User's Manual

Radius-7 Chapter 1- Technology Overview
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General Description for Perfusion Index (PI)
The Perfusion Index (PI) is the ratio of the pulsatile blood flow to the non-pulsatile or static
blood in peripheral tissue. PI thus represents a non-invasive measure of peripheral perfusion
that can be continuously and non-invasively obtained from a pulse oximeter.
General Description for Pulse Rate (PR)
Pulse rate (PR), measured in beats per minute (BPM) is based on the optical detection of
peripheral flow pulse.
General Description for Pleth Variability Index (PVI)
The pleth variability index (PVI) is a measure of the dynamic changes in the perfusion index
(PI) that occur during the respiratory cycle. The calculation is accomplished by measuring
changes in PI over a time interval where one or more complete respiratory cycles have
occurred. PVI is displayed as a percentage (0-100%).
The utility of PVI is unknown at this time and requires further clinical studies. Technical
factors that may affect PVI include probe malposition and patient motion.