Pulmonary mechanics of high‐altitude waterfowl

Abstract

Previous work in this lab found that while both low and high‐altitude adapted species increase ventilation in response to hypoxia, high‐altitude species primarily increase tidal volume whereas low‐altitude species increase breathing frequency. Thus, we hypothesized that high‐altitude species should have higher respiratory compliance when compared to low‐altitude species to reduce the cost of breathing deeper. We measured dynamic and static compliance of the total system in five Andean species of ducks resident at Lake Titicaca, Peru and compared them to the low‐altitude migratory barnacle goose (n蠅6 for all groups). Static compliance was significantly higher in the high‐altitude ducks than the barnacle geese (1.8 ± 0.18 compared to 1.3 ± 0.06). Among the high‐altitude ducks the compliance was highest in the species that has spent the most evolutionary time at high‐altitude (2.98 ± 0.36), while the lowest compliance was found in the one species of diving duck studied (1.63 ± 0.23). The high‐altitude species also had a higher inspiratory capacity (215 ± 17 mL/kg) than the low‐altitude geese (154 ± 21 mL/kg). Thus high‐altitude species breathe with a more effective breathing pattern, reducing pulmonary dead space, without incurring an increased cost of overcoming elastic recoil forces, by increasing compliance of their respiratory system.