The Use of the Pulse Oximeter in Limb Ischaemia: the PULSE study

Abstract

Abstract Purpose Does a non-invasive pulse oximeter probe accurately indicate limb ischaemia 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 (timepoint 0), at inflation (timepoint 1), just prior to deflation (timepoint 2) and after deflation when the waveform returned to a biphasic appearance (timepoint 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 normalised 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.