What is Perfusion Index (PI)?
Perfusion Index (PI) is the ratio of the pulsatile blood flow to the non-pulsatile static blood flow. It indicates the pulse strength at the sensor site. Higher perfusion rate= more blood flow, lower perfusion rate = less blood flow.
PI values
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Ranges from 0.02% to 20%.
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0.02% = very weak pulse
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20% = an extremely strong pulse
Did you know there are no specific normal PI values?
Every individual must establish their own normal/baseline values. Monitor in the morning versus after exercise. Write down any changes in PI if you feel different when PI is lower than usual.
Why is PI value important?
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Acts as a good indicator of the reliability of the pulse oximeter reading.
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Provides instant perfusion status of the selected monitoring site.
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Optimal monitoring sites are chosen with a relatively high, stable PI.
Fun facts about PI values
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The sensitivity of oximeter is determined by the PI value it is able to detect.
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The lower the PI value, the more reliable is the oximeter.
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For most pulse oximeters, the PI readings are above 0.6% or even unavailable.
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Good oximeters which are designed to detect extremely low PI (0.2-0.3%) would be more costly.
Prepared by: Chew Ee Wei, a HTM Pharmacist.
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