Reliability of transcutaneous oximeter electrode heating power during exercise in patients with intermittent claudication.

The purposes of this study were to (1) compare the reliability of transcutaneous oximeter electrode power with the reliability of oxygen tension and (2) compare the relationship of the oximetry measures with exercise performance in claudicants. One hundred ten PAOD patients with stable claudication symptoms performed a treadmill test and had the following exercise measures obtained: foot transcutaneous oxygen tension, oximeter electrode heating power, exercise duration, and peak oxygen consumption. A subset of 30 patients were tested once per week over three successive weeks to assess the reliability of the oximetry measures. The coefficient of variation of foot transcutaneous oxygen tension at peak exercise was 32.8%, whereas the variability of the oximeter electrode heating power was only 5.1%. Oximeter electrode heating power at peak exercise was related to maximal claudication pain time (r = 0.44, P < 0.001) and peak oxygen consumption (r = 0.36, P < 0.001), whereas foot transcutaneous oxygen tension was not related to either (r = 0.15, P = 0.119; r = 0.13, P = 0.189; respectively). Thus, transcutaneous oximeter electrode heating power was six to seven times less variable than transcutaneous oxygen tension, and the oximeter electrode power at peak exercise was more closely related to exercise capacity. It is concluded that the measurement of transcutaneous oximeter electrode heating power during exercise is more reliable and better correlated with exercise capacity in PAOD patients with intermittent claudication than the measurement of transcutaneous oxygen tension.