Figure 4
From: Using heart-lung interactions to assess fluid responsiveness during mechanical ventilation
Respiratory changes in systolic pressure in a mechanically ventilated patient. The difference between the maximal and minimal value of systolic pressure over a single respiratory cycle is called SPV (for Systolic Pressure Variation). The reference systolic pressure is measured during an end-expiratory pause (line of reference) and SPV is divided in two components: Δup and Δdown. Δup is the difference between the maximal and the reference systolic pressure. Δdown is the difference between the reference and the minimal systolic pressure. Adapted with permission [33].