Two series of experiments were performed on anesthetized dogs to study the steady-state ventilatory responses of the central respiratory mechanism to hypoxia and hypercapnia at three different levels of cartotid body stimulation. A cross-perfusion technique was used to perfuse a recipient dog's carotid bodies with blood of desired oxygen tension from a donor dog. Central hypoxia and hyper-capnia were induced by allowing the recipient dog to spontaneously breathe specific gas mixtures for 6-min periods. Findings indicate that: (1) Hypoxia depresses ventilation centrally, even at a moderate level of hypoxia (PaO2 = 45-55 mm Hg). This ventilatory depression by moderate hypoxia is probably due to central hypocapnia resulting from increased cerebral blood flow. (2) Central hypoxia shifts the -PaCO2 relationship toward a higher PCO2 range in addition to decreasing the slope. This may be due to metabolic depression of neurons produced by the coexistence of hypoxia and hypercapnia. This hypoxic depression of central CO2 sensitivity is diminished by an increase in carotid chemoreceptor drive.
|Number of pages||15|
|State||Published - Dec 1975|
Bibliographical noteFunding Information:
Alth~~~~ the results of several ~nvestigatwrs indicate that after ~ripheral chemw-receptor det~~rvatjwn~ ventilation is depressed by hypoxia (Dumke et af., 194I; Watt er al., 1943; Astrijm, 1952; Hwlton and Wood 1965; Wade et ud,, 1970; Lugliani B$ ial., 1971; Morrilt et &., 1975). the results of others da not agree (Moyer and Reecher, $942; Davenport at al., 1947; Guz er al., 1966), Among those finding central hypoxic depression of ventilation, conflicting results have been reported QD the level of hypoxia at which ventilation begins to be depressed, Dumke et ~1. (1941) Watt et al. (1943) and Astrijm (1952) observed central ventilatory depression at mild to moderate hypoxic levels (breathing l&14% 0,). However, Mwrrili et ai. (1975) found depression to exist only during severe hypoxia (alveolar Pw, at K-23 mm Hg), By comparing the respiratory responses ihccepracrf ar ~~~~~~~~f~ ~~~~~~~ ~~~~f9T7 5. i This work was supportedi n part by U. S. Public %afth Service grant number HL f I(i?8,
- Carotid receptors Hypercapnia Control of breathing Hypoxia Dog Interaction between hypoxia
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine