Key result
Hypercapnia increases mean circulatory filling pressure, with vagal chemoreceptors driving only ~25% of the response.
Why the study?
The influence of aortic chemoreceptors on vascular capacitance after changes in blood carbon dioxide and oxygen levels was not fully understood.
Do hypercapnia and hypoxia affect vascular capacitance, and what is the role of aortic chemoreceptors in this response in mongrel dogs?
Population
Mongrel dogs anesthetized with methoxyflurane and nitrous oxide
Comparison
Hypercapnia, hypoxia, hypoxic hypercapnia, and hypocapnia versus baseline blood gas tensions with intact receptors
Design
Preclinical experimental study with cold block of cervical vagosympathetic trunks
Authors
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Animal data on aortic chemoreceptors and Pmcf do not inform care; leaves open human capacitance regulation.
Do hypercapnia and hypoxia affect vascular capacitance, and what is the role of aortic chemoreceptors in this response in mongrel dogs?
Aortic and cardiopulmonary chemoreceptors mediate only a minor portion (~25%) of the reflex increase in vascular capacitance induced by hypercapnia or hypoxia.
Rothe et al. (1990) studied this question. Hypercapnia and hypoxia vs. Control was evaluated on Mean circulatory filling pressure (Pmcf). A 10 mmHg increase in arterial PCO2 caused a 0.36 mmHg increase in mean circulatory filling pressure, with vagal afferent chemoreceptors accounting for only ~25% of the total response.
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