Pulmonary Vascular Resistance Calculator

What Is Pulmonary Vascular Resistance (PVR)?

Pulmonary Vascular Resistance (PVR) is a key hemodynamic parameter that measures the resistance to blood flow through the pulmonary vascular bed (the blood vessels of the lungs). It reflects the ease with which the right ventricle pumps deoxygenated blood through the pulmonary arteries, pulmonary capillary bed, and into the left atrium.

PVR measurement is primarily performed during right heart catheterization (Swan-Ganz catheter) and is essential in the diagnosis, classification, and management of pulmonary hypertension, congenital heart defects, and left heart failure.

Pulmonary Vascular Resistance Formulas

PVR is mathematically defined by Ohm's law applied to fluid hemodynamics, where resistance equals the pressure drop across the pulmonary circulation divided by the volumetric blood flow (Cardiac Output):

Where:

• $\text{mPAP}$: Mean Pulmonary Artery Pressure (measured in mmHg).
• $\text{PCWP}$: Pulmonary Capillary Wedge Pressure (also called PAOP, pulmonary artery occlusion pressure, or left atrial pressure $LAP$, measured in mmHg).
• $\text{CO}$: Cardiac Output (measured in liters per minute, $\text{L/min}$).
• $\text{TPG}$: Transpulmonary Pressure Gradient ($\text{TPG} = \text{mPAP} - \text{PCWP}$).

Unit Conversions for PVR

PVR is reported in two primary standard measurement units:

• Wood Units (WU or $\text{mmHg}\cdot\text{min/L}$): Computed directly from $\frac{\text{mPAP} - \text{PCWP}}{\text{CO}}$.
• Absolute Metric Units ($\text{dyn}\cdot\text{s}\cdot\text{cm}^{-5}$): Converted by multiplying Wood Units by $80$: $$PVR \ (\text{dyn}\cdot\text{s}/\text{cm}^5) = PVR \ (\text{WU}) \times 80$$
• SI Units ($\text{kPa}\cdot\text{s/L}$ or $\text{MPa}\cdot\text{s/m}^3$): $1 \ \text{WU} = 8 \ \text{kPa}\cdot\text{s/L} = 8 \ \text{MPa}\cdot\text{s/m}^3$.

Pulmonary Vascular Resistance Index (PVRI)

To account for differences in body size and habitus across patients (especially in pediatric and critical care populations), PVR is indexed to Body Surface Area ($BSA$ in $\text{m}^2$):

Clinical Reference Ranges and Guidelines

Pre-capillary vs. Post-capillary Pulmonary Hypertension

Hemodynamic categorization using right heart catheterization relies on comparing $\text{mPAP}$, $\text{PCWP}$, and $\text{PVR}$:

• Isolated Pre-capillary PH (Group 1 PAH, Group 3 Lung Disease, Group 4 CTEPH): $\text{mPAP} > 20 \ \text{mmHg}$, $\text{PCWP} \le 15 \ \text{mmHg}$, and $\text{PVR} > 2.0 \ \text{WU}$.
• Isolated Post-capillary PH (Group 2 Left Heart Disease): $\text{mPAP} > 20 \ \text{mmHg}$, $\text{PCWP} > 15 \ \text{mmHg}$, and $\text{PVR} \le 2.0 \ \text{WU}$.
• Combined Pre- and Post-capillary PH (CpcPH): $\text{mPAP} > 20 \ \text{mmHg}$, $\text{PCWP} > 15 \ \text{mmHg}$, and $\text{PVR} > 2.0 \ \text{WU}$.

Explore related hemodynamic tools including our Mean Arterial Pressure Calculator and Doppler Echo Cardiac Output Calculator.