Reliability of transcutaneous oxygen tension (TcPO2) measurements in elderly normal subjects

This study was conducted to evaluate the reliability of TcPO2 measurements in a well characterized group of 10 elderly normal subjects with an age distribution typical for the population with peripheral vascular disease (PVD) and amputation. The TcPO2 values were obtained on three separate occasions at 2-week intervals at seven anatomic sites commonly measured in patients with PVD. The TcPO2 values were comparable to those previously reported for similar sites in normal elderly subjects. Measurement to measurement variation averaged 1.1 kPa (8 mmHg) for a coefficient of variation (CV) of 14.4%. Confidence intervals ranging from 2.1 kPa (16 mmHg) above a single TcPO2 value to 2.1 kPa (16 mmHg) below were necessary to contain the true value 95% of the time. While TcPO2 measurement is assuming an important role in the evaluation of disease states in both paediatric and adult medicine, our observations emphasize the importance of using such measurements as an adjunct in clinical decision making and not basing such decisions on a single TcPO2 value alone. The size of the confidence intervals can be reduced substantially for a given site by taking the mean of two or more TcPO2 measurements taken at separate times.