Abstract 2868: Using Near Infrared Spectroscopy to Evaluate Peripheral Arterial Disease
Objective: Patients with peripheral arterial disease (PAD) have decreased blood flow to their legs. Near infrared spectroscopy (NIRS) measures tissue oxygen saturation (StO2) in the muscle. The objective of this study was to quantify the tissue oxygen saturation in the gastrocnemius muscle of patients with PAD during exercise and associate those numbers with perceived pain in the leg muscle.
Methods: Individuals with PAD (ABI ≤ 0.90) completed a constant work rate (CWR) treadmill test (TMT) as part of baseline testing for a randomized trial. The CWR level was set at the workload associated with 85% of the patient’s peak oxygen uptake on a symptom-limited progressive TMT. Leg pain ratings were obtained every minute using the Borg ratio scale. StO2 measures were taken continuously during exercise and during recovery. The CWR TMT was repeated to obtain a stable baseline measure. The slopes of StO2 and leg pain were computed using regression analysis.
Findings: Sixteen older men (age = 69±10 years) with PAD (ABI = 0.68±0.18) completed a CWR TMT. Exercise duration on the CWR TMT was 8.65±3.5 min. StO2 declined rapidly as pain increased. See sample test for one patient below (exercies time=8 min). StO2 was highly correlated with exercise duration (r = 0.81, p = 0.001) and moderately related to the ankle-brachial index (r = 0.62, p = 0.025) and perceived leg pain (r = −0.56, p = 0.047). Test-retest reliability of the StO2 measure was supported (r = 0.67, p = 0.013).
Conclusion: StO2 measured using NIRS is a reliable tool to identify tissue deoxygenation in patients with PAD. There is a strong relationship between the decline in the slope of the StO2 measure and exercise duration in patients with PAD.