Measuring systolic ankle and toe pressure using the strain gauge technique – a comparison study between mercury and indium-gallium strain gauges

Abstract

Background. Measurement of the ankle and toe pressures are often performed using a plethysmograph, compression cuffs and a strain gauge. Usually, the strain gauge contains mercury but other alternatives exist. From 2014, the mercury-containing strain gauge will no longer be available in the European Union. The aim of this study was to compare an indium-gallium strain gauge to the established mercury-containing strain gauge. Methods. Consecutive patients referred to the Department of Clinical Physiology and Nuclear Medicine at Bispebjerg and Frederiksberg Hospitals for measurements of systolic ankle and toe pressures volunteered for the study. Ankle and toe pressures were measured twice with the mercury and the indium-gallium strain gauge in random order. Comparison of the correlation between the mean pressure using the mercury and the indium-gallium device and the difference between the two devices was performed for both toe and ankle level. Results. A total of 53 patients were included (36 male). Mean age was 69 (range, 45–92 years). Mean pressures at toe and ankle level with the mercury and the indium-gallium strain gauges were 77 (range, 0–180) mm Hg and 113 (range, 15–190) mm Hg, respectively. Comparison between the mercury and the indium-gallium strain gauge showed a difference in toe blood pressure values of − 0.7 mm Hg (SD: 7.0). At the ankle level, a difference of 2.0 mm Hg (SD: 8.6) was found. Conclusion. The two different devices agree sufficiently in the measurements of systolic ankle and toe pressure for the indium-gallium strain gauge to replace the mercury strain gauge.