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Pulmonary Vascular Resistance Calculator

Enter the mean pulmonary artery pressure, wedge pressure, and cardiac output.

How it is calculated

The tool starts with the transpulmonary gradient, TPG = mPAP − PCWP, in mmHg, where mPAP is the mean pulmonary artery pressure and PCWP is the pulmonary capillary wedge pressure. It then divides by the cardiac output in litres per minute: PVR = TPG ÷ CO, giving Wood units (mmHg·min/L). Multiplying by 80 converts this to dyn·s·cm⁻⁵. The Wood unit value and the TPG are shown to two decimals, the dyn value as a whole number. The cardiac output must be above zero. If the wedge pressure is higher than the mean pulmonary artery pressure, the result is negative and is shown as it is, which usually points to a measurement or entry error. Use values from the same catheterization, taken at the same moment; the tool does not validate clinical plausibility.

Worked example

A right heart catheterization records a mean pulmonary artery pressure of 35 mmHg, a wedge pressure of 12 mmHg and a cardiac output of 4.8 L/min. The transpulmonary gradient is 35 − 12 = 23.00 mmHg. Dividing by the output gives PVR = 23 ÷ 4.8 = 4.79 WU. Multiplying by 80 converts it to 383 dyn·s·cm⁻⁵. The same pressures at a higher cardiac output of 6.0 L/min would give a lower resistance, 23 ÷ 6 = 3.83 WU, which shows how strongly the flow figure affects the result.

Try this example →

Common mistakes

  • Using the systolic or diastolic pulmonary pressure instead of the mean. The formula needs the mean pulmonary artery pressure.
  • Entering cardiac output in mL/min or the cardiac index. The field expects litres per minute of total output, not a value normalised to body surface area.
  • Mixing pressure units, for example kPa for one value and mmHg for the other. Both must be in mmHg.
  • Comparing a Wood unit result with a threshold given in dyn·s·cm⁻⁵ without converting. The two differ by a factor of 80.
  • Taking wedge and output readings from different times or conditions. The result is only as meaningful as the simultaneous measurement behind it.

Sources

About this calculator

Pulmonary vascular resistance (PVR) measures how much the pulmonary arteries resist blood flow from the right side of the heart into the lungs. It is derived from right heart catheterization data using the formula PVR = (mean pulmonary artery pressure − pulmonary capillary wedge pressure) ÷ cardiac output, expressed in Wood units (mmHg·min/L) or converted to dyn·s·cm⁻⁵ by multiplying by 80.

Cardiologists and pulmonologists use PVR to distinguish pulmonary arterial hypertension (a problem in the lung vessels themselves) from pulmonary venous hypertension caused by left heart disease, and to decide whether a patient with congenital heart disease or advanced heart failure is a candidate for surgery, transplant, or vasodilator therapy. A normal PVR is roughly under 2 Wood units, while values above 3 typically indicate clinically significant pulmonary vascular disease.

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