Calf Muscle Oxygen Saturation During Walking May Predict Ambulatory Function in Symptomatic PAD

Rapid decline in calf muscle oxygen saturation while walking was found to predict impaired ambulatory function and quality of life in patients with symptomatic peripheral artery disease, according to study results published in Journal of Vascular Surgery.

Researchers aimed to determine whether calf muscle oxygen saturation measured during standardized treadmill exercise had an impact on ambulatory function and health-related quality of life in patients with symptomatic peripheral artery disease.

Claudication onset time (ie, time walked before the first pain experienced), and peak walking time (ie, total time walked at which the patient couldn’t continue due to pain), were recorded using a standardized treadmill test. Calf muscle oxygen saturation was measured using continuous-wave near-infrared spectroscopy before and during the treadmill test.

In this cohort of 151 patients (46% women), the mean claudication onset time was 193±162 seconds (minimum, 21 seconds; maximum, 782 seconds) and the mean peak walking time was 398±262 seconds (minimum, 36 seconds; maximum, 1200 seconds). The median calf muscle oxygen saturation was 52% at rest and 22% after 1 minute of walking. Oxygen saturation declined over walking time, reaching a minimum value of 9% saturation after a median 87 seconds of walking. The median rate of decline in calf muscle oxygen saturation was 0.35% saturation per second. After reaching the minimum saturation value, oxygen saturation increased to a median of 15% saturation at the end of the treadmill test.

The log-transformed exercise time to the minimum calf muscle oxygen saturation was found to correlate with the claudication onset time (correlation coefficient [r], 0.49; P <.001), the peak walking time (r, 0.56; P <.001), and the total distance walked in 6 minutes (r, 0.31; P <.001).

Log-transformed exercise time to minimum oxygen saturation also correlated with the patient health-related quality of life assessed using the Medical Outcomes Study 36-Item Short Form Health Survey (r, 0.32; P <.001).

Study limitations include its cross-sectional nature, which prevented to assess the causal relationship between calf muscle oxygen saturation and exercise variables, and the fact that the results may not be generalizable to patients with asymptomatic peripheral artery disease.

“More rapid decline in oxygen saturation of the calf musculature during walking, indicative of impaired microcirculation, is predictive of impaired ambulatory function and [health-related quality of life] in patients with symptomatic [peripheral artery disease],” the study authors concluded. “[B]ehavioral and medical therapies that may improve the microcirculation of the calf muscle may be especially beneficial in improving ambulatory function and [health-related quality of life] in patients with symptomatic [peripheral artery disease].”

Reference

Gardner AW, Montgomery PS, Wang M, Shen B. Association between calf muscle oxygen saturation with ambulatory function and quality of life in symptomatic patients with peripheral artery disease [published February 17, 2020]. J Vasc Surg. doi:10.1016/j.jvs.2019.09.057