Transcutaneous oximetry measurements of the leg: comparing different measuring equipment and establishing values in healthy young adults

Abstract

Introduction: Transcutaneous oximetry measurement (TCOM) is a non-invasive method of determining oxygen tension at the skin level using heated electrodes.

Aim: To compare TCOM values generated by different machines and to establish lower limb TCOM values in a cohort of healthy individuals younger than 40 years of age.

Method: Sixteen healthy, non-smoking volunteers aged 18 to 39 years were recruited. TCOM was obtained at six locations on the lower leg and foot using three different Radiometer machines. Measurements were taken with subjects lying supine, breathing air.

Results: Except for one sensor site, there were no statistical differences in measurements obtained by the different TCOM machines. There was no statistical difference in measurements comparing left and right legs. Room air TCOM values for the different lower leg sites were (mean (SD) in mmHg): lateral leg 61.5 (9.2); lateral ankle 61.1 (9.7); medial ankle 59.1 (10.8); foot, first and second toe 63.4 (10.6); foot, fifth toe 59.9 (13.2) and plantar foot 74.1 (8.8). The overall mean TCOM value for the lower limb was 61 (10.8; 95% confidence intervals 60.05-62.0) mmHg.

Conclusion: Lower-leg TCOM measurements using different Radiometer TCOM machines were comparable. Hypoxia has been defined as lower-leg TCOM values of less than 40 mmHg in non-diabetic patients and this is supported by our measurements. The majority (96.9%) of the lower leg TCOM values in healthy young adults are above the hypoxic threshold.

Keywords: Hyperbaric oxygen therapy; Patient monitoring; Standards; Wounds.

Figures

TCOM leg sensor placement: sensor 1 – 10 cm distal to the lateral femoral epicondyle; sensor 2 – 5 cm proximal to the anterior aspect of the lateral malleolus; sensor 3 – 5 cm proximal from the centre of the medial malleolus; sensor 4 − dorsum of the foot between the first and second metatarsal heads away from any obvious veins; sensor 5 − dorsum of the foot proximal to the head of the fifth metatarsal; sensor 6 − plantar first metatarsal area (proximal to the fat pad at the base of the great toe)

TCOM leg sensor placement: sensor 1 – 10 cm distal to the lateral femoral epicondyle; sensor 2 – 5 cm proximal to the anterior aspect of the lateral malleolus; sensor 3 – 5 cm proximal from the centre of the medial malleolus; sensor 4 − dorsum of the foot between the first and second metatarsal heads away from any obvious veins; sensor 5 − dorsum of the foot proximal to the head of the fifth metatarsal; sensor 6 − plantar first metatarsal area (proximal to the fat pad at the base of the great toe)

Figure 2

Combined TCOM readings for all three models of oximetry devices at each monitoring site on the lower leg of 16 healthy subjects