PVR Calculator - Pulmonary Vascular Resistance in Dynes and Wood Units

A PVR calculator turns mean pulmonary arterial pressure, left atrial pressure, and cardiac output from a right heart catheterization into pulmonary vascular resistance in dynes sec cm to the minus 5 and Wood units, paired with the published 2 Wood unit pulmonary hypertension threshold. The calculator is built for a fast bedside check of a hemodynamic report.

• • Pre-rounds chart review: paste the latest MPAP, LAP, and cardiac output from a right heart catheterization, get the PVR in both unit conventions, and read the band before the team conversation.
• • Walk-through of a published example: recheck the Omni Calculator worked example of MPAP 23 mmHg, LAP 4 mmHg, and cardiac output 6 L per minute producing 253.3 dynes sec cm to the minus 5 and 3.17 Wood units.
• • Repeat scoring after a vasodilator challenge: re-enter the post-vasodilator MPAP, LAP, and cardiac output to see whether the PVR drops below 2 Wood units, the published responder pattern for a calcium channel blocker trial.

The PVR is most useful when all three inputs come from the same right heart catheterization report, since mixing a post-vasodilator cardiac output with a baseline mean PAP produces a misleading result. Treat the band as a triage prompt.

A second lab-to-single-number pattern that uses the same right heart catheterization input is the Aortic Valve Area Calculator, which turns mean gradient, peak velocity, and left ventricular ejection time into a single aortic valve area for the same hemodynamic workup.

The PVR calculator subtracts left atrial pressure from mean pulmonary arterial pressure to get the transpulmonary gradient in mmHg, multiplies the gradient by 80, and divides by cardiac output to get pulmonary vascular resistance in dynes sec cm to the minus 5. Dividing by 80 gives the Wood unit readout.

• mpap: Mean pulmonary arterial pressure from the right heart catheterization, in mmHg. A typical adult range is 10 to 20 mmHg.
• lap: Left atrial pressure from the right heart catheterization, often estimated from the pulmonary capillary wedge pressure, in mmHg. A typical adult range is 6 to 12 mmHg.
• cardiacOutput: Cardiac output measured by thermodilution or direct Fick on the right heart catheterization, in liters per minute. A typical adult range is 4 to 8 L per minute.
• pvr: Pulmonary vascular resistance in dynes sec cm to the minus 5, equal to 80 times the transpulmonary gradient in mmHg divided by cardiac output.

The 80 multiplier is the published conversion factor that turns a pressure gradient in mmHg divided by flow in liters per minute into the older CGS resistance unit, and dividing by 80 yields the modern Wood unit. The result should be paired with the 20 mmHg mean PAP and the 15 mmHg pulmonary capillary wedge pressure.

According to the Clinical Cardiology paper by Skimming, Cassin, and Nichols, pulmonary vascular resistance in dynes sec cm to the minus 5 is calculated as 80 times the transpulmonary gradient in mmHg divided by cardiac output in liters per minute, and dividing that result by 80 yields the same number in Wood units. The same formula is also restated in the Omni Calculator PVR reference, which adds a normal PVR below 250 dynes sec cm to the minus 5 and a borderline elevation above 2 Wood units.

A second bedside tool that uses the same arterial blood gas inputs to surface a respiratory failure pattern is the AA Gradient Calculator, which turns the alveolar and arterial oxygen tensions into a single A-a gradient number for the same pulmonary workup.

Four concepts drive the PVR result. Naming them keeps the calculator from being read as a stand alone diagnosis.

PVR is one half of the modern pulmonary hypertension definition. The other half is the mean PAP threshold of 20 mmHg at rest.

A second calculator that uses a similar mmHg pressure convention to surface a screening band is the Blood Pressure Calculator, which turns systolic and diastolic cuff readings into a published stage label for a different cardiovascular workup.

The form takes three right heart catheterization inputs and returns the PVR in both common unit conventions. Each input should come from the same right heart catheterization report.

1. 1 Enter the mean pulmonary arterial pressure: type the MPAP from the right heart catheterization summary, in mmHg. A typical adult range is 10 to 20 mmHg.
2. 2 Enter the left atrial pressure: use the LAP from the right heart catheterization report, often estimated from the pulmonary capillary wedge pressure. A typical adult range is 6 to 12 mmHg.
3. 3 Enter the cardiac output: type the cardiac output measured by thermodilution or direct Fick on the same right heart catheterization, in liters per minute. A typical adult range is 4 to 8 L per minute.
4. 4 Read the PVR in both unit conventions: the result panel shows the PVR in dynes sec cm to the minus 5 and the PVR in Wood units, paired with the band label and the 2 Wood unit PH threshold.

A patient with suspected right heart failure has a right heart catheterization showing MPAP 35 mmHg, LAP 10 mmHg, and cardiac output 4 L per minute. Entering those numbers gives a PVR of 500 dynes sec cm to the minus 5 and 6.25 Wood units. The band is labeled elevated, well above the 2 Wood unit PH threshold.

A second lab-to-single-number pattern that pairs naturally with the PVR in an inpatient or emergency department workup is the Anion Gap Calculator, which turns a basic metabolic panel into the serum anion gap and a high, normal, or low band for the same bedside read.

Using a PVR calculator offers several practical advantages over mental math and a separate unit conversion step.

• • Standardized dynes sec cm to the minus 5 unit: the calculator returns the PVR in dynes sec cm to the minus 5, the resistance unit used in the older hemodynamic literature and still common in textbooks.
• • Wood unit readout for the modern report: the calculator divides the dynes result by 80 to render the PVR in Wood units, the convention used in the 2022 ESC and ERS guidelines and in most current reports.
• • Built-in 2 Wood unit threshold: the result is paired with the 2 Wood unit pulmonary hypertension threshold, so the next step is implied by the same number rather than a separate lookup.

The same dynes and Wood unit readouts are used bedside, in the ICU, and in the procedural lab, giving the right heart catheterization team, the consultant, and the follow up clinic a shared language.

A second critical care score that turns a bundle of bedside inputs into a single triage band is the Apache II Calculator, which combines age, vital signs, and labs into a published ICU mortality band for the same hemodynamically unstable patient.

The output depends on the three right heart catheterization inputs and on the patient. Small input changes can move the PVR by a full Wood unit.

• • PVR is a hemodynamic screening number, not a stand alone diagnosis. A formal pulmonary hypertension workup with a repeat right heart catheterization and a vasoreactivity test is required before any PH specific therapy is started.
• • Children, pregnant patients, and patients with intracardiac shunts can have atypical PVR patterns that the calculator may overestimate or underestimate.

PVR sits inside a published hemodynamic definition, not outside it. The 2022 ESC and ERS guidelines pair the 2 Wood unit PVR threshold with a mean PAP above 20 mmHg.

According to the 2022 ESC and ERS pulmonary hypertension guidelines, a PVR at or above 2 Wood units, a mean PAP above 20 mmHg, and a pulmonary capillary wedge pressure below 15 mmHg together define pre-capillary pulmonary hypertension, and the calculator result is a screening number for that published definition rather than a stand alone diagnosis.

According to Medscape Pulmonary Hypertension reference, pulmonary hypertension is defined as a mean pulmonary arterial pressure above 20 mmHg at rest, and a progressive rise in pulmonary vascular resistance drives the right ventricular remodeling and failure seen in the disease.

A second bedside calculator that turns arterial blood gas inputs into a single acid-base classification is the Arterial Blood pH Calculator, which applies Henderson-Hasselbalch to PaCO2 and HCO3 for the same cardiopulmonary workup.