IDENTIFICATION OF PERIPHERAL VASCULAR-DISEASE IN ELDERLY SUBJECTS USING OPTICAL SPECTROSCOPY

The purpose of this study was to determine the usefulness of near-infr ared spectroscopy (NIRS) measurements to identify peripheral vascular disease (PVD). Usefulness was determined by the frequency of a success ful test, as well as comparison with standard clinical assessments. St udy subjects (N = 117, mean age = 67.8 +/- 8.1 yrs) responded to a fre e screening for PVD. NIRS was used to measure the relative O-2 saturat ion of hemoglobin in the soleus muscle. The time to 1/2 recovery of O- 2 saturation (O2T1/2) was measured after 1 minute of repeated plantar flexions using a Cybex Eagle seated calf machine. O2T1/2 was used as m any subjects had recovery curves that did not have an exponential line shape. The test was done on both legs and the worst leg was used for analysis. For comparative purposes, a clinical history and physical ex amination were performed by a physician or nurse practitioner, which i ncluded questions on intermittent claudication, examination of periphe ral pulses, and questions to identify cardiovascular risk factors. NIR S signals were obtained on 105 of 117 subjects (89% success rare). Sub jects with body mass index (BMI) values above 32 appeared to have NIRS O2T1/2 values that were less reliable than subjects with BMI values l ess than or equal to 32 (77% success rate). The O2T1/2 was longer in s ubjects with claudication and reduced pulses than in subjects without these conditions. Sensitivity comparing O2T1/2 to claudication and red uced pulses varied from 51-76% and specificity from 65-80%, depending on the cutoff value for O2T1/2 that was used (normal value plus 1 or 2 SD). A longer O2T1/2 was significantly associated with incidence of d iabetes, smoking, hypercholesterol, and coronary bypass surgery. In su mmary successful NIRS O2T1/2 measurements were made in 77% of the subj ects, with failure primarily occurring in obese subjects. NIRS O2T1/2 measurements showed reasonable although not strong agreements with cli nical assessments of PVD, and with some risk factors for cardiovascula r disease.