What is Perfusion Index in Pulse Oximetry

What is Perfusion Index (PI)? | CMI Health

  • 12 August, 2021
  • Dallas Akins

What is Perfusion Index?

Perfusion Index, often abbreviated PI, is a measurement obtained from a pulse oximeter that is calculated as the ratio of pulsatile blood flow to the non-pulsatile blood in peripheral tissues (Hales et al. 1989). Simply put, it is the ratio of pulsing blood to non-pulsing blood. This measurement can be acquired non-invasively and is a good indicator of a user’s pulse strength. Measurements generally range from 0.02% (very weak pulse) to 20% (very strong pulse). The plethysmograph generated by the pulse oximeter is a graphical illustration of the user’s PI. Physician’s often use this measurement to gain a better understanding of the effects of a drug or treatment on a patient. It can also be used to gain insight into medicinal efficacy and track disease progression.


What is a “Normal” PI value?

PI is affected by a variety of factors that are directly attributed to the user’s physiological condition, and the site at which the measurement is being taken (fingertip, earlobe, forehead, etc.) Because there is such a high degree of variability in these parameters, individual users should establish their own normal PI percentage with a doctor.

It is good to keep in mind that pulse oximeters also measure blood oxygen saturation (SpO2 levels) and pulse rate (PR). These values together can provide basic, yet necessary information regarding the user’s current well-being and health condition.

Interested in monitoring your PI? CMI Health offers a variety of Pulse Oximeters and sensors designed to suit each user’s individual needs. This includes Handheld Pulse Oximeters, recommended for spot checking or continuous, overnight use. There are a variety of sensors available to pair with this device, each designated to meet different user requirements. We also offer portable, digital spot-checking fingertip pulse oximeters. These devices are great for on-the-go monitoring. If your looking for an easy to wear overnight pulse oximeter, we suggest checking out the OxyKnight Watch wrist oximeter, designed for comfortable, continuous use.

If you have any questions or concerns regarding the above information, please feel free to contact us at info@cmihealth.com or 888-985-1125.




What is perfusion index (pi). AmperorDirect. (n.d.). https://www.amperordirect.com/pc/help-pulse-oximeter/z-what-is-pi.html.

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