Ventilation and gas exchange before and after voluntary static surface breath-holds in clinically healthy bottlenose dolphins, <i>Tursiops truncatus</i>

Abstract

We measured respiratory flow (<i>V̇</i>), breathing frequency (<i>f</i>_R), tidal volume (<i>V</i>_T), breath duration and end-expired O₂ content in bottlenose dolphins (<i>Tursiops truncatus</i>) before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O₂, <i>V</i>_T and <i>f</i>_R following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering <i>V</i>_T and <i>f</i>_R to rapidly replenish the O₂ stores. For the first breath following a surface breath-hold, the end-expired O₂ decreased with dive duration, while <i>V</i>_T and <i>f</i>_R increased. Throughout the recovery period, end-expired O₂ increased while the respiratory effort (<i>V</i>_T, <i>f</i>_R) decreased. We propose that the dolphins alter respiratory effort following a breath-hold according to the reduction in end-expired O₂ levels, allowing almost complete recovery after 1.2 min.