Ostriches (Struthio camelus) are the only birds known that can increase post-dead space ventilation during severe heat stress without experiencing hypocapnia and respiratory alkalosis. To determine whether this phenomenon occurs due to redistribution of pulmonary blood flow during panting, thus creating an extreme ventilation-perfusion (V̇/Q̇) imbalance, the distributions of pulmonary blood flow in ostriches at rest (15°C) and in severe panting (45° C) were determined using radioactively labeled microspheres. Blood flow distribution at rest was greatest in the neopulmo [18% > mean pulmonary blood flow (MPBF)] and the cranial (23% > MPBF) and distal (12% > MPBF) regions of the paleopulmo. During panting blood flow was not shunted around the lung, and flow to the neopulmo decreased to MPBF, became more homogeneous along the craniocaudal axis, and remained nonhomogeneous along the mediolateral axis. The results suggest that the observed decrease in gas exchange during panting is probably due primarily to shunting of the increased ventilation around the parabronchial exchange region rather than to alterations in the patterns of V̇/Q̇ within the lung.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Applied Physiology Respiratory Environmental and Exercise Physiology|
|State||Published - 1982|
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