory physiology. Recent work indicates that there is great variability in the structural properties of the respiratory system between marine mammal species. Our objective was to measure the pulmonary compliance, respiratory flow-rates, and end-tidal gases in six bottlenose dolphins (body mass range: 167-250 kg), under a variety of circumstances. A custom made pneumotachometer allowed measurement of respiratory flow rates, an esophageal balloon catheter measured the pressure over the lung, and a fast response O₂ and CO₂ analyzer measured expiratory gas composition. A total of 128 spontaneous and 41 forced breaths (trained “chuffs”) were collected. The average (± SD) expiratory duration was significantly longer (spontaneous: 0.31 ± 0.04 sec; chuff: 0.26 ± 0.04 sec) and the inspiratory duration shorter (spontaneous: 0.43 ± 0.05 sec; chuffs: 0.66 ± 0.11 sec) during spontaneous breaths as compared with chuffs. Maximum expiratory flow rates exceeded 120 l sec^-1, while maximum inspiratory flow rates ranged between 12 to 30 l sec^-1. The esophageal pressure suggests that dolphins exhale passively during spontaneous respiration, but actively during chuffs. Our results provide data that confirm an amazing respiratory capacity in cetaceans, and provide new data on chest compliance in dolphins.