Systolic pressure variation and pulse pressure variation

Respiratory variations in arterial pressure during positive pressure mechanical ventilation. SPV is a direct measurement of the difference between the highest systolic blood pressure (SBP_MAX) and lowest systolic blood pressure (SBP_MIN) values occurring over a respiratory cycle and is reported in mmHg. In contrast, PPV is reported as a percentage and is equal to the difference between the maximal PP (PP_MAX) and the minimal pulse pressure (PP_MIN) divided by the average of these two values (PP_MEAN = [PP_MAX + PP_MIN]/2). To account for slight variations between respiratory cycles, both SPV and PPV are usually measured over three or more breaths, and an average value is then reported.