Near-infrared spectroscopy in the routine diagnostic work-up of patients with leg ischaemia

Objective. To examine the reproducibility and clinical applicability of near-infrared spectroscopy (NIRS) in patients with leg ischaemia. Design. Prospective comparative diagnostic study. Materials and methods. Routinely measured peripheral blood pressure and microcirculatory parameters were compared with tissue oxygen saturation (TsO2) measurements using a new NIRS device on the calf muscle and the foot. Healthy subjects (n = 20) and patients in different stages of leg ischaemia (n = 45) were investigated at rest and after provocation: a treadmill test, arterial occlusion and a change in posture. Healthy volunteers Were used as all age-matched reference population. Results. Reproducibility of the NIRS was excellent (intraclass correlation coefficient at rest was 0.91 (95% confidence interval: 80-99). Resting TsO2 (65%) in healthy controls did not differ significantly from that in patients (Fontaine 2: 66%; F3/4: 68%). After exercise, a significant reduction in TsO2 was observed only in patients: Fontaine 1: 60%; Fontaine 2: 21 %, Fontaine 3/4: 29%, The ankle/brachial index after exercise showed a good correlation (R= 0.73) with TsO2 at the end of the treadmill test. No correlation between NIRS and other micro- or macrocirculatory parameters was found. Conclusion. NIRS is a very reproducible tool to assess tissue oxygen saturation, bill is not useful for the routine work-up of patients with leg ischaemia.