Local thermal control of the human cutaneous circulation

Enhanced TLR7-dependent production of type I interferon by pDCs underlies pandemic chilblains

Outbreaks of chilblains were reported during the COVID-19 pandemic. Given the essential role of type I interferon (I-IFN) in protective immunity against SARS-CoV-2 and the association of chilblains with inherited type I interferonopathies, we hypothesized that excessive I-IFN responses to SARS-CoV-2 might underlie the occurrence of chilblains in this context. We identified a transient I-IFN signature in chilblain lesions, accompanied by an acral infiltration of activated plasmacytoid dendritic cells (pDCs). Patients with chilblains were otherwise asymptomatic or had mild disease without seroconversion. Their leukocytes produced abnormally high levels of I-IFN upon TLR7 stimulation with agonists or ssRNA viruses-particularly SARS-CoV-2-but not with DNA agonists of TLR9 or the dsDNA virus HSV-1. Moreover, the patients' pDCs displayed cell-intrinsic hyperresponsiveness to TLR7 stimulation regardless of TLR7 levels. Inherited TLR7 or I-IFN deficiency confers a predisposition to life-threatening COVID-19. Conversely, our findings suggest that enhanced TLR7 activity in predisposed individuals could confer innate, pDC-mediated, sterilizing immunity to SARS-CoV-2 infection, with I-IFN-driven chilblains as a trade-off.

Wearable Multimodal Optical Analyzers: Physiological Variability and Reproducibility of Measurements

The work is devoted to the study of the physiological variability of the microcirculatory-tissue system (MTS) parameters under normal conditions and during functional tests. The results were obtained in vivo using multimodal wearable analyzers implementing methods of laser Doppler flowmetry and fluorescence spectroscopy. Comprehensive data analysis and calculation of the coefficients of variation of the MTS parameters of the human body for various topographic and anatomical areas of the skin were carried out. The obtained results showed higher values of the coefficient of variation of MTS parameters in the area of the toes and wrists, while the fingers and forehead skin showed lower levers of variation. In all areas of the study, reproducibility of the parameters obtained for the right and left areas of the study is observed.

Heel Warming in Very-Low-Birth-Weight Newborns for Capillary Blood Sampling

OBJECTIVE

To determine if performing heel stick procedures for capillary blood sampling without prior heel warming is noninferior to the standard practice of warming the heel in very-low-birth-weight newborns.

DESIGN

Noninferiority randomized control trial.

SETTING

The study took place in two Level 3 NICUs in The Netherlands.

PARTICIPANTS

Newborns born at less than 32 weeks gestation in their second or third week of life without an arterial line in situ or known coagulopathy (N = 100).

METHODS

We randomized participants to undergo a heel stick procedure in one of two groups: without heel warming (n = 50) and heel warming with a washcloth warmed with 37 °C tap water (n = 25) or with a microwaved hot pack (n = 25). The primary outcome was length of time for obtaining the required blood sample. The secondary outcomes were number of attempts, reliability of the blood sample, newborn comfort, and adverse events.

RESULTS

We observed no differences in background characteristics between groups and found no statistically significant or clinically relevant differences in primary or secondary outcomes.

CONCLUSION

Among participants, not warming the heel before a heel stick was noninferior to warming the heel. Therefore, preheating the heel as a standard of care may be an unnecessary nursing intervention.

Effects of Skin Blood Flow Fluctuations on Non-Invasive Glucose Measurement and a Feasible Blood Flow Control Method

In non-invasive blood glucose measurement (NBGM) based on near-infrared spectroscopy, fluctuations in blood flow represent a primary source of interference. This paper proposes a local blood flow pre-stimulation method in which the local skin is heated to dilate blood vessels and increase blood flow. This approach aims to mitigate the impact of environmental temperature variations, emotional fluctuations, and insulin secretion on blood flow, thereby enhancing the accuracy of glucose measurement. To evaluate the effectiveness of this method, a blood flow interference experiment was conducted to compare the stability of the measured spectra with and without blood flow pre-stimulation. The results demonstrated that the pre-stimulation method presents good anti-interference capabilities. Furthermore, 45 volunteers underwent oral glucose tolerance tests (OGTTs) as a part of the validation experiments. In these tests, the forearm skin blood flow of 24 volunteers was pre-stimulated using elevated temperature, while the skin of the remaining 21 subjects was maintained at a natural temperature level without stimulation. The results indicate that compared to the non-stimulated condition, the correlation between the optical signal at 1550 nm and blood glucose levels was significantly enhanced under the pre-stimulation condition. Furthermore, the root mean square error (RMSE) of the linear prediction model was reduced to just 0.92 mmol/L. In summary, this paper presents a feasible blood flow control strategy that effectively stabilizes internal blood flow, thereby improving the accuracy of NBGM.

Water retention influences thigh skin temperature variation post-exercise: preliminary study of bioimpedance analysis and thermography data

Objectives

This study aimed to investigate the influence of body composition variables, focusing on the extracellular water level and gender difference, on infrared thermography detection during and post exercise.

Method

One hundred two participants were included in the study. Body composition was analyzed by bioimpedance, and three thermal imaging were taken before, at the end, and 5 min after a vigorous exercise. First, participants were divided by gender, and differences in skin temperature variation during exercise were highlighted. In the second analysis, the subjects were divided into three groups depending on the percentage of extracellular water. The correlation between body composition variables and skin temperature at the 3-time points was studied.

Results

an association between extracellular water (%) and basal thigh temperature both in the dominant leg (r: -0.27, p < 0.01) and non-dominant leg (r: -0.26, p < 0.01) was found; temperature variation analysis shows a significative temperature reduction between baseline and the end of exercise in both leg for (non-dominant: p < 0.001; dominant: p < 0.001) and a significative skin temperature increase after 5 min recovery, 0.14°C for the dominant leg (p > 0.05) and 0.12°C for the non-dominant leg (p > 0.05) considering the whole group. However, when we considered the separate group for extracellular contente the same significative decrease was found just in the lower water retention group (p < 0.05) and medium water retention group (p < 0.05). The high water retention group showed an opposite skin temperature trend in 5-min post-exercise recovery and had lower skin temperature at each time point compared with the other groups. The female group had lower skin temperature than the male at each time point.

Conclusion

Water retention could influence basal skin temperature and the temperature variation following vigorous exercise. A value of less than 45% of extracellular water should be considered for reliable use of thermal imaging. Further studies are needed to confirm this value.

Medical mud-pack treatment with different temperatures in patients with knee osteoarthritis

To compare the effects of medical mud-pack (MMP) treatments applied at different temperatures on the pain and joint functions of patients with knee osteoarthritis (KOA). Kellgren Lawrence (KL) stage 3 or 4 KOA patients were included and randomized into three groups. Patients in groups 1, 2, and 3 took MMP treatment to both knees at 39 °C, 42 °C, and 45 °C, respectively. The treatment was performed for 12 days (only weekdays) and was 30 min long per day. The same blinded physician evaluated the patients at baseline and at the end of the treatment. The assessments were done before and after the intervention. The primary outcome was to achieve a minimal clinically important improvement (MCII) for KOA (decrease of at least 19 mm (-40.8%) on the VAS for pain, a decrease of 18.3 mm (-39%) on the patient's global assessment (PGA), and/or a decrease of at least 9.1 points (-26%) on the Western Ontario and McMaster Universities Osteoarthritis Index function subscale (WOMAC-FS). Secondary outcomes were pain (VAS), patient's global assessment (VAS), physician's global assessment (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Patient's health state, Patient Acceptable Symptom State (PASS). 217 patients were analyzed. Groups 1, 2, and 3 had 68, 81,68 patients, respectively. The MCII measurement revealed that MMP treatment did not show a significant difference between groups 2 and 3 (p > 0.05). Also, it was observed that more patients in groups 2 and 3 reached the MCII compared to group 1 (p < 0.001). For the secondary outcomes, significant improvements were observed within-group evaluations for each of the three groups (p < 0.001). Between groups comparisons, the improvements at the end of the treatment were found to be superior for group 2 and group 3 compared to group 1 (p < 0.001). There was no statistically significant difference between groups 2 and 3 for any parameters (p > 0.05). The number of patients who achieved the PASS was statistically lower for group 1 compared to groups 2 and 3 (p < 0.001). We observed significant improvements in all groups after treatment. The main result, as measured by MCII, suggests that MMP treatments at 42-45 °C is more effective than at 39 °C in managing severe KOA patients' pain and functional status. We found no significant difference in pain and joint function improvement between 42 °C and 45 °C after MMP.

Relationship between skin temperature and blood flow during exposure to radio frequency energy: implications for device development

BACKGROUND

The ST response to high frequency EM heating may give an indication of rate of BF in underlying tissue. This novel method, which we have termed REFLO (Rapid Electromagnetic Flow) has potential for applications such as detection of PAD. The method utilizes the relationship between blood flow rate and tissue temperature increase during exposure to radio frequency (RF) energy. We are developing an REFLO device to screen for peripheral artery disease (PAD). PAD is characterized by impaired blood flow to the legs, as reflected in the skin microcirculation. The REFLO system incorporates a radio frequency transmitter and a compact transducer housing a micropatch antenna and an infrared (IR) temperature sensor. At high RF frequencies (> 6 GHz) tissue heating is confined to the skin, such that an indication of blood flow may be inferred from the temperature response to controlled heating. The objective of this study is to determine the extent to which the magnitude and depth of heating as well as device sensitivity are functions of (i) RF frequency and (ii) thickness of the dermal tissue layer.

RESULTS

Results show that it is feasible to measure blood flow rate with REFLO technology. Surface temperature increases were found to be more dependent upon the magnitude of power absorption than location of absorption within the skin. While surface temperature response does depend upon radio wave frequency and thickness of the dermis layer, such dependencies are mild. Sensitivity to blood flow rate was found to be proportional to the magnitude of absorbed power.

CONCLUSION

Results show that it is feasible to discriminate between blood flow rates using REFLO technology at frequencies within the 10-94 GHz range. All frequencies analyzed produced similar levels of sensitivity to blood flow rate despite significant differences in penetration depth. These results are being used in the development of a preclinical prototype for quick and easy detection of asymptomatic PAD in humans.

Pressure-Induced Microvascular Reactivity With Whole Foot Loading Is Unique Across the Human Foot Sole

BACKGROUND

Foot sole plantar pressure generates transient but habitual cutaneous ischemia, which is even more exacerbated in atypical gait patterns. Thus, adequate post-occlusive reactive hyperaemia (PORH) is necessary to maintain skin health. Plantar pressure regional variance during daily tasks potentially generates region-specific PORH, crucial for ischemic defence.

AIMS

The current work investigated regional PORH across the human foot sole resulting from stance-like loading.

MATERIALS & METHODS

A loading device equipped with an in-line laser speckle contrast imager measured blood flux before, during, and after whole-foot loading for 2 and 10 min durations at 15% and 50% body weight. Flux was compared between six regions: the heel, lateral arch, medial arch, and fifth, third, and first metatarsals (MT).

RESULTS

Baseline flux was significantly greater in the 1MT and 3MT than all other regions. Loading occluded the heel, 5MT and 3MT more than all other regions. Regional PORH peak, time to peak, area under the curve, and recovery rate were ranked between regions.

DISCUSSION

The 3MT, followed by 5MT, overall had the strongest PORH response, suggesting a heightened protection against ischemia compared to other regions.

CONCLUSION

This work highlights regional variations within a healthy foot, providing a framework for future ulcer risk assessments and interventions to preserve foot health.

Diagnosis, Pathophysiology and Management of Microvascular Dysfunction in Diabetes Mellitus

Microcirculation is an essential system that regulates oxygen and nutrients to cells and tissues in response to various environmental stimuli and pathophysiological conditions. Diabetes mellitus can cause microvascular complications including nephropathy, neuropathy, and retinopathy. The pathogenesis of microvascular dysfunction in diabetes is associated with hyperglycemia and the result of an interplay of various factors. Research studies have demonstrated that functional microvascular dysfunction appears much earlier than structural alterations in vasculature in diabetes. This finding of the progression from microvascular dysfunction to macrovascular disease establishes a foundation for the screening and early diagnosis of diabetes by assessing the microvascular function. This comprehensive review discusses technologies (laser Doppler, transcutaneous oximetry, infrared thermography and near-infrared spectroscopy) with computational methods (linear (time and frequency domains), nonlinear and machine learning approaches) for diagnosing microvascular dysfunction in diabetes. Pathophysiological changes of microvascular dysfunction leading to impaired vasomotion and blood flow oscillations in diabetes are reviewed. Recent findings in managing microvascular dysfunction using lifestyle modifications and force-based modulations are evaluated. A consensus endorsed by the American Diabetes Association has been reached that an effective exercise program would greatly slow down the progression of microvascular dysfunction and its impact on diabetic foot ulcers, muscle fatigue and weakness and peripheral neuropathy. However, it is imperative to determine the dose-response relationship of exercise and microvascular responses in patients with diabetes. Research studies have demonstrated that local vibration and whole-body vibration can improve microcirculation in various pathological conditions, including diabetes. Due to the complex nature of microvascular regulation, various computational methods have been developed to shed light on the influence of diabetes on microvascular dysfunction. This comprehensive review will contribute to the diagnosis and management of microvascular dysfunction in diabetes.

The effects of facial cooling on physiological and perceptual responses during a simulated Épée fencing competition: a pilot study

BACKGROUND

The aim of this study was to investigate the effects of facial cooling on physiological and perceptual responses during a simulated fencing competition.

METHODS

Using a randomized, crossover design, six competitive male fencers completed two trials of seven simulated fencing matches. Each match consisted of 22×10 s bouts of high-intensity fencing movements. Static rest (12 s) separated each bout, with 60-second rest after bouts seven and 14, during which, in the experimental condition, participants were sprayed with a facial water mist and fanned.

RESULTS

Relative to control, facial cooling reduced tympanic temperature (mean difference [MD]: 0.2±0.03 °C; 95% likely range [CL95]: 0.13-0.3 °C), heart rate (MD: 12±3 b·min-1; CL95: 5-20 b·min-1), and ratings of perceived exertion (RPE) for the dominant arm (MD: 2±0; CL95: 1-3), legs (MD: 2±0; CL95: 1-3), and total exertion (MD: 2±0; CL95: 1-3). Moreover, the benefits of facial cooling on RPE of the dominant arm and legs were magnified as the competition progressed. Facial cooling also improved ratings of perceived thermal comfort and perceived thermal strain.

CONCLUSIONS

While the performance benefits of the intervention require exploration, facial misting positively affects both physiological and perceptual responses during fencing.

Impact of Cryotreated and Warm Sodium Hypochlorite on Postoperative Pain in Teeth With Symptomatic Irreversible Pulpitis: A Randomized Controlled Trial

INTRODUCTION

The purpose of this study was to evaluate effect of cryotreated and warm sodium hypochlorite (NaOCl) on postoperative pain in patients with symptomatic irreversible pulpitis and symptomatic apical periodontitis.

METHODS

Sixty-six individuals with preoperative pain scores of ≥54 mm on the Heft Parker Visual Analogue Pain Scale (HP-VAS) diagnosed with symptomatic irreversible pulpitis and symptomatic apical periodontitis as per the American Association of Endodontists guidelines in mandibular molars were included. The preparation of the access and the root canals was instrumented and irrigated in accordance with a standard protocol. Based on the temperature of the final irrigant, the root canals were then randomly assigned to 3 groups and 3% NaOCl was irrigated: control (at 25°C), cold NaOCl (2°C), and warm NaOCl (60°C) (n = 22/group). Root canal treatment was completed at the same visit. Pre- and postoperative pain assessment at 6, 24, 48, and 72 hours was conducted using the HP-VAS, and analgesic consumption was noted. Suitable statistical tests were used to analyze the data.

RESULTS

In comparison with the other 2 groups, the cold NaOCl group had a lower HP-VAS score at all follow-up intervals. Between groups, there was a statistically significant difference in postoperative pain scores at 6 and 72 hours (P < .05). None of the subjects experienced any postoperative discomfort at 72 hours in the control and cold NaOCl groups.

CONCLUSION

Patients treated with cold NaOCl as the final irrigant experienced significantly less postoperative pain at 6 hours when compared with room temperature and warm NaOCl.

Altered Microvascular Reactivity During a Skin Thermal Challenge Is Associated With Organ Dysfunction and Slow Recovery After Cardiac Surgery

OBJECTIVES

To assess microvascular reactivity during a skin thermal challenge early post-cardiac surgery and its association with outcomes.

DESIGN

Noninvasive physiological study.

SETTING

Thirty-five-bed department of intensive care.

PARTICIPANTS

Patients admitted to the intensive care unit post-cardiac surgery.

INTERVENTIONS

Thermal challenge.

MEASUREMENTS AND MAIN RESULTS

A total of 46 patients were included; 14 needed vasoactive or ventilatory support for at least 48 hours (slow recovery), and 32 had a more rapid recovery. Skin blood flow (SBF) was measured on the anterior proximal forearm using skin laser Doppler. A thermal challenge was performed by abruptly increasing local skin temperature from 37°C to 43°C while monitoring SBF. The ratio between SBFs at 43°C and 37°C was calculated to measure microvascular reactivity. SBF at 37°C was not significantly different in patients with a slow recovery and those with a rapid recovery, but SBF after 9 minutes at 43°C was lower (48.5 [17.3-69.0] v 85.1 [45.2-125.7], p < 0.01), resulting in a lower SBF ratio (2.8 [1.5-4.7] v 4.8 [3.7-7.8], p < 0.01). Patients with lower SBF ratios were more likely to have dysfunction of at least one organ (assessed using the sequential organ dysfunction score) 48 hours post-cardiac surgery than those with higher ratios: 88% versus 40% versus 27% (p < 0.01), respectively, for the lowest, middle, and highest tertiles of SBF ratio. In multivariable analysis, a lower SBF ratio was an independent risk factor for slow recovery.

CONCLUSIONS

Early alterations in microvascular reactivity, evaluated by a skin thermal challenge, are correlated with organ dysfunction. These observations may help in the development of new, simple, noninvasive monitoring systems in postoperative patients.

Fluorescence Spectroscopy With Temperature Functional Tests in the Assessment of Markers of Intracellular Energy Metabolism: Spatial Heterogeneity and Reproducibility of Measurements

The fluorescence intensities of the cellular respiratory cofactors NADH (reduced nicotinamide adenine dinucleotide) and FAD++ (oxidized flavin adenine dinucleotide) reflect energy metabolism in skin and other tissues and can be quantified in vivo by fluorescence spectroscopy (FS). However, the variability of physiological parameters largely determines the reproducibility of measurement results and the reliability of the diagnostic test. In this prospective study, we evaluated the interday reproducibility of NADH and FAD++ fluorescence intensity measurements in the skin of 51 healthy volunteers assessed by the FS at baseline, after local cooling (10°C) and heating of the skin (35°C). Results showed that the fluorescence amplitude of NADH (AFNADH) in forearm skin was the most reproducible of the FS parameters studied. Assessment of AFNADH in the dorsal forearm in combination with a thermal functional test is the most promising method for clinical use for assessing energy metabolism in the skin.

A wirelessly programmable, skin-integrated thermo-haptic stimulator system for virtual reality

Sensations of heat and touch produced by receptors in the skin are of essential importance for perceptions of the physical environment, with a particularly powerful role in interpersonal interactions. Advances in technologies for replicating these sensations in a programmable manner have the potential not only to enhance virtual/augmented reality environments but they also hold promise in medical applications for individuals with amputations or impaired sensory function. Engineering challenges are in achieving interfaces with precise spatial resolution, power-efficient operation, wide dynamic range, and fast temporal responses in both thermal and in physical modulation, with forms that can extend over large regions of the body. This paper introduces a wireless, skin-compatible interface for thermo-haptic modulation designed to address some of these challenges, with the ability to deliver programmable patterns of enhanced vibrational displacement and high-speed thermal stimulation. Experimental and computational investigations quantify the thermal and mechanical efficiency of a vertically stacked design layout in the thermo-haptic stimulators that also supports real-time, closed-loop control mechanisms. The platform is effective in conveying thermal and physical information through the skin, as demonstrated in the control of robotic prosthetics and in interactions with pressure/temperature-sensitive touch displays.

Recent Technologies for Transcutaneous Oxygen and Carbon Dioxide Monitoring

The measurement of partial pressures of oxygen (O2) and carbon dioxide (CO2) is fundamental for evaluating a patient's conditions in clinical practice. There are many ways to retrieve O2/CO2 partial pressures and concentrations. Arterial blood gas (ABG) analysis is the gold standard technique for such a purpose, but it is invasive, intermittent, and potentially painful. Among all the alternative methods for gas monitoring, non-invasive transcutaneous O2 and CO2 monitoring has been emerging since the 1970s, being able to overcome the main drawbacks of ABG analysis. Clark and Severinghaus electrodes enabled the breakthrough for transcutaneous O2 and CO2 monitoring, respectively, and in the last twenty years, many innovations have been introduced as alternatives to overcome their limitations. This review reports the most recent solutions for transcutaneous O2 and CO2 monitoring, with a particular consideration for wearable measurement systems. Luminescence-based electronic paramagnetic resonance and photoacoustic sensors are investigated. Optical sensors appear to be the most promising, giving fast and accurate measurements without the need for frequent calibrations and being suitable for integration into wearable measurement systems.

Observations of cold-induced vasodilation in persons with spinal cord injuries

STUDY DESIGN

Acute experimental study.

OBJECTIVES

Cold-induced vasodilation is a local mechanism of protection against frostbite in non-injured persons. We assessed whether an increase in skin blood flow (SkBF) during local cooling (LC) was observed in individuals with spinal cord injuries (SCIs) and if the response patterns differed between region levels or sites.

SETTING

Laboratory of Wakayama Medical University and the affiliated clinics, Japan.

METHODS

A local cooler device (diameter 4 cm) was placed on the chest (sensate) and right thigh (non-sensate) in persons with cervical (SCIC; n = 9) and thoracolumbar SCIs (SCITL; n = 9). After the surface temperature under the device was controlled at 33 °C for 10 min (baseline), LC (-0.045 °C/s) was applied and the skin temperature was maintained at 15 and 8 °C for 15 min of each stage. SkBF (laser Doppler flowmetry) was monitored using a 1-mm needle-type probe inserted into its center.

RESULTS

The percent change in SkBF (%ΔSkBF) on the chest remained unchanged until the end of 15 °C stage; thereafter, it increased to a level at least 70% greater than the baseline during the 8 °C stage in both groups. The %ΔSkBF on the thigh in both SCIC and SCITL notably increased from 8 and 6 min respectively, during the 8°C stage, compared to 1 min before the stage; however, it did not exceed the baseline level.

CONCLUSIONS

An increase in SkBF during LC was observed both in the sensate and non-sensate areas in SCIs, although the magnitude was larger in the sensate area.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 2: physiological measurements

In this, the second of four historical reviews on human thermoregulation during exercise, we examine the research techniques developed by our forebears. We emphasise calorimetry and thermometry, and measurements of vasomotor and sudomotor function. Since its first human use (1899), direct calorimetry has provided the foundation for modern respirometric methods for quantifying metabolic rate, and remains the most precise index of whole-body heat exchange and storage. Its alternative, biophysical modelling, relies upon many, often dubious assumptions. Thermometry, used for >300 y to assess deep-body temperatures, provides only an instantaneous snapshot of the thermal status of tissues in contact with any thermometer. Seemingly unbeknownst to some, thermal time delays at some surrogate sites preclude valid measurements during non-steady state conditions. To assess cutaneous blood flow, immersion plethysmography was introduced (1875), followed by strain-gauge plethysmography (1949) and then laser-Doppler velocimetry (1964). Those techniques allow only local flow measurements, which may not reflect whole-body blood flows. Sudomotor function has been estimated from body-mass losses since the 1600s, but using mass losses to assess evaporation rates requires precise measures of non-evaporated sweat, which are rarely obtained. Hygrometric methods provide data for local sweat rates, but not local evaporation rates, and most local sweat rates cannot be extrapolated to reflect whole-body sweating. The objective of these methodological overviews and critiques is to provide a deeper understanding of how modern measurement techniques were developed, their underlying assumptions, and the strengths and weaknesses of the measurements used for humans exercising and working in thermally challenging conditions.

Serum uric acid: a futile bystander in endothelial function?

PURPOSE

This study aims to investigate the relationship between serum uric acid levels and endothelial function, oxidative stress, and hemodynamic parameters, and to determine if uric acid levels provide additional insights beyond traditional factors like ageing and hypertension in volunteers with low cardiovascular risk factors. Serum uric acid is known for its antioxidant properties, but it may also contribute to cardiovascular risk.

MATERIALS AND METHODS

The study enrolled 40 male participants, divided into three groups based on age and blood pressure status. Group 1 comprised younger participants, group 2 included older individuals without hypertension, and group 3 consisted of older patients with hypertension. The study assessed endothelial function using laser Doppler imaging and measured acetylcholine- and sodium nitroprusside-induced hyperaemia. The heat microcirculatory response was also examined in the presence of L-NAME, an inhibitor of NOS synthase. The study evaluated oxidative stress and arterial stiffness by measuring allantoin, angiotensin II, Homocitrulline/Lysine, and Chloro-Tyrosine/Tyrosine ratios, as well as by performing non-invasive measurements of aortic augmentation indexes and carotid-femoral pulse wave velocity.

RESULTS

The study found that uric acid levels did not differ significantly among the three groups. Augmentation indexes increased with ageing, but hypertension did not have an additional effect. Blood pressure and carotid-femoral pulse wave velocity differed among the groups, with the lowest values among younger participants and the highest values among older individuals with hypertension. Allantoin and angiotensin II levels did not differ among the groups. However, Homocitrulline/Lysine and Chloro-Tyrosine/Tyrosine ratios were significantly lower in young subjects. Correlation and multivariable analysis showed that uric acid had no effect on any of the studied parameters. Despite a strong association between ageing and systolic blood pressure with impaired endothelial function, oxidative stress, and arterial stiffness, only ageing retained a significant effect in the multivariable analysis.

CONCLUSION

In healthy or hypertensive adults with normal renal function, serum uric acid appears to be a futile bystander in endothelial function, oxidative stress, and arterial stiffness, in contrast to ageing, which reduces NO bioavailability. This study suggests that traditional factors such as ageing and hypertension should be the focus of clinical assessment and management of cardiovascular risk, rather than uric acid levels.

Wireless Dynamic Light Scattering Sensors Detect Microvascular Changes Associated With Ageing and Diabetes

This article presents clinical results of wireless portable dynamic light scattering sensors that implement laser Doppler flowmetry signal processing. It has been verified that the technology can detect microvascular changes associated with diabetes and ageing in volunteers. Studies were conducted primarily on wrist skin. Wavelet continuous spectrum calculation was used to analyse the obtained time series of blood perfusion recordings with respect to the main physiological frequency ranges of vasomotions. In patients with type 2 diabetes, the area under the continuous wavelet spectrum in the endothelial, neurogenic, myogenic, and cardio frequency ranges showed significant diagnostic value for the identification of microvascular changes. Aside from spectral analysis, autocorrelation parameters were also calculated for microcirculatory blood flow oscillations. The groups of elderly volunteers and patients with type 2 diabetes, in comparison with the control group of younger healthy volunteers, showed a statistically significant decrease of the normalised autocorrelation function in time scales up to 10 s. A set of identified parameters was used to test machine learning algorithms to classify the studied groups of young controls, elderly controls, and diabetic patients. Our conclusion describes and discusses the classification metrics that were found to be most effective.

Natural history of changes in knee skin temperature following total knee arthroplasty: a systematic review and meta-analysis

Patients undergoing total-knee arthroplasty (TKA) have transient increases in anterior knee skin temperature (ST) that subside as recovery progresses-except in cases of systemic or local prosthetic joint infections (PJI). This meta-analysis was designed to quantify the changes in knee ST following TKA in patients with uncomplicated recovery as a prerequisite for assessing the usefulness of thermal imaging for diagnosis of PJI. This meta-analysis (PROSPERO-CRD42021269864) was performed according to PRISMA guidelines. PUBMED and EMBASE were searched for studies reporting knee ST of patients that underwent unilateral TKA with uncomplicated recovery. The primary outcome was the weighted means of the differences in ST between the operated and the non-operated knees (ΔST) for each time point (before TKA, and 1 day; 1,2, and 6 weeks; and 3,6, and 12-months post-TKA). For this analysis, 318 patients were included from 10 studies. The elevation in ST was greatest during the first 2-weeks (ΔST = 2.8 °C) and remained higher than pre-surgery levels at 4-6 weeks. At 3-months, ΔST was 1.4 °C. It decreased to 0.9 °C and 0.6 °C at 6 and 12-months respectively. Establishing the baseline profile of knee ST following TKA provides the necessary first step for evaluating the usefulness of thermography for the diagnosis of post-procedural PJI.

Dentatorubropallidoluysian Atrophy with Prominent Autonomic Dysfunction

We herein report a 45-year-old man with dentatorubropallidoluysian atrophy (DRPLA) who presented with mild dementia, ataxia, and involuntary movement and developed constipation, dysuria, and orthostatic hypotension. Thermography revealed an abnormal thermal response of the skin to cold stimulation. Skin temperature reflects the skin blood flow and is regulated by the sympathetic nervous system. Thermography is currently used to study diseases associated with vasomotor dysfunction of the skin. The thermography results suggested the possibility of autonomic dysfunction. Although little is known regarding autonomic dysfunction in DRPLA, this report demonstrates the importance of autonomic dysfunction in DRPLA.

Cold-induced vasodilation response in a Japanese cohort: insights from cold-water immersion and genome-wide association studies

BACKGROUND

Cold-induced vasodilation (CIVD) occurs after blood vessels in the skin are constricted due to local cold exposure. Although many CIVD studies have been conducted, the underlying molecular mechanisms are yet to be clarified. Therefore, we explored genetic variants associated with CIVD response using the largest-scale dataset reported to date in a CIVD study involving wavelet analysis; thus, the findings improve our understanding of the molecular mechanisms that regulate the CIVD response.

METHODS

We performed wavelet analysis of three skin blood flow signals [endothelial nitric oxide (eNO)-independent, eNO-dependent, and neurogenic activities] during finger cold-water immersion at 5 °C in 94 Japanese young adults. Additionally, we conducted genome-wide association studies of CIVD using saliva samples collected from the participants.

RESULTS

We found that the mean wavelet amplitudes of eNO-independent and neurogenic activities significantly increased and decreased prior to CIVD, respectively. Our results also implied that as many as ~ 10% of the Japanese subjects did not show an apparent CIVD response. Our genome-wide association studies of CIVD using ~ 4,040,000 imputed data found no apparent CIVD-related genetic variants; however, we identified 10 genetic variants, including 2 functional genes (COL4A2 and PRLR) that are associated with notable blunted eNO-independent and neurogenic activity responses in individuals without CIVD response during local cold exposure.

CONCLUSIONS

Our findings indicate that individuals without CIVD response differentiated by genotypes with COL4A2 and PRLR genetic variants exhibited notable blunted eNO-independent and neurogenic activity responses during local cold exposure.

Quantification of catecholamine neurotransmitters released from cutaneous vasoconstrictor nerve endings in men with cervical spinal cord injury

Control of cutaneous circulation is critically important to maintain thermoregulation, especially in individuals with cervical spinal cord injury (CSCI) who have no or less central thermoregulatory drive. However, the peripheral vasoconstrictor mechanism and capability have not been fully investigated after CSCI. Post- and presynaptic sensitivities of the cutaneous vasoconstrictor system were investigated in 8 CSCI and 7 sedentary able-bodied (AB) men using an intradermal microdialysis technique. Eight doses of norepinephrine (NE, 10^-8 to 10^-1 M) and five doses of tyramine (TY, 10^-8, 10^-5 to 10^-2 M) were administered into the anterior right and left thigh, respectively. Endogenous catecholamines, noradrenaline, and dopamine, collected at the TY site, were determined by high-performance liquid chromatography with electrochemical detection. Regardless of vasoconstrictor agents, cutaneous vascular conductance decreased dose-dependently and responsiveness was similar between the groups (NE: Group P = 0.255, Dose P = 0.014; TY: Group P = 0.468, Dose P < 0.001), whereas the highest dose of each drug induced cutaneous vasodilation. Administration of TY promoted the release of noradrenaline and dopamine in both groups. Notably, the amount of noradrenaline released was similar between the groups (P = 0.819), although the concentration of dopamine was significantly greater in individuals with CSCI than in AB individuals (P = 0.004). These results suggest that both vasoconstrictor responsiveness and neural functions are maintained after CSCI, and dopamine in the skin is likely to induce cutaneous vasodilation.

N(Omega)-nitro-l-arginine methyl ester potentiates lidocaine analgesic and anaesthetic effect in rats

OBJECTIVES

The purpose of the experiment was to study the effect of L-NAME (N(Omega)-nitro-L-arginine methyl ester) and its cotreatment with lidocaine on the spinal block and infiltrative cutaneous analgesia.

METHODS

The quality of cutaneous analgesia was examined by the block of the cutaneous trunci muscle reflexes following needle stimuli in the rat. Spinal anaesthetic potency was assessed by measuring three neurobehavioral examinations of nociceptive, proprioceptive and motor function following intrathecal injection in the rat.

KEY FINDINGS

L-NAME (0.6, 6 and 60 nmol) when cotreatment with lidocaine (ED50) produced dose-related cutaneous analgesia. Coadministration of L-NAME (0.6 μmol) with lidocaine intensified (P < 0.01) and prolonged (P < 0.001) cutaneous analgesia, whereas subcutaneous L-NAME (0.6 μmol) and saline did not provoke cutaneous analgesic effects. Adding L-NAME (2.5 μmol) to lidocaine intrathecally prolonged spinal sensory and motor block (P < 0.01), while intrathecal L-NAME (2.5 μmol) or 5% dextrose (vehicle) produced no spinal block.

CONCLUSIONS

L-NAME at 60 nmol (the minimum effective dose) increases and prolongs the effect of cutaneous analgesia of lidocaine. L-NANE at an ineffective dose potentiates lidocaine analgesic and anaesthetic effects.

Twelve-Week Daily Gluteal and Hamstring Electrical Stimulation Improves Vascular Structure and Function, Limb Volume, and Sitting Pressure in Spinal Cord Injury: A Pilot Feasibility Study

OBJECTIVE

We examined the long-term effects of low-intensity electrical stimulation on (micro)vasculature and sitting pressure of a home-based, wearable electrical stimulation device in a pilot feasibility study.

DESIGN

In a cohort observation before-after trial, nine middle-aged male (n = 8) and female (n = 1) individuals (48 ± 15 yrs) with American Spinal Injury Association A-C classified chronic (1-24 yrs) spinal cord injury underwent 12 wks of self-administered daily, low-intensity gluteal and hamstring electrical stimulation (50 Hz, 6 hrs [30-min electrical stimulation, 15-min rest]). Common femoral artery diameter and blood blow were determined with ultrasound, skin vascular function during local heating was assessed using Laser-Doppler flowmetry, thigh volume was estimated using leg circumferences and skinfolds, and interface sitting pressure was measured using pressure mapping.

RESULTS

Resting common femoral artery diameter increased (0.73 ± 0.20 to 0.79 ± 0.22 cm, P < 0.001) and baseline common femoral artery blood flow increased (0.28 ± 0.12 to 0.40 ± 0.15 l/min, P < 0.002). Gluteal cutaneous vascular conductance showed a time*temperature interaction (P = 0.01) with higher conductance at 42°C after 12 wks. Ischial peak pressure decreased (P = 0.003) by 32 ± 23 mm Hg and pressure gradient decreased (23 ± 7 to 16 ± 6 mm Hg, P = 0.007). Thigh volume increased (+19%, P = 0.01).

CONCLUSIONS

Twelve-week daily home-based gluteal and hamstring electrical stimulation is feasible and effective to improve (micro)vasculature and sitting pressure, and electrical stimulation may have clinical implications for ameliorating pressure ulcers and (micro)vascular complications in spinal cord injury.

Sex differences during a cold-stress test in normobaric and hypobaric hypoxia: A randomized controlled crossover study

Cold and hypoxia are two stressors that are frequently combined and investigated in the scientific literature. Despite the growing literature regarding normobaric hypoxia (NH) and hypobaric hypoxia (HH), responses between females and males are less often evaluated. Therefore, this study aims to investigate the physiological sex differences following a cold-stress test under normoxia, normobaric- and hypobaric hypoxia. A total of n = 10 females (24.8 ± 5.1 years) and n = 10 males (30.3 ± 6.3 years) from a university population volunteered for this study. The cold-stress test (CST) of the right hand (15°C for 2 min) was performed using a randomised crossover design in normobaric normoxia, NH and HH. The change (∆) from baseline to post-CST up to 15 min was analysed for cutaneous vascular conductance (CVC) and the hands’ skin temperature, whilst the mean values across time (post-CST up to 15 min) were assessed for peripheral oxygen saturation (SpO₂), thermal sensation- and comfort. Pressure pain threshold (PPT) was assessed after the post-CST 15 min period. The hands’ skin temperature drop was higher (p = 0.01) in the female group (∆3.3 ± 1.5°C) compared to the male group (∆1.9 ± 0.9°C) only in NH. Females (−0.9 ± 0.5) rated this temperature drop in NH to feel significantly colder (p = 0.02) compared to the males (−0.2 ± 0.7). No differences were observed between sexes in NN, NH, and HH for ∆CVC, SpO₂, thermal comfort and PPT. In conclusion, females and males show similar reactions after a CST under normoxia and hypoxia. Sex differences were observed in the local skin temperature response and thermal sensation only in NH.

Novel Method to Assess Endothelial Function via Monitoring of Perfusion Response to Local Heating by Imaging Photoplethysmography

Endothelial dysfunction is one of the most important markers of the risk of cardiovascular complications. This study is aimed to demonstrate the feasibility of imaging photoplethysmography to assess microcirculation response to local heating in order to develop a novel technology for assessing endothelial function. As a measure of vasodilation, we used the relative dynamics of the pulsatile component of the photoplethysmographic waveform, which was assessed in a large area of the outer surface of the middle third of the subject's forearm. The perfusion response was evaluated in six healthy volunteers during a test with local skin heating up to 40-42 °C and subsequent relaxation. The proposed method is featured by accurate control of the parameters affecting the microcirculation during the prolonged study. It was found that in response to local hyperthermia, a multiple increase in the pulsation component, which has a biphasic character, was observed. The amplitude of the first phase of the perfusion reaction depends on both the initial skin temperature and the difference between the basal and heating temperatures. The proposed method allows the assessment of a reproducible perfusion increase in response to hyperthermia developed due to humoral factors associated with the endothelium, thus allowing detection of its dysfunction.

Effects of regular physical exercise on skin blood flow and cardiovascular risk factors in overweight and obese subjects

Objective: it is well known that low omentin levels and reduced bioavailability of nitric oxide (NO) are outgrowth of obesity. Besides, in obese subjects, microvascular dysfunction can be an initial stage of cardiovascular diseases. This situation can be evaluated with skin laser–Doppler flowmetry (LDF).Methods: in this study we investigated the effects of 12 weeks moderate physical exercise on microvascular reactivity and plasma levels of omentin and NO in 25 overweight and obese subjects. Control group was composed of 28 sedentary participants who were neither obese nor overweight. Microvascular reactivity was handled by measurement of skin blood flow from the ring finger of the right hand with LDF, which is a non–invasive method for evaluation. With this method, it was aimed to examine the post–occlusive reactive hyperemia response of the patients. None of the participants in both groups have never followed a regular exercise schedule in their life span.Results: with regular exercise, there was a statistically significant decrease in glucose (p=0.008), cholesterol (p=0.05), and triglyceride (p=0.048) levels, while body mass index, high–density lipoprotein, and low–density lipoprotein levels did not change significantly in overweight/obese group. Also, the omentin level significantly increased (p=0.01), but NO level did not change significantly. Moreover, the amount of change in omentin and NO levels measured before and after the physical exercise were significantly correlated (r=0.57). Considering the microcirculation, rest flow (p=0.001) and peak flow value of LDF (p=0.001) increased after the physical exercise.Conclusion: our study shows that moderate physical exercise affects microvascular reactivity and plasma levels of omentin in overweight and obese subjects.

Feasibility of Diagnosing Initial Orthostatic Hypotension Using a Continuous Blood Pressure Device in Geriatric Rehabilitation Inpatients: RESORT

Background

Initial orthostatic hypotension (IOH) is highly prevalent in older adults and may interfere with the ability to regain function after acute hospitalization. IOH assessment requires a non-invasive, beat-to-beat continuous blood pressure device, which is not widely used in geriatric rehabilitation. Our aim was to test the feasibility of diagnosing IOH using a continuous blood pressure device in geriatric rehabilitation inpatients.

Methods

Geriatric rehabilitation inpatients of the REStORing Health of Acutely Unwell AdulTs (RESORT) cohort admitted to a tertiary hospital were randomly selected to undergo continuous blood pressure monitoring (Finapres) for 5 min in the supine position and 3 min of standing or sitting when unable to stand. Interventions to warm hands and adjusting the cuff pressure sizes were attempted if no signal was obtained or an error message occurred.

Results

Of 37 randomly selected inpatients, 29 {55.2% female; mean age 82.8 (standard deviation [SD]) 6.6 years} agreed to the continuous blood pressure measurement. Successful measurements were achieved in 20 out of 29 inpatients, two after hand warming. Patients with unsuccessful measurements were likely to be older (mean age 87.2 [SD] 4.4 years, p = 0.03), have cerebrovascular disease (p = 0.006), lower body mass index (p = 0.012), and a lower short physical performance battery score (p = 0.039). Eight out of 20 patients had IOH.

Conclusion

The number of unsuccessful continuous blood pressure measurements was high in a population with high IOH prevalence despite multiple interventions to establish a signal. Future research should focus on improving the efficiency of continuous blood pressure devices in hospitalized patients with unsuccessful signals.

Impact of tetraplegia vs. paraplegia on venoarteriolar, myogenic and maximal cutaneous vasodilation responses of the microvasculature: Implications for cardiovascular disease

Objective: Cardiovascular disease (CVD) is a leading cause of mortality in persons with SCI. While macrovascular remodeling and function after SCI is well documented, changes in the microvascular structure and function are comparably understudied, but importantly predict CVD risk. Specifically, the integrity of venoarteriolar (VAR), myogenic (MYO) and maximal vasodilation responses are largely unknown after SCI, especially in persons with tetraplegia (TP) at highest risk of CVD. This is the first to examine the differences in VAR (cuff inflation), MYO (limb dependency) and maximal vasodilation responses of the microvasculature between able bodied (AB) versus those with TP and paraplegia (PP).Design: Observational.Setting: Laboratory.Participants: Eight AB, 6 TP, and 8 PP persons.Interventions: One forearm and calf were treated topically with lidocaine 2.5%/prilocaine 2.5% while contralateral limb served as a control. Laser doppler flowmeters were applied over treated and control sites during limb dependency, cuff inflation and local skin heating (Tloc) up to 42°C.Outcome measures: Skin vascular resistance (SkVR) change with cuff inflation and limb dependency and maximal cutaneous vascular conductance (CVC) during local heating.Results: Change in SkVR was not significantly different between groups or extremity (upper vs. lower) during cuff inflation or limb dependency. However, CVC at Tloc 42°C was significantly different in the lower extremity (LE) of TP and PP (P = 0.007, 0.35) compared to AB.Conclusion: Increases in SkVR during cuff inflation (VAR) and limb dependency (VAR and MYO) are unaltered after SCI, however maximal vasodilation in the LE post-SCI is higher than AB persons.

Cutaneous iontophoresis of vasoactive medications in patients with scleroderma-associated pulmonary arterial hypertension

BACKGROUND

It remains unknown whether the cutaneous microvascular responses are different between patients with scleroderma-associated pulmonary arterial hypertension (SSc-PAH) and SSc without pulmonary hypertension (PH).

METHODS

We included 59 patients with SSc between March 2013 and September 2019. We divided patients into 4 groups: (a) no PH by right heart catheterization (RHC) (n = 8), (b) no PH by noninvasive screening tests (n = 16), (c) treatment naïve PAH (n = 16), and (d) PAH under treatment (n = 19). Microvascular studies using laser Doppler flowmetry (LDF) were done immediately after RHC or at the time of an outpatient clinic visit (group b).

RESULTS

The median (IQR) age was 59 (54-68) years, and 90% were females. The responses to local thermal stimulation and postocclusive reactive hyperemia, acetylcholine, and sodium nitroprusside iontophoresis were similar among groups. The microvascular response to treprostinil was more pronounced in SSc patients without PH by screening tests (% change: 340 (214-781)) compared with SSc-PAH (naïve + treatment) (Perfusion Units (PU) % change: 153 (94-255) % [p = .01]). The response to A-350619 (a soluble guanylate cyclase (sGC) activator) was significantly higher in patients with SSc without PH by screening tests (PU % change: 168 (46-1,296)) than those with SSc-PAH (PU % change: 22 (15-57) % [p = .006]). The % change in PU with A350619 was directly associated with cardiac index and stroke volume index (R: 0.36, p = .03 and 0.39, p = .02, respectively).

CONCLUSIONS

Patients with SSc-PAH have a lower cutaneous microvascular response to a prostacyclin analog treprostinil and the sGC activator A-350619 when compared with patients with SSc and no evidence of PH on screening tests, presumably due to a peripheral reduction in prostacyclin receptor expression and nitric oxide bioavailability.

Acute effects of hypouricemia on endothelium, oxidative stress, and arterial stiffness: A randomized, double-blind, crossover study

We hypothesized acute moderate and drastic reductions in uric acid concentration exert different effects on arterial function in healthy normotensive and hypertensive adults. Thirty-six adults (aged 58 [55;63] years) with or without primary hypertension participated in a three-way, randomized, double-blind, crossover study in which [placebo] and [febuxostat] and [febuxostat and rasburicase] were administered. Febuxostat and rasburicase reduce the uric acid concentration by xanthine oxidoreductase inhibition and uric acid degradation into allantoin, respectively. Endothelial function was assessed in response to acetylcholine, sodium nitroprusside, heating (with and without nitric oxide synthase inhibition) using a laser Doppler imager. Arterial stiffness was determined by applanation tonometry, together with blood pressure, renin-angiotensin system activity, oxidative stress, and inflammation. Uric acid concentration was 5.1 [4.1;5.9], 1.9 [1.2;2.2] and 0.2 [0.2;0.3] mg/dL with [placebo], [febuxostat] and [febuxostat-rasburicase] treatments, respectively (p < 0.0001). Febuxostat improved endothelial response to heat particularly when nitric oxide synthase was inhibited (p < 0.05) and reduced diastolic and mean arterial pressure (p = 0.008 and 0.02, respectively). The augmentation index decreased with febuxostat (ANOVA p < 0.04). Myeloperoxidase activity profoundly decreased with febuxostat combined with rasburicase (p < 0.0001). When uric acid dropped, plasmatic antioxidant capacity markedly decreased, while superoxide dismutase activity increased (p < 0.0001). Other inflammatory and oxidant markers did not differ. Acute moderate hypouricemia encompasses minor improvements in endothelial function, blood pressure, and arterial stiffness. Clinical Trial Registration: NCT03395977, https://clinicaltrials.gov/ct2/show/NCT03395977.

Using reactive hyperemia to investigate the effect of cupping sizes of cupping therapy on skin blood flow responses

BACKGROUND

Various cupping sizes of cupping therapy have been used in managing musculoskeletal conditions; however, the effect of cupping sizes on skin blood flow (SBF) responses is largely unknown.

OBJECTIVE

The objective of this study was to compare the effect of three cupping sizes of cupping therapy on SBF responses.

METHODS

Laser Doppler flowmetry (LDF) was used to measure SBF on the triceps in 12 healthy participants in this repeated measures study. Three cup sizes (35, 40 and 45 mm in diameter) were blinded to the participants and were tested at -300 mmHg for 5 minutes. Reactive hyperemic response to cupping therapy was expressed as a ratio of baseline SBF.

RESULTS

All three sizes of cupping cups resulted in a significant increase in peak SBF (p< 0.001). Peak SBF of the 45 mm cup (9.41 ± 1.32 times) was significantly higher than the 35 mm cup (5.62 ± 1.42 times, p< 0.05). Total SBF of the 45 mm cup ((24.33 ± 8.72) × 103 times) was significantly higher than the 35 mm cup ((8.05 ± 1.63) × 103 times, p< 0.05). Recovery time of the 45 mm cup (287.46 ± 39.54 seconds) was significantly longer than the 35 mm cup (180.12 ± 1.42 seconds, p< 0.05).

CONCLUSIONS

Our results show that all three cup sizes can significantly increase SBF. The 45 mm cup is more effective in increasing SBF compared to the 35 mm cup.

In elderly Caucasian women, younger facial perceived age correlates with better forearm skin microcirculation reactivity

BACKGROUND

Visual and molecular changes occurring upon aging are rather well characterized. Still, aging signs show great significant inter-individual variations, and little is known concerning the link between perceived age and cutaneous microcirculation.

MATERIALS AND METHODS

To investigate this point, we recruited Caucasian women in their mid-50's to mid-70's and subsampled women looking older or younger than their age. We studied their facial skin color, as well as their microvascular reactivity to local heating assessed in the forearm skin. We also used skin biopsies from some of these women for gene expression or immunohistochemical analysis.

RESULTS

Clinical and instrumental analysis of skin color revealed that subjects who look 5 years younger differ only by a higher glowing complexion. Our most striking result is that subjects looking 5 years younger than their age present a higher microcirculation reactivity in forearm skin. Transcriptome comparison of skin samples from women looking older or younger than their age revealed 123 annotated transcripts differentially expressed, among which MYL9 relates to microcirculation. MYL9 is downregulated in the group of women looking younger than their real age. Microscopy shows that the labeling of MYL9 and CD31 are altered and heterogeneous with age, as is the morphology of microvessels.

CONCLUSION

Therefore, assessing generalized vascular reactivity in non-photo-exposed skin to focus on the intrinsic aging allows subtle discrimination of perceived age within elderly healthy subjects.

Assessment of the Dynamics of Temperature Changes in the Knee Joint Area in Response to Selected Cooling Agents in Thermographic Tests

Although local cryotherapy (LC) is performed with various cooling agents (C_Ag) such as ice, water, and gasses, in clinical practice, it is mostly performed with cooling gasses. Presently, LC with cooling gasses is very popular but the inference about the thermal (stimulus) effect on the tissues is mainly based on research carried out using ice packs. The proposed objective of the study was to evaluate the dynamics of temperature changes in the knee joint area in response to a 3-min exposure to liquid nitrogen vapors (LNVs), cold air (CA) and ice bag (IB). The study group included 23 healthy volunteers with an average age of 26.67 ± 4.56. The exposed (ROI_E) and contralateral (ROI_NE) areas of the knee joint after exposure to C_Ag were observed. Immediately after 3 min of LC, the ROI_E temperature dropped by 10.11 ± 0.91 °C after LNV, 7.59 ± 0.14 °C after IB and 6.76 ± 1.3 °C after CA. Significant tissue cooling was maintained up to 15 min after LNV (p < 0.01), 10 min after IB (p < 0.05) and 5 min after CA (p < 0.05). LC causes significant temperature changes both in ROI_E and ROI_NE. The greatest cooling potential was demonstrated for LNV and the lowest for CA.

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.

Effects of acute dietary nitrate supplementation on cold-induced vasodilation in healthy males

PURPOSE

Cold-induced vasodilation (CIVD) is a paradoxical rise in blood flow to the digits that occur during prolonged cold exposure. CIVD is thought to occur through active vasodilation and/or sympathetic withdrawal, where nitric oxide (NO) may play a key role in mediating these mechanisms. Beetroot juice (BRJ) is high in dietary nitrate (NO₃^-) which undergoes sequential reduction to nitrite (NO₂^-) and subsequently NO. Using a double-blind, randomized, crossover design, we examined the effect of acute BRJ supplementation on the CIVD response in 10 healthy males.

METHODS

Participants had a resting blood pressure measurement taken prior to ingesting 140 mL of nitrate-rich BRJ (13 mmol NO₃^-) or a NO₃^--free placebo (PLA). After 2 h, participants immersed their hand in neutral water (~ 35 °C) for 10 min of baseline before cold water immersion (~ 8 °C) for 30 min. Laser-Doppler fluxmetry and skin temperature were measured continuously on the digits.

RESULTS

Compared to PLA (100 ± 3 mmHg), acute BRJ supplementation significantly reduced mean arterial pressure at -30 min (96 ± 2 mmHg; p = 0.007) and 0 min (94 ± 2 mmHg; p = 0.008). Acute BRJ supplementation had no effect on Laser-Doppler fluxmetry during CIVD (expressed as cutaneous vascular conductance) measured as area under the curve (BRJ: 843 ± 148 PU mmHg^-1 s; PLA: 1086 ± 333 PU mmHg^-1 s), amplitude (BRJ: 0.60 ± 0.12 PU mmHg^-1; PLA: 0.69 ± 0.14 PU mmHg^-1), and duration (BRJ: 895 ± 60 s; PLA: 894 ± 46 s).

CONCLUSION

Acute BRJ supplementation does not augment the CIVD response in healthy males.

Non-Contact Assessment of Peripheral Artery Haemodynamics Using Infrared Video Thermography

Skin temperature has long been used as a natural indicator of vascular diseases in the extremities. Considerable correlation between oscillations in skin surface temperature and oscillations of skin blood flow has previously been demonstrated. We hypothesised that the impairment of blood flow in stenotic (subcutaneous) peripheral arteries would influence cutaneous temperature such that, by measuring gradients in the temperature distribution over skin surfaces, one may be able to diagnose or quantify the progression of vascular conditions in whose pathogenesis a reduction in subcutaneous blood perfusion plays a critical role (e.g. peripheral artery disease). As proof of principle, this study investigates the local changes in the skin temperature of healthy humans (15 male, [Formula: see text] years old, BMI [Formula: see text] kg/m ²) undergoing two physical challenges designed to vary their haemodynamic status. Skin temperature was measured in four central regions (forehead, neck, chest, and left shoulder) and four peripheral regions (left upper arm, forearm, wrist, and hand) using an infrared thermal camera. We compare inter-region patterns. Median temperature over the peripheral regions decreased from baseline after both challenges (maximum decrease: [Formula: see text] °C at 60 s after exercise; [Formula: see text] and [Formula: see text] °C at 180 s of cold-water immersion; [Formula: see text]). Median temperature over the central regions showed no significant changes. Our results show that the non-contact measurement of perfusion-related changes in peripheral temperature from infrared video data is feasible. Further research will be directed towards the thermographic study of patients with symptomatic peripheral vascular disease.

Evaluation of sympathetic adrenergic branch of cutaneous neural control throughout thermography and its relationship to nitric oxide levels in patients with fibromyalgia

BACKGROUND

Fibromyalgia syndrome is defined as a complex disease, characterized by chronic widespread musculoskeletal pain and other symptoms. The factors underlying physiopathology of fibromyalgia are not well understood, complicating its diagnosis and management.

OBJECTIVES

To evaluate the peripheral vascular blood flow of the skin of the hands and the core body temperature as indirect measures of sympathetic adrenergic activity of the nervous system and its relationship to nitric oxide levels (NO) in women with fibromyalgia compared with healthy controls.

METHODS

Forty-two women with fibromyalgia and 52 healthy women were enrolled in this observational pilot study. We used infrared thermography of the hands and an infrared dermal thermometer to evaluate the peripheral vascular blood flow and tympanic and axillary core body temperature, respectively. We measured NO levels using the ozone chemiluminescence-based method.

RESULTS

Two-way analysis of covariance (ANCOVA) showed that the tympanic (P=0.002) and hand temperatures were significantly higher in the patients with fibromyalgia than in the controls (P≤0.001). Significant associations were also found between serum NO levels and minimum temperatures at the dorsal center of the dominant hand (β=-3.501; 95% confidence interval [CI] -6.805, ‑0.198; P= 0.038), maximum temperature (β=-5.594; 95% CI ‑10.106, ‑1.081; P=0.016), minimum temperature (β=-4.090; 95% CI ‑7.905, ‑0.275; P=0.036), and mean temperature (β=-5.519; 95% CI ‑9.933, ‑1.106; P=0.015) of the center of the palm of the non-dominant hand, maximum temperature at the thenar eminence of the dominant hand (β=-5.800; 95% CI ‑10.508, ‑1.092; P=0.017), and tympanic temperature (β=-9.321; 95% CI ‑17.974, ‑0.669; P=0.035) in the controls.

CONCLUSIONS

Our findings indicate that the women with fibromyalgia showed higher tympanic core body and hand temperature than the healthy controls. Moreover, there were negative associations between hand peripheral vasodilation and NO in the healthy women but not in those with fibromyalgia, suggesting a dysfunction of sympathetic cutaneous neural control.

Local knee heating increases spinal and supraspinal excitability and enhances plantar flexion and dorsiflexion torque production of the ankle in older adults

PURPOSE

Aging is associated with progressive loss of active muscle mass and consequent decreases in resting metabolic rate and body temperature, and slowing of nerve conduction velocities and muscle contractility. These effectors compromise the ability of the elderly to maintain an upright posture during sudden balance perturbation, increase the risk of falls, and lead to self-imposed reduction in physical activity. Short-term superficial acute heating can modulate the neural drive transmission to exercising muscles without any marked change in deep-muscle temperature.

METHODS

To determine whether the short-term (5 min) application of local passive knee-surface heating (next-to-skin temperature, ~ 44 °C) in healthy older subjects of both sexes (64-74 years; eight men/eight women) enhances reflex excitability, we compared the voluntarily and electrically induced ankle muscle torque production and contractile properties with those of healthy younger subjects of both sexes (21-35 years, 10 men/10 women).

RESULTS

The application of local heating (vs. control) increased the maximal Hoffman reflex (H_max), the maximal volitional wave (V_sup) amplitude, and the H_max/M_max amplitude ratio, and decreased V_sup latency only in older adults. In the older adults (vs. younger adults), the application of local heating (vs. control trial) was accompanied by a significant increase in maximal voluntary peak torque, rate of torque development, and isokinetic peak torque of plantar flexion/dorsiflexion muscle contraction.

CONCLUSION

The spinal and supraspinal reflex excitability of older adults increased during local knee-heating application. The improved motor drive transmission observed in older adults was accompanied by increased voluntarily induced torque production of the ankle muscles during isometric/isokinetic contractions.

Topical Nifedipine Administration for Secondary Prevention in Frostbitten Patients

Frostbite is a cold-related injury with a growing incidence among healthy subjects. Sequelae after frostbite are frequent and vary among individuals. Here, we studied the thermal response in the digits of hands and feet of five subjects who had recovered from previous frostbite, except for their lasting sequelae. We considered three different conditions: digits unaffected by frostbite nor sequelae (healthy), those affected but which did not suffer amputation (frostbitten without amputation), and the remainder/stumps of digits that underwent partial amputation (frostbitten with amputation). Three consecutive immersions in cold water (8°C; 3 min) interspersed by 1 minute of thermal recovery were performed. After 30 min, a topical 10% nifedipine preparation was applied to hands and feet, and the same cold exposure protocol to evaluate its effect was followed. In basal condition and immediately after each immersion, the temperature of individual digits was assessed using thermography. We observed different thermal responses among the different digits of hands and feet, even without the nifedipine treatment. Nifedipine had a cooling effect on healthy and post-amputated tissue without thermal stress. In cold conditions, topic nifedipine application improved the cold response in healthy fingers but had a negative effect on those from which parts had been amputated. The topical nifedipine had detrimental effects on toes in all conditions. Topical nifedipine can help to the preservation of healthy fingers exposed to cold, with adequate thermal insulation; but it is necessary to remark its potentially harmful effects on previously frostbitten tissue. Because of the differences observed on individual regional response to cold, thermography can be a useful tool in the frostbite prevention for subjects habitually exposed to cold environment.

Muscle cooling modulates tissue oxidative and biochemical responses but not energy metabolism during exercise

PURPOSE

This study investigated whether muscle cooling and its associated effects on skeletal muscle oxidative responses, blood gases, and hormonal concentrations influenced energy metabolism during cycling.

METHODS

Twelve healthy participants (Males: seven; Females: five) performed two steady-state exercise sessions at 70% of ventilatory threshold on a cycle ergometer. Participants completed one session with pre-exercise leg cooling until muscle temperature (T_m) decreased by 6 °C (LCO), and a separate session without cooling (CON). They exercised until T_m returned to baseline and for an additional 30 min. Cardiovascular, respiratory, metabolic, hemodynamic variables, and skeletal muscle tissue oxidative responses were assessed continuously. Venous blood samples were collected to assess blood gases, and hormones.

RESULTS

Heart rate, stroke volume, and cardiac output all increased across time but were not different between conditions. V̇O₂ was greater in LCO when muscle temperature was restored until the end of exercise (p < 0.05). Cycling in the LCO condition induced lower oxygen availability, tissue oxygenation, blood pH, sO₂%, and pO₂ (p < 0.05). Insulin concentrations were also higher in LCO vs. CON (p < 0.05). Importantly, stoichiometric equations from respiratory gases indicated no differences in fat and CHO oxidation between conditions.

CONCLUSION

The present study demonstrated that despite muscle cooling and the associated oxidative and biochemical changes, energy metabolism remained unaltered during cycling. Whether lower local and systemic oxygen availability is counteracted via a cold-induced activation of lipid metabolism pathways needs to be further investigated.

Cutaneous sensory nerve-mediated microvascular vasodilation in normotensive and prehypertensive non-Hispanic Blacks and Whites

Relative to non-Hispanic Whites, non-Hispanic Blacks are disproportionately affected by elevated blood pressure (BP). It is unknown whether race or subclinical increases in BP affect the ability of cutaneous sensory nerves to induce cutaneous microvascular vasodilation. Sixteen participants who self-identified as non-Hispanic Black (n = 8) or non-Hispanic White (n = 8) were subgrouped as normotensive or prehypertensive. Participants were instrumented with three intradermal microdialysis fibers: (a) control, (b) 1 μM sodium nitroprusside (SNP), an exogenous nitric oxide (NO) donor, and (c) 20 mM NG -nitro-l-arginine methyl ester (L-NAME), a non-selective NO synthase inhibitor. A slow local heating protocol (33-40°C, 0.1°C/min) was used to assess the onset of cutaneous sensory nerve-mediated vasodilation (temperature threshold) and skin blood flow was measured using laser-Doppler flowmetry. At control sites, the temperature threshold occurred at a higher temperature in non-Hispanic Blacks (normotensive: 37.2 ± 0.6°C, prehypertensive: 38.9 ± 0.5°C) compared to non-Hispanic Whites (normotensive: 35.2 ± 0.8°C, prehypertensive: 35.2 ± 0.9°C). L-NAME shifted the temperature threshold higher in non-Hispanic Whites (normotensive: 37.8 ± 0.7°C, prehypertensive: 38.2 ± 0.8°C), but there was no observed effect in non-Hispanic Blacks. SNP did not affect temperature threshold in non-Hispanic Whites, but shifted the temperature threshold lower in non-Hispanic Blacks (normotensive: 34.6 ± 1.2°C, prehypertensive: 34.8 ± 1.1°C). SNP mitigated differences in temperature threshold across all groups. There was no effect found for BP status in either the non-Hispanic Black or non-Hispanic White groups. These data suggest that reduced NO bioavailability affects the ability of cutaneous sensory nerves to induce microvascular vasodilation in young, otherwise healthy non-Hispanic Blacks.

Optical coherence tomography for the investigation of skin adaptation to mechanical stress

BACKGROUND

Skin breakdown due to limb-socket interface stress is a significant problem for lower limb prosthesis users. While it is known that skin can adapt to stress to become more resistant to breakdown, little is understood about skin adaptation and few methods exist to noninvasively investigate it. In this study, we present novel, noninvasive imaging methods using Optical Coherence Tomography (OCT) to assess key features of the cutaneous microvasculature that may be involved in skin adaptation.

MATERIALS AND METHODS

Eight able-bodied participants wore a modified below-knee prosthetic socket for two weeks to stress the skin of their lower limb. Two OCT-based imaging tests were used to assess the function and structure, respectively, of the cutaneous microvasculature at multiple time points throughout the socket wear protocol.

RESULTS

A measurable reactive hyperemia response was reliably induced in the skin of study participants in the vascular function assessment test. The vascular structure assessment demonstrated excellent field-of-view repeatability, providing rich data sets of vessel structure. No statistically significant differences were found in any of the measurements when compared between time points of the adaptation protocol. The participants' limbs were likely not stressed enough by the able-bodied socket to induce measurable skin adaptation.

CONCLUSION

This study introduced new techniques to investigate skin adaptation to mechanical stress. If the key limitations are addressed, these methods have the potential to provide insight into the function and structure of the cutaneous microvasculature that previously could not be attained noninvasively.