Purpose: The purpose of this study was to compare the effects of propofol on ventilation with those of halothane.
Methods: Respiration was studied in 20 spontaneously breathing children undergoing elective dental restoration randomized to receive either propofol (Group P) or halothane (Group H) anaesthesia. Data were recorded at different inspired concentrations of halothane (F1H) or propofol (RivP) during a washout of the anaesthetic agent. The F1H 2%, 1% and 0% corresponded to an end-tidal halothane concentration of 1.38 +/- 0.06%, 0.857 +/- 0.03% and 0.191 +/- 0.01% respectively. The RivP were 18, 15, 12, 9 and 0 mg.kg-1.hr-1. The inspiratory flow waveform, the CO2 waveform and the occluded inspiratory pressure waveform were recorded. The flow waveform was analyzed for minute ventilation (Vi), and tidal volume (VT), parameters of breath Timing [Total time (Ttot), Inspiratory time (Ti)] and parameters of breath Amplitude [mean inspiratory flow (VT/Ti)]. The slope of the initial 100 msec (dP/dt0.1) of an occluded inspiration, together with the occluded inspiratory time (Tiocc) and the ratio of the occluded to unoccluded inspiratory time (Tiocc/Ti) were obtained.
Results: There were intergroup differences in the preemergence values of Ttot, dP/dt0.1 and Tiocc/Ti. In group P the Vi, VT and Ttot increased and PETCO2 decreased during a washout of propofol. The values of dP/dt0.1 in Group P at all RivP were half the values of those in Group H. The ratio Tiocc/Ti did not change in Group P and increased in Group H during a washout of halothane.
Conclusion: Propofol anaesthesia was associated with a decrease in Vi whereas during halothane anaesthesia, Vi did not change. Ventilation in Group P differed from Group H in parameters of both breath Drive and Timing.