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

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