COMPARISON OF RESPIRATORY CHARACTERISTICS DURING ENFLURANE AND HALOTHANE ANAESTHESIA

The effects of enflurane on certain respiratory characteristicswere compared with those of halothane in 70 patients duringanaesthesia with spontaneous breathing using a specially designedcircuit. The rate of respiration with enflurane (mean 22 b.p.m.)was slower than with halothane (mean 31 b.p.m.; P<0.001)and the tidal volume greater (enflurane mean 240ml, halothane180ml; P<0.05). There was no statistically significant differencein the minute volume of ventilation or end-tidal carbon dioxideconcentration between the two agents. The effects of a narcoticpremedication were observed in 16 patients in the study. Themain effect was to produce slowing of respiratory rate (enfluranemean 16 b.p.m.; halothane 18 b.p.m.). The value of the respiratorypattern compared with the measurement of heart rate and arterialpressure as a clinical guide during anaesthesia is discussed.