TWO NOVEL METHODS USING PULSE OXIMETRY FOR MEASUREMENT OF ARTERIAL TOE PRESSURE from EASD-meeting in Wien in September 1996; abstract

Pär Samuelsson, diabetessjuksköterska, G Blohmé, J Fowelin1 and J W Eriksson2, Diabetes Unit, Dept. of Medicine, Sahlgrenska Univerity Hospital, Göteborg, Sweden, 1Dept. of Medicine, Falkenberg Hospital, Falkenberg, Sweden and 2Dept.of Medicine, Norrland University Hopital, Umeå, Sweden.

Occlusive arterial disease in the lower extremities is a common and serious problem in diabetes patients. Systolic ankle pressures are often misleading due to medial sclerosis, and arterial toe pressure (ATP) assessed with the strain gauge technique is a cumbersome method.

We evaluated a novel, simple, noninvasive approach to assess ATP by monitoring pulsatile toe blood flow with a regular pulse oximeter (POX).It was employed in 70 subjects, of which 44 had suspected or established lower extremity asterial disease (LEAD) and 26 did not. 55 of the subjects had diabetes and 15 where non-diabetic. The POX sensor was placed on the tip of the great toe. A small blood pressure cuff was placed around the proximal part of the toe and connected to a sphygmomanometer. Systolic pressure was estimated as the cuff pressure at which pulsatile blood flow ceased during cuff inflation. In parallell, ATP was obtained using the established strain gauge (SG) phletysmographic technique.

There was a good concordance between the two methods (linear regression: r=0.93, ATPPOX=1.1*ATPSG - 6.4 (mmHg), p<0.01). The POX method was reproducible and CV for duplicate measurements was 3.7%. However, patients with systolic toe pressure <20 mm Hg could not be reliably assessed with this method. We also evaluated a modified so called pole test to estimate ATP in patients with threatening/critical ischemia. The POX sensor but no cuff was used. The leg of the supine patient was gradually elevated, and the vertical distance above the heart level, where pulse signals ceased, was used as an estimation of ATP (cm divided by 1.3 to adjust for the densities of blood and Hg). This method also correlated fairly well with ATPSG (r=0.69, p=<0.05).

CONCLUSION: The two novel methods amploying pulse oximetry for the measurement of ATP seem promising for rapid, simple, cost-effective and reliable estimation of the functional degree of LEAD in diabetes patients.