SummaryWe measured the tidal volumes and peak in¯ation pressures generated during manual hyperventilation for chest physiotherapy in 25 adult ventilated patients. The average tidal volume ranged from 711 to 1511 ml, with a mean (SD) of 1120 (274) ml. There was a negative correlation (p < 0.05) between the average tidal volume and the lung injury, as measured by the Murray lung injury score. The average peak in¯ation pressure ranged from 37 to 74 cmH 2 O with a mean (SD) of 51.5 (7.6) cmH 2 O. There was a positive correlation (p < 0.05) between average peak in¯ation pressure and the lung injury score. Mean (SD) P a O 2 improved by 18.3 (14.3) kPa from baseline after physiotherapy (p < 0.05). Mean (SD) P a CO 2 decreased by 0.1 (0.4) kPa. As the lung score increases higher in¯ation pressures and smaller tidal volumes are used suggesting an increased potential for barotrauma or volutrauma in susceptible lungs.

SummaryIn a double-blind, placebo-controlled study of 90 ASA 1 and 2 patients scheduled for elective surgery we compared the effect of pre-administering midazolam 2 mg or propofol 30 mg on the dose of propofol subsequently required to induce anaesthesia. Using loss of response to verbal command and tolerance to placement of a facemask as end-points, the dose of propofol required to induce anaesthesia was significantly smaller in the patients given propofol (1.87 mg.kg À1 ) or midazolam (1.71 mg.kg À1) when compared to the control group (2.38 mg.kg À1). Although the decrease in blood pressure following induction was significantly greater in the propofol group when compared to the control group, there was no difference between the two study groups and the decrease was felt not to be of clinical significance in this group of patients. As propofol is presented ' F F F for use in a single patient only' and the technique of predosing with propofol allowed induction of all patients with less than 200 mg (a single ampoule), we question on a cost basis whether midazolam co-induction is necessary to reduce propofol induction doses.

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