The use of elevation and dependency to enhance the predictive value of transcutaneous oxygen pressure measurements in the assessment of foot amputation healing

Abstract

Objective: To determine whether transcutaneous oxygen pressure (TcPO₂) measurements taken while the patient is supine, with the limb elevated, and/or with the limb dependent (below the level of the heart) can be used to predict the healing of partial-foot amputations.

Design: Retrospective, observational study.

Setting: A tertiary care, outpatient, multidisciplinary practice.

Patients: A total of 373 patients who had supine, elevated, and dependent TcPO₂ measurements and underwent partial-foot amputation were identified by the use of a search of the Surgical Index database for procedure crossed with an electronic note retrieval database search.

Intervention: None.

Main outcome measurements: Amputation site healing.

Results: For patients who underwent partial-foot amputation and healed in 3 months, the mean TcPO₂ value was 40.37 torr (SD 0.09); in the delayed-healing group, the mean TcPO₂ value was 28.36 torr (SD 1.16); in the nonhealed group, the mean TcPO₂ value was 22.79 torr (SD 1.14; P < .01 for each torr value). For the subgroup of patients with a TcPO₂ greater than 20 torr and less than 40 torr, in whom healing is more difficult to predict, the use of maneuvers of elevation and dependency increased both the positive and negative predictive values (56% and 74%, respectively) of the test compared with the use of supine measurements in isolation.

Conclusion: Supine TcPO₂ measurements can help predict amputation site healing in patients with ischemic wounds who require a partial-foot amputation. For the subgroup of patients with TcPO₂ values greater than 20 torr and less than 40 torr, adding TcPO₂ measurements with the limb elevated and/or dependent further improves the posttest probability and predictive values of the TcPO₂ measurements.