[The effect of IPPV, with or without PEEP, on central venous pressure]

Changes in central venous pressure (CVP) during intermittent positive pressure ventilation with a Bennett 7200 respirator were measured in 30 postoperative patients without hemodynamic abnormalities. The tidal volume was changed from 300 ml to 900 ml and the PEEP was changed from 0 cmH2O to 8 cmH2O, step by step, respectively. Mean airway pressure (Pmean), maximal airway pressure (Pmax), arterial blood pressure, and heart rate were measured simultaneously with the measurement of CVP. CVP increased linearly with increases in the tidal volume and PEEP. A linear correlation was seen between Pmean and CVP. The value of A was 7.5 +/- 6.2 cmH2O and that of B was 0.32 +/- 0.13 when the equation of the regression line was Y = A + BX, where X was Pmean and Y was CVP. The coefficient of correlation was 0.88 +/- 0.09 (n = 30, P less than 0.01). The value of CVP during intermittent positive pressure ventilation increased linearly at rate which was 32% of the increase in Pmean. The value of CVP was considered to be 7.5 +/- 6.2 cmH2O when Pmean was zero. There was no change in the arterial blood pressure and heart rate throughout the measurement. This suggests that increases in CVP might not reflect any accompanying hemodynamic change.