Effects of hypoxia and hypercapnia on VT, f, and VI of nestling and adult bank swallows.
The effects of hypoxia, hypercapnia, and hypoxic hypercapnia on ventilation, and breathing pattern in adult and nestling bank swallows (Riparia riparia) were assessed. The CO2 threshold above which inhaled minute volume (VI) increased significantly in adults and nestlings was 0.045. At each level of fractional concentration of inspired CO2 (FICO2), ventilation in nestlings was lower than that in adults. At a FICO2 of 0.09, VI of adults increased by 284%, whereas VI in nestlings changed 238%. Adult bank swallows also showed a blunted ventilatory response to hypoxia, and the nestling's response was similar to other birds. Adults exhibited greater changes in VI at all levels of hypoxic hypercapnia compared with nestlings. Combined hypoxic and hypercapnic stimuli had an additive effect on ventilation in both groups. Chronic exposure of nestlings to the hypercapnia and hypoxia within burrows seems to significantly alter their ventilatory response to these respiratory stimuli.
Department of Zoology, University of Montana, Missoula 59812.
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D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001717:Birds / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D012016:Reference Values; D012119:Respiration; D013990:Tidal Volume