Response hypoxia (Part 7)

To determine whether this ventilatory rolloff is a manifestation of changes in the carotid body, in central translation of chemoreceptor input into respiratory neural traffic, or in the peripheral respiratory apparatus, studies were done in cats that demonstrate a ventilatory rolloff during sustained hypoxia similar to that observed in humans. Measurements during sustained hypoxia showed that this decrease in ventilation from early peak values is accompanied by a decline in phrenic neural activity, but carotid sinus nerve traffic showed no parallel decline. Taken together, these results suggest that changes within the central nervous system are likely important contributors to the observed rolloff. However, these findings do not indicate whether this reflects true hypoxic depression of the central nervous system or a withdrawal of central ventilatory drive, reflecting either hypoxia-induced cerebral vasodilation with C02 washout and brain-stem alkalinization or the influence of hypoxia-induced release of neurotransmitters. Whatever the mechanism, it appears that moderate hypoxia, when sustained beyond a few minutes, can act as a ventilatory depressant; this could explain the variable, sometimes paradoxical, increase in ventilation with oxygen administration in hypoxic patients with chronic obstructive pulmonary disease. buy levaquin online


Category: Hypoxia

Tags: Chronic obstructive pulmonary disease, Hypercapnia, Hypoxia

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