Pulmonary vascular resistance (PVR) is similar to systemic vascular resistance (SVR) except it refers to the arteries that supply blood to the lungs. If the pressure in the pulmonary vasculature is high, the right ventricle must work harder to move the blood forward past the pulmonic valve. Over time, this may cause dilation of the right ventricle, and require additional volume to meet the preload needs of the left ventricle (Breitenbach, 2010).

How to Calculate PVR 

PVR can be calculated by subtracting the left atrial pressure from the mean pulmonary artery pressure (PAP), divided by the cardiac output (CO) and multiplied by 80. To obtain the left atrial pressure, a pulmonary artery catheter (PAC) is needed to perform a pulmonary artery occlusion pressure (PAOP), also known as pulmonary artery wedge pressure (PAWP). Normal PVR is 100 – 200 dynes/sec/cm^-5.

Here’s an example:
If a patient's mean PAP is 16 mmHg, his PAOP is 6 mmHg, and his cardiac output is 4.1 L/minute, his PVR would be 195 dynes/sec/cm^-5.
 

 

Factors that Increase PVR

Factors that increase PVR include (Breitenbach, 2010):

• Vasoconstricting drugs
• Hypoxemia
• Acidemia
• Hypercapnia (high partial pressure of arterial carbon dioxide [PaCO₂])
• Atelectasis

Factors that Decrease PVR

Factors that decrease PVR include (Breitenbach, 2010):

• Vasodilating drugs
• Alkalemia
• Hypocapnia (low PaCO₂)
• Strenuous exercise

The accuracy of PVR depends on the direct pressure measurements and indirect cardiac outputs from a pulmonary artery catheter which are subject to error. However, PVR is useful when diagnosing the severity of pulmonary hypertension (Fleitman, 2022). Understanding these parameters will help the bedside clinician better manage medications and hemodynamic instability.
 
*You may also see pulmonary vascular resistance index (PVRI) reported; this is calculated by substituting cardiac index (CI) for CO in the equation.
 

References:
Breitenbach, J. (2010). Putting an end to perfusion confusion. Nursing Made Incredibly Easy!. 5(3), 50-60. https://www.doi.org/10.1097/01.NME.0000393028.13649.14

Fleitman, J. (2022, July 6). Pulmonary artery catheterization: interpretation of hemodynamic values and waveforms in adults. UpToDate. https://www.uptodate.com/contents/pulmonary-artery-catheterization-interpretation-of-hemodynamic-values-and-waveforms-in-adults

Gowda, C. (2008). Don’t be puzzled by cardiovascular concepts. Nursing Made Incredibly Easy!. 6(4), 27-30. https://www.doi.org/10.1097/01.NME.0000324936.03867.c5

 

More Resources
Blog	Blog	Blog
Cardiac Output and Cardiac Index – What's the Difference?	Preload and Afterload – What's the Difference?	Calculating the mean arterial pressure (MAP)