Overview
The pressure summary uses time-weighted samples from the pressure functions. It does not obtain every mean by averaging the systolic and diastolic labels. Computed resistance and output retain underlying precision even when pressures are displayed as whole numbers.
Different displays answer different questions: the baseline catalogue describes reference inputs, the table summarizes a repeating signal, the live beat readout follows the current rhythm, and the paused cycle figure can hold a chosen respiratory phase.
Sampling window
Standard pressure summaries use 4,096 midpoint samples over 48 nominal cardiac cycles. NSVT summaries use the complete repeating NSVT schedule so the total average is not dependent on whether the screen happened to stop during a run.
During NSVT the live aortic/peripheral readout can instead sample the last completed beat, using 192 samples and accounting for peripheral delay. It therefore falls during the run even though a long-window table value averages baseline and VT periods.
Definitions
RAP and PAWP are atrial means; RVEDP/LVEDP are end-diastolic parameters; ventricular minimum and ventricular mean are separate sampled values. Mean PA pressure reflects its contour. A baseline BP-derived MAP and the mean of a modified arterial waveform can differ after waveform shape, assistance, respiration or damping.
SV = 1,000 × forward CO / ventricular rate in an organized steady rhythm, modified by actual beat strength for individual beats. CI divides CO by the body-surface-area input used by the relevant calculation. An absent or zero-flow measurement is withheld rather than divided by zero.
Precision and units
Pressure labels round to the nearest mmHg; CO and similar flow readouts generally retain one decimal. Resistance/formula panels may show additional precision where useful. Rounding is presentation only. Recalculating from two rounded numbers can differ slightly from the displayed derived result.
PVR is in Wood units, equivalent to mmHg·min/L. Multiply WU by 80 for dyn·s/cm⁵. Airway pressure in cmH₂O uses 98.0665 / 133.3224 ≈ 0.73556 mmHg per cmH₂O internally. A pressure-height graphic is not a separate measurement.
PADP, PAWP and LVEDP discrepancies
A PADP–PAWP gap can reflect pulmonary vascular load, high pulmonary flow or different measurement phases. A large MR v wave can put mean wedge above PA diastolic pressure; pulmonic regurgitation can also lower PADP.
Mean wedge above LVEDP can reflect MS, MR or atrial timing. LVEDP above mean wedge can reflect late filling of a stiff LV or AR. The explanatory prompts are triggered by selected numerical gaps; they do not establish the cause. Mean wedge minus LVEDP is not a time-aligned mean transmitral gradient.
References & further reading
