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. 1970 Nov;211(1):139–155. doi: 10.1113/jphysiol.1970.sp009271

Stimulus—response curves for the pulmonary vascular bed to hypoxia and hypercapnia

Gwenda R Barer, P Howard, J W Shaw
PMCID: PMC1395597  PMID: 5500988

Abstract

1. In anaesthetized open-chest cats and dogs, blood flow and gas tensions were measured in a circuit inserted into a pulmonary vein while ventilating the lobe which it drained with low O2 and high CO2 mixtures.

2. Both hypoxic and hypercapnic mixtures caused a reduction in blood flow from the lobe.

3. Stimulus—response curves relating blood flow to pulmonary venous PO2 and PCO2 were obtained. Those for hypoxia were usually asymptotic in shape; the curves became steep below 100 torr and flow sometimes fell to zero. The mean reduction in blood flow for every 20 torr fall in PO2 was 15·7% in cats and 11·8% in dogs. Those for hypercapnia were steep at first but levelled out at high PCO2 values; the maximum reduction in flow was 40-60% as vasoconstriction was only observed over a limited PCO2 range.

4. Hypoventilation of the lobe led to a reduction in blood flow. This was mainly attributable to hypoxia though other factors such as hypercapnia may sometimes have contributed.

5. Total occlusion of the bronchus of an O2-filled lobe caused blood flow to fall in two phases. The first phase could be attributed to a rise in PCO2 and the second to a fall in PO2.

6. The results confirm the hypothesis that hypoxia is an important factor regulating local blood flow in relation to local ventilation.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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