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 TcPO ₂ 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 TcPO ₂'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 TCPO ₂ 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.