Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure

In mechanically ventilated patients with acute circulatory failure related to sepsis, we investigated whether the respiratory changes in arterial pres sure could be related to the effects of volume expansion (VE) on cardiac in dex (CI). Forty patients instrumented with indwelling systemic and pulmonar y artery catheters were studied before and after VE. Maximal and minimal va lues of pulse pressure (Pp(max) and Pp(min)) and systolic pressure (Ps(max) and Ps(min)) were determined over one respiratory cycle. The respiratory c hanges in pulse pressure (Delta Pp) were calculated as the difference betwe en Pp(max) and Pp(min) divided by the mean of the two values and were expre ssed as a percentage. The respiratory changes in systolic pressure (Delta P s) were calculated using a similar formula. The VE-induced increase in CI w as greater than or equal to 15% in 16 patients (responders) and < 15% in 24 patients (nonresponders). Before VE, Delta Pp (24 +/- 9 versus 7 +/- 3%, p < 0.001) and Delta Ps (15 +/- 5 versus 6 +/- 3%, p < 0.001) were higher in responders than in nonresponders. Receiver operating characteristic (ROC) curves analysis showed that Delta Pp was a more accurate indicator of fluid responsiveness than Delta Ps. Before VE, a Delta Pp value of 13% allowed d iscrimination between responders and nonresponders with a sensitivity of 94 % and a specificity of 96%. VE-induced changes in CI closely correlated wit h Delta Pp before volume expansion (r(2) = 0.85, p < 0.001). VE decreased D elta Pp from 14 +/- 10 to 7 +/- 5% (p < 0.001) and VE-induced changes in De lta Pp correlated with VE-induced changes in CI (r(2) = 0.72, p < 0.001). i t was concluded that in mechanically ventilated patients with acute circula tory failure related to sepsis, analysis of Delta Pp is a simple method for predicting and assessing the hemodynamic effects of VE, and that Delta Pp is a more reliable indicator of fluid responsiveness than Delta Ps.