TcPO2 Measurements Research Articles

Great Saphenous Vein Arterialization in Patients with Severe Chronic Limb Threatening Ischemia: A Last Resort for Limb Salvage

ObjectiveIn one-fifth of patients with chronic limb-threatening ischemia there are no revascularisation options. In those cases, venous arterialisation could be a last resort for limb salvage. This study examines the clinical outcome of 17 patients, with non-healing wounds (Fontaine 4), who underwent Great Saphenous Vein (GSV) arterialisation leaving the distal saphenous side branches open and avoiding incisions in the lower leg and foot. MethodsIn this retrospective study all the patients who underwent GSV arterialisation between 1 January 2020 and 1 October 2023 were included. During the procedure, a small incision was made in the groin to identify the GSV and SFA. The GSV was detached from the deep venous system, the upper leg side branches were ligated, and the side branches distal to the knee joint were left open to create a pressure drop. Valvulotomy of the GSV down to the foot was performed in all patients. This approach does not necessitate the use of grafts or stents so that a serious infected foot can also be treated. For this study we have analysed the Limb salvage, wound healing, and mobility after treatment and observed pre and postoperative skin oxygenation over a one-year period. ResultsThis intervention resulted in a limb salvage rate of 46% and a secondary patency of 88% after one year in cases where amputation would have otherwise been necessary. Pre- and postoperative TcPO2 measurements indicated a gradual but consistent increase in skin oxygenation in 71% of the patients with a GSV larger than 3mm, underscoring the importance of future patient selection. All patients who successfully received arterialisation showed complete wound healing and improved mobility. ConclusionThis study introduced a promising approach to venous arterialisation in patients with severe CLTI who have no other treatment options, potentially impacting disease burden and quality of life significantly.

The Influence of Dapagliflozin on Foot Microcirculation in Patients with Type 2 Diabetes with and without Peripheral Arterial Disease-A Pilot Study.

The results of large cardiovascular studies indicate that SGLT-2 inhibitors may increase the risk of leg amputations. This study aims to investigate whether dapagliflozin therapy affects peripheral vascular oxygenation, i.e., microcirculation in the foot, as measured by transcutaneous oxygen pressure (TcPO2) in patients with type 2 diabetes (T2DM) and peripheral arterial disease (PAD) compared to patients without PAD. The patients with PAD were randomized into two groups. In the first 35 patients with PAD, dapagliflozin was added to the therapy; in the other 26 patients with PAD, other antidiabetic drugs were added to the therapy. Dapagliflozin was added to the therapy in all patients without PAD. TcPO2 measurement, Ankle Brachial Index (ABI), anthropometric measurements, and laboratory tests were performed. After a follow-up period of 119.35 days, there was no statistically significant difference in the reduction of mean TcPO2 values between the group with T2DM with PAD treated with dapagliflozin and the group with T2DM with PAD treated with other antidiabetic drugs (3.88 mm Hg, SD = 15.13 vs. 1.48 mm Hg, SD = 11.55, p = 0.106). Patients with control TcPO2 findings suggestive of hypoxia (TcPO2 < 40 mm Hg) who were treated with dapagliflozin had a clinically significant decrease in mean TcPO2 of 10 mm Hg or more (15.8 mm Hg and 12.90 mm Hg). However, the aforementioned decrease in TcPO2 was not statistically significantly different from the decrease in TcPO2 in the group with PAD treated with other diabetic medications (p = 0.226, p = 0.094). Based on the available data, dapagliflozin appears to affect tissue oxygenation in T2DM with PAD. However, studies with a larger number of patients and a longer follow-up period are needed to determine the extent and significance of this effect.

Transcutaneous oxygen tension-guided hyperbaric oxygen therapy for preventing skin necrosis after hyaluronic acid filler injections.

Hyaluronic acid (HA) fillers, popular for facial cosmetic enhancements, pose risks of vascular complications like skin necrosis due to arterial blockage, necessitating effective treatments such as hyperbaric oxygen therapy (HBOT). This study presents a series of cases where measurements of transcutaneous oxygen pressure (TcPO2) informed the application of HBOT for skin necrosis induced by HA. In cases 1 and 3, following the injection of HA, potential skin necrosis was observed. In addition to standard treatment, TcPO2 revealed values below 40mmHg, indicating tissue hypoxia. Treatment with HBOT increased TcPO2 levels to above 200mmHg, suggesting that HBOT could correct the hypoxia. Monitoring TcPO2 levels also aided in determining the optimal time to discontinue HBOT. In cases 2 and 4, patients received standard treatment, resulting in TcPO2 levels above 40mmHg, indicating adequate tissue oxygenation, and no additional HBOT was administered. All four patients mentioned above showed good clinical recovery. This study investigates the application of TcPO2 measurement technology in aiding decisions on whether to utilize HBOT in the treatment of complications arising from HA fillers, as well as in optimizing HBOT protocols.

Changes of transcutaneous oxygen pressure in compressed areas of surgical patients: A prospective study of influencing factors

ObjectiveTo compare the transcutaneous oxygen pressure (tcpO2) measurement values and changes in compressed areas of surgical patients before and after surgery and to explore the related factors influencing the tcpO2 changes before and after surgery. MethodsResearchers selected 100 patients who underwent elective surgery in a tertiary comprehensive hospital from November 2021 to September 2022. A self-designed general information questionnaire was used to collect patient general information and disease-related data, including gender, age, smoking and drinking history, hypertension, diabetes, local skin temperature and humidity, related biochemical indicators, and activities of daily living score. Researchers used a transcutaneous oxygen pressure meter to measure and record the tcpO2 of the compressed areas (sacrococcygeal area, scapula area, and heel area) before and after surgery. ResultsAmong the 100 patients, 37.00 % (37/100) developed type I/II pressure ulcers after surgery, and 30 patients (81.08 %) showed regression within 2 h after surgery. There was no statistically significant difference in the preoperative tcpO2 measurement values of the scapula and heel areas between the group with and without pressure ulcers, but the preoperative tcpO2 measurement value of the sacrococcygeal area in the group without pressure ulcers was higher than that in the group with pressure ulcers (P < 0.01). The factors affecting the preoperative tcpO2 measurement value of the sacrococcygeal area were smoking and surgical type. After surgery, the tcpO2 measurement values of the three areas in the group with pressure ulcers were significantly lower than those in the group without pressure ulcers (P < 0.01). Comparing the tcpO2 values of different areas, it was found that the tcpO2 value was lowest in the sacrococcygeal area, followed by the heel area, and the tcpO2 value in the scapula area was highest both before and after surgery (P < 0.01). The main factors affecting the postoperative tcpO2 measurement value were diabetes, Glassgow score, surgical time, and intraoperative red blood cell transfusion. ConclusionThe measurement of tcpO2 is related to the incidence of surgically acquired pressure ulcers, and this technology may become an important tool for quantitative assessment of the risk of pressure ulcers.

Liraglutide for Lower Limb Perfusion in People With Type 2 Diabetes and Peripheral Artery Disease

Peripheral artery disease (PAD) in diabetes may lead to diabetic foot ulcer and lower-extremities amputation. Glucagon-like peptide 1 receptor agonists have proven cardiovascular benefits in trials of people with type 2 diabetes at high cardiovascular risk. To examine the effect of liraglutide on peripheral perfusion measured as peripheral transcutaneous oxygen pressure (TcPo2) in individuals with type 2 diabetes and PAD. This open-label randomized clinical trial was conducted between February 1, 2021, and June 30, 2022, with a final follow-up on December 30, 2022, at University of Campania "Luigi Vanvitelli," Naples, Italy. Fifty-five individuals with type 2 diabetes, PAD, and TcPo2 between 30 and 49 mm Hg were included. Patients were randomized to receive 1.8 mg of subcutaneous liraglutide or conventional treatment of cardiovascular risk factors (control group) for 6 months. Coprimary outcomes were the change from baseline of peripheral perfusion between groups and the comparison of the proportion of individuals who reached 10% increase of TcPo2 from baseline in each group. Fifty-five participants (mean [SD] age, 67.5 [8.5] years; 43 [78%] male) were randomized (27 to the liraglutide group and 28 to the control group) and analyzed. Participants had a median (IQR) hemoglobin A1c level of 6.9% (6.5%-7.8%) and a mean (SD) TcPo2 of 40.3 (5.7) mm Hg. Transcutaneous Po2 increased over time in both groups, with significant differences favoring the liraglutide group after 6 months (estimated treatment difference, 11.2 mm Hg; 95% CI, 8.0-14.5 mm Hg; P < .001). The 10% increase of TcPo2 occurred in 24 participants (89%) in the liraglutide group and 13 (46%) in the control group (relative risk, 1.91; 95% CI, 1.26-2.90; P < .001). Compared with the control group, individuals in the liraglutide group had a significant reduction of C-reactive protein (-0.4 mg/dL; 95% CI, -0.7 to -0.07 mg/dL; P = .02), urinary albumin to creatinine ratio (-119.4 mg/g; 95% CI, -195.0 to -43.8 mg/g; P = .003), and improvement of 6-minute walking distance (25.1 m; 95% CI, 21.8-28.3 m; P < .001). In this randomized clinical trial of people with type 2 diabetes and PAD, liraglutide increased peripheral perfusion detected by TcPo2 measurement during 6 months of treatment. These results support the use of liraglutide to prevent the clinical progression of PAD in individuals with type 2 diabetes. ClinicalTrials.gov Identifier: NCT04881110.

In Association with Other Risk Factors, Smoking Is the Main Predictor for Lower Transcutaneous Oxygen Pressure in Type 2 Diabetes.

Type 2 diabetes mellitus (T2DM) significantly increases the risk of peripheral artery disease (PAD), and diabetes is the leading cause of nontraumatic amputations. This study investigated the risk factors for transcutaneous oxygen pressure (TcPO2) in T2DM, a noninvasive method to quantify skin oxygenation and the underlying microvascular circulation. The study included 119 T2DM patients (91 male/28 female). TcPO2 measurements were conducted with the Tina TCM4 Series transcutaneous monitor (Radiometer, Copenhagen, Sweden) and skin electrodes. Patients with TcPO2 < 40 mmHg were younger (p = 0.001), had significantly higher systolic blood pressure (SBP) (p = 0.023), glycated hemoglobin (HbA1c) (p = 0.013), fasting plasma glucose (fPG) (p = 0.038), total cholesterol (p = 0.006), LDL cholesterol (p = 0.004), and had more frequent smoking habits (p = 0.001) than those with TcPO2 ≥ 40 mmHg. The main predictors for the TcPO2 value (R2 = 0.211) obtained via stepwise regression analysis were age, smoking, SBP, HbA1c, fPG, and total and LDL cholesterol. Among all the listed predictors, smoking, HbA1c, and LDL cholesterol were found to be the most significant, with negative parameter estimates of -3.051310 (p = 0.0007), -2.032018 (p = 0.0003), and -2.560353 (p = 0.0046). The results of our study suggest that in association with other risk factors, smoking is the main predictor for lower TcPO2 in T2DM.

Use of consecutive transcutaneous oxygen measurement when assessing the need for revascularization and association with the outcomes of ischemic diabetic ulcers.

This study compared the ankle-brachial index (ABI) with transcutaneous oxygen pressure (TcPO2 ) in assessing peripheral vascular disease (PVD) prevalence in 100 diabetic foot ulcer (DFU) patients. Patients were categorized into vascular or nonvascular reconstruction groups and underwent both ABI and TcPO2 measurements four times over 6 months. Predictive validity for PVD diagnosis was analysed using the area under the receiver-operating characteristic curve (AUC). The study found TcPO2 to be a superior predictor of PVD than ABI. Among the DFU patients, 51 with abnormal TcPO2 values underwent vascular reconstruction. Only TcPO2 values showed significant pretreatment differences between the groups and increased post-reconstruction. These values declined over a 6-month follow-up, whereas ABI values rose. For those with end-stage renal disease (ESRD), TcPO2 values saw a sharp decrease within 3 months. Pre-reconstruction TcPO2 was notably lower in amputation patients versus limb salvage surgery patients. In conclusion, TcPO2 is more effective than ABI for evaluating ischemic limb perfusion and revascularization necessity. It should be prioritized as the primary follow-up tool, especially for ESRD patients.

Analyses of transcutaneous oxygen pressure values stratified for foot angiosomes to predict diabetic foot ulcer healing

AimsPrevious research suggested that diabetic foot ulcer (DFU) location could affect transcutaneous oxygen pressure (TcPO2) values following the angiosome concept. Up to our knowledge no studies have yet analyzed if the location of a diabetic foot ulcer can be a confounding factor that modifies TcPO2 values. The primary aim of this study was to compare the potential healing prognosis of TcPO2 differentiated for diabetic foot ulcers in different angiosome locations. Methodsa 2-years observational cohort prospective study was performed in 81 patients with diabetic foot ulcers. Transcutaneous oxygen pressure measurements were performed at baseline by placing the electrode on two different angiosomes: dorsal zone of the foot (dorsalis pedis angiosome) and between the navicular bone and the tibial malleolus (posterior tibial angiosome). The main outcome was establishing the effectiveness of TcPO2 measurements (dorsalis pedis angiosome and posterior tibial angiosome) for predicting DFU healing. ResultsTranscutaneous oxygen pressure probe placed in the dorsum of the foot (dorsalis pedis angiosome) yielded a sensitivity (S) of 95 % and specificity (SP) of 73 %, and an area under the curve (AUC) of 0.902 (p < 0.001 [0.84–0.96]) for ulcers located in the forefoot and toes; while TcPO2 placed in the posterior tibial angiosome yielded an S of 100 % and SP of 85 % and an AUC of 0.894 (p < 0.001 [0-822-0.966]) for DFU located in the midfoot and heel. ConclusionThis study suggests that angiosome-guided TcPO2 contributes to a prognosis of successful foot ulcer healing.

Application of deep oscillation therapy in the treatment of peripheral arterial diseases

Intermittent claudication is a common symptom of peripheral arterial disease, affecting up to 50% of patients over the age of 50, which is characterized by pain, discomfort, and cramping in the leg muscles during physical activity. Intermittent claudication is a common symptom of lower extremity arterial disease (LEAD), which significantly impacts patients’ quality of life and drives healthcare costs. Current treatments for intermittent claudication are often inadequate, leading to a need for more effective treatments. Developing new treatments is critical to improve outcomes for patients and address the public health implications of LEAD. This study’s aim was to present the impact of comprehensive physiotherapy, conducted independently, with the supervision of a physiotherapist, for 14 weeks, on a patient with intermittent claudication caused by peripheral arterial disease. The therapy included bicycle training in a form of physical therapy at home, combined with deep oscillation therapy. Deep oscillation therapy involved the use of an electrostatic field with a frequency of 5 to 250 Hz. The field was applied following the lymphatic drainage methodology. In the discussed case, a statistically significant and favourable increase in the measured variables was observed, such as the increase of bone-brachial index from 0.65 to 0.8, the increase of tissue perfusion, measured by laser Doppler flowmetry, from 12.3% to 61%, depending on the measurement site, and the increase in pain-free walking distance by 451%. TcPO2 measurement in the affected leg increased from 31 to 48 mmHg. The use of physical therapy at home combined with deep oscillation showed improvements in pain-free walking distance, Ankle Brachial Index, and other measures in patients with peripheral arterial disease. Deep oscillation therapy demonstrated potential analgesic effects but also raised concerns about possible nerve damage. The study indicated that physical therapy at home might serve as an alternative to supervised exercise therapy, but it had limitations like a small sample size and lack of direct comparisons.

Examination of Lower Limb Microcirculation in Diabetic Patients with and without Intermittent Claudication.

Intermittent claudication is a frequent complaint in lower extremity artery disease, but approximately two thirds of patients are asymptomatic, most of which are diabetic patients. Non-invasive angiological and microrheological tests on diabetic subjects with and without intermittent claudication were performed in the present study. In total, 98 diabetic patients were included and divided into two groups: 20 patients (63.5 ± 8.8 years, 55% men, 45% women) had intermittent claudication, 78 patients (65.5 ± 9.3 years, 61.5% men, 38.5% women) were asymptomatic. Hand-held Doppler ultrasound examination, transcutaneous tissue partial oxygen pressure (tcpO2) measurement, Rydel-Seiffer tuning fork tests, and 6-min walk tests were performed, and erythrocyte aggregation was investigated. Ankle-brachial index (p < 0.02) and tcpO2, measured during provocation tests (p < 0.003) and the 6-min walk test (p < 0.0001), significantly deteriorated in the symptomatic group. A higher erythrocyte aggregation index and faster aggregate formation was observed in claudication patients (p < 0.02). Despite the statistically better results of the asymptomatic group, 13% of these patients had severe limb ischemia based on the results of tcpO2 measurement. Claudication can be associated with worse hemodynamic and hemorheological conditions in diabetic patients; however, severe ischemia can also develop in asymptomatic subjects. Non-invasive vascular tests can detect ischemia, which highlights the importance of early instrumental screening of the lower limbs.

Convenient prediction of TcPO2 level using machine learning techniques with the PPG signal’s characteristic features

BackgroundTranscutaneous oxygen tension (TcPO2) is a noninvasive method for assessing the oxygen supply of the skin in clinics. However, it is difficult to deploy broadly in primary care settings due to its high cost and time-consuming. This study proposed a fast and inexpensive technique for predicting TcPO2 using the characteristic features of the photoplethysmography (PPG) signals and various machine learning algorithms. MethodsThe toe PPG signals of 149 subjects were collected, and 12 characteristic features were extracted according to contour analysis, followed by TcPO2 measurements. TcPO2 measurements were performed on the dorsum of the foot by PeriFlux 6000 TcPO2 system. In addition to PPG features, physiological parameters were also taken into account. A variety of machine learning regression approaches, including extreme gradient boost (XGBoost), random forest regression (RFR), support vector machine regression (SVR) and Ridge regression (Ridge), were used to predict TcPO2 levels. To evaluate the performance of machine learning algorithms, different performance indicators such as mean absolute error (MAE), root mean square error (RMSE), mean absolute percentage error (MAPE) and correlation coefficient were employed. Correlation analysis and Bland-Altman plot analysis were performed to visualize the data. ResultsXGBoost outperformed the other three regression models in predicting TcPO2 (R = 0.835, MAE = 5.23 mmHg, RMSE = 6.87 mmHg, MAPE = 9.99%). Reflection index, diabetes, duration of diabetes, heart rate, crest time, the time between the systolic and diastolic peaks (ΔT) were the top six contributions to TcPO2 prediction in the XGBoost model. The PPG characteristic features play a dominant role in TcPO2 estimation. Diabetes and duration of diabetes were also significant factors in TcPO2 prediction. ConclusionsWe compared four machine learning methods for TcPO2 prediction. The XGBoost model had the best predictive performance of all the algorithms investigated and could be used to forecast TcPO2 values. The TcPO2 prediction model based on PPG signal reduces the cost and shortens the measurement time of TcPO2, providing significant benefits for primary care.

Laser Doppler Flowmetry Combined with Spectroscopy to Determine Peripheral Tissue Perfusion and Oxygen Saturation: A Pilot Study in Healthy Volunteers and Patients with Peripheral Arterial Disease.

Background: In this study, we assessed the ability of the EPOS system (Perimed AB, Järfälla, Stockholm, Sweden) to detect differences in tissue perfusion between healthy volunteers and patients with peripheral arterial disease (PAD) with different severity of disease. Methods: This single-center prospective pilot study included 10 healthy volunteers and 20 patients with PAD scheduled for endovascular therapy (EVT). EPOS measurements were performed at rest at 32 °C and 44 °C, followed by transcutaneous oxygen pressure (TcPo2) measurements. The measurements were performed on the dorsal and medial side of the foot, as well as the lateral side of the calf. EPOS parameters included hemoglobin oxygen saturation (HbSo2) and speed-resolved red blood cell (RBC) perfusion. Results: HbSo2 at 44 °C was significantly different between the three groups for all measurement locations. The overall speed-resolved RBC perfusion at 44 °C was statistically significant between the groups on the dorsal and medial side of the foot but not on the calf. TcPo2 values were not significantly different between the three groups. Conclusions: This study demonstrates that the EPOS system can depict differences in tissue perfusion between healthy volunteers, patients with Fontaine class IIb PAD, and those with Fontaine class III or IV PAD but only after heating to 44 °C.

The Infected Diabetic Foot: A Microbiological Analysis

Category:Basic Sciences/Biologics; DiabetesIntroduction/Purpose:Diabetic foot infections show increasing prevalence. Their therapy is time consuming and expensive. Standardized antibiotic treatments do not exist. Suboptimal antibiotic therapy increases the morbidity of the patient. The aim of the study was to evaluate the dominating bacterial colonization in the diabetic foot. Furthermore we evaluated the changes of the colonization during surgical and antibiotic treatment and the efficiency of the therapy.Methods:The study included 100 patients with a diabetic foot syndrome and a pedal ulcer. Ulcers were classified according to Wagner Classification. HbA1c, CRP and patients BMI were documented. All patients underwent an angiologic investigation with arterial doppler ultrasonography and TcpO2 measurement. An MRI of the affected foot was performed to rule out osteomyelitis. All patients underwent surgical and antibiotic treatment. Surgery included debridement, abscess drainage, VAK therapy, bony resection, minor amputation, resection arthroplasty, Helal osteotomies. Osteomyelitis was pathologically verified. Microbiological results of superficial and deep smears, which were taken during the surgical therapy were analyzed. The antibiotic treatment was adapted to the bacterial resistance.Results:The duration of antibiotic treatment varied from 1 to 136 days (Mean:19.6 days, SD:17.3 ). The mean number of surgical interventions was 2.6. The dominating initial antibiotic treatment was Clindamycin/ Cefuroxim (48%) followed by Clindamycin (11%),Cefuroxim (7%), Clindamycin/ Ciprofloxacin (6%), Tazobactam (3%). The dominating bacteria were gram +. The difference of the percentage distribution compared to the gram- bacteria was statistically significant. The only significant percentage change of the antibiotic treatment was seen after the first surgical intervention, when the initial antibiotic treatment was significantly more effective against gram - bacteria. A change of the antibiotic treatment was seen with 1. Clindamycin / Ciprofloxacin in 66%, 2. Tazobactam in 67%, 3.Clindamycin in 36% and Clindamycin/ Cefuroxim in 35%.Conclusion:The dominating bacteria of the infected diabetic feet were gram +. The initial i.v. antibiotic treatment with Clindamycin/ Cefuroxim was effective in 66%. An optimization of the initial antibiotic treatment with greater focus on the gram + bacteria seems to be necessary.

Validation of a new combined transcutaneous tcPCO2 and tcPO2 sensor in children in the operating theater.

BackgroundArterial blood gas analysis is the gold standard for monitoring of PaCO2 and PaO2 during mechanical ventilation. However, continuous measurements would be preferred. Transcutaneous sensors continuously measure blood gases diffusing from the locally heated skin. These sensors have been validated in children mostly in intensive care settings. Accuracy in children during general anesthesia is largely unknown.AimsWe conducted a study in children undergoing general anesthesia to validate the use and to determine the accuracy of continuous transcutaneous measurements of the partial pressures of PCO2 (tcPCO2) and PO2 (tcPO2).MethodsA prospective observational study in a tertiary care pediatric hospital in The Netherlands, from April to October 2018, in children aged 0–18 years undergoing general anesthesia. Patients were included when endotracheally intubated and provided with an arterial catheter for regular blood sampling. Patients with a gestational age <31 weeks, burn victims, and patients with skin disease were excluded. TcPCO2 and tcPO2 measurements were performed with a SenTec OxiVenT™ sensor (SenTec AG). Accuracy was determined with an agreement analysis between arterial and transcutaneous PCO2 and PO2 values, and between arterial and endtidal PCO2 (etCO2) values, according to Bland and Altman, accounting for multiple measurements per subject.ResultsWe included 53 patients (median age 4.1 years, IQR 0.7–14.4 years) and retrieved 175 samples. TcPCO2‐PaCO2 agreement analysis provided a bias of 0.06 kPa (limits of agreement (LOA) −1.18 to 1.31), the etCO2‐PaCO2 agreement showed a bias of −0.31 kPa (LOA −1.38 to 0.76). Results of the tcPO2‐PaO2 agreement showed a bias of 3.40 to 0.86* (mean tension) kPa.ConclusionsThis study showed good agreement between PaCO2 and tcPCO2 in children of all ages during general anesthesia. Both transcutaneous and endtidal CO2 measurements showed good accuracy. TcPO2 is only accurate under 6 months of age.

Application of Intelligent Monitoring of Percutaneous Partial Oxygen Pressure in Evaluating the Evolution of Scar Hyperplasia.

The study aimed to investigate the dynamic changes of percutaneous partial oxygen pressure during the development and evolution of a hypertrophic scar. Twenty cases of hypertrophic scar patients at different stages were selected. A percutaneous oxygen monitor was used to measure oxygen partial pressure in the scar and normal skin tissue at 14, 30, 60, and 90 days after surgery. The changes of oxygen partial pressure, tissue structure, HIF-1α, and VEGF expression in the scar tissue were observed, and the correlation was analyzed. In the scar maturation process, with the prolongation of time, the partial oxygen pressure in the tissue increased gradually. The expression intensity of HIF-1α and VEGF decreased gradually, HIF-1α was positively correlated with VEGF (r = 0.98, P < 0.01), there was a negative correlation between oxygen partial pressure and HIF-1 α expression (r = −0.92, P < 0.01), and it was negatively correlated with VEGF (r = −0.88, P < 0.01). TcPO2 measurement can be used to assess scar maturity; HIF-1 α and VEGF may play an essential role in regulating partial oxygen pressure in the scar tissue.

Effect of electrode temperature on measurements of transcutaneous carbon dioxide partial pressure and oxygen partial pressure in very low birth weight infants.

To evaluate the accuracy and safety of measurements of transcutaneous carbon dioxide partial pressure (TcPCO2) and transcutaneous oxygen partial pressure (TcPO2) at electrode temperatures lower than the value used in clinical practice in very low birth weight infants. A total of 45 very low birth weight infants were enrolled. TcPCO2 and TcPO2 measurements were performed in these infants. Two transcutaneous monitors were placed simultaneously for each subject. One electrode was set and maintained at 42℃ used in clinical practice for neonates (control group), and the other was successively set at 38℃, 39℃, 40°C, and 41℃ (experimental group). The paired t-test was used to compare the measurement results between the groups. A Pearson correlation analysis was used to analyze the correlation between the measurement results of the experimental group and control group, and between the measurement results of experimental group and arterial blood gas parameters. There was no significant difference in TcPCO2 between each experimental subgroup (38-41℃) and the control group. TcPCO2 in each experimental subgroup (38-41℃) was strongly positively correlated with TcPCO2 in the control group (r>0.9, P<0.05) and arterial carbon dioxide partial pressure (r>0.8, P<0.05). There were significant differences in TcPO2 between each experimental subgroup (38-41℃) and the control group (P<0.05), but TcPO2 in each experimental subgroup (38-41℃) was positively correlated with TcPO2 in the control group (r=0.493-0.574, P<0.05) and arterial oxygen partial pressure (r=0.324-0.399, P<0.05). No skin injury occurred during transcutaneous measurements at all electrode temperatures. Lower electrode temperatures (38-41℃) can accurately measure blood carbon dioxide partial pressure in very low birth weight infants, and thus can be used to replace the electrode temperature of 42°C. Transcutaneous measurements at the lower electrode temperatures may be helpful for understanding the changing trend of blood oxygen partial pressure.

Intraprocedural Transcutaneous Oxygen Pressure and Systolic Toe Pressure Measurements During and After Endovascular Intervention in Patients with Chronic Limb Threatening Ischaemia

The aim of this study was to evaluate changes in transcutaneous oxygen pressure (tcpO2) and systolic toe pressure (TP) during endovascular intervention. This was a single centre prospective, non-randomised, observational feasibility study. Patients with chronic limb threatening ischaemia (CLTI) due to infrainguinal disease scheduled for endovascular treatment were included between March 2018 and December 2019. TcpO2 was measured continuously bilaterally at foot level throughout the procedure and at follow up. Specific time points during the intervention were chosen for comparison to baseline (before arterial puncture): average tcpO2 level five minutes prior to percutaneous transluminal angioplasty (PTA); 10 minutes after PTA; and at completion. Bilateral TP was recorded using laser Doppler flowmetry before arterial puncture, at completion, and at clinical follow up. Angiograms were analysed for successful revascularisation and vascular lesions classified according to the Global Limb Anatomical Scoring System (GLASS). Rutherford and WIfI (Wound, Ischaemia, and foot Infection) classifications were registered, as well as clinical outcome. Twenty-one patients completed the study. Completion angiograms showed inline flow to the foot in all but two patients. Median time to follow up was 10 weeks (range 8 - 13 weeks) and all patients except one improved clinically. TcpO2 decreased during the initial stage of the intervention, from before arterial puncture to five minute average before PTA (p < .001) and did not recover to above baseline values at the end of intervention. TcpO2 increased significantly at follow up (p < .001). TP increased statistically significantly during intervention (p < .001) and at follow up (p < .001) compared with baseline. TcpO2 and TP measurements are safe and feasible non-invasive techniques for haemodynamic monitoring during endovascular revascularisation. TP increased significantly immediately after completion of the successful intervention, whereas tcpO2 did not. Both TP and tcpO2 demonstrated a significant increase at the 10 week follow up.

Reliability assessment of hyperspectral imaging with the HyperView™ system for lower extremity superficial tissue oxygenation in young healthy volunteers

Purpose: Hyperspectral imaging (HSI) is a noninvasive spectroscopy technique for determining superficial tissue oxygenation. The HyperView™ system is a hand-held camera that enables perfusion image acquisition. The evaluation of superficial tissue oxygenation is warranted in the evaluation of patients with peripheral arterial disease. The aim was to determine the reliability of repeated HSI measurements. Methods: In this prospective cohort study, HSI was performed on 50 healthy volunteers with a mean age of 26.4 ± 2.5 years, at the lower extremity. Two independent observers performed HSI during two subsequent measurement sessions. Short term test–retest reliability and intra- and inter-observer reliability were determined, and generalizability and decision studies were performed. Transcutaneous oxygen pressure (TcPo2) measurements were also performed. Results: The short term test–retest reliability was good for the HSI values determined at the lower extremity, ranging from 0.72 to 0.90. Intra- and inter-observer reliability determined at different days were poor to moderate for both HSI (0.24 to 0.71 and 0.30 to 0.58, respectively) and TcPo2 (0.54 and 0.56, and 0.51 and 0.31, respectively). Reliability can be increased to >0.75 by averaging two measurements on different days. Conclusion: This study showed good short term test–retest reliability for HSI measurements, however low intra- and inter-observer reliability was observed for tissue oxygenation measurements with both HSI and TcPo2 performed at separate days in young healthy volunteers. Reliability of HSI can be improved when determined as a mean of two measurements taken on different days.

What Is Currently the Role of TcPO2 in the Choice of the Amputation Level of Lower Limbs? A Comprehensive Review.

Some patients still require major amputation for lower extremity peripheral arterial disease treatment. The purpose of pre-operative amputation level selection is to determine the most distal amputation site with the highest healing probability without re-amputation. Transcutaneous oximetry (TcPO2) can detect viable tissue with the highest probability of healing. Several factors affect the accuracy of TcPO2; nevertheless, surgeons rely on TcPO2 values to determine the optimal amputation level. Background about the development of TcPO2, methods of measurement, consequences of lower limb amputation level, and the place of TcPO2 in the choice of the amputation level are reviewed herein. Most of the retrospective studies indicated that calf TcPO2 values greater than 40 mmHg were associated with a high percentage of successful wound healing after below-knee-amputation, whereas values lower than 20 mmHg indicated an increased risk of unsuccessful healing. However, a consensus on the precise cut-off value of TcPO2 necessary to assure healing is missing. Ways of improvement for TcPO2 performance applied to the optimization of the amputation-level are reported herein. Further prospective data are needed to better approach a TcPO2 value that will promise an acceptable risk of re-amputation. Standardized TcPO2 measurement is crucial to ensure quality of data.

Skin oxygenation impairment is associated with increased total cholesterol level in children with short-lasting type 1 diabetes mellitus.

IntroductionTranscutaneous oxygen pressure (tcPO2) is a non-invasive method of measuring skin oxygenation that may reflect its superficial perfusion. Skin microvasculature may be impaired in patients with late onset of type 1 diabetes (DM1). However, its condition in children has not been fully determined.AimTo compare tcPO2 in children with short-lasting non-complicated DM1 and age-matched healthy controls with regard to concomitant vascular risk factors.Material and methodsThe study group consisted of 51 paediatric patients aged 14.9 (8.4–18.0) years with short-lasting DM1 without clinical evidence of diabetic micro- or macroangiopathy and 28 control subjects aged 14.8 (11.3–17.7) years. TcPO2 was tested prior, during and after applying post-occlusive reactive hyperaemia (PORH) test in standardized conditions. Biochemical parameters were assessed and then compared between the groups.ResultsTcPO2 at maximal ischemia during PORH was higher in the DM1 patients than in healthy controls (2.4 (0.7–18.8) vs. 1.6 (0.4–12.0), p = 0.002). No differences were found regarding the tcPO2 measurements recorded prior to ischemia or after recovery. In DM1, concentrations of total cholesterol, triglycerides, HbA1c and TSH were significantly higher than in healthy controls. The fT4 levels were significantly lower in the DM1 group. After adjusting for lipid levels, no differences in tcPO2 were found, and a multivariate analysis showed the cholesterol levels have a significant impact on tcPO2 response to maximal ischemia.ConclusionsOur results indicate that increased lipid levels are responsible for the impaired skin response to ischemic stimuli in short-lasting DM1. This supports the importance of aggressive lipid control in prevention of early onset microangiopathy in those patients.