Figure 1.

Respiratory changes in arterial pressure in a mechanically ventilated patient. The pulse pressure (PP; systolic minus diastolic pressure) is minimal (PPmin) three heart beats after its maximal value (PPmax). The respiratory changes in pulse pressure (ΔPP) can be calculated as the difference between PPmax and PPmin, divided by the mean of the two values, and expressed as a percentage: ΔPP (%) = 100 × (PPmax - PPmin)/([PPmax + PPmin]/2). In this case, the high value of ΔPP (30%) suggests that the patient would be potentially responsive to volume resuscitation.