Changes in the O2 and CO2 content of respired gases can alter regional pulmonary blood flow distribution in the mammalian lung. It is known that alterations in respiratory gases can cause a non-homogenous redistribution of pulmonary blood flow between the paleopulmo (PALEO) and neopulmo (NEO) of the avian lung; however the effect of alterations in respired gas content on the distribution of pulmonary blood flow in birds, such as the chicken, which possess a highly developed NEO is not known. This study utilized a colorimetric microsphere method to determine the effects of hypoxia and hypercapnia on the relative distribution of pulmonary blood flow in anesthetized chickens (Gallus domesticus) during control (normoxic) and experimental (hypoxic or hypercapnic) conditions where the relative regional distribution of blood flow in the lung is expressed as the ratio NEO/ PALEO. Administration of a hypoxic gas mixture (16.0% O2) produced a 13.4% increase in NEO/ PALEO, and, administration of a hypercapnic gas mixture (5.0% CO2) resulted in a 27.8% increase in NEO/PALEO. NEO/PALEO was not changed in normoxic sham controls. Our results are consistent with a mechanism in which the regional redistribution of pulmonary blood flow is mediated by local intrapulmonary factors.
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