Effect of a sub-anaesthetic concentration of halothane on the ventilatory response to sustained hypoxia in healthy humans.
We selected nine normal subjects (8M, 1F; aged 25-43 yr) with brisk hypoxic ventilatory responses, and studied their ventilatory response to sustained isocapnic hypoxia (SaO2 82 (SEM 0.1) % for 25 min) in the presence and absence of 0.1% inspired halothane. Halothane had no significant effect on baseline ventilation or gas exchange. In the absence of halothane, ventilation increased initially from mean 7.57 (0.35) litre min-1 to 14.54 (0.91) litre min-1, and decreased subsequently to 10.74 (0.32) litre min-1 during hypoxia (both P < 0.05). In the presence of 0.1% inspired halothane, ventilation increased initially from 7.19 (0.47) litre min-1 to 12.08 (0.99) litre min-1 (P < 0.05), then decreased to 10.12 (0.28) litre min-1 during sustained hypoxia (ns compared with baseline normoxic ventilation). Halothane reduced significantly the initial increase in ventilation (P < 0.05), but did not enhance the subsequent decrease. These results confirm that a sub-anaesthetic concentration of halothane depresses the initial hypoxic ventilatory response; the response during prolonged periods of hypoxia is, however, less than the initial response and is reduced in the presence or absence of a sub-anaesthetic concentration of halothane.
Young
C H
CH
Department of Anaesthetics, University of Edinburgh.
Drummond
G B
GB
Warren
P M
PM
D000328:Adult; D002245:Carbon Dioxide / Q000502:physiology; D005260:Female; D006221:Halothane / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010100:Oxygen / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*; D015656:Respiratory Mechanics / Q000502:physiology; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen; D006221:Halothane