Flow Properties of Expiration and Inspiration in a Trained Bottle-Nosed Porpoise

The flow characteristics of both expiration and inspiration were determined in a trained, 285-kg bottle-nosed porpoise. The largest tidal volume measured was 26.4 liters. For purposes of scaling we assumed this to be vital capacity (VC). The maximum peak expiratory flow rate measured was 6.1 VC·sec⁻¹. The maximum peak inspiratory flow rate was 2.1 VC·sec⁻¹. The time required for a complete expiration was about 0.3 sec. The flow rates of both expiration and inspiration remain near their maximum for nearly all of the VC. We conclude that these properties of the ventilation maneuver are important in achieving adequate turnover of lung gases during the short period that the blowhole is above water as the porpoise passes through the air/water interface when it is up to cruising speed.