Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP

In ventilated patients with acute lung injury (ALI) we investigated whether respiratory changes in arterial pulse pressure (Delta PP) could be related to the effects of PEEP and fluid loading (FL) on cardiac index (CI). Measurements were performed before and after application of a PEEP (10 cm H2O) in 14 patients. When the PEEP-induced decrease in CI was > 10% (six patients), measurements were also performed after FL. Maximal (PPmax) and minimal (PPmin) values of pulse pressure were determined over one respiratory cycle and Delta PP was calculated: Delta PP (%) = 100 x {(PPmax - PPmin)/ ([PPmax + PPmin]/2)}. PEEP decreased CI from 4.2 +/- 1.1 to 3.8 +/- 1.3 L/min/m(2) (p < 0.01) and increased Delta PP from 9 +/- 7 to 16 +/- 13% (p < 0.01). The PEEP-induced changes in CI correlated with Delta PP on ZEEP (r = -0.91, p < 0.001) and with the PEEP-induced increase in Delta PP (r = -0.79, p < 0.001). FL increased CI from 3.5 +/- 1.1 to 4.2 +/- 0.9 L/min/m(2) (p < 0.05) and decreased Delta PP from 27 +/- 13 to 14 +/- 9% (p < 0.05). The FL-induced changes in CI correlated with Delta PP before FL (r = 0.97, p < 0.01) and with the FL-induced decrease in Delta PP (r = -0.85, p < 0.05). In ventilated patients with ALI, Delta PP may be useful in predicting and assessing the hemodynamic effects of PEEP and FL.