The Use of the Pulse Oximeter in Limb Ischemia: The Pulse Study

Purpose: Does a non-invasive pulse oximeter probe accurately indicate limb ischemia with inflation of a tourniquet? How are the pulse waveform, perfusion index and oxygen saturations affected? Does pulse oximetry return to normal with restoration of blood flow? Are the findings similar, regardless of which probe is used? Methods: Single Centre, pilot, proof of concept study. Each volunteer staff member had two probes applied to both lower limbs and then to both upper limbs. One limb had a tourniquet applied (experimental limb). The pulse oximeter trace, perfusion index and oxygen saturations were recorded before tourniquet inflation (time point 0), at inflation (time point 1), just prior to deflation (time point 2) and after deflation when the waveform returned to a biphasic appearance (time point 3). Results: Changes in both pulse oximeter waveforms occurred within 45 seconds of tourniquet inflation, with flattening of the biphasic trace followed by complete loss of amplitude, which normalized on release of the tourniquet. Perfusion index values for the experimental arms and legs were statistically significantly smaller than the control sides during tourniquet inflation and exceeded baseline on deflation, due to reperfusion. Oxygen saturations were unreliable and did not reflect tourniquet inflation. Conclusion: Pulse Oximeter waveform and perfusion index provide a noninvasive, sensitive, responsive, available, repeatable, objective measure of vascular supply in the limbs in healthy volunteers, although oxygen saturation is not a reliable indicator of perfusion. Objective assessment using the pulse oximeter could aid clinical judgement in initiating early vascular intervention in limb injury.