Transcutaneous oxygen tension: a useful predictor of ulcer healing in critical limb ischaemia

Objective: To investigate the threshold of transcutaneous oxygen tension (TcPO2) values in predicting ulcer healing in patients with critical limb ischaemia in a prospective study. Method: 50 patients suffering from critical limb ischaemia with chronic ischemic ulcers or gangrenous toes were enrolled in this study between January and December 2008. Their demographic data and ankle brachial pressure index (ABPI) were collected. Baseline ulcers were measured with a wound measurement system (Visitrak, Smith & Nephew). TcPO2 was measured at rest in the supine position and with 30 degrees leg elevation. The patients with infective and ischemic ulcers underwent debridement and gangrenous toes were amputated. Ulcer outcome was classified as either: (1) A healing ulcer, showing good epithelialisation or granulation at both base and edges, or a decrease in ulcer area during the study; or (2) A non-healing ulcer, showing poor granulation tissue formation or a pale base and necrotic edges, or deterioration in an ischaemic ulcer. Results: The mean age of the patients was 67.6 +/- 10.8 years. The most common risk factor was hypertension (90%). Mean ABPI was 0.75 +/- 0.39. 13 patients (26%) had a TcPO2 of less than 20mmHg, of which none showed any improvement in ulcer healing (p<0.001). 15 patients (30%) had a TcPO2 of more than 40mmHg, of which all progressed to complete ulcer healing (p<0.001). In the borderline group (20-40mmHg, 22 patients, 44%), 10 patients (45%) had a TcPO2 drop of <= 10mmHg with 30 degrees leg elevation, of which 8 achieved complete ulcer healing (p<0.001). 12 patients (55%) had a TcPO2 drop of >10mmHg with 30 degrees leg elevation, of which 11 showed no ulcer healing (p<0.001). Conclusion: TcPO2 measurement is an accurate, non-invasive, and good predictor of ischemic ulcer healing, for cut-off TcPO2 values of less than 20mmHg and more than 40mmHg. In addition, the leg elevation method for TcPO2 might provide an important adjunct in the assessment of patients with borderline values.