Wood Units Calculator

Wood Units Calculator: Calculates Pulmonary Vascular Resistance (PVR) in Wood units (mmHg/L/min) and CGS units (dynes·sec/cm⁻⁵).

mPAP (mmHg)

PCWP (mmHg)

C.O. (L/min)

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Right heart catheterization interpretation

PAH classification and severity assessment

Lung transplant candidacy evaluation (PVR threshold)

Alternative to CGS units; older convention still used widely

Helps clinicians understand traditional reporting

Section 2

Formula & Logic

Formula

PVR (Wood units) = (mPAP − PCWP) / CO mPAP = mean pulmonary artery pressure (mmHg) PCWP = pulmonary capillary wedge pressure (mmHg) CO = cardiac output (L/min) Result in mmHg/L/min (Wood units) Conversion: 1 Wood unit = 80 dynes•sec•cm⁻⁵

PAH Severity (Wood Units)

PVR (Wood units)	Classification	Clinical Status
<3	Normal	Normal PVR
3–5	Mild elevation	Borderline PH
5–8	Moderate elevation	Mild-moderate PAH
>8	Severe elevation	Severe PAH
>12	Very severe	Advanced/transplant candidate

Section 3

Pearls/Pitfalls

Thresholds & Decisions

PVR >6 Wood units usually defines PAH diagnosis

PVR >12–16 Wood units: lung transplant evaluation warranted

Response to acute vasodilator challenge: >20% PVR drop may indicate IPAH

Serial PVR increase despite therapy = disease progression

Last Comprehensive Review: 2026

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