Free PVR Calculator

Mean Pulmonary Arterial Pressure (MPAP)

Left Atrial Pressure (LAP)

Cardiac Output (CO)

L/min

Enter MPAP, LAP and CO to calculate PVR

Pulmonary Vascular Resistance (PVR) and Its Clinical Significance

The pulmonary vascular resistance (PVR) calculator provides a quick assessment of the resistance to blood flow in the pulmonary circulation. Elevated PVR is a hallmark of pulmonary hypertension and can indicate right ventricular dysfunction. By inputting hemodynamic measurements, clinicians can estimate the severity of pulmonary vascular disease and guide management decisions.

What Is PVR?

PVR reflects the opposition to flow encountered by blood as it travels from the right ventricle through the pulmonary arteries, capillaries, and veins. This resistance is analogous to systemic vascular resistance but specific to the lung circuit. When pulmonary arterial or venous pressures rise, the right ventricle must work harder to maintain cardiac output, eventually leading to right heart failure if untreated.

Normal PVR Range

Normal PVR values are generally below 250 dyn·s·cm⁻⁵ or 3.125 Wood units (Wood units = mmHg·min/L). The normal hemodynamic parameters underpinning PVR are:

Variable	Normal Range
Mean Pulmonary Artery Pressure (MPAP)	10 – 20 mmHg
Left Atrial Pressure (LAP) / Pulmonary Capillary Wedge Pressure	6 – 12 mmHg
Cardiac Output (CO)	4 – 8 L/min

Using these values, the calculated PVR typically stays under 250 dyn·s·cm⁻⁵.

Factors Influencing PVR

Low PVR can result from:

Vasodilator medications
Alkalemia (elevated blood pH)
Hypocapnia (low PaCO₂)
Strenuous exercise

High PVR may be caused by:

Vasoconstrictor drugs
Hypoxemia (low PaO₂)
Acidemia (reduced blood pH)
Hypercapnia (elevated PaCO₂)
Atelectasis or lung collapse
Pulmonary embolism (consider using a PERC rule to rule out)

PVR Formula

The standard formula for PVR is:

\text{PVR (dyn·s·cm}^{-5}) = \frac{80 \times (\text{MPAP} - \text{LAP})}{\text{CO}}

Where:

MPAP = mean pulmonary artery pressure (mmHg)
LAP = left atrial pressure (mmHg) – often approximated by pulmonary capillary wedge pressure
CO = cardiac output (L/min)

To express PVR in Wood units, simply omit the factor 80:

\text{PVR (Wood units)} = \frac{\text{MPAP} - \text{LAP}}{\text{CO}}

One Wood unit equals 80 dyn·s·cm⁻⁵.

Example Calculation

Consider a patient suspected of right heart dysfunction with the following values:

MPAP = 23 mmHg
LAP = 4 mmHg
CO = 6 L/min

First compute the pressure gradient: $23 - 4 = 19$ mmHg.

Then apply the formula:

\text{PVR} = \frac{80 \times 19}{6} = \frac{1520}{6} \approx 253.3\ \text{dyn·s·cm}^{-5}

In Wood units: $19 / 6 \approx 3.17$ Wood units.

Both results exceed the normal threshold (< 250 dyn·s·cm⁻⁵ or < 3.125 Wood units), indicating elevated pulmonary vascular resistance consistent with pulmonary hypertension.

Practical Application

This pulmonary vascular resistance calculator is essential for pulmonary hypertension assessment and right heart function testing. It integrates directly with cardiac output calculator inputs, making it a convenient tool in catheterization labs and critical care settings. Understanding PVR helps differentiate pre‑capillary from post‑capillary pulmonary hypertension and monitor response to therapy.

FAQ

1. What is the normal range for pulmonary vascular resistance (PVR)?

Normal PVR is generally below 250 dyn·s·cm⁻⁵ or 3.125 Wood units, based on typical hemodynamic values (MPAP 10–20 mmHg, LAP 6–12 mmHg, CO 4–8 L/min).

2. How do you calculate PVR?

PVR (dyn·s·cm⁻⁵) = 80 × (MPAP - LAP) / CO. Alternatively, in Wood units: (MPAP - LAP) / CO. MPAP, LAP, and CO stand for mean pulmonary artery pressure, left atrial pressure, and cardiac output, respectively.

3. What does an elevated PVR indicate?

A PVR above the normal range suggests increased resistance in the pulmonary vessels, often associated with pulmonary hypertension. This condition forces the right ventricle to work harder, potentially leading to right ventricular dysfunction and failure.

4. What is the relationship between Wood units and dyn·s·cm⁻⁵?

One Wood unit equals 80 dyn·s·cm⁻⁵. PVR in Wood units is calculated as (MPAP - LAP) / CO, while the conventional unit in dyn·s·cm⁻⁵ requires multiplying by 80.

How to Use

Enter the mean pulmonary arterial pressure (MPAP) and select the appropriate pressure unit.
Enter the left atrial pressure (LAP) and select the appropriate pressure unit.
Enter the cardiac output (CO) in L/min. The PVR result will update automatically.