PVR Calculator (pulmonary vascular resistance in Wood units and dyn·s·cm⁻⁵)

Understanding the PVR calculator — concept and principle

Pulmonary vascular resistance (PVR) describes how hard the right heart must work to push blood through the lungs. This calculator works it out from right heart catheterisation measurements, in Wood units and dyn·s·cm⁻⁵, with the PVR index and the 2022 ESC/ERS haemodynamic classification of pulmonary hypertension.

Pressure drop ÷ flow: with the default inputs the result is 4 WU (= 320 dyn·s·cm⁻⁵).

How it is calculated

Transpulmonary gradient (TPG) = mean pulmonary artery pressure (mPAP) − pulmonary artery wedge pressure (PAWP)

PVR (Wood units) = TPG ÷ cardiac output (L/min)

PVR (dyn·s·cm⁻⁵) = Wood units × 80

PVR index (WU·m²) = Wood units × body surface area

Classification (when mPAP > 20 mmHg): pre-capillary PH = PAWP ≤ 15 and PVR > 2; isolated post-capillary = PAWP > 15 and PVR ≤ 2; combined = PAWP > 15 and PVR > 2.

The principle

Resistance is pressure drop divided by flow, the same idea as Ohm's law for electricity. The pressure that drives blood across the lungs is the difference between the pulmonary artery and the left atrium; the wedge pressure stands in for left atrial pressure. Dividing by cardiac output gives resistance. The factor 80 converts mmHg·min/L to the CGS unit dyn·s·cm⁻⁵.

Worked example

Default inputs: mPAP 32, PAWP 12 mmHg, cardiac output 5.0 L/min, BSA 1.8 m².

TPG = 32 − 12 = 20 mmHg.
PVR = 20 ÷ 5.0 = 4 Wood units = 4 × 80 = 320 dyn·s·cm⁻⁵.
PVR index = 4 × 1.8 = 7.2 WU·m².
mPAP > 20, PAWP ≤ 15, PVR > 2 → Pre-capillary PH.

Each point is the calculator re-run with only “Cardiac output (L/min)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Cardiac output (L/min)	PVR (Wood units)
1.25	16
2.5	8
3.75	5.33
5	4
6.25	3.2
7.5	2.67
10	2

How to read the result

Where does your result fall?

The 2022 ESC/ERS guidelines take PVR above 2 Wood units as the upper limit of normal; a usual range is about 100–250 dyn·s·cm⁻⁵. Pre-capillary PH points to disease of the lung vessels or lungs; post-capillary PH points to left heart disease. Classification guides further tests and treatment.

Common mistakes

Using echo estimates of pressure as if they were catheter values.
Mixing up indexed and non-indexed cardiac output.
Measuring wedge pressure at the wrong point of the breathing cycle (it should be end-expiration).

Keep in mind: This is a calculation aid for clinicians, not a diagnosis. Pulmonary hypertension is diagnosed and managed by specialist teams.

Frequently asked questions

What is a Wood unit?

One mmHg per litre per minute; it is named after the physiologist Paul Wood.

What is a normal PVR?

Up to 2 Wood units by the 2022 ESC/ERS definition.

Why does the wedge pressure matter?

It separates problems in the lung circulation itself from back-pressure caused by the left heart.

Sources: Humbert M, Kovacs G, Hoeper MM, et al., "2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension", Eur Heart J 2022;43(38):3618–3731

Checked 9 Nov 2026. Humbert M, Kovacs G, Hoeper MM, et al., 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension — haemodynamic definitions as reproduced in SEC Working Group, “Comments on the 2022 ESC/ERS guidelines…”, Rev Esp Cardiol (Engl Ed) 2023;76(5):294–300, Table 1; PVR = (mPAP − PAOP) × 80/CO and range 100–250 dyn·s·cm⁻⁵ from Edwards “Normal Haemodynamic Parameters and Laboratory Values” (2022).

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