Skin Oxygen 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.

Effect of cardiopulmonary resuscitation on perfusion in a porcine model of severe hemorrhagic shock.

Pulseless electrical activity from hemorrhagic shock has not been shown to benefit from cardiopulmonary resuscitation (CPR). Using a porcine model, our objective was to determine the effects of CPR on brain and skin oxygenation as a measure of perfusion in the setting of severe hemorrhagic shock. Adult swine randomized to non-CPR and CPR were anesthetized. Tissue oxygen sensors were inserted into the parietal cerebral parenchyma and skin. Controlled hemorrhagic shock with mean arterial pressure (MAP) <30 mm Hg was achieved and allowed to persist for 10 minutes. Animals were randomized to either receive automated CPR or no treatment. They were then autotransfused with sufficient blood to achieve MAP >60 mm Hg. Measurements were obtained before, during, and after shock state. Outcomes were modeled using mixed-effects lognormal models. A total of 12 swine were used, and the results were analyzed (non-CPR, n = 5; CPR, n = 7). One animal in the CPR group died during shock. One cerebral probe sensor malfunctioned, and these data were excluded. Baseline characteristics were similar between groups. MAP during shock was similar between groups; however, the CPR group had significantly higher systolic blood pressure (62.8 vs. 48.8 mm Hg, p = 0.010) and lower diastolic blood pressure (12.8 vs. 27.8 mm Hg, p < 0.001). Both cerebral (pBO2) and skin oxygenation (TcO2) dropped significantly as a result of shock. The CPR group had lower overall measures of tissue perfusion during shock, but only TcO2 at the shoulder was significantly lower during shock (11.5 vs. 21.1 mm Hg, p = 0.027) and recovery (33.3 vs. 62 mm Hg, p = 0.033). Our model showed that adding CPR during hemorrhagic shock did not improve end-organ oxygenation/perfusion, but did significantly diminish skin perfusion. This experiment corroborates existing literature on the potential detrimental effects of CPR during hemorrhagic pulseless electrical activity, but further work is needed to confirm this observation.

Oxygen Consumption In Vivo by Ultra-High Dose Rate Electron Irradiation Depends Upon Baseline Tissue Oxygenation

Purpose: This study aimed to assess the impact of tissue oxygen levels on transient oxygen consumption induced by ultra-high dose rate (UHDR) electron radiation in murine flank and to examine the effect of dose rate variations on this relationship. Methods: Real-time oximetry using the phosphorescence quenching method and Oxyphor PdG4 molecular probe was employed. Continuous measurements were taken during radiation delivery on a UHDR-capable Mobetron linear accelerator (linac). Oxyphor PdG4 was administered into the subcutaneous tissue of the flank skin one hour before irradiation. Skin oxygen tension (pO2) was manipulated by adjusting oxygen content in the inhaled gas mixture and/or by vasculature compression. A skin surface radiation dose of 19.8±0.3Gy was verified using a calibrated semiconductor diode dosimeter. Dose rate was varied across the UHDR range by changing linac cone length and pulse repetition frequency (PRF). Results: The decrease in pO2 per unit dose during radiation delivery, termed oxygen consumption g-value (gO2, mmHg/Gy), was significantly influenced by tissue oxygen levels in the range 0-65mmHg under UHDR conditions. Within the 0-20mmHg range, gO2 exhibited a sharp increase with rising baseline pO2, plateauing at 0.26mmHg/Gy. Dose rate variations (mean values 25-1170Gy/s, per-pulse doses of 2.5-9.8Gy) were explored by varying both cone length and PRF (10-120Hz) with no significant changes in gO2. Conventional dose rate irradiation resulted in no discernible changes in pO2. Conclusions: The results show significant differences in the radiation-chemical effects of UHDR radiation between hypoxic and well-oxygenated tissues. Similar trends between earlier published in vitro and in vivo experiments presented herein suggest the chemical mechanisms driving the dependencies of gO2 on pO2 are similar, potentially underpinning the FLASH effect. Importantly, significant variations in baseline pO2 were observed in animals kept under identical conditions, underscoring the necessity to control and monitor tissue oxygen levels for preclinical investigations and future clinical applications of FLASH-RT.

Pycnogenol® + Centellicum® supplementation improves skin elasticity and microperfusion. Implication for surgical patients: a conceptual registry study.

The aim of this registry study was to evaluate the effects of Pycnogenol® and Centellicum® (PYCE) on skin perfusion and skin elasticity in healthy women over a period of 4 weeks. The supplemented women used 150 mg of Pycnogenol® and 450 mg of Centellicum® daily. The supplemented group used the combination PYCE daily for 4 weeks and followed the standard management (SM) in addition. A control group used only the SM. SM for all subjects included a healthy diet (low levels of NaCl, low sugar, low calories), vitamin supplementation (C, E, B), daily mild outdoors exercise, regular washing with neutral soap; the same non-clinical, non-specific hydrating cream (Nivea) was used once daily. Sixty-three women completed the registry study. Thirty women using the PYCE combination and 33 women in the control group. The groups were comparable at baseline. No clinical condition was observed during the registry; no drug was used. There were no side effects or tolerability problems with the supplements. After 4 weeks, ultrasound elastosonography showed that skin elasticity significantly improved with the PYCE combination (P<0.05) without significant changes in the control group. In parallel, transcutaneous skin PO<inf>2</inf> increased significantly with PYCE compared to controls and transcutaneous skin PCO<inf>2</inf> decreased significantly compared to controls (P<0.05). This showed that skin oxygenation and nutrition improved with PYCE. Skin hydration also significantly improved with PYCE (P<0.05) in comparison with controls. Skin flow, indicating skin blood perfusion (thermoregulatory flow), assessed by laser Doppler flowmetry significantly improved over 4 weeks compared to controls (P<0.05). More specifically, the most superficial part of the flow, in the most superficial layer of the skin, corresponding to the nutritional blood flow, significantly improved with the combination PYCE compared to controls (P<0.05). Skin and tissue elasticity are crucial in surgery for healing, scarring, and wound closure. Reduced elasticity can lead to irregular or delayed healing. This preliminary concept study suggests that PYCE supplementation enhances skin elasticity, perfusion, and nutrition, with visible effects seen in just 4 weeks. This preliminary, concept study indicates that skin elasticity, skin perfusion, and skin nutrition improved with the supplementation of PYCE and the effects of PYCE were visible after only 4 weeks. A longer observation period should be considered in future studies. In conclusion, this pilot concept study shows a significant activity of the combination Pycnogenol® and Centellicum® on skin elasticity over a short period of supplementation.

Gender-Related Difference in Skin Oxygenation in Young Patients with Uncomplicated Type 1 Diabetes.

Gender, through genetic, epigenetic and hormonal regulation, is an important modifier of the physiological mechanisms and clinical course of diseases. In diabetes mellitus, there are gender differences in incidence, prevalence, morbidity, and mortality. This disease also has an impact on the microvascular function. Therefore, this cross-sectional study was designed to investigate how gender affects the cutaneous microcirculation. We hypothesized that gender should be an important factor in the interpretation of capillaroscopy and transcutaneous oxygen saturation results. The study group consisted of 42 boys and 55 girls, uncomplicated diabetic pediatric patients. Females (F) and males (M) did not differ in terms of age, age at onset of diabetes, or diabetes duration. Furthermore, they did not differ in metabolic parameters. The comparison showed that group F had lower BP, higher pulse, and higher HR than group M. Group F had significantly lower creatinine and hemoglobin levels than group M. In children and adolescents with type 1 diabetes without complications, there was a gender difference in microcirculatory parameters. The resting transcutaneous partial pressure of oxygen was significantly higher in females than in males. However, there were no gender-related differences in basal capillaroscopic parameters or vascular reactivity during the PORH test. Our results indicate that studies investigating the structure and function of the microcirculation should consider the role of gender in addition to known cofactors such as puberty, body mass index, physical activity, and cigarette smoking.

Anesthetic Oxygen Use and Sex Are Critical Factors in the FLASH Sparing Effect

IntroductionUltra-high dose-rate (UHDR) radiation has been reported to spare normal tissue compared to conventional dose-rate (CDR) radiation. However, important work remains to be done to improve the reproducibility of the FLASH effect. A better understanding of the biological factors that modulate the FLASH effect may shed light on the mechanism of FLASH sparing. Here, we evaluate whether sex and/or use of 100% oxygen as carrier gas during irradiation contribute to the variability of the FLASH effect. MethodsC57BL/6 mice (24 male, 24 female) were anesthetized using isoflurane mixed with either room air or 100% oxygen. Subsequently, the mice received 27 Gy of either 9 MeV electron UHDR or CDR to a 1.6 cm2 diameter area of the right leg skin using the Mobetron linear accelerator. The primary post-radiation endpoint was time to full thickness skin ulceration. In a separate cohort of mice (4 male, 4 female) skin oxygenation was measured using PdG4 Oxyphor under identical anesthesia conditions. ResultsIn the UHDR group, time to ulceration was significantly shorter in mice that received 100% oxygen compared to room air, and amongst them female mice ulcerated sooner compared to males. However, no significant difference was observed between male and female UHDR mice that received room air. Oxygen measurements showed significantly higher tissue oxygenation using 100% oxygen as the anesthesia carrier gas compared to room air, and female mice showed higher levels of tissue oxygenation compared to males under 100% oxygen. ConclusionThe FLASH sparing effect is significantly reduced using oxygen during anesthesia compared to room air. The FLASH sparing was significantly lower in female mice compared to males. Both tissue oxygenation and sex are likely sources of variability in UHDR studies. These results suggest an oxygen-based mechanism for FLASH, as well as a key role for sex in the FLASH skin sparing effect.

Skin perfusion and oxygen saturation after mastectomy and radiation therapy in breast cancer patients

The pathophysiological mechanism behind complications associated with postmastectomy radiotherapy (PMRT) and subsequent implant-based breast reconstruction are not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion and saturation in the skin after mastectomy and assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate – MN).Skin microvascular perfusion and oxygenation >2 years after PMRT were measured using white light diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) in the irradiated chest wall of 31 women with the contralateral breast as a control. In the non-irradiated breast, the perfusion after application of MN (median 0.84, 25th–75th centile 0.59–1.02 % RBC × mm/s) was higher compared to the irradiated chest wall (median 0.51, 25th–75th centile 0.21–0.68 % RBC × mm/s, p < 0.001). The same phenomenon was noted for saturation (median 91 %, 25th–75th centile 89–94 % compared to 89 % 25th–75th centile 77–93 %, p = 0.001). Eight of the women (26%) had a ≥10 % difference in skin oxygenation between the non-irradiated breast and the irradiated chest wall.These results indicate that late microvascular changes caused by radiotherapy of the chest wall significantly affect skin perfusion and oxygenation.

Near-infrared spectroscopy data for foot skin oxygen saturation in healthy subjects.

Our objective was to evaluate normative data for near-infrared spectroscopy (NIRS) in 110 healthy volunteers by Fitzpatrick skin type (FST) and region of the foot. We obtained measurements of the dorsum and plantar foot using a commercially available device (SnapshotNIR, Kent Imaging, Calgary Canada). On the dorsum of the foot, people with FST6 had significantly lower oxygen saturation compared to FST1-5 (p < 0.001), lower oxyhaemoglobin compared to FST2-5 (p = 0.001), but there was no difference in deoxyhaemoglobin. No differences were found on the plantar foot. When comparing dorsal and plantar foot, there was higher oxyhaemoglobin (0.40 ± 0.09 vs. 0.51 ± 0.12, p < 0.001) and deoxyhaemoglobin (0.16 ± 0.05 vs. 0.21 ± 0.05, p < 0.001) on the plantar foot, but no differences in oxygen saturation (dorsal 70.7 ± 10.8, plantar 70.0 ± 9.5, p = 0.414). In 6.4% of feet, there were black areas, for which no NIRS measurements could be generated. All areas with no data were on the dorsal foot and only found in FST 5-6. People with FST6 had significantly larger areas with no data compared to FST 5 (22.2 cm2 ± 20.4 vs. 1.9 cm2 ± 0.90, p = 0.007). These findings should be considered when using NIRS technology. Skin pigmentation should be evaluated in future NIRS studies.

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.

Continuous intrafemoral artery infusion of urokinase improves diabetic foot ulcers healing and decreases cardiovascular events in a long-term follow-up study

IntroductionDiabetic foot ulcer (DFU) is a disabling complication of diabetes mellitus. Here, we attempted to assess whether long-term intrafemoral artery infusion of low-dose urokinase therapy improved DFUs and decreased cardiovascular...

Bedside Hyperspectral Imaging and Organ Dysfunction Severity in Critically Ill COVID-19 Patients-A Prospective, Monocentric Observational Study.

Hyperspectral imaging (HSI) is a non-invasive technology that provides information on biochemical tissue properties, including skin oxygenation and perfusion quality. Microcirculatory alterations are associated with organ dysfunction in septic COVID-19 patients. This prospective observational study investigated associations between skin HSI and organ dysfunction severity in critically ill COVID-19 patients. During the first seven days in the ICU, palmar HSI measurements were carried out with the TIVITA® tissue system. We report data from 52 critically ill COVID-19 patients, of whom 40 required extracorporeal membrane oxygenation (ECMO). HSI parameters for superficial tissue oxygenation (StO2) and oxygenation and perfusion quality (NPI) were persistently decreased. Hemoglobin tissue content (THI) increased, and tissue water content (TWI) was persistently elevated. Regression analysis showed strong indications for an association of NPI and weaker indications for associations of StO2, THI, and TWI with sequential organ failure assessment (SOFA) scoring. StO2 and NPI demonstrated negative associations with vasopressor support and lactate levels as well as positive associations with arterial oxygen saturation. These results suggest that skin HSI provides clinically relevant information, opening new perspectives for microcirculatory monitoring in critical care.

The Potential Role of Hyperbaric Oxygen Therapy in Psoriasis Treatment: A Review of PI3K/AKT/FOXO Signaling Cascade and Interleukin-1β

Psoriasis is a chronic, immune-mediated inflammatory skin disorder that affects 2-3% of the population worldwide. Current therapies, including biologic agents, often have adverse effects and incomplete efficacy. Recent studies suggest that the PI3K/AKT/FOXO signalling cascade and interleukin-1 β play a crucial role in the pathogenesis of psoriasis. Hyperbaric oxygen therapy, a safe and well-tolerated procedure, has been suggested as a potential treatment for psoriasis due to its ability to increase tissue oxygenation and reduce inflammation. This review article summarizes the current understanding of the pathophysiology of psoriasis and the potential benefits of hyperbaric oxygen therapy as a treatment modality. The authors suggest that hyperbaric oxygen therapy may modulate the PI3K/AKT/FOXO signalling cascade, reduce interleukin-1 β levels, and improve skin oxygenation, leading to the attenuation of psoriatic plaques. Further clinical studies are needed to confirm the safety and efficacy of hyperbaric oxygen therapy in psoriasis treatment.

Microalgae Microneedle Supplies Oxygen for Antiphotoaging Treatment.

UV exposure often triggers photoaging of the skin. Pharmacological treatment suffers from severe side effects as well as poor efficacy because of insufficient skin penetration. Dissolved oxygen has been previously shown to reverse photoaged skin; however, the treatment is often limited by the availability of equipment (e.g., high-pressure oxygen). Poor oxygen diffusion into the skin has also limited its therapeutic efficacy. Herein, we developed a microneedle patch to deliver living microalgae to the deeper layers of the skin for efficient oxygenation and reversal of photoaging. The continuous release of oxygen from microalgae in the skin through photosynthesis reversed the inflammatory microenvironment and reduced reactive oxygen species levels in the photodamaged skin, leading to collagen regeneration and reduced wrinkles. This study provides not only a means for highly efficient skin oxygenation and reversal of photoaging but also an important theoretical basis for the clinical treatment of photoaging.

Calculation of Tissue Oxygenation via an Inverse Boundary Problem for Transcutaneous Oxygenation Wearable Applications.

In this article, we present a toolset to fully leverage a previously developed transcutaneous oxygenation monitor (TCOM) wearable technology to accurately measure skin oxygenation values. We describe numerical models and experimental characterization techniques that allow for the extraction of precise tissue oxygenation measurements. The numerical model is based on an inverse boundary problem of the parabolic equation with Dirichlet boundary conditions. To validate this model and characterize the diffusion of oxygen through the oxygen sensing materials, we designed a series of control/calibration experiments modeled after the device's clinical application using oxygenation values in the physiological range expected for healthy tissue. Our results demonstrate that it is possible to obtain accurate tissue pO2 measurements without the need for long equilibration times with a small wearable device.

Proton FLASH effects on mouse skin at different oxygen tensions

Objective. Irradiation at FLASH dose rates (>40 Gy s−1) has received great attention due to its reported normal tissue sparing effect. The FLASH effect was originally observed in electron irradiations but has since been shown to also occur with both photon and proton beams. Several mechanisms have been proposed to explain the tissue sparing at high dose rates, including effects involving oxygen, such as depletion of oxygen within the irradiated cells. In this study, we investigated the protective role of FLASH proton irradiation on the skin when varying the oxygen concentration. Approach. Our double scattering proton system provided a 1.2 × 1.6 cm2 elliptical field at a dose rate of ∼130 Gy s−1. The conventional dose rate was ∼0.4 Gy s−1. The legs of the FVB/N mice were marked with two tattooed dots and fixed in a holder for exposure. To alter the skin oxygen concentration, the mice were breathing pure oxygen or had their legs tied to restrict blood flow. The distance between the two dots was measured to analyze skin contraction over time. Main results. FLASH irradiation mitigated skin contraction by 15% compared to conventional dose rate irradiation. The epidermis thickness and collagen deposition at 75 d following 25 to 30 Gy exposure suggested a long-term protective function in the skin from FLASH irradiation. Providing the mice with oxygen or reducing the skin oxygen concentration removed the dose-rate-dependent difference in response. Significance. FLASH proton irradiation decreased skin contraction, epidermis thickness and collagen deposition compared to standard dose rate irradiations. The observed oxygen-dependence of the FLASH effect is consistent with, but not conclusive of, fast oxygen depletion during the exposure.

Does Fitzpatrick Score Predict Flap Loss? Microsurgical Breast Reconstruction Outcomes of Varying Skin Color.

This is a retrospective study conducted on patients who underwent any type of autologous flap breast reconstruction performed by the two senior authors at an academic center between January 2010 and December 2021. The sole primary outcome variable was flap loss. Patient skin tone was assessed using the Fitzpatrick scale on clinical photographs of patients. A total of 1115 pateints underwent autologous flap breast reconstruction, of which only 56 met both exclusion and inclusion criteria with 58 individual breasts being included in the final study population. The most common race of subjects was White (n = 33; 56.9%) while the most common Fitzpatrick score skin tone was type II (n = 22; 37.9%). The Cochran-Armitage test of trend showed a statistically significant linear trend, P = 0.006, with darker Fitzpatrick score skin tones associated with a higher proportion of flap loss in patients who had vascular compromise. A logistic regression showed that none of the predictor variables were significant. Patients with darker Fitzpatrick skin tones were associated with flap loss after vascular compromise. To prevent flap loss in patients who have darker Fitzpatrick score skin tones, more aggressive flap monitoring should be taken into consideration in the immediate postoperative setting.

Transcutaneous Oximetry Does Not Reliably Predict Wound-healing Complications in Preoperatively Radiated Soft Tissue Sarcoma.

Surgical wound-healing complications after tumor resections in tissue that has been preoperatively radiated are a major clinical problem. Most studies have reported that complications occur in more than 30% of patients undergoing such resections in the lower extremity. There is currently no available method to predict which patients are likely to have a complication. Transcutaneous oximetry has been identified in preliminary studies as potentially useful, but the available evidence on its efficacy for this application thus far is inconclusive. (1) Does transcutaneous oximetry measurement below 25 mmHg at any location in the surgical wound bed predict a wound-healing complication? (2) Does recovery (increase) in transcutaneous oxygen measurement during the rest period between the end of radiation and the time of surgery protect against wound-healing complications? A prospective, multi-institution study was coordinated to measure skin oxygenation at three timepoints in patients undergoing surgery for a lower extremity soft tissue sarcoma after preoperative radiation. Between 2016 and 2020, the five participating centers treated 476 patients for lower extremity soft tissue sarcoma. Of those, we considered those with a first-time sarcoma treated with radiation before limb salvage surgery as potentially eligible. Based on that, 21% (98 of 476) were eligible; a further 12% (56 of 476) were excluded because they refused to participate or ultimately, they were treated with a flap, amputation, or skin graft. Another 1% (3 of 476) of patients were lost because of incomplete datasets or follow-up less than 6 months, leaving 8% (39 of 476) for analysis here. The mean patient age was 62 ± 14 years, 62% (24 of 39) of the group were men, and 18% (7 of 39) of patients smoked cigarettes; 87% (34 of 39) of tumors were intermediate/high grade, and the most common histologic subtype was undifferentiated pleomorphic sarcoma. In investigating complications, a cutoff of 25 mmHg was chosen based on a pilot investigation that identified this value. All patients were assessed for surgical wound-healing complications, which were defined as: those resulting in a return to the operating room, initiation of oral or IV antibiotics, intervention for seroma, or prolonged wound packing or dressing changes. To answer the first research question, we compared the proportion of patients who developed a wound-healing complication between those patients who had any reading below 25 mmHg (7 of 39) and those who did not (32 of 39). To answer the second question, we compared the group with stable or decreased skin oxygenation (22 of 37 patient measurements [two patients missed the immediate postoperative measurement]) to the group that had increased skin oxygen measurement (15 of 37 measurements) during the period between the end of radiation and the surgical procedure; again, the endpoint was the development of a wound-healing complication. This study was powered a priori to detect an unadjusted odds ratio for wound-healing complications as small as 0.71 for a five-unit (5 mmHg) increase in TcO 2 between the groups, with α set to 0.05, β set to 0.2, and a sample size of 40 patients. We found no difference in the odds of a wound-healing complication between patients whose transcutaneous oxygen measurements were greater than or equal to 25 mmHg at all timepoints compared with those who had one or more readings below that threshold (odds ratio 0.27 [95% confidence interval (CI) 0.05 to 1.63]; p = 0.15). There was no difference in the odds of a wound-healing complication between patients who had recovery of skin oxygenation between radiation and surgery and those who did not (OR 0.63 [95% CI 0.37 to 5.12]; p = 0.64). Transcutaneous oximetry cannot be considered a reliable test in isolation to predict wound-healing complications. This may be a function of the fact that transcutaneous oximetry samples a relatively small portion of the landscape in which a wound-healing complication could potentially arise. In the absence of a reliable diagnostic test, clinicians must still use their best judgment regarding surgical timing and work to address modifiable risk factors to avoid complications. The unanswered question that remains is whether there is a skin perfusion or oxygenation issue at the root of these complications, which seems likely. Alternative approaches that can assess the wound more broadly and in real time, such as fluorescent probes, may be deserving of further investigation. Level II, diagnostic study.

Quantification of Dermal Microcirculatory Changes after Topical Administration of Capsaicin: A Randomized Placebo-Controlled Study in 46 Subjects

Background Dermal blood flow is crucial for wound healing and survival of flaps in dermatologic surgery. To improve flap viability in cases of compromised perfusion topical agents can easily be applied. The aim of this placebo-controlled study was to characterize changes of DBF in healthy subjects by quantitatively assessing perfusion dynamics after application of capsaicin to establish a reference for measurements at injured sites. Methods In 46 healthy subjects perfusion dynamics after local application with capsaicin and placebo was noninvasively assessed, determining cutaneous oxygen saturation, relative hemoglobin count and blood flow using an Oxygen-to-See device. Results A significant raise in superficial (162% p = 0.000) and deep (144%, p = 0.000) skin oxygenation after 30 min was provoked. A highly significant raise in measurements of flow and velocity was present in superficial (523%, p = 0.000) and deep (242%, p = 0.000) sites. Conclusion With the introduced model applied to observe changes in parameters of dermal blood flow in healthy subjects the authors can reliably monitor effects of topically administered capsaicin. This baseline can be used as reference for further studies in the settings of endangered flap survival or critically perfused wounds as has been proven in animal studies.

Investigation of oxygen saturation in regions of skin by near infrared spectroscopy.

Oxygen is essential for life, and investigation of the skin's oxygen environment and identification of its effects on the skin may lead to the discovery of new antiaging targets. To understand individual skin differences and age-related changes, we developed a noninvasive method using near infrared spectroscopy (NIRS) to measure the regional saturation of oxygen (rSO2 ) of human skin. To construct an NIRS sensor probe specialized for skin measurement, the distance between the sensor transmitter and receiver was optimized based on data for the thickness of the facial skin to the subcutaneous fat layer. To analyze the relationship between skin oxygen saturation and body oxygen saturation, rSO2 was measured by NIRS, oxygen saturation of peripheral artery (SpO2 ) was measured by pulse oximeter, and physical conditions were considered, such as body mass index (BMI) and muscle mass, in Japanese women (age 20s-60s). Both skin rSO2 and SpO2 varied among individuals and decreased with age. Only SpO2 showed a relationship with BMI and muscle mass, whereas rSO2 showed no relationship with these physical conditions. No relationship between rSO2 and SpO2 was observed. Individual and age-related differences in skin by rSO2 values were found by NIRS optimized for local skin; however, the factors affecting rSO2 differed from those affecting SpO2 , and further study is needed.

Relationship Between Inflow Impairment and Skin Oxygen Availability to the Upper Limb During Standardized Arm Abduction in Patients With Suspected Thoracic Outlet Syndrome.

ObjectiveThoracic outlet syndrome (TOS) should be considered of arterial origin only if patients have clinical symptoms that are the result of documented symptomatic ischemia. Simultaneous recording of inflow impairment and forearm ischemia in patients with suspected TOS has never been reported to date. We hypothesized that ischemia would occur in cases of severely impaired inflow, resulting in a non-linear relationship between changes in pulse amplitude (PA) and the estimation of ischemia during provocative attitudinal upper limb positioning.DesignProspective single center interventional study.MaterialFifty-five patients with suspected thoracic outlet syndrome.MethodsWe measured the minimal decrease from rest of transcutaneous oximetry pressure (DROPm) as an estimation of oxygen deficit and arterial pulse photo-plethysmography to measure pulse amplitude changes from rest (PA-change) on both arms during the candlestick phase of a “Ca + Pra” maneuver. “Ca + Pra” is a modified Roos test allowing the estimation of maximal PA-change during the “Pra” phase. We compared the DROPm values between deciles of PA-changes with ANOVA. We then analyzed the relationship between mean PA-change and mean DROPm of each decile with linear and second-degree polynomial (non-linear) models. Results are reported as median [25/75 centiles]. Statistical significance was p < 0.05.ResultsDROPm values ranged −11.5 [−22.9/−7.2] and − 12.3 [−23.3/−7.4] mmHg and PA-change ranged 36.4 [4.6/63.8]% and 38.4 [−2.0/62.1]% in the right and left forearms, respectively. The coefficient of determination between median DROPm and median PA-change was r2 = 0.922 with a second-degree polynomial fitting, but only r2 = 0.847 with a linear approach.ConclusionOxygen availability was decreased in cases of severe but not moderate attitudinal inflow impairments. Undertaking simultaneous A-PPG and forearm oximetry during the “Ca + Pra” maneuver is an interesting approach for providing objective proof of ischemia in patients with symptoms of TOS suspected of arterial origin.