Response hypoxia (Part 5)

Response hypoxia (Part 5)Whether such interindividual variation in the strength of the hypoxic ventilatory response reflects differences in sensitivity of the primary hypoxic chemosensor, the carotid body, or in central integration of chemoreceptor information, or to differences in response of the respiratory apparatus (lungs and respiratory muscles) cannot be readily determined from studies in humans. To explore this question, experiments have been carried out in cats, both awake and anesthetized, which demonstrate an interindividual variation in strength of this response over a sixfold range comparable to that observed on humans. Also, as with humans, this variation is reproducible in repeated testing— that is, animals that test low or high on one occasion tend to do so on another. This variation in strength of the ventilatory response among individual cats is paralleled by differences in carotid body hypoxic sensitivity assessed by recording from the carotid sinus nerve during progressive hypoxia (Fig 4).
Thus, it appears that there are substantial interindividual differences in the strength of the hypoxic ventilatory response which are in part familial, possibly genetic in origin and may partly reflect differences in hypoxic sensitivity of the carotid body.


Figure 4. Ventilatory (open circles) and carotid sinus nerve {filled circles) responses measured during progressive isocapnic hypoxia in a cat with a high hypoxic ventilatory response (A) and in another with a low hypoxic ventilatory response (B). Interindividual differences in strength of the ventilatory response to hypoxia tend to be associated with parallel differences in the carotid sinus nerve responses, suggesting that differences in hypoxic ventilatory response may be related to variable sensitivity of the carotid body to hypoxia.

Category: Hypoxia

Tags: Chronic obstructive pulmonary disease, Hypercapnia, Hypoxia

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