TcPO2 Levels Research Articles

Midterm Outcomes From a Pilot Study of Percutaneous Deep Vein Arterialization for the Treatment of No-Option Critical Limb Ischemia

Purpose: To report the initial clinical experience with percutaneous deep vein arterialization (PDVA) to treat critical limb ischemia (CLI) via the creation of an arteriovenous fistula. Methods: Seven patients (median age 85 years; 5 women) with CLI and no traditional endovascular or surgical revascularization options (no-option CLI) were recruited in a pilot study to determine the safety of PDVA. All patients were diabetic; 4 had Rutherford category 6 ischemia. Six were classified at high risk of amputation based on the Society for Vascular Surgery WIfI (wound, ischemia, and foot infection) classification. The primary safety endpoints were major adverse limb events and major adverse coronary events through 30 days and serious adverse events through 6 months. Secondary objectives included clinical efficacy based on outcome measures including thermal measurement, transcutaneous partial pressure of oxygen (TcPO2), clinical improvement at 6 months, and wound healing. Results: The primary safety endpoints were achieved in 100% of patients, with no deaths, above-the-ankle amputations, or major reinterventions at 30 days. The technical success rate was 100%. Two myocardial infarctions occurred within 30 days, each with minor clinical consequences. All patients demonstrated symptomatic improvement with formation of granulation tissue, resolution of rest pain, or both. Complete wound healing was achieved in 4 of 7 patients and 5 of 7 patients at 6 and 12 months, respectively, with a median healing time of 4.6 months (95% confidence interval 84–192). Median postprocedure peak TcPO2 was 61 mm Hg compared to a preprocedure level of 8 mm Hg (p=0.046). At the time of wound healing, 4 of 5 of patients achieved TcPO2 levels of >40 mm Hg. There were 2 major amputations, 1 above the knee after PDVA thrombosis and 1 below the knee for infection. Three patients died of causes unrelated to the procedure or study device at 6, 7, and 8 months, respectively. Limb salvage was 71% at 12 months. Conclusion: PDVA is an innovative approach for treating no-option CLI and represents an alternative option for the “desert foot,” potentially avoiding major amputation. Our results demonstrate its safety and feasibility, with promising early clinical results in this small cohort.

Pressure signatures can influence tissue response for individuals supported on an alternating pressure mattress

Prolonged mechanical loading can lead to the breakdown of skin and underlying tissues which can, in turn, develop into a pressure ulcer. The benefits of pressure relief and/or redistribution to minimise risk have been well documented. Manufacturers have developed alternating air pressure mattresses (APAMs) to provide periodic relief for individuals on prolonged bed-rest. The present study describes the development of a control system, termed Pneumatic Manager which can vary the signature of an APAM, namely its pressure amplitude, cell profile and cycle period. An experimental array was designed to investigate the effects of varying these parameters, particularly with respect to its ability to maintain skin viability in a group of five healthy volunteers lying in a supine position. Transcutaneous gas (TcPO2/TcPCO2) tensions at the sacrum were monitored. In addition, pressures and microclimate parameters at the loaded support interface were also measured.In the majority of test conditions the alternating support produced sacral TcPO2 values, which either remained relatively high or fluctuated in concert with cycle period providing adequate viability. However, in 46% of cases at the extreme pressure amplitude of 100/0 mmHg, there was compromise to the skin viability at the sacrum, as reflected in depressed TcPO2 levels associated with an elevation of TcPCO2 levels above the normal range. In all cases, both the humidity and temperature levels increased during the test period. It is interesting to note that interface pressures at the sacrum rarely exceeded 60 mmHg. Although such studies need to be extended to involve bed-bound individuals, the results provide a design template for the optimum pressure signatures of APAM systems to ensure maintenance of skin viability during pronged loading.

What's the remedy for the distal necrosis of DIEP flap, better venous drain or more arterial supply?

BackgroundWe developed a novel pedicled DIEP flap model in rat to explore the possible remedy for the distal necrosis of the flap.MethodsA deep inferior epigastric perforator (DIEP) flap, based on the second right cranial perforator (P2) as the main pedicle, was elevated in 48 Sprague-Dawley rats. The rats were randomized into 4 groups: group I, the left P2 remaining intact as supercharging; group II, the left P2 artery alone kept as supercharging; group III, the left P2 vein alone kept as supercharging; group IV, no supercharging. Transcutaneous oxygen pressure (TcPO2) and transcutaneous carbon dioxide pressure (TcPCO2) were measured immediately after flap elevation, protein level of Hif-1a was measured 48 hours later, and flap survival was assessed 7 days postoperatively.ResultsBlockade of artery led to significantly lower TcPO2, higher TcPCO2, and higher expression level of Hif-1a in the distal side of the flap in group III and group IV, than those of group I and group II. At 7 days post surgery, significantly lower flap survival rates were observed in group III (81.9 ± 5.7%) and group IV (78.4 ± 6.5%), compared to observed in group I (97.2 ± 3.0%) and group II (94.2 ± 6.2%).ConclusionsIt might be arterial insufficiency, not venous congestion, which mainly caused the distal necrosis of the DIEP flap in rat. Arterial instead of venous supercharging might be a more effective procedure that improves circulation to zone IV of the flap.

Below-Knee Amputation Failure and Poor Functional Outcomes Are Higher Than Predicted in Contemporary Practice.

The perceived functional benefit of below-knee amputation (BKA) must be carefully weighed against the need for potential reinterventions. This study sought to examine the contemporary clinical and functional outcomes of patients undergoing BKA in the endovascular era. All patients who underwent BKA from January 2008 to December 2014 at a single tertiary medical center were retrospectively reviewed. Demographics, comorbidities, ambulation status, and transcutaneous oximetry (TcPO2) values were recorded. Study end points included freedom from conversion to above-knee amputation (AKA), freedom from conversion to AKA or death, BKA healing, and ambulation. Statistical modeling was performed to determine associations with BKA failure. Over the study interval, 130 limbs underwent BKA in 120 patients. Transcutaneous oximetry studies were obtained in 65% (n = 85). Thirty-eight percent (n = 46) of all BKA patients went on to heal and ambulate. Twenty-five percent (n = 33) required reintervention, 24 with conversion to AKA, and 9 with BKA revision. One-year freedom from conversion to AKA was 76% and was decreased among those with lower TcPO2 levels (60% TcPO2 <40 vs 81% TcPO2 ≥40; P = .04). One-year composite freedom from conversion to AKA/death was 60% and was decreased among those with lower TcPO2 readings (39% TcPO2 <40 vs 69% TcPO2 ≥40; P = .01). Despite a perceived functional bias toward knee salvage at the time of major amputation, most patients failed to postoperatively ambulate. Those with decreased TcPO2 levels (<40 mm Hg) have a 2-fold higher risk of AKA conversion or death, while nearly one-fourth of all BKA patients will succumb to the same fate irrespective of TcPO2. This suggests that many BKA patients in the endovascular era fail to derive the perceived benefit of knee salvage at the time of their index amputation. These findings highlight the need for careful patient selection and for a shared decision-making model in this frail population.

Silent ischemia of lower extremities in patients with diabetic peripheral polyneuropathy without pathosis of large arteries

Aim – to study the prevalence of lower limb tissue ischemia among patients with diabetic neuropathy and preserved blood flow of large arteries and determine its relation with the duration of disease, the level of control of diabetes and smoking.Materials and methods. We examined 178 patients with type 2 diabetes mellitus and severe diabetic peripheral polyneuropathy. Patients with other possible causes of neuropathy : metabolic disorders other than diabetes were excluded. Patients were investigated to exclude the presence of occlusions of the large arteries of the lower extremities. Transcutaneous oximetry(TсPO2) was performed in all the patients. A total of 178 patients (82 men and 96 women) aged 39 to 62 years were investigated. The average age of men was (48,56±9,23) years, women (51,58±8,35) years. The average level of glycated hemoglobin in men 8.97+2.53%, women 8.39+1.87%. The duration of diabetes was up to 7 years in 28 men and 34 women, 7-10 years – 36 men and 44 women, more than 12 years – 18 men and 18 women. Smokers at the time of the survey were 33 men and 13 women.Results and discussion. TcPO2 in tissues of the foot was reduced in comparison with the norm in 139 (78%) patients. In 39 cases this index was in the range 55-63 mmHg. Statistical relationship of TcPO2 with the level of glycated hemoglobin was not found, except for the fact that in all six patients with levels of glycosylated hemoglobin &gt;10.0% TcPO2 level did not exceed 30 mmHg., which indicates critical ischemia of the lower limbs. However, the BPI in all the patients was within 0,87-1,04, that is, there were no signs of angiopathy of large vessels. Due to the small sample significant difference between smoking and non-smoking group was not established. Also no significant difference between men and women was seen , both in general and within the groups of the study. A clear difference was seen in TcPO2 values depending on the duration of diabetes, with a reliable trend towards decreased oxygenation of the lower extremities directly proportional to the duration of the disease. We found a direct statistically significant relation between the degree of tissue ischemia of the lower limbs and the duration of diabetes, with the worst figures of TcPO2 in patients with diabetes for more than 12 years.Conclusions. Due to the absence of instrumentally confirmed occlusion of the large and medium leg arteries we concluded that the cause of silent ischemia of foot tissues is the development arteriolovenular shunts.

Influence of Negative-Pressure Wound Therapy on Tissue Oxygenation in Diabetic Feet.

Negative-pressure wound therapy (NPWT) has become a common wound care treatment modality for a variety of wounds. Several previous studies have reported that NPWT increases blood flow in the wound bed. However, NPWT might decrease tissue oxygenation in the wound bed because the foam sponge of NPWT compresses the wound bed under the influence of the applied negative pressure. Adequate tissue oxygenation is an essential consideration during diabetic foot management, and the foot is more sensitive to ischemia than any other region. Furthermore, the issue as to whether NPWT reduces or increases tissue oxygenation in diabetic feet has never been correctly addressed. The aim of this study was to evaluate the influence of NPWT on tissue oxygenation in diabetic feet. Transcutaneous partial oxygen pressures (TcPO2) were measured to determine tissue oxygenation levels beneath NPWT dressings on 21 feet of 21 diabetic foot ulcer patients. A TcPO2 sensor was fixed at the tarsometatarsal area of contralateral unwounded feet. A suction pressure of -125 mm Hg was applied until TcPO2 reached a steady state. The TcPO2 values for diabetic feet were measured before, during, and after NPWT. The TcPO2 levels decreased significantly after applying NPWT in all patients. Mean TcPO2 values before, during, and after therapy were 44.6 (SD, 15.2), 6.0 (SD, 7.1), and 40.3 (SD, 16.4) mm Hg (P < .01), respectively. These results show that NPWT significantly reduces tissue oxygenation levels in diabetic feet.

PC148. Below-Knee Amputation Failure and Poor Functional Outcomes Are Higher Than Predicted in Contemporary Practice

The perceived functional benefit of below-knee amputation (BKA) must be carefully weighed against the need for potential reinterventions among marginal candidates. Furthermore, the traditional bias towards preservation of the knee joint in the setting of an unknown ambulation probability may paradoxically expose patients to surgical reinterventions. This study sought to examine the contemporary functional outcomes of patients undergoing BKA in the endovascular era, and correlate results with preoperative transcutaneous oximetry (TcPo2) values. All patients who underwent BKA from January 2008 to December 2014 at Dartmouth-Hitchcock Medical Center were retrospectively reviewed. Patients who underwent amputation for trauma and venous disease were excluded. Demographics, comorbidities, ambulation status and TcPo2 values were recorded. Study end points included freedom from conversion to above-knee amputation (AKA), freedom from conversion to AKA or death, BKA healing, and ambulation. Statistical modeling was performed to determine associations with BKA failure. Over the study interval, 130 limbs underwent BKA in 120 patients (68% male). Mean age was 65 years, 67% were diabetic, and 66% had a history of smoking. TcPo2 studies were obtained in 65% (n = 85) of cases before amputation. A total of 38% (n = 46) of all BKA patients went on to heal and ultimately ambulate. A total of 25% (n = 33) of the BKA cohort required reintervention, 24 with conversion to AKA, and 9 with BKA revision. One-year freedom from conversion to AKA was 76% and was decreased among those with lower TcPo2 levels (60% TcPo2 <40 vs 81% TcPo2 ≥40; P = .04). One-year composite freedom from conversion to AKA/death was 60% and was decreased among those with lower TcPo2 readings (39% TcPo2 <40% vs 69% TcPo2 ≥40; P = .01). Despite a historical bias towards knee-salvage at the time of major amputation, a substantial proportion of patients will never ambulate. Furthermore, those with decreased TcPo2 levels (<40 mm Hg) have a twofold higher risk of AKA conversion or death, and nearly one-quarter of all BKA patients will succumb to the same fate irrespective of TcPo2. This suggests that many BKA patients in the endovascular era fail to derive the perceived benefit of knee salvage at the time of their index amputation. These findings highlight the need for careful patient selection and underscore the need for a shared decision-making model in this frail population.

Lipoprotein apheresis in patients with peripheral artery disease and hyperlipoproteinemia(a)

ObjectiveHyperlipoproteinemia(a) [Lp(a)-HLP] is a major risk factor for severe atherosclerosis. The present investigation sought to assess the effect of lipoprotein apheresis (LA) in patients with peripheral artery disease (PAD) and Lp(a)-HLP. MethodsIn January 2013, we started a registry for Lp(a)-HLP patients who receive weekly LA in our center. So far, ten patients with severe PAD and isolated Lp(a)-HLP who recently underwent revascularization (index procedure) have been included. Pain level, ankle-brachial-index (ABI), transcutaneous oxygen pressure (tcpO2) and walking distance were determined before, as well as 1, 3, 6 and 12 months after initiation of LA. Furthermore, the mean time interval between revascularizations within the 12 months prior to the index procedure and up to 12 months after the index procedure was assessed. ResultsAll analyzed parameters significantly improved under LA. When comparing the results before LA with the results after 12 months, the ankle-brachial-index increased from 0.5 ± 0.2 to 0.9 ± 0.1 (P < 0.001). The tcpO2 levels also increased from 42.9 ± 2.3 mmHg to 59.0 ± 8.9 mmHg (P < 0.001). The improved microcirculation was associated with a reduction of the mean pain level from 7.0 ± 1.5 to 2.0 ± 0.8 (P < 0.001) as determined using the visual analog scale. The walking distance increased from 87 ± 60 m to 313 ± 145 m (P < 0.001). Importantly, the frequency of revascularization procedures was strongly decreased under LA. All patients combined underwent 35 revascularizations within the 12 months prior to the index procedure (mean interval between two revascularizations: 104.3 days). Since the index procedure, only one revascularization was necessary within 79 patient-months under LA (mean interval: 2404.5 days, P < 0.001). ConclusionLA improves circulation, oxygen supply, level of pain and walking distance in patients with severe PAD and Lp(a)-HLP. The frequency of revascularization procedures is strongly reduced under LA treatment.

Valor pronóstico de la TcPO2 en la cicatrización de lesiones en pie diabético tras revascularización

IntroductionThe measurement of transcutaneous oxygen pressure (TcPO2) is a useful tool in non-invasive vascular diagnosis, as well as being a valuable prognostic test of vascular ulcer healing before and after revascularization. ObjectiveThe aim of this study was to determine the most reliable TtPO2 cut—off value for predicting healing, as well as to find out if the increase in the TcPO2 after revascularization can be predictor of a good outcome after this intervention in diabetic patients with ischemic ulcers. Material and methodsA retrospective study was performed using the prospectively maintained data base of the Diabetic Foot Unit of the Hospital Universitario Fundación de Alcorcón. Diabetic patients with ulceration and critical ischemia criteria were included, particularly those that had TcPO2 performed before and after revascularization, successful wound healing and time to healing. ResultsA total of 18 patients were found, of whom 72% were males and 28% females. The mean age was 68 years, with 94.7% hypertension, 73.7% dyslipidemia, and 63.2% retinopathy. A total of 19 revascularizations were performed, of which 13 were endovascular, 4 bypass, and 2 hybrid procedures. The ankle-brachial index was not assessable in 68%. A healing rate of 53% and a median time to healing of 103 days were obtained. The mean preoperative TcPO2 values in healed and non-healed was 14.6±9.40 and 18.6±12.93mmHg, respectively (P=.4404). The mean postoperative levels of TcPO2 were 40.8±10.85mmHg in healed and 23.5±13.27mmHg in non-healed (P=.0063). Using ROC curve analysis, it was determined that TcPO2 levels equal to or greater than 35mmHg were indicators of a good prognosis for wound healing. An increase in the TcPO2 above 15mmHg is a factor of a good prognosis after revascularization of diabetic foot. ConclusionsTcPO2 is a useful tool for determining the prognostic value in wound healing in the diabetic patient with critical ischemia, particularly in patients with non-assessable partial pressures. The cut-off for a good prognosis of wound healing, according to this study, is equal to or greater than 35mmHg. An increase in the TcPO2 above 15mmHg from the baseline value is also a factor of a good prognosis after revascularization.

Effect of normobaric hyperoxic therapy on tissue oxygenation in diabetic feet: A pilot study

Adequate tissue oxygenation is an essential factor in diabetic foot management. Hyperbaric oxygen (HBO) therapy has been successfully used as adjunctive treatment to improve the healing of diabetic foot ulcers. However, the clinical uses of HBO therapy are limited due to the low availability of HBO chambers, poor patient compliance, and high oxidative potential. Normobaric hyperoxic (NBO) therapy may be a potentially attractive alternative to HBO therapy because of its high availability, good patient compliance, and few technical requirements. Several studies on NBO therapy to attenuate infarct volume after stroke have provided compelling evidence. However, there have been no reports regarding the effect of NBO therapy in the field of wound healing. The purpose of this study was to evaluate the effect of NBO therapy on tissue oxygenation of diabetic feet. This study included 100 patients with diabetic foot ulcers (64 males and 36 females). Transcutaneous partial oxygen tension (TcPO₂) values of diabetic feet were measured before, during, and after NBO therapy. The mean TcPO₂ values before, during, and after therapy were 46.6 ± 21.5, 88.9 ± 48.0, and 49.9 ± 23.8 mmHg (p < 0.001), respectively. The lower the initial TcPO₂ level, the more TcPO₂ increased. The results reveal that NBO therapy significantly increases the tissue oxygenation level of diabetic feet.

Hyperoxia affects the regional pulmonary ventilation/perfusion ratio: an electrical impedance tomography study

The way in which hyperoxia affects pulmonary ventilation and perfusion is not fully understood. We investigated how an increase in oxygen partial pressure in healthy young volunteers affects pulmonary ventilation and perfusion measured by thoracic electrical impedance tomography (EIT). Twelve semi-supine healthy male volunteers aged 21-36 years were studied while breathing room air and air-oxygen mixtures (FiO2) that resulted in predetermined transcutaneous oxygen partial pressures (tcPO2) of 20, 40 and 60 kPa. The magnitude of ventilation (ΔZv) and perfusion (ΔZQ)-related changes in cyclic impedance variations, were determined using an EIT prototype equipped with 32 electrodes around the thorax. Regional changes in ventral and dorsal right lung ventilation (V) and perfusion (Q) were estimated, and V/Q ratios calculated. There were no significant changes in ΔZv with increasing tcPO2 levels. ΔZQ in the dorsal lung increased with increasing tcPO2 (P = 0.01), whereas no such change was seen in the ventral lung. There was a simultaneous decrease in V/Q ratio in the dorsal region during hyperoxia (P = 0.04). Two subjects did not reach a tcPO2 of 60 kPa despite breathing 100% oxygen. These results indicate that breathing increased concentrations of oxygen induces pulmonary vasodilatation in the dorsal lung even at small increases in FiO2. Ventilation remains unchanged. Local mismatch of ventilation and perfusion occurs in young healthy men, and the change in ventilation/perfusion ratio can be determined non-invasively by EIT.

A study of prognostic factors in Chinese patients with diabetic foot ulcers.

ObjectiveFew studies have identified factors as predictors of clinical prognosis of patients with diabetic foot ulcers (DFUs), especially of Chinese patients. In this study, we assessed the prognostic factors of Chinese patients with DFUs.Methods and materialsThis was a retrospective study (January 2009–January 2011) of 194 DFUs conducted in an inpatient population at PLA 454 Hospital in Nanjing, China, to determine the prognostic influential factors of DFUs in Chinese patients. All of the studied patients were grouped into an amputation group, a non-healing group, and a cured group, according to the clinical prognosis. Patient parameters, including gender, age, smoking habits, education level, family history of diabetes mellitus, medical history, duration of foot lesions and complications, ankle-brachial index (ABI), transcutaneous oxygen pressure (TcPO2), urinary albumin/creatinine ratio (Alb/Cr), fundus oculi, electrocardiogram, DFU characteristics, bacterial nature, and neuropathy, were cross-studied among the three groups.ResultsCompared with the other two groups, the amputation group showed a higher number of males, older in age, lower ABI and TcPO2 levels, higher Wagner wound grading and size, and significantly higher urinary Alb/Cr ratio, blood urea nitrogen, serum creatinine, white blood cell count, and erythrocyte sedimentation rate. Compared to the cured group (162 patients), more patients with an older age, smoking, family history of diabetes mellitus, medical history of foot ulcerations, lower ABI and TcPO2 levels, higher urine Alb/Cr ratio, and serum creatinine were found in the non-healing group. Regression analysis was used to study the correlation between various factors and clinical prognosis, and the results were as follows: age, Wagner wound classification, and heel ulcerations were negatively correlated to the DFU prognosis, whereas the female population, ABI, and TcPO2 were positively correlated with DFU prognosis.ConclusionIn this retrospective study, we conclude that the DFU prognosis may be related to age, gender, wound location (heel), Wagner wound classification, ABI, and TcPO2 levels in the Chinese population.

Application of gentamicin-collagen sponge shortened wound healing time after minor amputations in diabetic patients - a prospective, randomised trial.

IntroductionDiabetic foot infections are frequently polymicrobial. The lower tissue concentration of systemically administered antibiotics in diabetic patients was reported. Collatamp®EG (Syntacoll GmbH Saal/Donau, Germany) is a bioabsorbable, gentamicin impregnated collagen spongeused for local treatment. The aim of this randomized trial was to assess influence of gentamicin-collagen sponge applied to a wound on surgical outcomes after minor amputations in diabetic patients.Material and methodsFifty diabetic patients indicated for minor amputation in 2009 at our surgery department were included in the study. Patients were pre-operatively randomised into two groups. Twenty-five patients in group A were treated with gentamicin impregnated collagen sponge applied into wound peri-operatively while 25 patients in group B had minor amputation without gentamicin sponge.ResultsThere was no significant difference in the demographic data, procedures performed, diabetes duration and peripheral vascular disease severity between the groups. The median glycosylated haemoglobin was 6.0% (range: 4.6–9.5%) in group A and 6.2% (range: 4.0–8.4%) in control group B (non-significant). Median TcPO2 level was 44 (range: 13–67) in group A and 48 (range: 11–69) in control group B (non-significant). The median of wound healing duration in group A was 3.0 weeks (range: 1.7–17.1 weeks) compared to 4.9 weeks (range: 2.6–20.0 weeks) in control group B. This was with a statistically significant difference (p < 0.05).ConclusionsApplication of gentamicin impregnated collagen sponge shortened wound healing duration after minor amputations in diabetic patients by almost 2 weeks.

Transcutaneous Oxygen Pressure Measurement in Diabetic Foot Ulcers

The purpose of this study was to investigate mean values and cut-point of transcutaneous oxygen pressure (TcPO2) measurement in patients with diabetic foot ulcers. Prospective, descriptive study. Sixty-one patients with diabetes mellitus and foot ulcers comprised the sample. The research setting was Sun Yat-sen Memorial Hospital of SunYat-sen University, Guangzhou, China. Participants underwent transcutaneous oxygen (TcPO2) measurement at the dorsum of foot. Patients were classified into 3 groups according to clinical outcomes: (1) ulcers healed with intact skin group, (2) ulcer improved, and (3) ulcer failed to improve. TcPO2 was assessed and cut-points for predicting diabetic foot ulcer healing were calculated. Thirty-six patients healed with intact skin, 8 experienced improvement, and 17 showed no improvement. Mean TcPO2 levels were significantly higher (P< .001) in healed ulcers with intact skin (32 ± 10 mmHg) when compared to the improvement group (30 ± 7 mmHg) and the nonhealing group (15 ± 12 mmHg). All patients with TcPO2≤ 10 mmHg failed to heal or experienced deterioration in their foot ulcers. In contrast, all patients with TcPO2≥ 40 mmHg achieved wound closure. Measurement of TcPO2 in the supine position revealed a cut-point value of 25 mmHg as the best threshold for predicting diabetic foot ulcer healing; the area under the curve using this cut-point was 0.838 (95% confidence interval = 0.700-0.976). The sensitivity, specificity, positive predictive value, and negative predictive value for TxPO2 were 88.6%, 82.4%, 90.7%, and 72.2%, respectively. TcPO2≥ 40 mmHg was associated with diabetic foot ulcer healing, but a TcPO2≤ 10 mmHg was associated with failure of wound healing. We found that a cut-point of 25 mmHg was most predictive of diabetic foot ulcer healing.

The physiological response of skin tissues to alternating support pressures in able-bodied subjects

Prolonged mechanical loading can lead to breakdown of skin and underlying tissues which can, in turn, develop into a pressure ulcer. The benefits of pressure relief and/or redistribution to minimise risk have been well documented and these strategies can be provided by employing support mattresses in which internal air pressures can be alternated to minimise the risk of pressure ulcers in patients during prolonged periods of bed-rest. The paper describes the performance of a prototype alternating pressure air mattress (APAM), in terms of its ability to maintain skin viability in a group of healthy volunteers lying in a supine position. In particular, the mattress includes a sacral section supported with alternating low pressure (ALP), with values adjusted to subject morphology, using an in-built pressure sensor. The mattress was supported at four different head of bed (HOB) angles ranging from 0 to 60°. Internal mattress pressures and transcutaneous gas (TcPO2/TcPCO2) tensions at the sacrum and a control site, the scapula, were monitored. Interface pressures were also measured. The sensor was found to be sensitive to the BMI values of the 12 healthy volunteers. In the majority of test conditions the internal support produced sacral TcPO2 values, which either remained similar to those at the scapula or fluctuated at levels providing adequate viability. However in a few cases, associated with a raised HOB angle (≥45°), there was compromise to the skin viability at the sacrum, as reflected in depressed TcPO2 levels associated with an elevation of TcPCO2 levels above the normal range. In all cases, interface pressures at the sacrum rarely exceeded 60mmHg. Although such studies need to be extended to involve bed-bound individuals, the results offer the potential for the development of intelligent APAM systems, whose characteristics can be adjusted to an individual morphology. Such preventive strategies to maintain skin viability at loaded sites will be designed for subjects deemed to be at high risk of developing pressure ulcers.

Transcutaneous oximetry but not arterial toe blood pressure or ankle-brachial index is related to macular thickness in patients with chronic diabetic foot ulcers

Objectives: Diabetes related vascular complications of the lower extremity could be classified as micro- and macrovascular. Ankle-brachial index (ABI) and toe blood pressure (TBP) measurements evaluate macro-circulation, whereas transcutaneous oximetry (TcPO2) is considered to be a composite measure of vascular function, thereby also reflecting microcirculation. Microvascular disease in the eye involves abnormal capillary permeability and possibly thereby increased macular thickness. The aim of the present clinical study was to evaluate if microvascular disease in the eye was related to measures of foot ischemia in patients with diabetes mellitus. Methods: Twenty consecutive patients with diabetes and chronic full-thickness foot ulcers were included. Peripheral ischemia was diagnosed using TcPO2, TBP and ABI. Macular thickness was measured with optical coherence tomography technique. Results: Based on TcPO2, TBP and ABI measurements 14, 13 and 13 patients, respectively, were classified as ischemic. Patients with ischemic TcPO2 levels at the dorsum of the foot had significantly higher macular thicknesses. This was not the case in patients with ischemic TBP or ABI levels. Conclusion: TcPO2, unlike TBP and ABI, seems to be a clinically relevant measure of peripheral microvascular disease in patients with diabetes mellitus and may, if low, indicate an increased risk of macular edema.

Dialysis Access Steal Syndromes

Dialysis-associated steal syndromes remain a vexing problem for the busy vascular access surgeon. Those factors associated with ischemia include the elderly, diabetic, female, preexisting cardiac disease and brachial anastomosis, and previous ipsilateral access. A constellation of symptoms and findings based on underlying arterial disease and flow characteristics are necessary to provide prompt diagnosis and initiate treatment. Although a digital brachial index (DBI) >1 and transcutaneous oxygen tension (TCPO(2) ) measurements >60 mm Hg accurately predict a patient not at risk, no DBI or TCPO2 levels below that accurately predict if a patient will develop dialysis-associated ischemia. The goal of the vascular access surgeon is to provide prompt recognition and treatment of the disorder to maximize both limb salvage and access salvage. Continuation of angio access in the same extremity can be accomplished in most individuals.

Early non invasive detection of hypercarbia in two cardiac surgical patients

The availability of transcutaneous monitors has provided a means of non invasive assessment of CO(2) tension and a trend of the ventilation status commonly in infants and neonates. The authors describe two cases of hypercapnia diagnosed early in adults by the non invasive transcutaneous measurement of carbon dioxide (tcpCO(2)) using TINA TCM4 in postoperative cardiac surgical patients who were mechanically ventilated. Curiously, this increase in tcpCO(2) levels was associated with a false increase in the tcpO(2) values though no changes in the ventilatory parameters to increase oxygenation were made. The probable mechanism of the increase in tcpO(2) levels with hypercarbia is discussed.

A study of biofilm-based wound management in subjects with critical limb ischaemia

Bacterial biofilms cause or complicate numerous medical conditions, including chronic wounds. Biofilm-based wound care (BBWC) management strategies that suppress biofilm have been designed and are used extensively at the Southwest Regional Wound Care Center in Lubbock, Texas and are described in this article. This retrospective single-centre study was designed to evaluate the frequency of complete healing in subjects with a chronic wound in a limb with critical limb ischaemia (CLI) when managed using BBWC. Of the 4500 subjects admitted with wounds between August 2002 and January 2006, 1400 subjects' TCpO2 levels were measured, and 266 included were identified as having CLI (TCpO2 < 20mmHg). Of these, 190 subjects were considered in the analysis because they received a substantial course of therapy (more than five visits). Each subject was individually managed to reinforce natural healing and suppress bacterial biofilm. Successful healing was defined as complete closure by March 2007. Of the 190 subjects with CLI, 146 (77%) healed completely, and 44 (23%) were categorised as non-healing. The healed group included 47% (68/146) with osteomyelitis and 69% (101/146) with diabetes mellitus. In the non-healed group, 75% (33/44) had osteomyelitis and 77% (34/44) had diabetes mellitus. Ninety-one per cent (30/33) of the subjects without osteomyelitis or diabetes mellitus healed, and 67% (53/79) of the subjects with both osteomyelitis and diabetes mellitus healed. When comparing the healing frequency in this study with a previously published study, BBWC strategies significantly improved healing frequency. These findings demonstrate that effectively managing the biofilm in chronic wounds is an important component of consistently transforming 'non-healable' wounds into healable wounds.

Predictive Values of Transcutaneous Oxygen Tension for Above-the-ankle Amputation in Diabetic Patients with Critical Limb Ischemia

To assess the values of transcutaneous oxygen tension (TcPO2) capable of predicting above-the-ankle amputation in diabetic patients diagnosed for critical limb ischemia (CLI) according to the criteria of the TransAtlantic Inter-Society Consensus. Retrospective study. From January 1999 to December 2003, 564 diabetic patients were consecutively hospitalized for CLI in one limb. Revascularization with angioplasty or bypass graft was performed when possible and, if not possible, prostanoid therapy was used. In patients in whom therapies did not relieve the rest pain or the gangrene was extended above the Chopart joint, an above-the-ankle-amputation was performed. After treatment TcPO2 values were evaluated in all patients at the dorsum of the foot. Fifty-five (9.8%) patients underwent an above-the-ankle amputation: 22 of 420 patients who underwent angioplasty, 17 of 117 patients who underwent bypass (14.5%) and 16 of 27 patients in whom revascularization was not possible. Post-treatment TcPO2, measured by a receiver operating characteristic (ROC) curve, showed a value 34 mmHg as the best threshold for determining the need for revascularization, with an area under the curve of 0.89 (95%CI 0.85-0.94). Using logistic regression analysis the probability of above-the-ankle amputation for this threshold is 9.7% and reduces to 3% for TcPO2 > 40 mmHg. TcPO2 levels<34 mmHg indicate the need for revascularization, while for values >or= 34 < 40 mmHg this need appears less pressing, although there remains a considerable probability of amputation. TcPO2 levels greater than 40 mmHg suggest that revascularization is dependent on the severity of tissue loss and possible morbidity caused by the procedure.