Non-invasive methods and stimuli for evaluating the skin's microcirculation

Scanning optoacoustic angiography for assessing structural and functional alterations in superficial vasculature of patients with post-thrombotic syndrome: A pilot study

This study highlights the potential of scanning optoacoustic angiography (OA) in identifying alterations of superficial vasculature in patients with post-thrombotic syndrome (PTS) of the foot, a venous stress disorder associated with significant morbidity developing from long-term effects of deep venous thrombosis. The traditional angiography methods available in the clinics are not capable of reliably assessing the state of peripheral veins that provide blood outflow from the skin, a key hallmark of personalized risks of PTS formation after venous thrombosis. Our findings indicate that OA can detect an increase in blood volume, diameter, and tortuosity of superficial blood vessels. The inability to spatially separate vascular plexuses of the dermis and subcutaneous adipose tissue serves as a crucial criterion for distinguishing PTS from normal vasculature. Furthermore, our study demonstrates the ability of scanning optoacoustic angiography to detect blood filling decrease in an elevated limb position versus increase in a lowered position.

Biomechanical Profile after Dry Needling in Mixed Martial Arts

The purpose of this study was to compare the effects of dry needling (DN) intervention on the responses of muscle tone, stiffness, and elasticity, as well as power, pressure pain thresholds, and blood perfusion of the flexor carpi radialis muscle in mixed martial arts (MMA) athletes. Thirty-two trained/developmental men MMA fighters (25.5±4.5 years; 24.5±3 body mass index) participated in a randomized crossover study. Participants underwent a single intervention, receiving both DN and placebo. Laser Doppler flowmetry measured blood perfusion, while a myotonometer assessed the mechanical characteristics of muscle tone, stiffness, and elasticity of the flexor carpi radialis muscle. Pressure pain thresholds (PPT) were measured using an algometer, and maximal forearm muscle force was measured using a hand dynamometer. Outcomes were assessed at baseline, immediately after, and 24 hours and 48 hours post-intervention. A two-way repeated-measures ANOVA revealed significant Intervention*Time interaction for all outcomes: perfusion unit (p<0.001), muscle tone (p<0.001), stiffness (p<0.001), elasticity (p<0.001), PPT (p<0.001) and maximal forearm muscle force (p<0.001). The current study suggests that a single session of DN enhances muscle recovery, increases muscle strength, and improved PPT in MMA athletes. These positive adaptations appear to last up to 48 hours in some variables.

An evaluation of the effects of localised skin cooling on microvascular, inflammatory, structural, and perceptual responses to sustained mechanical loading of the sacrum: A study protocol

This study protocol aims to investigate how localised cooling influences the skin's microvascular, inflammatory, structural, and perceptual tolerance to sustained mechanical loading at the sacrum, evaluating factors such as morphology, physiology, and perceptual responses. The protocol will be tested on individuals of different age, sex, skin tone and clinical status, using a repeated-measure design with three participants cohorts: i) young healthy (n = 35); ii) older healthy (n = 35); iii) spinal cord injured (SCI, n = 35). Participants will complete three testing sessions during which their sacrum will be mechanically loaded (60 mmHg; 45 min) and unloaded (20 min) with a custom-built thermal probe, causing pressure-induced ischemia and post-occlusive reactive hyperaemia. Testing sessions will differ by the probe's temperature, which will be set to either 38°C (no cooling), 24°C (mild cooling), or 16°C (strong cooling). We will measure skin blood flow (via Laser Doppler Flowmetry; 40 Hz); pro- and anti-inflammatory biomarkers in skin sebum (Sebutape); structural skin properties (Optical Coherence Tomography); and ratings of thermal sensation, comfort, and acceptance (Likert Scales); throughout the loading and unloading phases. Changes in post-occlusive reactive hyperaemia will be considered as the primary outcome and data will be analysed for the independent and interactive effects of stimuli's temperature and of participant group on within- and between-subject mean differences (and 95% Confidence Intervals) in peak hyperaemia, by means of a 2-way mixed model ANOVA (or Friedman). Regression models will also be developed to assess the relationship between absolute cooling temperatures and peak hyperaemia. Secondary outcomes will be within- and between-subject mean changes in biomarkers' expression, skin structural and perceptual responses. This analysis will help identifying physiological and perceptual thresholds for the protective effects of cooling from mechanically induced damage underlying the development of pressure ulcers in individuals varying in age and clinical status.

Peripheral blood flow estimated by laser doppler flowmetry provides additional information about sleep state beyond that provided by pulse rate variability

Pulse rate variability (PRV), derived from Laser Doppler flowmetry (LDF) or photoplethysmography, has recently become widely used for sleep state assessment, although it cannot identify all the sleep stages. Peripheral blood flow (BF), also estimated by LDF, may be modulated by sleep stages; however, few studies have explored its potential for assessing sleep state. Thus, we aimed to investigate whether peripheral BF could provide information about sleep stages, and thus improve sleep state assessment. We performed electrocardiography and simultaneously recorded BF signals by LDF from the right-index finger and ear concha of 45 healthy participants (13 women; mean age, 22.5 ± 3.4 years) during one night of polysomnographic recording. Time- and frequency-domain parameters of peripheral BF, and time-domain, frequency-domain, and non-linear indices of PRV and heart rate variability (HRV) were calculated. Finger-BF parameters in the time and frequency domains provided information about different sleep stages, some of which (such as the difference between N1 and rapid eye movement sleep) were not revealed by finger-PRV. In addition, finger-PRV patterns and HRV patterns were similar for most parameters. Further, both finger- and ear-BF results showed 0.2-0.3 Hz oscillations that varied with sleep stages, with a significant increase in N3, suggesting a modulation of respiration within this frequency band. These results showed that peripheral BF could provide information for different sleep stages, some of which was complementary to the information provided by PRV. Furthermore, the combination of peripheral BF and PRV may be more advantageous than HRV alone in assessing sleep states and related autonomic nervous activity.

Exploring the relationship between capillary refill time, skin blood flow and microcirculatory reactivity during early resuscitation of patients with septic shock: a pilot study

Capillary refill time (CRT), a costless and widely available tool, has emerged as a promising target to guide septic shock resuscitation. However, it has yet to gain universal acceptance due to its potential inter-observer variability. Standardization of CRT assessment may minimize this problem, but few studies have compared this approach with techniques that directly assess skin blood flow (SBF). Our objective was to determine if an abnormal CRT is associated with impaired SBF and microvascular reactivity in early septic shock patients. Twelve septic shock patients were subjected to multimodal perfusion and hemodynamic monitoring for 24 h. Three time-points (0, 1, and 24 h) were registered for each patient. SBF was measured by laser doppler. We performed a baseline SBF measurement and two microvascular reactivity tests: one with a thermal challenge at 44 °C and other with a vascular occlusion test. Ten healthy volunteers were evaluated to obtain reference values. The patients (median age 70 years) exhibited a 28-day mortality of 50%. Baseline CRT was 3.3 [2.7-7.3] seconds. In pooled data analysis, abnormal CRT presented a significantly lower SBF when compared to normal CRT [44 (13.3-80.3) vs 193.2 (99.4-285) APU, p = 0.0001]. CRT was strongly associated with SBF (R² 0.76, p < 0.0001). An abnormal CRT also was associated with impaired thermal challenge and vascular occlusion tests. Abnormal CRT values observed during early septic shock resuscitation are associated with impaired skin blood flow, and abnormal skin microvascular reactivity. Future studies should confirm these results.

Characterization of Baseline Temperature Characteristics Using Thermography in The Clinical Setting

BACKGROUND

Thermography is a diagnostic method based on the ability to record infrared radiation emitted by the skin and is unique in its ability to accurately show physiological and/or pathological cutaneous temperature changes in a non-invasive way. This method can be used to indirectly assess changes or impairments in cutaneous perfusion. Significant technological advancements have allowed thermography to be more commonly utilized by clinicians, yet a basic consensus of patient characteristics that may affect temperature recordings is not established.

MATERIALS AND METHODS

We evaluated cutaneous temperature in a cohort of outpatients to understand what factors, including tobacco use and other high-risk characteristics, contribute to cutaneous tissue perfusion as measured by thermography. Participants were prospectively enrolled if they were a combustible cigarette smoker, an electronic cigarette (e-cigarette) user, or a never smoker. Standardized thermographic images of the subject's facial profiles, forearms, and calves were taken and demographic characteristics, medical comorbidities, and tobacco product use were assessed. These variables were statistically tested for associations with temperature at each anatomic site.

RESULTS

We found that gender had a significant effect on thermographic temperature that differed by anatomic site, and we found a lack of significant difference in thermographic temperature by race. Our regression analysis did not support significant differences in thermographic temperatures across smoking groups, while there was a trend for decreased perfusion in smokers relative to non-smokers and e-cigarette users relative to non-smokers.

CONCLUSION

Thermographic imaging is a useful tool for clinical and research use with consideration of sex and other perfusion-affecting characteristics.

Thermographic analysis of postoperative changes in the nasal breathing efficiency in infants and young children with unilateral cleft lip

PURPOSE

Nowadays, cheilorhinoseptoplasty is one of the most efficient methods of cleft lip primary surgical treatment eliminating both functional and esthetic issues. In this work, we have proposed, developed, and experimentally tested a new thermography-based algorithm for studying the efficiency and symmetry of nasal breathing prior to and after the surgery.

METHODS

To investigate and analyze the external respiration function of an infant with unilateral cleft lip after surgical respiration symmetry restoration followed by anatomically shaped postoperative endonasal retainer installation, we have applied contactless thermal imaging in real time.

RESULTS

The developed algorithm enables effective analysis of the respiratory function in infants before and after the surgery. Its combination with applied surgical technique experimentally demonstrated the potential of this approach for improving further the efficiency and symmetry of the airflows through the patient's nasal passages after the primary cheilorhinoseptoplasty.

CONCLUSIONS

The results of our study constitute a novel and promising avenue of investigation into the breathing function in infants and young children prior to and after their surgery for unilateral cleft lip. The adaptation of our technique to the conditions of a pediatric hospital will make it a safe and informative tool for noninvasive diagnosing the respiratory function in infants in the early postoperative period.

High Precision Human Skin Temperature Fluctuations Measuring Instrument

This paper describes the experimental results of testing a prototype of a high precision human skin rapid temperature fluctuations measuring instrument. Based on the author’s work, an original circuit solution on a miniature semiconductor diode sensor has been designed. The proposed circuitry provides operation in the full voltage range with automatic setting and holding the operating point, as well as the necessary slope of the conversion coefficient (up to 2300 mV/°C), which makes it possible to register fast temperature oscillations from the surface of the human body and other biological objects. Simulation results in the Microcap 12 software and laboratory tests have confirmed all declared design specifications: temperature resolution of 0.01 °C, transducer thermal time constant of 0.05 s. An original thermostat and an experimental setup for the simultaneous registration of the electrocardiogram, pulse wave signals from the Biopac polygraph MP36 and a signal of temperature oscillations from the prototype thermometer have been designed for further investigations. The preliminary test results indicates that using the designed measuring instrument gives a possibility to provide an in-depth study of the relationship between micro- and macro-blood circulations manifested in skin temperature fluctuations.

Infrared thermography for assessment of thoracic paravertebral block: a prospective observational study

Background

There was no “gold standard” to assess the success or failure of thoracic paravertebral block (TPVB). Measurement of skin temperature with infrared thermography (IT) would be a reliable method to evaluate the effectiveness of regional blocks. This study aimed to explore the feasibility of using skin temperature difference (Td) determined by IT between the blocked and unblocked side to predict the spread of TPVB.

Methods

Sixty-one patients undergoing elective unilateral breast or thoracoscopic surgery were enrolled in this prospective observational study. TPVB was performed at T4 and T5 under real-time ultrasound guidance with 10 mL of 0.4% ropivacaine for each patient, respectively. Td between the blocked and unblocked side were measured with IT from T2 to T10 at the anterior chest wall before TPVB and 5 min, 10 min, 15 min and 20 min after TPVB. Pinprick test was performed at 20 min after TPVB. Successful TPVB was defined as no sensation to pinprick in 3 or more adjacent dermatomes corresponding to the site of injection at 20 min after TPVB. Td was compared to pinprick test for evaluating its effectiveness in predicting the success of TPVB. The sensitivity, specificity, and cut-off value of Td for predicting successful TPVB were determined by receiver operator characteristic (ROC) curve analysis.

Results

Compared with the baseline value before block, Td from T2 to T10 were significantly increased at each time point in successful blocks. In failed blocks, Td was not increased in any dermatome. The increase of Td at T4-T7 was more than 1 °C 20 min after successful TPVB. Fifteen minutes after block, Td increase at T4 had the greatest potential to predict block success. The area under the ROC curve was 0.960 at a cut-off value of 0.63 °C with a sensitivity of 83.3% and a specificity of 100.0%.

Conclusions

This study suggested that the increase of Td at T4 dermatome determined by IT between the blocked and unblocked side is an early, quantitative, and reliable predictor of successful TPVB.

Trial registration

Clinical trial registration: NCT04078347.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01389-4.

Finger constrictor and thermoperceptual responsiveness to localised cooling following 5 weeks of intermittent regional exposures to moderately augmented transmural vascular pressure

PURPOSE

To examine the effects of prolonged intermittent exposures to moderately increased transmural pressure on finger vasoreactivity and thermoperception to localised cooling.

METHODS

Eleven men completed a 5-week regimen (3 sessions·week^-1; 55 min·session^-1), during which the vasculature in one arm (EXP) was exposed intermittently (10-min exposure: 5-min pause) to increased transmural pressure (from +65 mmHg week-1 to +105 mmHg week-5). Before and after the regimen, finger cutaneous vascular conductance (CVC), temperature (T_avg), and thermoperception (thermal sensation, discomfort and pain) were monitored during a 30-min hand cold (8 °C water) provocation trial. The responses of the non-trained hand were examined during an additional cold trial.

RESULTS

After the regimen, baseline finger CVC and T_avg were higher in both hands (p ≤ 0.01). During cooling, neither finger CVC nor T_avg were modified (p > 0.05). Yet the magnitude of the cold-induced drop of CVC was augmented in both hands, and to a similar extent (p ≤ 0.02). The regimen alleviated thermal pain in both hands (p ≤ 0.02); the sensation of coldness and thermal discomfort were attenuated mainly in the EXP hand (p = 0.02).

CONCLUSIONS

Present findings indicate that iterative local exposures to augmented intravascular pressure do not alter finger vasoreactivity to localised cooling. The pressure training, however, might impair finger basal vasomotor tone, and aggravate the magnitude of constrictor responsiveness to cooling. The pressure training also elicits thermoperceptual desensitisation to noxious thermal stimulus. To large extent, these vascular and perceptual adjustments seem to be transferred to the cutaneous vasculature of the non-trained limb.

<p>Blood Flow Index and Skin Temperature Measured by Laser Speckle Contrast Imaging and Infrared Thermography After Specific Ultrasound-Guided Blocking of the C6, C7 Nerve Root: A Case Report</p>

Ultrasound-guided cervical nerve root block is the technique of injecting local anesthetic or steroid into the intertubercular groove outside of the cervical foramen under real-time ultrasound guidance. It has established diagnostic and therapeutic employment for patients suffering symptoms caused by cervical disc disorders and foraminal stenosis. Measures of selective nerve root blockade would have vital clinical utility, especially in multilevel disease or combined with atypical symptoms, where subjective assessment is difficult. This case reported a 47-year-old male patient who suffered from severe radicular pain confined to the index and middle fingers, with weakness of the right upper extremity. He was successfully treated with selective C6, C7 nerve root under ultrasound guidance. For confirmation of the proper analgesia range, laser speckle contrast imaging (LSCI) and infrared thermography (IT) were both constructed over the dorsum of the hands and forearms during the procedure. The results of the off-line analysis suggested LSCI and IT might be considered as alternative measurements for the selective cervical nerve root.

Contactless Monitoring of Microcirculation Reaction on Local Temperature Changes

Assessment of skin blood flow is an important clinical task which is required to study mechanisms of microcirculation regulation including thermoregulation. Contactless assessment of vasomotor reactivity in response to thermal exposure is currently not available. The aim of this study is to show the applicability of the imaging photoplethysmography (IPPG) method to measure quantitatively the vasomotor response to local thermal exposure. Seventeen healthy subjects aged 23 ± 7 years participated in the study. A warm transparent compress applied to subject’s forehead served as a thermal impact. A custom-made IPPG system operating at green polarized light was used to monitor the subject’s face continuously and simultaneously with skin temperature and electrocardiogram (ECG) recordings. We found that the thermal impact leads to an increase in the amplitude of blood pulsations (BPA) simultaneously with the skin temperature increase. However, a multiple increase in BPA remained after the compress was removed, whereas the skin temperature returned to the baseline. Moreover, the BPA increase and duration of the vasomotor response was associated with the degree of external heating. Therefore, the IPPG method allows us to quantify the parameters of capillary blood flow during local thermal exposure to the skin. This proposed technique of assessing the thermal reactivity of microcirculation can be applied for both clinical use and for biomedical research.

Radiofrequency Electromagnetic Field Exposure and the Resting EEG: Exploring the Thermal Mechanism Hypothesis

There is now strong evidence that radiofrequency electromagnetic field (RF-EMF) exposure influences the human electroencephalogram (EEG). While effects on the alpha band of the resting EEG have been repeatedly shown, the mechanisms underlying that effect have not been established. The current study used well-controlled methods to assess the RF-EMF exposure effect on the EEG and determine whether that effect might be thermally mediated. Thirty-six healthy adults participated in a randomized, double-blind, counterbalanced provocation study. A water-perfusion suit (34 °C) was worn throughout the study to negate environmental influences and stabilize skin temperature. Participants attended the laboratory on four occasions, the first being a calibration session and the three subsequent ones being exposure sessions. During each exposure session, EEG and skin temperature (8 sites) were recorded continuously during a baseline phase, and then during a 30 min exposure to a 920 MHz GSM-like signal (Sham, Low RF-EMF (1 W/kg) and High RF-EMF (2 W/kg)). Consistent with previous research, alpha EEG activity increased during the High exposure condition compared to the Sham condition. As a measure of thermoregulatory activation, finger temperature was found to be higher during both exposure conditions compared to the Sham condition, indicating for the first time that the effect on the EEG is accompanied by thermoregulatory changes and suggesting that the effect of RF-EMF on the EEG is consistent with a thermal mechanism.

The response of peripheral microcirculation to gravity-induced changes

BACKGROUND

The peripheral microcirculation supplies fresh blood to the small blood vessels, providing oxygen and nutrients to the tissues, removing waste, and maintaining normal homeostatic conditions. The goal of this study was to characterize the response of the peripheral microcirculation, in terms of blood flow and tissue oxygenation variables, to gravity-induced changes.

METHODS

The study included 20 healthy volunteers and the experiment involved monitoring central and peripheral variables with the right hand positioned at different heights. These positions correspond to various gravitational levels. Peripheral perfusion and oxygenation were monitored using a laser Doppler flowmeter, photoplethysmograph, and transcutaneous oxygen tension monitor. Local blood pressure and respiration rate were also measured.

FINDINGS

At the heart level, tissue oxygenation displayed a nadir, while capillary flow displayed a peak. Similar but weaker changes were observed at the control hand. In contrast, the photoplethysmograph's amplitude strongly decreased upon reducing the arm position below heart level. Both systolic and diastolic pressures decreased linearly between the highest to lowest arm position.

INTERPRETATION

The results may reflect peripheral compensation mechanisms, as well as an interaction between the central and peripheral cardiovascular systems, in response to local changes in blood pressure. The observed dependence of the oxygenation pattern on height could lead to important new insights for the diagnosis and treatment of problems in the regulation of tissue perfusion.

Skin microcirculatory reactivity assessed using a thermal challenge is decreased in patients with circulatory shock and associated with outcome

Background

Shock states are characterized by impaired tissue perfusion and microcirculatory alterations, which are directly related to outcome. Skin perfusion can be noninvasively evaluated using skin laser Doppler (SLD), which, when coupled with a local thermal challenge, may provide a measure of microcirculatory reactivity. We hypothesized that this microvascular reactivity would be impaired in patients with circulatory shock and would be a marker of severity.

Methods

We first evaluated skin blood flow (SBF) using SLD on the forearm and on the palm in 18 healthy volunteers to select the site with maximal response. Measurements were taken at 37 °C (baseline) and repeated at 43 °C. The 43 °C/37 °C SBF ratio was calculated as a measure of microvascular reactivity. We then evaluated the SBF in 29 patients with circulatory shock admitted to a 35-bed department of intensive care and in a confirmatory cohort of 35 patients with circulatory shock.

Results

In the volunteers, baseline SBF was higher in the hand than in the forearm, but the SBF ratio was lower (11.2 [9.4–13.4] vs. 2.0 [1.7–2.6], p < 0.01) so we used the forearm for our patients. Baseline forearm SBF was similar in patients with shock and healthy volunteers, but the SBF ratio was markedly lower in the patients (2.6 [2.0–3.6] vs. 11.2 [9.4–13.4], p < 0.01). Shock survivors had a higher SBF ratio than non-survivors (3.2 [2.2–6.2] vs. 2.3 [1.7–2.8], p < 0.01). These results were confirmed in the second cohort of 35 patients. In multivariable analysis, the APACHE II score and the SBF ratio were independently associated with mortality.

Conclusions

Microcirculatory reactivity is decreased in patients with circulatory shock and has prognostic value. This simple, noninvasive test could help in monitoring the peripheral microcirculation in acutely ill patients.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0393-7) contains supplementary material, which is available to authorized users.

Effects of topical anaesthetic and buccal meloxicam on average daily gain, behaviour and inflammation of unweaned beef calves following surgical castration

Although the pain caused by castration of calves is a significant animal welfare issue for the beef industry, analgesia is not always used for this procedure, largely because of practical limitations associated with injectable forms of pain relief. Novel analgesic formulations have now been developed for livestock to allow topical and buccal administration, offering practical options to improve cattle welfare if shown to be effective. To assess the effects of topical anaesthetic (TA) and buccal meloxicam (BM) on average daily gain (ADG), behaviour and inflammation following surgical castration of beef calves, a total of 50 unweaned bull calves were randomly allocated to: (1) sham castration (SHAM, n=10); (2) surgical castration (C, n=10); (3) surgical castration with pre-operative buccal meloxicam (CBM, n=10); (4) surgical castration with post-operative topical anaesthetic (CTA, n=10); and (5) surgical castration with pre-operative buccal meloxicam and post-operative topical anaesthetic (CBMTA, n=10). Calves were recorded on video for 5 h following treatment and the frequency and duration of specific behaviours displayed by each animal was later observed for 5 min every hour (total of 25 min). Average daily gain was calculated 1, 2 and 6 days following treatment. Scrotal diameter measurements and photographs of wounds were collected from all castrated calves 1, 2 and 6 days following treatment to evaluate inflammation and wound healing. Infrared photographs were used to identify maximum scrotal temperature. Digital photographs were used to visually score wounds on a numerical rating scale of 1 to 5, with signs of inflammation increasing and signs of healing decreasing with progressive scores. Sham castration calves displayed significantly less, and C calves displayed significantly more foot stamps than all other calves (P=0.005). Observations on the duration of time that calves displayed a hypometric 'stiff gait' locomotion, indicated that SHAM calves tended to spend no time, C calves tended to spend the greatest time and all other calves tended to spend an intermediate time displaying this behaviour (P=0.06). Maximum scrotal temperatures were lower in CBM and CBMTA calves than C and CTA calves 2 days following treatment (P=0.004). There was no significant effect of treatment on ADG (P=0.7), scrotal diameter (P=0.09) or wound morphology score (P=0.5). These results suggest that TA and BM, alone or in combination, reduced pain and BM reduced inflammation following surgical castration of calves.

Prospects of Laser Doppler flowmetry application in assessment of skin microcirculation in diabetes

This review includes results of scientific and clinical use of laser Doppler flowmetry (LDF) in patients with diabetes mellitus. LDF is a non-invasive method for the quantitative evaluation of microcirculation, which can assess microcirculatory rhythms and conduct functional tests with various impacts, allowing the exploration of regulatory mechanisms of microcirculation. LDF reveals specific diabetes changes in the regulatory function of microcirculation. Microcirculation disturbances, which are traditionally associated with the pathogenesis of complications, also occur in patients with early disorders of carbohydrate metabolism and may precede the manifestation of diabetes. However, this method is still not applied in clinical practice. In this review, we analysed factors limiting the implementation of LDF in practical medicine and suggest ways to improve its clinical significance.

A temperature-controlled glove with non-invasive arterial pulse sensing for active neuro-vascular assessment

A non-invasive, active neuro-vascular assessment system was developed using a modified temperature-controlled glove and feedback techniques. The glove incorporates local heating and cooling of the hand using multi-point skin temperature measurements as feedback, and thereby induces local and central mechanisms involved in thermoregulation. Electrocardiogram (ECG), photoplethysmogram (PPG) and non-invasive finger-cuff based blood pressure (BP) measurements were used to monitor electrophysiology and hemodynamic changes in response to temperature modulation. Then, the triggered neuro-vascular mechanisms associated with thermoregulation were quantified by extracting parameters from the measured waveforms, specifically heart rate variability (HRV), vascular tone, and BP. The system was tested on six young, healthy individuals with no history of microvascular diseases. During heating, vasodilation, decrease in systolic BP, and a decrease in parasympathetic tone were observed, while during cooling, vasoconstriction and increased BP were observed. While such changes are expected physiologically using passive experiments, the ability to modulate the physiology non-invasively with a controlled, quantitative, and inexpensive instrument can potentially enable serial assessments of neuro-vascular control outside of clinical settings.

Retention of finger blood flow against postural change as an indicator of successful sympathetic block in the upper limb

Background

Sympathetic block in the upper limb has diagnostic, therapeutic and prognostic utility for disorders in the upper extremity that are associated with sympathetic disturbances. Increased skin temperature and decreased sweating are used to identify the adequacy of sympathetic block in the upper limb after stellate ganglion block (SGB). Baroreflexes elicited by postural change induce a reduction in peripheral blood flow by causing sympathetic vasoconstriction. We hypothesized that sympathetic block in the upper limb reduces the decrease in finger blood flow caused by baroreflexes stimulated by postural change from the supine to long sitting position. This study evaluated if sympathetic block of the upper limb affects the change in finger blood flow resulting from postural change. If change in finger blood flow would be kept against postural changes, it has a potential to be a new indicator of sympathetic blockade in the upper limb.

Methods

Subjects were adult patients who had a check-up at the Department of Pain Management in our university hospital over 2 years and 9 months from May 2012. We executed a total of 91 SGBs in nine patients (N=9), which included those requiring treatment for pain associated with herpes zoster in seven of the patients, tinnitus in one patient and upper limb pain in one patient. We checked for the following four signs after performing SGB: Horner’s sign, brachial nerve blockade, finger blood flow measured by a laser blood flow meter and skin temperature of the thumb measured by thermography, before and after SGB in the supine position and immediately after adopting the long sitting position.

Results

We executed a total of 91 SGBs in nine patients. Two SGBs were excluded from the analysis due to the absence of Horner’s sign. We divided 89 procedures into two groups according to elevation in skin temperature of the thumb: by over 1°C (sympathetic block group, n=62) and by <1°C (nonsympathetic block group, n=27). Finger blood flow decreased significantly just after a change in posture from the supine to long sitting position after SGB in both groups. In the sympathetic block group, the ratio of finger blood flow in the long sitting position/supine position with a change in posture significantly increased after SGB compared with before SGB (before SGB: range 0.09–0.94, median 0.53; after SGB: range 0.33–1.2, median 0.89, p<0.0001).

Conclusion

Our study shows that with sympathetic block in the upper limb, the ratio of finger blood flow significantly increases despite baroreflexes stimulated by postural change from the supine to long sitting position. Retention of finger blood flow against postural changes may be an indicator of sympathetic block in the upper limb after SGB or brachial plexus block.

The association between diabetes and dermal microvascular dysfunction non-invasively assessed by laser Doppler with local thermal hyperemia: a systematic review with meta-analysis

Background/Introduction

Diabetes and cardiovascular disease develop in concert with metabolic abnormalities mirroring and causing changes in the vasculature, particularly the microcirculation. The microcirculation can be affected in different parts of the body of which the skin is the most easily accessible tissue.

Purpose

The association between diabetes and dermal microvascular dysfunction has been investigated in observational studies. However, the strength of the association is unknown. Therefore we conducted a systematic review with meta-analysis on the association between diabetes and dermal microvascular dysfunction as assessed by laser Doppler/laser speckle contrast imaging with local thermal hyperaemia as non-invasive indicator of microvascular functionality.

Methods

PubMed and Ovid were  systematically searched for eligible studies through March 2015. During the first selection, studies were included if they were performed in humans and were related to diabetes or glucose metabolism disorders and to dermal microcirculation. During the second step we selected studies based on the measurement technique, measurement location (arm or leg) and the inclusion of a healthy control group. A random effects model was used with the standardised mean difference as outcome measure. Calculations and imputation of data were done according to the Cochrane Handbook.

Results

Of the 1445 studies found in the first search, thirteen cross-sectional studies were included in the meta-analysis, comprising a total of 857 subjects. Resting blood flow was similar between healthy control subjects and diabetes patients. In contrast, the microvascular response to local skin heating was reduced in diabetic patients compared to healthy control subjects [pooled effect of −0.78 standardised mean difference (95% CI −1.06, −0.51)]. This effect is considered large according to Cohen’s effect size definition. The variability in effect size was high (heterogeneity 69%, p < 0.0001). However, subgroup analysis revealed no difference between the type and duration of diabetes and other health related factors, indicating that diabetes per se causes the microvascular dysfunction.

Conclusion

Our meta-analysis shows that diabetes is associated with a large reduction of dermal microvascular function in diabetic patients. The local thermal hyperaemia methodology may become a valuable non-invasive tool for diagnosis and assessing progress of diabetes-related microvascular complications, but standardisation of the technique and quality of study conduct is urgently required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0487-1) contains supplementary material, which is available to authorized users.

Thermography-based blood flow imaging in human skin of the hands and feet: a spectral filtering approach

The determination of the relationship between skin blood flow and skin temperature dynamics is the main problem in thermography-based blood flow imaging. Oscillations in skin blood flow are the source of thermal waves propagating from micro-vessels toward the skin's surface, as assumed in this study. This hypothesis allows us to use equations for the attenuation and dispersion of thermal waves for converting the temperature signal into the blood flow signal, and vice versa. We developed a spectral filtering approach (SFA), which is a new technique for thermography-based blood flow imaging. In contrast to other processing techniques, the SFA implies calculations in the spectral domain rather than in the time domain. Therefore, it eliminates the need to solve differential equations. The developed technique was verified within 0.005-0.1 Hz, including the endothelial, neurogenic and myogenic frequency bands of blood flow oscillations. The algorithm for an inverse conversion of the blood flow signal into the skin temperature signal is addressed. The examples of blood flow imaging of hands during cuff occlusion and feet during heating of the back are illustrated. The processing of infrared (IR) thermograms using the SFA allowed us to restore the blood flow signals and achieve correlations of about 0.8 with a waveform of a photoplethysmographic signal. The prospective applications of the thermography-based blood flow imaging technique include non-contact monitoring of the blood supply during engraftment of skin flaps and burns healing, as well the use of contact temperature sensors to monitor low-frequency oscillations of peripheral blood flow.

Dry skin conditions are related to the recovery rate of skin temperature after cold stress rather than to blood flow

BACKGROUND

Cutaneous blood flow plays an important role in the thermoregulation, oxygen supply, and nutritional support necessary to maintain the skin. However, there is little evidence for a link between blood flow and skin physiology. Therefore, we conducted surveys of healthy volunteers to determine the relationship(s) between dry skin properties and cutaneous vascular function.

METHODS

Water content of the stratum corneum, transepidermal water loss, and visual dryness score were investigated as dry skin parameters. Cutaneous blood flow in the resting state, the recovery rate (RR) of skin temperature on the hand after a cold-stress test, and the responsiveness of facial skin blood flow to local cooling were examined as indices of cutaneous vascular functions. The relationships between dry skin parameters and cutaneous vascular functions were assessed.

RESULTS

The RR correlated negatively with the visual dryness score of skin on the leg but correlated positively with water content of the stratum corneum on the arm. No significant correlation between the resting state of blood flow and dry skin parameters was observed. In both the face and the body, deterioration in skin dryness from summer to winter was significant in subjects with low RR. The RR correlated well with the responsiveness of facial skin blood flow to local cooling, indicating that the RR affects systemic dry skin conditions.

CONCLUSIONS

These results suggest that the RR but not blood flow at the resting state is associated with dry skin conditions and is involved in skin homeostasis during seasonal environmental changes.

Exercise and Repeated Testing Improves Accuracy of Laser Doppler Assessment of Microvascular Function Following Shortened (1-minute) Blood Flow Occlusion

OBJECTIVES

To determine whether stability/accuracy of post-occlusive LDF following shortened, one-minute blood flow occlusion, increases in the post-exercise state or by averaging multiple measurements.

METHODS

Six healthy adults (3F) underwent LDF eight times at rest and following exercise, assessing post-occlusive (one-minute occlusion) reactive hyperemia in the cutaneous microcirculation of the forefinger. Measured variables included: pre- and post-occlusion steady-state perfusion (Plat1, Plat2), maximum post-occlusive perfusion (Max), PkT, and the ratio Max/Plat1.

RESULTS

Stability/accuracy of all variables improved performing measurements after exercise (p < 0.05 Plat 1, Plat 2, Max and Max/Plat1). PkT and Max/Plat 1 displayed the greatest accuracy at rest (26.6 ± 5.1% and 26.6 ± 4.4% average difference, %Diff, of single measurements from individual "true" means, respectively); for these variables, %Diff improved to 19.5 ± 5.3 and 17.6 ± 2.1, respectively, following exercise. Overall, averaging multiple measurements performed at rest also improved stability/accuracy in all variables. This improvement was comparable to that obtained with a single measurement following exercise.

CONCLUSIONS

A standardized exercise stimulus prior to testing significantly improves stability/accuracy of LDF following shortened, one-minute blood flow occlusion. Our results suggest the possibilities of broader applications of exercise to optimize measurements from a variety of skin perfusion methodologies.

Preliminary methods for wearable neuro-vascular assessment with non-invasive, active sensing

In this study, a non-invasive and active sensing scheme that is ultimately aimed to be integrated in a wearable system for neuro-vascular health assessment is presented with preliminary results. With this system, vascular tone is modulated by local heating and cooling of the palm, and the resulting changes in local hemodynamics are monitored via impedance plethysmography (IPG) and photoplethysmography (PPG) sensors interfaced with custom analog electronics. Proof-of-concept measurements were conducted on three subjects using hot packs/ice bags to modulate the palmar skin temperature. From ensemble averaged and smoothed versions of pulsatile IPG and PPG signals, the effects of local changes in skin temperature on a series of parameters associated with neuro-vascular mechanisms (heart rate, blood volume, blood flow rate, blood volume pulse inflection point area ratio, and local pulse transit time) have been observed. The promising experimental results suggest that, with different active temperature modulation schemes (consisting of heating/cooling cycles covering different temperature ranges at different rates), it would be possible to enhance the depth and specificity of the information associated with neuro-vascular health by using biosensors that can fit inside a wearable device (such as a sleeve). This study sets the foundation for future studies on designing and testing such a wearable neuro-vascular health assessment system employing active sensing.

The role of cyclo-oxygenase-1 in high-salt diet-induced microvascular dysfunction in humans

KEY POINTS

Recent studies have shown that some of the deleterious effects of a high-salt (HS) diet are independent of elevated blood pressure and are associated with impaired endothelial function. Increased generation of cyclo-oxygenase (COX-1 and COX-2)-derived vasoconstrictor factors and endothelial activation may contribute to impaired vascular relaxation during HS loading. The present study aimed to assess the regulation of microvascular reactivity and to clarify the role of COX-1 and COX-2 in normotensive subjects on a short-term HS diet. The present study demonstrates the important role of COX-1 derived vasoconstrictor metabolites in regulation of microvascular blood flow during a HS diet. These results help to explain how even short-term HS diets may impact upon microvascular reactivity without changes in blood pressure and suggest that a vasoconstrictor metabolite of COX-1 could play a role in this impaired tissue blood flow.

ABSTRACT

The present study aimed to assess the effect of a 1-week high-salt (HS) diet on the role of cyclo-oxygenases (COX-1 and COX-2) and the vasoconstrictor prostaglandins, thromboxane A2 (TXA2 ) and prostaglandin F2α (PGF2α ), on skin microcirculatory blood flow, as well as to detect its effect on markers of endothelial activation such as soluble cell adhesion molecules. Young women (n = 54) were assigned to either the HS diet group (N = 30) (∼14 g day(-1) NaCl ) or low-salt (LS) diet group (N = 24) (<2.3 g day(-1) NaCl ) for 7 days. Post-occlusive reactive hyperaemia (PORH) in the skin microcirculation was assessed by laser Doppler flowmetry. Plasma renin activity, plasma aldosterone, plasma and 24 h urine sodium and potassium, plasma concentrations of TXB2 (stable TXA2 metabolite) and PGF2α , soluble cell adhesion molecules and blood pressure were measured before and after the diet protocols. One HS diet group subset received 100 mg of indomethacin (non-selective COX-1 and COX-2 inhibitor), and another HS group subset received 200 mg of celecoxib (selective COX-2 inhibitor) before repeating laser Doppler flowmetry measurements. Blood pressure was unchanged after the HS diet, although it significantly reduced after the LS diet. Twenty-four hour urinary sodium was increased, and plasma renin activity and plasma aldosterone levels were decreased after the HS diet. The HS diet significantly impaired PORH and increased TXA2 but did not change PGF2α levels. Indomethacin restored microcirculatory blood flow and reduced TXA2 . By contrast, celecoxib decreased TXA2 levels but had no significant effects on blood flow. Restoration of of PORH by indomethacin during a HS diet suggests an important role of COX-1 derived vasoconstrictor metabolites in the regulation of microvascular blood flow during HS intake.

Finger skin temperatures in 8- to 11-year-old children: determinants including physical characteristics and seasonal variation. The Physical Activity and Nutrition in Children (PANIC) Study

PURPOSE

The fingertip skin temperature (FST) reflects skin blood flow, and FST measurement has been suggested for the investigation of vascular responses. As a limitation, the multifactorial nature and the seasonal variation in measured values have been earlier described in adults but not in children. In the present study, we identify the modifiers of FST in a population sample of Finnish children.

METHODS

FST was measured in children (age range 8-11 years, n = 432) with infrared thermometer, and its possible determinants including the subjects' physical characteristics and seasonal variables, such as daylight time and outdoor temperature, were identified.

RESULTS

In univariate regression models, FST was dependent on the sex, age and anthropometric characteristics of the children with the higher body fat content-related variables and a lower surface area-to-mass ratio as strongest single modifiers of FST. There was interaction between sex and puberty with FST. In addition, FST was directly related to daylight time and outdoor temperature although the children had stayed inside for at least 2 h before the measurements. The FST values were lowest in the winter and highest in the summer. In multivariate regression model, main determinants of FST were a higher body fat percentage (standardized regression coefficient β = 0.472; p < 0.001), male sex (β = 0.291; p < 0.001) and longer daylight time (0.226; p < 0.001).

CONCLUSIONS

Altogether, complex effects of body composition and sex with the confounding effect of seasonal variation may complicate the use of FST as a tool to study the vascular function in children.

Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow

Continuous monitoring of variations in blood flow is vital in assessing the status of microvascular and macrovascular beds for a wide range of clinical and research scenarios. Although a variety of techniques exist, most require complete immobilization of the subject, thereby limiting their utility to hospital or clinical settings. Those that can be rendered in wearable formats suffer from limited accuracy, motion artifacts, and other shortcomings that follow from an inability to achieve intimate, noninvasive mechanical linkage of sensors with the surface of the skin. We introduce an ultrathin, soft, skin-conforming sensor technology that offers advanced capabilities in continuous and precise blood flow mapping. Systematic work establishes a set of experimental procedures and theoretical models for quantitative measurements and guidelines in design and operation. Experimental studies on human subjects, including validation with measurements performed using state-of-the-art clinical techniques, demonstrate sensitive and accurate assessment of both macrovascular and microvascular flow under a range of physiological conditions. Refined operational modes eliminate long-term drifts and reduce power consumption, thereby providing steps toward the use of this technology for continuous monitoring during daily activities.

Noninvasive monitoring of peripheral microcirculatory hemodynamics under varying degrees of hypoxia

The effect of hypoxia on skin blood flow was examined in anesthetized rabbits during induction of various levels of hypoxia. Peripheral perfusion and oxygenation were monitoring using a combined system (LPT) composed of a laser Doppler flowmeter (LDF), a photoplatysmograph (PPG), and a transcutaneous oxygen tension monitor (tc-PO2). Central blood parameters (PaO2, HCO3(-), SaO2, pH, and lactate) were measured concomitantly throughout the experiment. A continuous decline was found in both peripheral and central values, depending on the severity of the hypoxia. The results clearly indicate that monitoring peripheral indices with the LPT system enables monitoring changes of vital blood parameters during hypoxia. The system has clinical potential for sensitive and noninvasive monitoring of vital variables during medical procedures in clinics, as well as for homecare for patients with respiratory diseases. Minimizing the system may be useful in various conditions of exposure to low oxygen levels, such as during mountain climbing.

Early microvascular changes in the preterm neonate: a comparative study of the human and guinea pig

Dysfunction of the transition from fetal to neonatal circulatory systems may be a major contributor to poor outcome following preterm birth. Evidence exists in the human for both a period of low flow between 5 and 11 h and a later period of increased flow, suggesting a hypoperfusion–reperfusion cycle over the first 24 h following birth. Little is known about the regulation of peripheral blood flow during this time. The aim of this study was to conduct a comparative study between the human and guinea pig to characterize peripheral microvascular behavior during circulatory transition. Very preterm (≤28 weeks GA), preterm (29–36 weeks GA), and term (≥37 weeks GA) human neonates underwent laser Doppler analysis of skin microvascular blood flow at 6 and 24 h from birth. Guinea pig neonates were delivered prematurely (62 day GA) or at term (68–71 day GA) and laser Doppler analysis of skin microvascular blood flow was assessed every 2 h from birth. In human preterm neonates, there is a period of high microvascular flow at 24 h after birth. No period of low flow was observed at 6 h. In preterm animals, microvascular flow increased after birth, reaching a peak at 10 h postnatal age. Blood flow then steadily decreased, returning to delivery levels by 24 h. Preterm birth was associated with higher baseline microvascular flow throughout the study period in both human and guinea pig neonates. The findings do not support a hypoperfusion–reperfusion cycle in the microcirculation during circulatory transition. The guinea pig model of preterm birth will allow further investigation of the mechanisms underlying microvascular function and dysfunction during the initial extrauterine period.

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A period of high microvascular flow occurs after birth, however, no period of low flow (hypoperfusion stage) precedes this, suggesting that no hypoperfusion–reperfusion cycle exists during early extrauterine life. The data strongly support the use of the preterm guinea pig in future studies to allow further investigation of the interrelationship between cardiac output, preload, afterload, microvascular flow, and SVC flow. Elucidation of these processes may then aid clinicians in managing the circulatory dysfunction of preterm neonates, particularly those at greatest risk, preterm male neonates.

Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress

The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio2: 0.21; AIR), or a hypoxic gas mixture (Fio2: 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 ± 0.5°C, HYPO: 10.0 ± 0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 ± 3.4°C; HYPO: 22.0 ± 3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

Associations Between Dietary Patterns and Skin Microcirculation in Healthy Subjects

Objective—

Microvascular dysfunction is suggested to be a marker of common pathophysiological mechanisms in the development of insulin resistance, cardiovascular diseases, and type 2 diabetes mellitus. Given the established relationship of diet with the macrovascular disease, the aim of this study was to investigate for the first time the possible associations between dietary patterns and microcirculation.

Approach and Results—

Two hundred ninety-one healthy men and women selected from the Supplementation en Vitamines et Mineraux Antioxydants 2’ cohort were assessed for anthropometric, nutritional, biochemical, and microcirculation parameters using finger skin capillaroscopy. Dietary intake was assessed cross-sectionally using a food frequency questionnaire, and principal component analysis was used to identify dietary patterns from 40 food groups. Six dietary patterns were identified. A dietary pattern characterized by increased consumption of vegetable oils, poultry, and fish and seafood was positively associated with both functional and anatomic capillary density after adjusting for confounders ( β =0.13, P =0.05 and β= 0.20, P= 0.00, respectively). A second dietary pattern with increased consumption of sweets was inversely associated with functional and anatomic capillary density in all multivariate models ( β =−0.14, P =0.03 and β= −0.17, P= 0.01). There were no associations between any of the derived dietary patterns and capillary recruitment.

Conclusions—

In healthy subjects, a dietary pattern characterized by an increased consumption of vegetable oils, poultry, and fish and seafood and low consumption of sweets was associated with better microvascular function. Further prospective studies are needed to confirm the present association.

Determination of the amplitude and phase relationships between oscillations in skin temperature and photoplethysmography-measured blood flow in fingertips

It is well established that skin temperature oscillations in fingertips coexist with blood flow oscillations and there is a certain correlation between them. At the same time, the reasons for differences in waveform and the delay between the blood flow and temperature oscillations are far from being fully understood. In this study we determine the relationships between spectral components of the blood flow and temperature oscillations in fingertips, and we ascertain the frequency dependences of amplitude attenuation and delay time for the temperature oscillations. The blood flow oscillations were considered as a source of thermal waves propagating from micro-vessels towards the skin surface and manifesting as temperature oscillations. The finger temperature was measured by infrared thermography and blood flow was assessed by photoplethysmography for ten healthy subjects. The time-frequency analysis of oscillations was based on the Morlet wavelet transform. The frequency dependences of delay time and amplitude attenuation in temperature compared with blood flow oscillations have been determined in endothelial (0.005-0.02 Hz) and neurogenic (0.02-0.05 Hz) frequency bands using the wavelet spectra. We approximated the experimental frequency dependences by equations describing thermal wave propagation through the medium and taking into account the thermal properties and thickness of a tissue. Results of analysis show that with the increase of frequency f the delay time of temperature oscillations decreases inversely proportional to f(1/2), and the attenuation of the amplitude increases directly proportional to exp f(1/2). Using these relationships allows us to increase correlation between the processed temperature oscillations and blood flow oscillations from 0.2 to 0.7 within the frequency interval 0.005-0.05 Hz. The established experimental and theoretical relationships clarify an understanding of interrelation between the dynamics of blood flow and skin temperature, and define possibilities and limitations of temperature measurements as a method of blood flow assessment in extremities.

Effect of low-level laser therapy on blood flow and oxygen- hemoglobin saturation of the foot skin in healthy subjects: a pilot study

BACKGROUND AND AIMS

This study on healthy test subjects intends to show whether one-off Low-Level Laser Therapy (LLLT) has an instant effect on the perfusion or the oxygenation of the skin tissue. These possible instant effects may have an influence on the accelerated wound healing which is often observed after application of LLLT, in addition to the usual postulated effects of LLLT which occur with a time delay normally.

STUDY DESIGN/MATERIALS AND METHODS

The study was carried out double-blind and placebo-controlled in two batches of testing. The test subjects received one-off LLLT on a defined area of the arch of the foot. Simultaneously a placebo treatment was carried out on the corresponding contralateral area. In the first batch of tests, the blood flow was measured immediately before and after treatment using thermography and LDI. In the second batch of tests, the blood flow and the oxygen saturation were determined immediately before and after the treatment using an O2C device.

RESULTS

No evidence that the LLLT has a significant instant effect on the circulation or the oxygen saturation could be found.

CONCLUSION

No immediate effect of an LLLT on the perfusion or oxygenation situation is to be expected with physiologically normal starting conditions. An additional investigation should be carried out in which either the radiation dose is varied or the starting conditions are pathological (e.g. chronic wounds) in order to rule out immediate effects on circulation or oxygen saturation as the cause of the improved wound healing which is often observed.

Effects of AT1 receptor blockade on plasma thromboxane A2 (TXA2) level and skin microcirculation in young healthy women on low salt diet

OBJECTIVE

To determine the effect of AT1 receptor antagonism on skin microcirculation and plasma level of thromboxane A2 (TXA2).

METHODS

Healthy women (n=20) maintained 7 days low salt (LS) diet (intake <40 mmol Na/day) without (LS) or together with 50 mg/per day of losartan (a selective AT1 receptor inhibitor) (LS diet+losartan group). Laser Doppler flowmetry (LDF) measurements of changes in post occlusive hyperemic blood flow, plasma concentration of stable TXA2 metabolite thromboxane B2 (TXB2) and plasma renin activity (PRA) aldosterone concentration, electrolytes (Na(+), K(+)), as well as blood pressure and heart rate were determined before and after study protocols.

RESULTS

PRA and aldosterone increased significantly after 7 days of both LS diet and LS diet+losartan. LS diet or LS diet+losartan administrations had no significant effect on post-occlusion hyperemia While there was no change in TXB2 after LS diet TXB2 significantly increased after one week of LS+losartan compared to control levels (cTXB2 pg/mL control 101±80 vs. LS diet+losartan 190±116, p<0.05).

CONCLUSION

These data suggest that inhibition of AT1 receptors could lead to activation of AT2 receptors, which maintain hyperemia, despite the increased level of vasoconstrictor TXA2. These findings also suggest an important role of crosstalk between renin-angiotensin system (RAS) and arachidonic acid metabolites in the regulation of microcirculation under physiological conditions.

Functional and structural age-related changes in the scalp skin of Caucasian women

BACKGROUND

Ageing of the skin, being chronological or sun induced is highly documented. Scalp, as a specific skin site, has, however, received little attention. This work attempted to describe functional and structural alterations that occur in scalp skin with ageing.

METHODS

Two different age groups (N = 15 each; 30 ± 3 and 62 ± 2 y.o. respectively) of Caucasian women participated in the study. Some functional parameters (TEWL, Sebum level, Hydration, T°) were recorded on the vertex part of the scalp, after having cut the hair flat on the scalp surface. Imaging of some structural criteria was carried out using high-frequency ultrasound technique and optical coherence tomography on the same scalp site and on the mid-forehead, as a close control skin site.

RESULTS

As compared with the younger group, the scalp of older women significantly showed a decreased TEWL and a slightly lower T°. The thickness of total skin (epidermis + dermis) increased with age on both scalp and on forehead. The thickness of scalp epidermis decreased with age while not significantly altered on forehead. Pseudoattenuation of ultrasound images increased in the older age group. Other criteria, such as sebum level, stratum corneum hydration, stratum corneum thickness, were not found altered with age.

CONCLUSION

With ageing, some few functional and structural changes are observed in the scalp of Caucasian women. Similarities or differences with those previously reported in other skin sites are discussed.

'Go with the flow ': a review of methods and advancements in blood flow imaging

Physics has delivered extraordinary developments in almost every facet of modern life. From the humble thermometer and stethoscope to X-Ray, CT, MRI, ultrasound, PET and radiotherapy, our health has been transformed by these advances yielding both morphological and functional metrics. Recently high resolution label-free imaging of the microcirculation at clinically relevant depths has become available in the research domain. In this paper, we present a comprehensive review on current imaging techniques, state-of-the-art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm.

Time to wound closure in trauma patients with disorders in wound healing is shortened by supplements containing antioxidant micronutrients and glutamine: a PRCT

BACKGROUND & AIMS

: We hypothesize that wound closure in trauma patients with disorders in wound healing is accelerated by supplementation of antioxidant micronutrients and glutamine.

METHODS

In a randomized, double-blind, placebo-controlled trial, 20 trauma patients with disorders in wound healing were orally supplemented with antioxidant micronutrients (ascorbic acid, α-tocopherol, β-carotene, zinc, selenium) and glutamine (verum) or they received isoenergetic amounts of maltodextrine (placebo) for 14 days. Plasma/serum levels of micronutrients, glutamine, and vascular endothelial growth factor-A (VEGF-A) were determined before and after supplementation. In the wound, several parameters of microcirculation were measured. Time from study entry to wound closure was recorded.

RESULTS

Micronutrients in plasma/serum did not change except for selenium which increased in the verum group (1.1 ± 0.2 vs. 1.4 ± 0.2 μmol/l; P = 0.009). Glutamine decreased only in the placebo group (562 ± 68 vs. 526 ± 55 μmol/l; P = 0.047). The prevalence of hypovitaminoses and the concentration of VEGF-A did not change. Considering microcirculation, only O(2)-saturation decreased in the placebo group (56.7 ± 23.4 vs. 44.0 ± 24.0 [arbitrary units]; P = 0.043). Wound closure occurred more rapidly in the verum than in the placebo group (35 ± 22 vs. 70 ± 35 d; P = 0.01).

CONCLUSIONS

Time to wound closure can be shortened by oral antioxidant and glutamine containing supplements in trauma patients with disorders in wound healing.

NIR and skin impedance spectroscopic measurements for studying the effect of coffee and alcohol on skin, and dysplastic naevi

BACKGROUND/PURPOSE

Near infrared and impedance spectroscopy can be used for clinical skin measurements and need to be evaluated for possible confounding factors; (i) are skin conditions of the patient and the subsequent skin measurements influenced by alcohol and/or coffee consumption and (ii) are measurements of dysplastic naevi (DN) reproducible over time and significantly different compared to reference skin.

METHODS

Near infrared and skin impedance spectroscopic data were analysed multivariately. In the first study, the skin characteristics of 15 healthy individuals were examined related to body location, gender, individual differences, and consumption of coffee or alcohol. The second study included five patients diagnosed with dysplastic naevi syndrome. Measurements were taken on DN and reference skin over time.

RESULTS

In the first study, body location and gender had a major influence on measurement scores. Inter-individual skin characteristics and coffee or alcohol effects on skin characteristics were of minor importance. In the second study, it was shown that DN can be differentiated from reference skin and the measurements are stable over time.

CONCLUSIONS

Moderate consumption of alcohol and coffee did not influence the results of the measurements. It is possible to follow, stable or changed, characteristics of DN over time.

In vivo assessment of peripheral vascular function by tcpO₂ and skin blood flow modelling

There are multiple techniques and methods to assess peripheral vascular function in vivo but not without limitations. More discriminative, sensitive and also practical evaluation strategies are needed to fully characterize the peripheral vascular function. In the present work, a new quantitative descriptor, the 'elimination half-life time' was developed from flow-related variables as a non-invasive microcirculatory rate parameter to describe vascular dynamics. Fifty-four healthy volunteers and six type 2 diabetic patients, both genders, were submitted to a dynamical procedure consisting in the inhalation of a 100% saturated atmosphere of oxygen for 10 min. The tcpO(2) and microcirculatory blood flow [Laser Doppler Flowmetry (LDF)] were measured in a randomly selected leg with a Periflux 5000 system before, during and after the procedure. A monocompartmental model was adjusted to tcpO(2) and LDF data. The tcpO(2) constant elimination rate, expressed as the Oxygen elimination half-life, was used as an indicator of the vulnerability of peripheral tissue and compared in healthy versus non-healthy individuals. Under normal conditions, the saturated ventilation increases the tissue's O(2) availability, as an expression of the natural capacity to adjust the tissue hemodynamics to new metabolical/perfusion conditions. Diabetic patients are expected to suffer vascular impairment and ischemia. Under O(2) overloading conditions, those hypoxic territories tend to uptake all the delivered oxygen, expressed as a significant increase in the O(2) elimination half-life. This approach allows to propose 'elimination half-life time' as the first quantitative descriptive parameter combining miogenic, hemodynamic and metabolic aspects of the microcirculatory physiology and to help to identify the individual's vascular vulnerability.