Enter the pulsatile signal (AC) and the nonpulsatile signal (DC) into the Calculator. The calculator will evaluate the Perfusion Index. 

Perfusion Index Formula

PI = PS / NS * 100


  • PI is the Perfusion Index (%)
  • PS is the pulsatile signal (AC)
  • NS is the nonpulsatile signal (DC)

To calculate Perfusion Index, divide the pulsatile signal by the nonpulsatile signal, then multiply by 100.

How to Calculate Perfusion Index?

The following steps outline how to calculate the Perfusion Index.

  1. First, determine the pulsatile signal (AC). 
  2. Next, determine the nonpulsatile signal (DC). 
  3. Next, gather the formula from above = PI = PS / NS * 100.
  4. Finally, calculate the Perfusion Index.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

pulsatile signal (AC) = 400

nonpulsatile signal (DC) = 300

Frequently Asked Questions

What is the significance of the Perfusion Index in medical diagnostics?

The Perfusion Index (PI) is a numerical value that indicates the strength of blood flow to the peripheral tissues. It is used in medical diagnostics to assess blood circulation efficiency and can help detect conditions related to poor blood flow.

How does the Perfusion Index differ from other blood flow measurement techniques?

The Perfusion Index is a non-invasive, simple, and quick measurement that provides immediate results about peripheral circulation. Unlike other techniques, such as Doppler ultrasound, it does not require specialized equipment or extensive operator training, making it accessible for routine checks.

Can the Perfusion Index be used to monitor conditions over time?

Yes, the Perfusion Index can be used to monitor changes in blood flow over time, making it valuable for tracking the progress of treatment for conditions affecting circulation or for monitoring the impact of lifestyle changes on vascular health.

What factors can affect the accuracy of the Perfusion Index?

Several factors can affect the accuracy of the Perfusion Index, including the patient’s movement during measurement, the presence of nail polish or artificial nails in finger-based sensors, ambient temperature, and the specific characteristics of the device used for measurement.