Differences In Skin Blood Flow Research Articles

Cardiovascular responses to orthostasis during a simulated 3-day heatwave

Global warming has caused an increase in the frequency, duration, and intensity of summer heatwaves (HWs). Prolonged exposure to hot environments and orthostasis may cause conflicting demands of thermoregulation and blood pressure regulation on the vasomotor system, potentially contributing to cardiovascular complications and occupational heat strain. This study assessed cardiovascular and skin blood flow (SkBF) responses to orthostasis before, during and after a 3-day simulated HW. Seven male participants maintained a standard work/rest schedule for nine consecutive days split into three 3-day parts; thermoneutral pre-HW (25.4 °C), simulated HW (35.4 °C), thermoneutral post-HW. Gastrointestinal (Tgi) and skin (Tsk) temperatures, cardiovascular responses, and SkBF were monitored during 10-min supine and 10-min 60° head-up tilt (HUT). SkBF, indexed using proximal–distal skin temperature gradient (∆TskP-D), was validated using Laser-Doppler Flowmetry (LDF). The HW significantly increased heart rate, cardiac output and SkBF of the leg in supine; HUT increased SkBF of the arm and leg, and significantly affected all cardiovascular variables besides cardiac output. Significant regional differences in SkBF presented between the arm and leg in all conditions; the arm displaying vasodilation throughout, while the leg vasoconstricted in non-HW before shifting to vasodilation in the HW. Additionally, ∆TskP-D strongly correlated with LDF (r = −.78, p < 0.001). Prolonged HW exposure and orthostasis, individually, elicited significant changes in cardiovascular and SkBF variables. Additionally, varying regional blood flow responses were observed, suggesting the upper and lower vasculature receives differing vasomotor control. Combined cardiovascular alterations and shifts towards vasodilation indicate an increased challenge to industrial workers during HWs.

The Impact of ET B Receptors on the Axon Reflex During Local Heating in Healthy Young Women

Endothelin-1 (ET-1) is a vasoconstrictor that acts on the vasculature through ETA and ETB receptors. Both ETA and ETB receptors are located in the skin and are involved in regulating skin blood flow. ETB receptors are also located on axon terminals on c-type nociceptor fibers. Rapid local heating stimulates the axon reflex which has been established as a mediator of the initial vasodilation response. Although ETA receptors have been shown to augment the axon reflex resulting in a vasodilation, less is known about the role of the ETB receptors on the axon reflex. Purpose The purpose of this study was to determine the contribution of ETB receptors to the axon reflex response. Methods We retrospectively analyzed data in 24 healthy young women (27±10 yrs). Cutaneous vasodilatory responses to local heating were measured using laser doppler flowmetry during microdialysis perfusions of lactated Ringer's (control) and ETB receptor blockade (BQ-788, 300nM). Cutaneous vascular conductance (CVC) was calculated during the initial peak and nadir of the axon reflex during local heating (42°C), and normalized to maximal vasodilation achieved by perfusion of sodium nitroprusside (28mM) and heating to 43°C. We used paired samples t-tests to analyze differences in vasodilation between control and ETB receptor blockade sites. Results All subjects were normotensive (MAP: 83±8 mmHg) and had a normal BMI (23±3 kg/m2). There were no significant differences in skin blood flow between control and ETB receptor blockade sites during initial peak (control: 63 ±15; ETB receptor blockade: 62±17 %CVC max, P=0.70) or nadir (control: 52±16; ETB receptor blockade: 50±18 %CVC max, P=0.49). There was also no significant difference between conditions in time to initial peak (control: 142±75; ETB receptor blockade: 140±53 s, P=0.79). Conclusions These preliminary findings suggest ETB receptors do not impact axon reflex mediated vasodilation during local heating in healthy young women. Future research is needed to understand the mechanisms contributing to the axon reflex to regulate blood flow in the cutaneous circulation.

Effect of Pressures and Durations of Cupping Therapy on Skin Blood Flow Responses

Cupping therapy has been widely used in treating musculoskeletal impairments. However, there is no specific guideline on selecting the intensity of cupping therapy, including the pressure and duration. The objective of this study was to investigate the effect of different pressures and durations of cupping therapy on skin blood flow responses. A 2 × 2 factorial design, including two negative pressures at −225 and −300 mmHg and two durations at 5 and 10 min, was tested in 12 healthy participants. The four protocols of cupping therapy were tested in four different days. Skin blood flow was measured using laser Doppler flowmetry on the left triceps (the SJ12 acupoint). Skin blood flow after cupping therapy was expressed as a ratio of skin blood flow before cupping therapy. The results showed that −300 mmHg caused a significant increase in peak skin blood flow (16.7 ± 2.6 times) compared to −225 mmHg (11.1 ± 2.2 times, p < 0.05) under 5-min duration. The largest difference in skin blood flow is between −300 mmHg for 5 min (16.7 ± 2.6 times) and −225 mmHg for 10 min (8.1 ± 2.3 times, p < 0.01). Our findings demonstrated that a higher value (300 mmHg) of negative pressure is more effective on increasing skin blood flow compared to a lower value (225 mmHg). Also, a shorter duration (5 min) causes a larger peak and total skin blood flow compared to a longer duration (10 min). This study provides the first evidence showing the effect of pressures and durations of cupping therapy on skin blood flow responses.

Sex Differences In Microvascular Function In Pre-pubertal Children

There is little research examining the effect of sex on skin blood flow (SkBF) in adults, and less in children. Sex-related differences in SkBF may help explain known thermoregulatory differences between males and females. PURPOSE: To determine whether there are sex-related differences in the SkBF response to exercise, local heating, and acetylcholine (ACh). Additionally, the role of nitric oxide (NO) was examined. METHODS: Laser-Doppler flowmetry was used to assess forearm SkBF. Responses to exercise (30 min cycling, 60%V˙O2max), local heating (44°C), and ACh iontophoresis were assessed in 15 pre-pubertal boys (age=10±1y, VO2max=1.66±0.25 l/min) and 10 girls (age=10±1y, VO2max=1.58±0.35 l/min), with and without NO synthase inhibition, using L-NAME iontophoresis. Three-way (group, time, treatment) repeated measures ANOVA was used to examine sex-related differences in the SkBF response during exercise and in the SkBF-ACh dose response. A two-way (group, treatment) repeated measures ANOVA was used to examine local heathing-induced increase in SkBF. RESULTS: Exercise-induced SkBF was greater in boys compared with girls (654±355 and 316±182% of baseline, respectively, p=<.0001). L-NAME blunted the SkBF response more in boys than in girls (group-by-treatment interaction, p=.004). Local heating-induced SkBF was not significantly different between boys and girls (1705±739% and 1488±600%, respectively, p=.35), with no effect of L-NAME. The maximal ACh-induced SkBF was similar in boys and girls (650±420% and 612±411%, respectively). L-NAME similarly blunted the SkBF response in boys and girls (group-by-treatment interaction, p=.52). CONCLUSION: These findings demonstrate that while maximal SkBF and the vasodilatory response to ACh stimulation are similar in boys and girls, boys display a greater increase in SkBF during exercise of similar intensity. Further, the role of NO in the SkBF response appears greater in boys than girls only during exercise. Since absolute and relative exercise intensity was similar in the two groups, it is suggested that sex-related factors (e.g., hormones) may interact with the exercise response or with other vasodilators, resulting in different SkBF response.

Thermal Behavior Augments Heat Loss Following Low Intensity Exercise.

We tested the hypothesis that thermal behavior alleviates thermal discomfort and accelerates core temperature recovery following low intensity exercise. Methods: In a 27 ± 0 °C, 48 ± 6% relative humidity environment, 12 healthy subjects (six females) completed 60 min of exercise followed by 90 min of seated recovery on two occasions. Subjects wore a suit top perfusing 34 ± 0 °C water during exercise. In the control trial, this water continually perfused throughout recovery. In the behavior trial, the upper body was maintained thermally comfortable by pressing a button to receive cool water (3 ± 2 °C) perfusing through the top for 2 min per button press. Results: Physiological variables (core temperature, p ≥ 0.18; mean skin temperature, p = 0.99; skin wettedness, p ≥ 0.09; forearm skin blood flow, p = 0.29 and local axilla sweat rate, p = 0.99) did not differ between trials during exercise. Following exercise, mean skin temperature decreased in the behavior trial in the first 10 min (by −0.5 ± 0.7 °C, p < 0.01) and upper body skin temperature was reduced until 70 min into recovery (by 1.8 ± 1.4 °C, p < 0.05). Core temperature recovered to pre-exercise levels 17 ± 31 min faster (p = 0.02) in the behavior trial. There were no differences in skin blood flow or local sweat rate between conditions during recovery (p ≥ 0.05). Whole-body thermal discomfort was reduced (by −0.4 ± 0.5 a.u.) in the behavior trial compared to the control trial within the first 20 min of recovery (p ≤ 0.02). Thermal behavior via upper body cooling resulted in augmented cumulative heat loss within the first 30 min of recovery (Behavior: 288 ± 92 kJ; Control: 160 ± 44 kJ, p = 0.02). Conclusions: Engaging in thermal behavior that results in large reductions in mean skin temperature following exercise accelerates the recovery of core temperature and alleviates thermal discomfort by promoting heat loss.

Differences in skin blood flow oscillations between the plantar and dorsal foot in people with diabetes mellitus and peripheral neuropathy

BackgroundUnderstanding the differences in skin blood flow (SBF) on the plantar and dorsal foot in people with diabetes mellitus (DM) may help to assess the influence of diabetes and neuropathy on microvascular dysfunction and risks of diabetic foot ulcers in this population. However, there is no study comparing SBF oscillations between the plantar and dorsal foot in people with DM and peripheral neuropathy (PN). ObjectiveThe objective of this study was to compare SBF oscillations between the plantar and dorsal foot in people with DM and PN and investigate the underlying mechanisms responsible for the differences. Methods18 people with Type 2 DM and PN and 8 healthy controls were recruited. Laser Doppler flowmetry (LDF) was used to measure SBF on the plantar and dorsal foot for 10 min when the subject was in the supine position. Wavelet analysis was used to quantify the relative amplitude of the characteristic frequency components of SBF oscillations. Sample entropy analysis was used to quantify the regularity degree of SBF oscillations. ResultsPeople with DM and PN had a higher SBF on the plantar foot compared to the dorsal foot. The relative wavelet amplitudes of metabolic and myogenic frequency components on the plantar foot were respectively higher and lower compared to the dorsal foot. Sample entropy analysis showed that SBF on the plantar foot had a higher degree of regularity compared to the dorsal foot. ConclusionsIn people with DM and PN, higher SBF on the plantar foot is attributed to the metabolic and myogenic controls, and SBF on the plantar foot exhibits a higher degree of regularity compared to the dorsal foot. People with DM and PN also had higher plantar and dorsal SBF compared to the healthy controls. This study provides evidence to document differences in SBF of the plantar and dorsal foot in people with DM and PN.

Microvascular Endothelial Function across the Cancer Survivorship Continuum

BackgroundChemotherapy for the treatment of various cancers has previously been shown to have direct cardiotoxic effects. However, changes in endothelial function due to chemotherapy‐induced toxicity in cancer survivors during the years following treatment remains poorly understood. Therefore, the purpose of this study was to evaluate microvascular endothelial‐dependent vasodilation across the cancer survivorship continuum as well as in healthy controls. We hypothesized that early cancer survivors would yield a decreased percent change in skin blood flow and cutaneous vascular conductance when compared to late survivors and controls.MethodsTo date, thirteen female cancer survivors and thirteen healthy controls (cancer free with no history of chemotherapy) participated in this study. Of the cancer survivors nine were defined as early survivors (within 5 years of chemotherapy treatment) and four as late survivors (&gt; 5 years post chemotherapy treatment). Skin blood flow (SkBF) was measured via integrated laser Doppler flowmetry. Mean arterial pressure (MAP) was measured and used to calculate cutaneous vascular conductance (CVC = SkBF/MAP *100). Endothelium‐dependent cutaneous microvascular function was determined as the percent change in SkBF and CVC in response to iontophoresis of 2% acetylcholine (ACh).ResultsThere were no differences in age between groups (early vs. late: P=0.8; late vs. control: P=0.7; early vs. control: P=0.8). The hyperemic responses for SkBF (early: 1081 ± 718% Δ; late: 1458 ± 653% Δ; P=0.4) and CVC (early: 1060 ± 694% Δ; late: 1499± 751% Δ; P=0.5) were not significantly different between early and late cancer survivors. Similarly, the SkBF (early: 1081 ± 718% Δ; control: 1554 ± 655% Δ; P=0.3) and CVC (early: 1060 ± 694% Δ; control: 1472 ± 626% Δ; P=0.1) were not significantly different in the early cancer survivors compared to controls. There was no significant difference in SkBF (late: 1458 ± 653% Δ; control: 1554 ± 655% Δ; P=0.8) and CVC (late: 1499± 751% Δ; control: 1472 ± 626% Δ; P=0.9) between late cancer survivors and controls.ConclusionEndothelium‐dependent cutaneous microvascular function is not different between early cancer survivors compared to those &gt;5 years post‐chemotherapy and healthy controls. These results suggest that microvascular endothelial function is restored in the early years following chemotherapy and is maintained in later years of survivorship. Additional work is required to determine if endothelial dysfunction occurs in other important vascular beds.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ultrasonography-guided Cannula Method for Hyaluronic Acid Filler Injection with Evaluation using Laser Speckle Flowgraphy.

Summary:Hyaluronic acid (HA) is present in the connective tissues of the skin and decreases with age. HA fillers are popular as facial rejuvenation treatments. They are generally considered safe; however, complications, such as cutaneous necrosis and blindness due to vascular embolism, sometimes occur. Because vascular embolisms are likely associated with the deep placement of HA fillers, a strategy that involves injection into superficial regions (the conventional method) is commonly used to reduce risks. However, deep injections to achieve revolumization are becoming common, even in high-risk areas for intravascular infusion. We aimed to study the usefulness of the ultrasonography-guided cannula method for preventing intravascular infusion of HA fillers. An HA filler was injected into the region just under the dermis on the left side of the face of a 38-year-old man using the conventional method, and another HA filler was injected into the periosteum on the right side using the ultrasonography-guided cannula method. The skin blood flow on both sides was compared using laser speckle flowgraphy (LSFG). The ultrasonography-guided method was successful in detecting the cannula and the blood vessel, and the HA filler was safely injected into a deep region. Using LSFG, a difference in skin blood flow between the 2 methods was detected. The ultrasonography-guided cannula method was effective in aiding the safe injection of an HA filler in a deep high-risk area and maintained skin blood flow. LSFG may be adopted to evaluate skin blood flow after HA filler injections.

Asymmetrical responses of skin blood flow in ischemic hindlimbs to electrical stimulation of the unilateral forelimb

The regulation of skin blood flow (SBF) is primarily mediated by the sympathetic nervous system, but the effects of electrical stimulation (ES) of one limb on SBF in the other limbs remain unknown. The present study investigated the effects of unilateral forelimb ES on SBF in the bilateral hindlimbs in anesthetized rats. Bilateral hindlimb ischemia was induced by tourniquet application for 60min. After reperfusion for 24h, ES (3 or 125Hz) was applied to the upper one-fourth of the triceps brachii muscle of the left or right forelimb for 30min. Rats that did not receive ES were used as the controls. Bilateral hindlimb SBF was measured by a laser Doppler line scanner for 20min before ES, 30min during ES, and 9min after ES. The results showed significant differences in SBF in the right but not left hindlimb between the control group and experimental group that received 125-Hz ES of the right forelimb. Right hindlimb SBF significantly increased within 3min following the application of 125-Hz ES to the right forelimb. No significant changes in SBF were observed in the left or right hindlimb when 125-Hz ES was applied to the left forelimb. Moreover, 3-Hz ES of the left or right forelimb did not significantly change SBF in either hindlimb compared with the control group. These results indicate that unilateral forelimb ES causes a differential SBF response in the hindlimb via a specific somatosympathetic reflex, and ES-induced SBF improvements in the ischemic hindlimb are frequency-dependent.

Effects of Low-Dose Aspirin Therapy on Thermoregulation in Firefighters.

BackgroundHeart attack is the most common cause of line-of-duty death in the fire service. Daily aspirin therapy is a preventative measure used to reduce the morbidity of heart attacks but may decrease the ability to dissipate heat by reducing skin blood flow.MethodsIn this double-blind, placebo-controlled, crossover study, firefighters were randomized to receive 14 days of therapy (81-mg aspirin or placebo) before performing treadmill exercise in thermal-protective clothing in a hot room [38.8 ± 2.1°C, 24.9 ± 9.1% relative humidity (RH)]. Three weeks without therapy was provided before crossing to the other arm. Firefighters completed a baseline skin blood-flow assessment via laser Doppler flowmetry; skin was heated to 44°C to achieve maximal cutaneous vasodilation. Skin blood flow was measured before and after exercise in a hot room, and at 0 minutes, 10 minutes, 20 minutes, and 30 minutes of recovery under temperature conditions (25.3 ± 1.2°C, 40.3 ± 13.7% RH). Platelet clotting time was assessed before drug administration, and before and after exercise.ResultsFifteen firefighters completed the study. Aspirin increased clotting time before and after exercise compared with placebo (p = 0.003). There were no differences in absolute skin blood flow between groups (p = 0.35). Following exercise, cutaneous vascular conductance (CVC) was 85 ± 42% of maximum in the aspirin and 76 ± 37% in the placebo groups. The percentage of maximal CVC did not differ by treatment before or after recovery. Neither maximal core body temperature nor heart rate responses to exercise differed between trials.ConclusionThere were no differences in skin blood flow during uncompensable heat stress following exercise after aspirin or placebo therapy.

Sex differences in thermoeffector responses during exercise at fixed requirements for heat loss

To assess potential mechanisms responsible for the lower sudomotor thermosensitivity in women during exercise, we examined sex differences in sudomotor function and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Eight men and eight women cycled at rates of metabolic heat production of 200, 250, and 300 W/m(2) of body surface area, with each rate being performed sequentially for 30 min. The protocol was performed in a direct calorimeter to measure evaporative heat loss (EHL) and in a thermal chamber to measure local sweat rate (LSR) (ventilated capsule), SkBF (laser-Doppler), sweat gland activation (modified iodine-paper technique), and sweat gland output (SGO) on the back, chest, and forearm. Despite a similar requirement for heat loss between the sexes, significantly lower increases in EHL and LSR were observed in women (P ≤ 0.001). Sex differences in EHL and LSR were not consistently observed during the first and second exercise periods, whereas EHL (348 ± 13 vs. 307 ± 9 W/m(2)) and LSR on the back (1.61 ± 0.07 vs. 1.20 ± 0.09 mg · min(-1) · cm(-2)), chest (1.33 ± 0.06 vs. 1.08 ± 0.09 mg · min(-1) · cm(-2)), and forearm (1.53 ± 0.07 vs. 1.20 ± 0.06 mg · min(-1) · cm(-2), men vs. women) became significantly greater in men during the last exercise period (P < 0.05). At each site, differences in LSR were solely due to a greater SGO in men, as opposed to differences in sweat gland activation. In contrast, no sex differences in SkBF were observed throughout the exercise period. The present study demonstrates that sex differences in sudomotor function are only evidenced beyond a certain requirement for heat loss, solely through differences in SGO. In contrast, the lower EHL and LSR in women are not paralleled by a lower SkBF response.

The Influence of Baroreceptor Loading Status on Muscle Metaboreceptor Modulation of Heat Loss Responses

Muscle metaboreceptors have been shown to have a profound effect on the control of the local heat loss responses of sweating (LSR) and skin blood flow (SkBF). Under experimental conditions which employ the ischemic isometric hand-grip exercise (IHG) model, muscle metaboreceptors tend to reduce active vasodilation and attenuate sweating. However, it remains unclear if non-pharmacologically-induced changes in baroreceptor status may mitigate this response. PURPOSE: To evaluate the influence of baroreceptor loading status on LSR and SkBF during postexercise ischemia. METHODS: Seven physically active males (19-24 years) completed two experimental trials under a normothermic (NS) and hyperthermic (whole-body warming, HS) state. Subjects performed 1-min of IHG exercise at 60% of their maximal voluntary contraction followed by 2-min of ischemia under simultaneous lower body positive pressure (LBPP, +40 mm Hg), negative pressure (LBNP, -20 mm Hg) and no pressure (CON). The sequence of these conditions was performed in random order with a 20-min recovery period between conditions to minimize muscular fatigue. RESULTS: No significant differences were observed during baseline rest or at the end of the IHG exercise. Under both NS and HS, mean arterial pressure (MAP) was increased above baseline resting during ischemia. However, the magnitude of increase in MAP was greater during LBPP for both NS (p<0.001) and HS (p<0.002), but lower during LBNP (p<0.028) under HS relative to CON. Despite differences in baroreceptor loading status under NS, no significant difference in LSR or SkBF were observed. In HS, no differences in SkBF were measured between CON and LBPP. However, SkBF response during ischemia was significantly reduced during LBNP as compared to CON (p=0.015) and LBPP (p=0.023). No differences in LSR were observed between CON and LBNP during ischemia. However, a marked reduction in LSR was measured in LBPP relative to CON (p=0.024) but not LBNP (p=0.092). CONCLUSIONS: These results suggest that baroreceptor loading status can mitigate muscle metaboreceptor-induced changes in local heat loss responses. However, this only appears to occur in a hyperthermic state. Funding support from the Natural Sciences and Engineering Research Council of Canada (held by Dr. G. Kenny).

Short-term exercise training does not improve whole-body heat loss when rate of metabolic heat production is considered

We evaluated the effects of an 8-week exercise training program in previously sedentary individuals on whole-body heat balance during exercise at a constant rate of metabolic heat production. Prior to and after 8 weeks of training, ten participants performed 60-min of cycling exercise at a constant rate of heat production (approximately 450 W) followed by 60-min of recovery, at 30 degrees C and 15% relative humidity. Rate of total heat loss was measured directly by whole-body calorimetry, while rate of metabolic heat production was measured simultaneously by indirect calorimetry. Esophageal (T(es)), skin blood flow (SkBF) and local sweat rate (LSR) were also measured continuously. The 8-week exercise training program elicited a 10% increase in maximal aerobic capacity (P < 0.001). Furthermore, exercise training reduced (P <or= 0.05) baseline (37.10 +/- 0.28 vs. 36.95 +/- 0.24 degrees C) and end-exercise (37.85 +/- 0.30 vs. 37.55 +/- 0.20 degrees C) values for T (es) as well as onset thresholds for LSR (37.23 +/- 0.26 vs. 36.96 +/- 0.22 degrees C, P < 0.001) and SkBF (37.16 +/- 0.38 vs. 36.83 +/- 0.26 degrees C, P < 0.001). However, these improvements in thermoregulatory function did not translate into a greater rate of total heat loss between the pre- and post-training exercise trials (P = 0.762). Furthermore, there were no differences in SkBF (P = 0.546) and LSR (P = 0.475) from pre- to post-training. Although physical training resulted in significant improvements of cardiorespiratory and thermoregulatory functions, these adaptations did not improve whole-body and local heat loss responses during exercise performed at a given rate of metabolic heat production.

Interrelationships between body fat and skin blood flow and the current required for electrical stimulation of human muscle

There is variability between individuals in the current needed to elicit a contraction in human muscle with surface electrodes. To understand what might be causing some of this variability, 25 subjects whose average age was 24.4 ± 2.3 years, whose height was 165.5 ± 9.5 cm, and whose average weight was 70.3 ± 21 kg were examined. Electrical stimulation was applied above the motor point of the quadriceps, biceps, and lateral gastrocnemius muscles. To assess body fat, 2D ultrasound was used with a 1 cm stand off. Electrical stimulation was applied with sine wave stimulation at 100 μs pulse width and at a frequency of 30 Hz. To alter skin blood flow, aside from the natural difference in skin blood flow at rest, hot packs and cold packs were used for 5 min. The average fat thickness below the quadriceps and gastrocnemius muscles was 0.75 ± 0.13 cm and under the biceps was 0.48 ± 0.16 cm. Without the use of hot or cold packs, the currents for the quadriceps and gastrocnemius muscles were significantly higher than that of the biceps ( p < 0.01). While there was some relationship between stimulation current and blood flow without the application of hot or cold packs, when hot packs were applied, skin blood flow increased as did the current required to stimulate muscle to threshold. When cold packs were applied, there was a decrease in the current required to stimulate these muscles. In conclusion, there is a causal relationship between skin blood flow, the thickness of the fat layer below the skin, and the current required to stimulate the muscle.

Decreased intramuscular blood flow in patients with lateral epicondylitis

The purpose of this pilot study was to investigate intramuscular microcirculation in extensor carpi radialis brevis (ECRB) in patients with lateral epicondylitis. Ten patients with unilateral epicondylitis, mean duration of symptoms of 39 (12-96) months participated. The diagnosis was based on clinical examination and none was under treatment for the last 6 months. Isometric handgrip strength, 2-pinch grip strength and muscle strength during radial deviation and dorsal extension were determined. Functional perceived pain was evaluated by a modified behaviour rating scale and perceived pain during contraction by visual analogue scale. Intramuscular and skin blood flow was recorded by a laser-Doppler flowmetry system technique (LDF) during stable temperature condition. Intramuscular blood flow was significantly lower in the affected side, 22.7+/-9.8 perfusion units (PU), as compared with 35.2+/-11.9 PU in the control side (P=0.01). There was no difference in skin blood flow or temperature between the affected and the control side. A positive correlation was found between the duration of symptoms and the difference in intramuscular blood flow between the affected and the control arm (r=0.65, P=0.06). The present data indicate that decreased microcirculation and anaerobic metabolism in ECRB may contribute to the lateral epicondylitis symptoms.

Decubitus Risk: Is Shear More Important than Pressure?

A mechanical load through which the capillaries are closed causes tissue ischaemia of the skin. Most authors agree that it is this tissue ischaemia that is the main factor in the cause of pressure sores. Different combinations of mechanical load on the skin may have the same effect within the skin. The aim of this study is to evaluate the effect that different combinations of pressure and shear have on blood flow within the skin. The skin blood flow was measured by means of skin oxygen tension. Different load combinations on the skin surface, for which the maximum shear stress within the skin remained equal, showed no significant difference in skin blood flow. Research should therefore focus on load situations within the skin instead of pressure measurements on the skin surface only.

Stroke volume during exercise: interaction of environment and hydration.

Euhydrated and dehydrated subjects exercised in a hot and a cold environment with our aim to identify factors that relate to reductions in stroke volume (SV). We hypothesized that reductions in SV with heat stress are related to the interaction of several factors rather than the effect of elevated skin blood flow. Eight male endurance-trained cyclists [maximal O(2) consumption (VO(2 max)) 4.5 +/- 0.1 l/min; means +/- SE] cycled for 30 min (72% VO(2 max)) in the heat (H; 35 degrees C) or the cold (C; 8 degrees C) when euhydrated or dehydrated by 1.5, 3.0, or 4.2% of their body weight. When euhydrated, SV and esophageal temperature (T(es) 38. 2-38.3 degrees C) were similar in H and C, whereas skin blood flow was much higher in H vs. C (365 +/- 64% higher; P < 0.05). With each 1% body weight loss, SV declined 6.4 +/- 1.3 ml (4.8%) in H and 3.4 +/- 0.4 ml (2.5%) in C, whereas T(es) increased 0.21 +/- 0.02 and 0. 10 +/- 0.02 degrees C in H and C, respectively (P < 0.05). However, reductions in SV were not associated with increases in skin blood flow. The reduced SV was highly associated with increased heart rate and reduced blood volume in both H (R = 0.96; P < 0.01) and C (R = 0. 85; P < 0.01). In conclusion, these results suggest that SV is maintained in trained subjects during exercise in euhydrated conditions despite large differences in skin blood flow. Furthermore, the lowering of SV with dehydration appears largely related to increases in heart rate and reductions in blood volume.

Heat stress and age: Skin blood flow and body temperature

1. 1. The ability to increase skin blood flow is an important mechanism for transferring heat from the body core to the skin for dissipation. 2. 2. During exercise, skin blood flow is typically 20–40% lower in men and women aged 55 and over (compared with 20–30 years old) at a given body core temperature. Yet criterion measures of heat tolerance (changes in core temperature, heat storage) often show minimal or no age-related alterations. From a series of studies conducted in our laboratory over the past 5 years, the following conclusions can be drawn. 3. 3. When fit healthy older subjects are matched with younger subjects of the same gender, size and body composition, V O 2max , acclimation state, and hydration level, age-related differences in skin blood flow are evident. However, these differences often do not translate into “poorer” heat tolerance or higher core temperatures. 4. 4. The larger core-to-skin thermal gradient maintained by the older individuals allows for effective heat transfer at lower skin blood flows. 5. 5. Furthermore, there is an increased coefficient of variation for thermoregulatory response variables with increasing age. 6. 6. Despite differences in the mechanisms underlying thermoregulation, true thermal tolerance is less a function of chronological age than of functional capacity and physiological health status. 7. 7. While this conclusion is based primarily on cross-sectional studies, it is supported by the results of more recent studies using multiple regression analyses. 8. 8. Implicit in this conclusion is the notion that thermal tolerance, at any age, is a modifiable individual characteristic.

Decreased skin blood flow early in the course of streptozotocin-induced diabetes mellitus in the rat.

We have previously used laser Doppler technology to demonstrate that skin blood flow is reduced in Type 1 (insulin-dependent) diabetic patients. The possibility of using the skin as an extremely accessible indicator of diabetic microvascular disease is attractive. The streptozotocin diabetic rat is an appealing potential animal model. We performed measurements of skin blood flow in two rat species, nine Sprague Dawley (SD) rats and nine Wistar Kyoto (WKY) rats, observing early changes following the inception of diabetes. Four of the SD rats and five of the WKY rats were made diabetic, the rest serving as controls. There were no significant differences in skin blood flow between the two rat strains. As in man, there appear to be rat skin sites with primarily nutritive capillary supply and those with arteriovenous anastomotic predominance. The back and base of tail, both hair-covered areas, demonstrated low flow characteristics, consistent with nutritive perfusion. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, sites of arteriovenous perfusion, with high basal flow and a marked increment with thermal stimulation. In diabetic rats of both species, there was significantly lower flow at the back and base of tail than in non-diabetic animals. The differences were of the order of 30-40%. As a function of time, the decrease in blood flow at the base of tail parallelled the increase in glycohaemoglobin levels in the diabetic rats. In contrast, blood flow at the plantar surface of the paw was unchanged throughout the 3-month post-streptozotocin observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermally-Induced Cutaneous Vasodilatation in Aging

A decrease in heat-induced cutaneous vasodilatation has been implicated as the cause of increased heat stress in the elderly. We used laser Doppler techniques to study the skin blood flow response to local heat in 82 healthy volunteers. There were 39 young volunteers, mean age 29 +/- 1, and 43 elderly volunteers, mean age 76 +/- 1. There was minimal difference in skin blood flow at 35 degrees C between the two groups. In contrast, skin blood flow at 44 degrees C was significantly lower in the older subjects at nutritively perfused sites, such as the knee and elbow. However, there was no difference between the young and old groups in skin blood flow at the finger or toe pulp, sites with primarily arteriovenous anastomotic (AVA) flow. In the older subjects, the two components of skin blood flow, microvascular volume (VOL) and red blood cell velocity (VEL), were both decreased at 44 degrees C at nutritive sites, but not at AVA sites. Regression analysis demonstrated a linear fall in blood flow, VOL, and VEL with advancing age at nutritive sites at 44 degrees C. We conclude that thermally-induced cutaneous blood flow is reduced in older persons at nutritive capillary sites, but not at AVA sites.