A new non-invasive method using pulse oximetry for the assessment of arterial toe pressure

We evaluated a novel, simple non-invasive method to assess systolic arterial toe pressures (ATP). It was employed in 63 subjects, of which 37 had suspected or established lower extremity arterial disease (LEAD) and 26 did not. 48 of the subjects had diabetes and 15 were non-diabetic. Pulsatile toe blood flow was monitored with a regular pulse oximeter (Biox 3700TM, BOC Ohmeda, Helsingborg, Sweden) (POX) with the sensor on the tip of the great toe. A small blood pressure cuff was placed around the proximal part of the toe and was connected to a sphygmomanometer (TycosTM, Levimed AB, Höganäs, Sweden). Systolic pressure was estimated as the cuff pressure at which pulsatile blood flow ceased during cuff inflation. Toe pressure measurement was obtained, in parallel, using the established strain gauge plethysmographic technique. There was a good concordance between the two methods (linear regression: r = 0.93; y = 1.1 x x-6.4; y = pressure obtained with the pulse oximeter, x = pressure obtained with strain gauge, in mmHg). However, patients with very low systolic toe pressures, < 20 mmHg, could not be reproducibly assessed using the POX method. In conclusion, the POX method was found to be a simple and reliable method for the estimation of systolic toe pressures, at least for those above the severely ischemic level. It may provide an easily accessible and cost-effective means of vascular assessment at the bedside, as well as for out-patients.