Measuring Transcutaneous Oxygenation to Validate the Duration Required to Achieve Electrode Equilibration.

OBJECTIVE: The transcutaneous oxygenation measurement (TCOM) system is useful in assessing tissue viability. There are no clear recommendations regarding the duration required for the electrode to equilibrate and reliably evaluate tissue oxygenation values. The objective of this study was to validate the duration required to achieve electrode equilibration in a clinical setting. METHODS: Minute-by-minute recordings using TCOM (TCOM3; Radiometer Medical ApS, Brønshøj, Copenhagen) were obtained for 82 limbs in 50 participants. Twenty-five limbs were in patients with peripheral vascular disease; 30 were in patients with no known peripheral vascular disease; and 27 were in healthy volunteers. Transcutaneous partial pressure of oxygen and carbon dioxide (TcPO2 and TcPCO2) were recorded over a 15-minute period. RESULTS: Participants' TcPO2 decreased and TcPCO2 increased over time. Both changed in a nonlinear fashion, eventually settling at an "equilibrium" where the measurements became stable. The difference in proportional change of TcPO2 between minutes 14 and 15 was 0.8%, and for TcPCO2was 2.9%. Changes in TCOM measurements over time were similar among the 3 groups. CONCLUSIONS: This is the first study to target minute-by-minute variation in TcPO2 and TcPCO2 measurements. Recording for a minimum of 15 minutes allows a reliable period for the TCOM electrode to equilibrate to record absolute values and determine wound healing potential.

Epidemiology and Outcomes of Abdominal Aortic Aneurysms in New Zealand: A 15-Year Experience at a Regional Hospital.

INTRODUCTION: Abdominal aortic aneurysms (AAA) account for approximately 400 deaths per year in New Zealand (NZ). Waikato Hospital caters to a diverse population comprising a high proportion of the indigenous Maori ethnic group considered to be at higher risk of mortality and morbidity. Despite these population factors, there is no screening program for AAA. The aim of this study was to further define the epidemiology and outcomes of AAA repairs in NZ to investigate the utility of implementing a population-specific screening program. METHODS: A retrospective study of all AAA repairs at Waikato Hospital between July 1996 and November 2010 was performed comparing long-term outcomes between Europeans and Maori considering acuity of presentation, age, gender, and type of repair. Perioperative and overall mortality data were obtained to generate Kaplan-Meier survival curves. RESULTS: 1,036 AAA repairs were performed. Maori presented younger (69.1 vs. 74.5, P < 0.001), had lower male predominance (1.6:1 vs. 3.5:1, P < 0.001), less elective repairs (44% vs. 67%, P < 0.001), and more ruptured AAA (RAAA) (40% vs. 21%, P < 0.001) despite the overall incidence of RAAA decreasing from 26% to 7.8% (P = 0.01). Maori had a lower postoperative 10-year survival compared to Europeans (17.4% vs. 36.5%, P < 0.001). There was an initial survival benefit for endoluminal over open repair but this converged at 4.9 years post repair. CONCLUSIONS: This study highlights the epidemiological trends and survival outcomes of AAA management in Maori and Europeans over 15 years. It provides further evidence supporting the consideration of a population-specific screening program in future.

Evaluation of hyperspectral imaging technology in patients with peripheral vascular disease.

BACKGROUND: Hyperspectral imaging technology is a novel method of using transcutaneous measurement of oxyhemoglobin (HT-Oxy) and deoxyhemoglobin (HT-Deoxy) concentrations to create a two-dimensional, color-coded "oxygen map." The aims of this study were to compare the use of a hyperspectral imaging device with the transcutaneous oxygen measurement (TCOM), ankle-brachial index (ABI), and severity of peripheral vascular disease (PVD) and to assess their correlations. METHODS: This prospective study recruited 294 participants divided into three distinct groups composed of healthy volunteers and patients with PVD. Patients underwent measurements of lower limbs at a standardized point over the head of the first metatarsal on the plantar aspect using the hyperspectral imaging device, generating four outputs including HT-Oxy, HT-Deoxy, oxygen saturation (HT-Sat), and skin temperature, and the TCOM system, generating transcutaneous partial pressure of oxygen (TcpO2) and carbon dioxide (TcpCO2). Demographic data, severity of PVD, ABI, and other pertinent information were obtained from both the participants and medical records. RESULTS: Interoperator reliability ranged from 86% to 94% across the four hyperspectral imaging device outputs, whereas intraoperator reliability ranged from 92% to 94%. The HT-Oxy, HT-Sat, TcpCO2, and ABI of the diseased limb correlated significantly with the severity of PVD. HT-Sat significantly correlated with TcpO2 (R = 0.19), TcpCO2 (R = -0.26), ABI (R = 0.42), and skin temperature (R = 0.56). HT-Deoxy also correlated with TcpCO2 (R = 0.27). CONCLUSIONS: This study demonstrates the reliability of hyperspectral imaging in comparison to TCOM, ABI, skin temperature, and severity of PVD in a series of patients. Its correlation to other established modalities and low interoperator and intraoperator variability could enable this modality to be a useful screening tool in PVD.