Please see Bibliography of References for a list of abstracts, manuscripts and posters.
Comerota AJ, Throm RC, Kelly P, Jaff M. J Vasc Surg. 2003;38(4):724-729.
Objectives: Near-infrared spectroscopy provides a noninvasive method of measuring tissue oxygen saturation and has been used to monitor extremity compartment syndrome. Tissue O2 saturation (StO2) is potentially useful in assessing patients with peripheral arterial disease (PAD). The purposes of this feasibility study are to (1) explore the diagnostic sensitivity of StO2 in subjects with PAD and symptoms of intermittent claudication (IC) compared with normal subjects, and (2) correlate the change in StO2 during and after exercise with the ankle brachial index (ABI) in patients with IC.
Material and methods: Forty-nine subjects, 35 normal and 14 PAD, from two centers were evaluated in a prospective cross-sectional analysis comparing StO2 by using the InSpectra™ tissue spectrometer and ABI at rest (baseline) and after treadmill exercise. Measurements were obtained at baseline and peak exercise (normal subjects) and at baseline, initial claudication distance (ICD) and absolute claudication distance (ACD) in PAD subjects. Endpoint values were the mean of 15 data points. Times to 50% of StO2 recovery to baseline (T50) and complete recovery to baseline (T100) were measured. Receiver-operator characteristic curves were constructed to assess the sensitivity/specificity values associated with various StO2 cut-points.
Results: The PAD patients were older (P =.0002) and 57% were male, compared with 37% males in the normal group. The ABI was 0.68 ± 0.14 in PAD patients versus 1.14 ± 0.08 in normal subjects (P < .0001). The baseline StO2 was 65% in both groups. The peak exercise StO2 was significantly lower and the absolute change in StO2 and the percent change in StO2 were significantly greater in PAD patients (P < 0.45). The T50 and T100 were longer in the PAD patients compared to normal subjects (P <.0001 and .002, respectively); these results did maintain statistical significance upon inclusion of covariates. A T50 of >70 seconds yielded a sensitivity of 89% and a specificity of 85% for PAD.
Conclusions: StO2 is a new and potentially useful technique to evaluate patients with PAD. Resting StO2 was similar in PAD-IC subjects and normals. There was a significantly greater drop in StO2 and longer recovery times in PAD-IC subjects. Interestingly, StO2 at the ICD and ACD was similar. StO2 offers a different and perhaps more appropriate end pathophysiology of exercise-induced muscle ischemia and its recovery.