The pulse pressure (Pp) is calculated as the difference between systolic and diastolic arterial pressure. Maximal and minimal values for pulse pressure (Ppmax and Ppmin, respectively) are determined for each respiratory cycle. Pulse Pressure Variation (Delta Pp) is defined as:

Delta Pp = 100% * [(Ppmax - Ppmin)/((Ppmax + Ppmin)/2)]

Generally, Delta Pp is evaluated in triplicate over each of three consecutive respiratory cycles. The mean values of the three calculations are then used.

Pulse pressure variation is clinically useful in predicting fluid responsiveness in mechanically ventilated patients postoperative from cardiac surgery. The Delta Pp seems to be predictive of whether a given patient will respond by increasing cardiac output in response to fluid administration of not.

In this setting Delta Pp has been found superior in determining fluid responsiveness as compared to:

• Systolic pressure variation (SPV)
• Central venous pressure (CVP)
• Pulmonary artery occlusion pressure (PAOP)

In one trial, a Delta Pp of >=12% was found to be 97% sensitive and 95% specific in identifying those who would and would not respond to a 20 mL/kg bolus of Ringer's Lactate solution (over 20 minutes). In patients who were responders, their Delta Pp was 17%±3% whereas, non-responders had a Delta Pp of 9%±2% (P <0.001).

References:

• Auler JO, Galas F, Hajjar L, et al. Online monitoring of pulse pressure variation to guide fluid therapy after cardiac surgery. Anesth Analg. 2008;106(4):1201-6, table of contents.
• Kramer A, Zygun D, Hawes H, et al. Pulse pressure variation predicts fluid responsiveness following coronary artery bypass surgery. Chest. 2004;126(5):1563-8.
• Preisman S, Kogan S, Berkenstadt H, et al. Predicting fluid responsiveness in patients undergoing cardiac surgery: functional haemodynamic parameters including the Respiratory Systolic Variation Test and static preload indicators. Br J Anaesth. 2005;95(6):746-55.