Characterizing respiratory capacity in belugas (Delphinapterus leucas)

We measured respiratory flow, breath duration, and calculated tidal volume (V_T) in nine belugas (Delphinapterus leucas, mean measured body mass: 628 ± 151 kg, n = 5) housed in managed care facilities. Both spontaneous (resting at station) and trained maximal respirations (chuffs) were measured. The mean (±s.d.) inspiratory V_T for spontaneous breaths (16.7 ± 4.7 l, range: 7.5-18.7 l) was larger than those predicted based on respiratory scaling equations from terrestrial mammals and was 32 ± 10% of estimated total lung capacity (TLC_est) based on an equation from static measurements made on a range of cetaceans and pinniped lungs, and 52 ± 18% of estimated vital capacities (V_C, mean: 27.7 ± 8.9 l, range: 16.7-40.3 l) based on respiratory measurements obtained during trained maximal respirations. Expiratory flow (V˙_exp, spontaneous: 26.1 ± 5.5 l s^-1, chuff: 66.8 ± 22.5 l s^-1) was significantly higher as compared with inspiratory flow (V˙_insp, spontaneous: 22.3 ± 4.6 l s^-1, chuff: 30.1 ± 8.4 l s^-1), and the maximal expiratory flow recorded was 212 l s^-1. The breath duration was shorter for forced breaths (Expiration: 518 ± 101 ms; Inspiration: 905 ± 170 ms; Total: 1423 ± 227 ms) as compared with spontaneous breaths (Expiration: 995 ± 176 ms; Inspiration: 1098 ± 219 ms; Total: 2093 ± 302 ms). These data provide baseline estimates of the respiratory capacity of belugas.