Variability and reproducibility of transcutaneous oxygen tension measurements in the assessment of peripheral vascular disease.

Transcutaneous oxygen tension (TcPO2) was measured according to a standard protocol in 43 limbs from 23 subjects, by use of oxygen-sensing electrodes attached to the chest (at a single site) or dorsum of the foot (at proximal and distal sites, located 1-2 cm apart). With the subjects supine, distal foot TcPO2 differed from proximal by an average of +/- 7.4 mmHg, and in 80% of all limbs the differences were between -6 mmHg and +15 mmHg. The two TcPO2's were subsequently combined to yield a single "average" value for each foot. TcPO2 measurements were repeated twenty-four to forty-eight hours later; in the supine position the change in "average" foot TcPO2 from the first to second measurement was +/- 6.9 mmHg, and in 80% of limbs the changes were between -11 mmHg and +9 mmHg. Similar reproducibility data were also obtained for ankle/brachial blood pressure indices (ABIs), chest TcPO2, and foot TcPO2 during three minutes of leg elevation at 30 degrees. The authors conclude that: (1) TcPO2 measurements from adjacent areas on the dorsum of the foot usually differ by 20-25% or less and (2) the short-term reproducibility of TcPO2 between studies is comparable to that for ABIs.