Constant-depth halothane anesthesia in respiratory studies

Abstract

Respiratory depression from anesthetic drugs introduces an undefined variable into many experiments. We have produced constant-depth anesthesia in dogs by maintaining an unvarying alveolar concentration of halothane, and we have tested whether such anesthesia can produce a steady state with respect to the respiratory response to CO2. At a constant alveolar halothane concentration, the response to CO2 remained essentially unchanged for up to 8 hr. Carbon dioxide response curves were also obtained at several different alveolar concentrations of halothane. Carbon dioxide response was sensitive to small changes in halothane concentration; the slope of the response curve diminished linearly with increase in alveolar concentration of halothane. With alveolar halothane concentration held constant, a small dose of intravenous thiopental produced a depression of the CO2 response curve that remained for more than 2 hr. carbon dioxide response; control of respiration; depression; respiratory response Submitted on April 29, 1964