PMID: 7091912Jul 1, 1982Paper

Modification of phrenic nerve output to hypoxia after two hours of hypercapnia and increased cerebrospinal fluid [HCO3-

The American Review of Respiratory Disease
L Herrera, H Kazemi

Abstract

Decreased ventilatory response to hypoxia has been reported in patients with CO2 retention. The CO2 retention increases cerebrospinal fluid (CSF) [HCO3-], which could modify the ventilatory response to hypoxia. In order to evaluate the effect of increased CSF [HCO3-] as a consequence of hypercapnia on the response to hypoxia, phrenic nerve output during 5 min of progressive hypoxia was measured in anesthetized vagotomized and mechanically ventilated dogs when their acid-base was normal and when CSF [HCO3-] had increased. Peak phrenic nerve activity (PPNA), inspiratory time (TI), and expiratory time (TE) were recorded in 2 groups of dogs. Two hypoxic tests were conducted 2.5 h apart in each group. One group had normal acid-base status and the second group after the first hypoxic challenge breathed 10% CO2 for 2 h, and then ventilation was adjusted to bring CSF pH back to normal. The CSF [HCO3-] then had increased by 5.2 mEq/L and CSF PCO2 was 14.6 mmHg higher. With CSF [HCO3-] elevation, PPNA activity in response to hypoxia was significantly depressed, compared with that in animals with normal acid-base balance, TI was increased indicating slowing of nerve discharge, and TE was minimally increased indicating lessening of frequen...Continue Reading

Related Concepts

Anoxemia
Carbonic Acid Ions
Canis familiaris
Hypercapnia
Osmolality
Structure of Phrenic Nerve
Respiration

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