SAMMAMFATTNING Bakgrund: Reaktiv hyperemi definieras som ett övergående ökat blodflöde över det normala efter en tids ischemi. Det kan registreras med laserdopplerteknik. Att registrera reaktiv hyperemi är ett sätt att värdera mikrocirkulationen. Det finns många flödesvariabler att studera varav tid till maxflöde efter ocklusion är en. Det har gjorts studier som undersöker om det finns ett samband mellan reaktiv hyperemi och fysisk aktivitet/syreupptagningsförmåga. Det har inte gjorts någon studie som undersöker tid till maxflöde och fysisk aktivitet. Syftet var att undersöka om det finns ett samband mellan fysisk aktivitet och reaktiv hyperemi med avseende på tid till maxflöde. Material och metod: Testpersoner fick bära en accelerometer en vecka under dygnets alla vakna timmar samt göra en registrering av reaktiv hyperemi med laserdoppler. För statistiska beräkningar användes oparat T-test för att undersöka skillnad mellan olika grad av fysisk aktivitet och tid till maxflöde. Resultat: Ingen statistiskt signifikant skillnad mellan olika aktivitetsgrad och tid till maxflöde kunde observeras. Slutsats: Den här studien visade inte på statistiskt signifikant samband mellan blodflöde och fysisk aktivitet.

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.

O sinal de fluxo cutâneo obtido via fluxometria Laser Doppler (SFLD) tem flutuações de baixas frequências que estão relacionadas a mecanismos de controle do fluxo microvascular. Análises espectrais, via transformada de Fourier e transformada de wavelet, têm sido usadas para correlacionar as flutuações de SFLD com os seguintes mecanismos de controle de fluxo: metabólico, metabólico NO-dependente, neurogênico e miogênico, nos respectivos intervalos de frequência 0,005-0,0095 Hz, 0,0095-0,02 Hz, 0,02-0,05 Hz e 0,05-0,15 Hz. A potência do sinal, em cada intervalo de frequência, geralmente é usada como uma medida da atividade do mecanismo de controle microvascular relacionado. Uma vez que os métodos usados de análise são espectrais, as características das flutuações do SFLD, em cada intervalo de frequência, no domínio do tempo são desconhecidas. Como consequência, há ausência de critérios objetivos para medir adequadamente, em cada intervalo de frequência, os parâmetros hemodinâmicos relacionados. O objetivo deste trabalho foi caracterizar e quantificar flutuações temporais, espaciais e espaço-temporais do SFLD em cada faixa de frequência, usando um método no domínio do tempo. Os fluxos basais (320C) e termicamente estimulados à (420C) das regiões volares de antebraços de 20 voluntários saudáveis foram coletados em duas regiões próximas e analisados. As análises dos dados obtidos indicam que janelas temporais pequenas (1 minuto) são aceitáveis para a quantificação do fluxo médio, e que janelas temporais maiores são necessários para quantificar as flutuações de fluxo. A análise espaço-temporal revelou uma forte correlação entre sinais (em todas as bandas, exceto na banda B5) das duas regiões investigadas, durante longos intervalos de tempo, quando as duas regiões estudadas foram termicamente estimuladas, e menor variabilidade intragrupo quando comparada à obtida para os valores médios das flutuações, sugerindo que o intervalo de tempo de correlação é um parâmetro promissor para estudar mecanismos de controle do fluxo microvascular. / The laser Doppler flow signal from the skin (LDFS) has low-frequency fluctuations which are related to microvascular mechanisms of flow control. The Fourier and the wavelet spectral analysis has been used to correlate fluctuations in the LDFS with the metabolic, metabolic NO-dependent, neurogenic and myogenic mechanisms of control in the frequency intervals 0.005-0.0095 Hz, 0.0095-0.02 Hz, 0.02-0.05 Hz and 0.05-0.15 Hz, respectively. The signal power, in each frequency interval, is generally used as a measure of the activity of the related mechanism of microvascular control. Since spectral analysis methods have been used, the time-domain characteristics of the fluctuations in the LDFS in each frequency interval are unknown. As a consequence, there is a lack of objective criteria to properly measure, in each frequency interval, the related hemodynamic parameters. The aim of this work was characterizing and quantifying temporal, spatial and spatial-temporal fluctuations in the LDFS in each frequency band, using a time-domain method. Baseline (320C) and thermally stimulated (420C) LDFS of volar forearms from 20 healthy volunteers were collected from two close regions and analyzed. The data obtained indicate that short-time windows (1 minute) are acceptable for quantifying the mean flow, and that larger time-windows are needed for quantifying the flow fluctuations. The spatialtemporal analysis revealed strong correlations between signals (all bands, except B5) from the two investigated regions, during large time intervals when thermally stimulated, and lower intragroup variability than the ones obtained for the mean values of fluctuations, suggesting that the time interval of correlation is a promising parameter for studying mechanisms of microvascular flow control.

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.

This thesis sought to evaluate whether the increased risk of heat-related illness observed in black-African descendants stems from impairements in local- and whole-body heat loss responses in this ethnic group. To evaluate this, in separate studies local- (study 1) and whole–body (study 2) heat loss responses were compared in young men (18-30 y) of black-African (n=21) and Caucasian (n=21) descent, matched for physical characteristics and fitness and born and raised in the same temperate environment. In study 1, we compared nitric oxide-dependent skin blood flow and sweating responses in young men of black-African (n=10) and Caucasian (n=10) descent during rest, exercise, and recovery in the heat. Both groups rested for 10-min, and then performed 50-min of moderate-intensity exercise at 200 W/m2, followed by 30-min of recovery in hot-dry heat (35°C, 20% RH). Local cutaneous vascular conductance (CVC%max) and sweat rate (SR) were measured at two forearm skin sites treated with a) lactated-Ringer (Control), or b) 10 mM NG-nitro-L-arginine methyl ester (L‐NAME, NO synthase-inhibitor). L-NAME significantly reduced CVC%max throughout rest, exercise, and recovery in both groups (both p<0.001). However, there were no significant main effects for the NO contribution to CVC%max between groups (all p>0.500). L-NAME significantly reduced local SR in both groups (both p<0.050). The NO contribution to SR was similar between groups such that L-NAME reduced SR relative to control at 40 and 50 min into exercise (both p<0.050). In study 2, we assessed whole-body total heat loss (evaporative + dry heat exchange) in black-African (n=11) and Caucasian (n=11) men using direct calorimetry. Participants performed three, 30-min bouts of semi-recumbent cycling at fixed metabolic heat productions (and therefore matched heat loss requirements between groups) of 200 (light), 250 (moderate), and 300 W/m2 (vigorous), each followed by 15-min recovery, in dry heat (40°C, ~13% relative humidity). Across all exercise bouts, dry (p=0.435) and evaporative (p=0.600) heat exchange did not differ significantly between groups. As such, total heat loss during light, moderate and vigorous exercise was similar between groups (p=0.777), averaging ((mean (SD)); 177 (10), 217 (13) and 244 (20) W/m2 in men of black-African descent, and 172 (13), 212 (17) and 244 (17) W/m2 in Caucasian men. Accordingly, body heat storage across all exercise bouts (summation of metabolic heat production and total heat loss) was also similar between the black-African (568 (142) kJ) and Caucasian groups (623 (124) kJ; p=0.356). This thesis demonstrates that ethnicity does not influence NO-dependent cutaneous vasodilation and sweating in healthy, young black-African descent and Caucasian men during exercise in the heat. Furthermore, we extend upon these observations by showing no differences in whole-body dry and evaporative heat exchange and therefore body heat storage.

Background: Vascular dysfunction due to hyperglycemia in individuals with diabetes is a factor contributing to distal symmetric polyneuropathy (DSP). Reactive oxygen species (ROS) reduce the bioavailability of nitric oxide (NO), a powerful vasodilator, resulting in reduced circulation and nerve ischemia. Increases in blood NO concentrations and circulation have been attributed to whole body vibration (WBV). The purpose of this study was to the determine the effects of low frequency, low amplitude WBV on whole blood NO concentration and skin blood flow (SBF) in individuals with symptoms of DSP. Research Design and Methods: Ten subjects with diabetes and impaired sensory perception in the lower limbs participated in this cross-over study. Each submitted to two treatment conditions, WBV and sham, with a one week washout period between. Blood draws for NO analysis and Doppler laser image scans of SBF were performed before, immediately after and following a 5 minute recovery of each the treatments. Results: Low frequency, low amplitude WBV vibration significantly increased skin blood flow compared to the sham condition (p=0.0115). Whole blood nitric oxide concentrations did not differ between the WBV and sham condition immediately or 5 minutes post-treatment ( p=0.1813) Conclusions: These findings demonstrate that subjects with diabetes respond to whole body vibration with increased skin blood flow compared to sham condition. The implication is that WBV is a potential non-pharmacological therapy for neurovascular complications of diabetes.

Electrophysical agents (EPA) are a fundamental element of therapy practice and are vital for the treatment of a variety of conditions. Many of these agents employ some form of electromagnetic fields (EMF), in which radiofrequency (RF) is a major component. The therapeutic effects of RF are mainly linked to their effects on pain relief and potential effects on tissue repair. Although RF across various frequency ranges has been in use, reviews have shown that the frequency ranges currently used in therapy practice have narrowed to within 30 kHz-30,000 kHz (30 MHz). The most commonly used and hence the most commonly researched are shortwave therapies (SWT) that operate at 27.12 MHz, which is presently used predominantly in its pulsed form (PSWT). In addition to SWT, devices employing significantly lower RF ranges have also been used widely despite their lack of evidence. Capacitive Resistive Monopolar Radiofrequency (CRMRF) that operates at 448 kHz is one such RF. This programme of research was designed to investigate the physiological and clinical efficacy of CRMRF delivered using the 'Indiba Activ 902' device. The project also evaluated the scope and evidence for RF-based EPAs in therapy, through a comprehensive review of literature. A total of 120 relevant clinical studies on either acute (30 studies) or chronic (90 studies) conditions were reviewed. Notable evidence was identified for chronic OA knee and acute postoperative pain and wound healing. Some evidence also exists for chronic low back pain and healing of chronic wounds. Only eight studies reported devices that employed RF outside the shortwave frequency band. In a randomised crossover laboratory study on asymptomatic adults, the effects of contrasting doses of CRMRF on skin temperature (SKT), skin blood flow (SBF), nerve conduction velocity (NCV), deep blood flow and the extensibility of tissues were examined against a placebo dose and a control condition with no treatment. The study further compared CRMRF results with that of PSWT. The results showed that high (moderately thermal) and low (sub/minimally thermal) doses of CRMRF significantly enhanced and sustained SKT (p < 0.001), while only the high dose meaningfully increased SBF (p < 0.001). High dose PSWT increased SKT marginally (p < 0.001) but did not sustain it. Further, the high and low dose CRMRF significantly enhanced blood flow volume at depth (p=0.003), while PSWT failed to show any significant impact. None of the treatments significantly affected deep blood flow velocity, tissue extensibility or NCV. These results were reproduced on a cohort of patients affected by OA knee in a randomised controlled trial (RCT), and the effects appeared more pronounced in the patients than in the asymptomatic people. More importantly, the RCT showed that a four-week high dose CRMRF treatment (eight sessions) produced statistically and clinically significant gains in pain and function associated with OA knee in the short to medium term (p < 0.001), which was also significantly more pronounced than the gains produced by a placebo, or standard care (p=0.001for pain; p=0.031 for function). The findings of this study were considered promising. It is therefore suggested that CRMRF-based treatment can potentially be used as an adjunct to current therapeutic methods to enhance the clinical outcomes. However, further studies are needed to substantiate this, and the current results will provide credible baseline data for future research.

Three studies were performed to examine biophysical sources of individual variability in the thermoregulatory responses to exercise, and the influence of skin blood flow on heat loss potential during severe heat stress. Study 1 investigated whether unbiased comparisons of changes in rectal temperature (ΔTre) should be compared at a fixed absolute rate of heat production (Hprod; W) or a fixed Hprod per unit mass (W/kg), and whether local sweat rates (LSR) should be compared at a fixed evaporative requirement for heat balance (Ereq; W) or a fixed Ereq per unit of surface area (W/m2), between independent groups of unequal body mass and body surface area (BSA). Study 2 examined whether individual variation in ΔTre, whole-body sweat loss (WBSL), and steady-state LSR is best explained by biophysical factors related to Hprod, Ereq, and body size, and if factors related to aerobic fitness (VO2max) and body fatness correlate with the residual variance in these responses. Study 3 tested whether alterations in skin blood flow shift the critical vapour pressure (Pcrit) above which core temperature could no longer be regulated in hot/humid conditions, indicating altered heat loss potential from the skin. In study 1, exercise at fixed absolute Hprod and Ereq resulted in greater ΔTre and LSR in smaller individuals (smaller mass and BSA), but exercise at set Hprod in W/kg and Ereq in W/m2 resulted in no differences in ΔTre and LSR, respectively, regardless of body size and %VO2max. In study 2, 50-71% of the individual variation in ΔTre, whole-body sweat loss (WBSL), and steady-state LSR was explained by Hprod (W/kg), absolute Ereq (W) and Ereq (W/m2) respectively, while body fat percentage and %VO2max contributed merely 1-4% to the total variability. In study 3, despite a ~20% lower skin blood flow, Pcrit was unaffected by a large reduction in skin blood flow following iso-smotic dehydration, with no differences in core and skin temperatures and sweating observed. Collectively, these findings suggest that between-group comparisons and modelling of thermoregulatory responses must first consider biophysical factors related to metabolic heat production and body size, rather than factors related to VO2max and body fatness. Furthermore, lower levels of skin blood flow may not impair maximum heat dissipation from the skin to the external environment during severe passive heat stress as previously thought.

La microcirculation cutanée a été proposée comme modèle d’étude de la dysfonction microvasculaire globale dans les maladies cardiovasculaires. Par ailleurs, elle est spécifiquement atteinte dans la sclérodermie systémique (SSc), qui est une maladie dysimmunitaire rare, particulièrement invalidante, caractérisée par une fibrose cutanée et viscérale associée à une atteinte microvasculaire diffuse et la présence d’auto anticorps dirigés contre des antigènes cellulaires. L’exploration de la fonction microvasculaire cutanée suscite donc un réel intérêt, même s’il n’existe pas de technique standardisée pour l’étude de la fonction microvasculaire, en particulier endothéliale.La première partie de ce travail a porté sur l’étude physiologique de la microcirculation cutanée chez le volontaire sain, en utilisant les méthodes les plus récentes adaptées à l’étude fonctionnelle de la microcirculation (tests de réactivité vasculaire couplés à l’enregistrement du flux sanguin cutané par laser speckle contrast imaging). Dans une seconde partie, nous avons étudié la pathologie de la microcirculation cutanée dans la sclérodermie systémique, en utilisant les mêmes d’étude fonctionnelle de la microcirculation. La dernière partie de cette thèse a été consacrée à l’étude d’une nouvelle approche pharmacologique et thérapeutique dans la prise en charge des manifestations vasculaires cutanées périphériques identifiées chez les patients. Nous avons évalué l’effet vasodilatateur du tréprostinil, analogue de la prostacycline, sur le flux sanguin cutané de divers zones anatomiques, chez le volontaire sain, le patient atteint de SSc, le patient diabétique et lors d’un refroidissement local dans la SSc. / Cutaneous microcirculation has been proposed as a model to study the global microvascular dysfunction occurring in cardiovascular diseases. Furthermore, it is specifically impaired in systemic sclerosis (SSc), which is a rare and particularly invalidating auto-immune disease, characterized by a cutaneous and visceral fibrosis, associated with a diffuse microvascular impairment and auto-antibodies targeting some cellular antigens. The study of cutaneous microvascular function provides a real interest despite the lack of available standardized techniques, particularly to explore endothelial microvascular function.In the first part of this work, we aimed to study the physiology of cutaneous microcirculation in healthy volunteers, using the more recent methods in this field, adapted to functional study of microcirculation (vascular reactivity tests coupled with cutaneous blood flow recording by laser speckle contrast imaging). The second part of our work aimed to study the pathology of cutaneous microcirculation in SSc volunteers, by using the same functional exploration methods. The last part of this work has been dedicated to a new pharmacologic and therapeutic approach for the management of peripheral cutaneous vascular manifestations in patients, using innovating technics as cutaneous iontophoresis. We studied the vasodilator effect of treprostinil, a prostacycline analogue, on cutaneous blood flow in several anatomic regions in healthy subject, SSc patient and diabetic patient, and also during a local cooling in SSc.

La thérapie par compression médicale est reconnue comme une composante essentielle dans le traitement des pathologies veineuses et demeure incontournable dans la prise en charge des affections veineuses aux différents stades de la pathologie (jambes lourdes, œdèmes, ulcères). Si le bénéfice est reconnu par les patients eux-mêmes ainsi que par les médecins, il n’existe à l’heure actuelle que peu d’éléments permettant de quantifier ce bénéfice. Dans ce contexte, l’objectif de ces travaux de thèse est d’apporter des éléments de compréhension et d’objectiver les effets bénéfiques des bas médicaux de compression (BMC) aux niveaux physiologique, neurophysiologique et comportemental. Trois axes de recherche ont été dégagés. Le premier axe de recherche est l’étude de l’effet de la compression sur l’activité microcirculatoire cutanée dans les membres inférieurs en utilisant le dispositif Hématron, dispositif ambulatoire exclusif d’évaluation de l’activité microcirculatoire cutanée. Les résultats ont montré une amélioration de l’activité microcirculatoire pour différentes classes de BMC et pour différentes positions. Ces résultats tendraient à mettre en cause l’hypothèse, largement admise, que les BMC améliorent le retour veineux principalement en diminuant la section des veines (superficielles voire profondes). La deuxième piste de recherche concerne l’objectivation de l’amélioration de la qualité de vie liée au port des BMC, généralement exprimée subjectivement par les personnes atteintes de pathologie veineuse. Les résultats préliminaires montrent que l’analyse de la variabilité cardiaque permet de mettre en évidence une relation entre le paramètre indicateur de l’activité de la balance sympatho-vagale et le port de la compression médicale au cours d’une journée. Compte tenu de la grande dispersion des résultats, cette étude serait à poursuivre sur une population plus large pour aboutir à des conclusions fiables. Le dernier axe de recherche est lié à l’impact du port des BMC sur le comportement du sujet et plus précisément sur sa déambulation. Les patients déclarent une fatigue physique dans les membres inférieurs moins intense en fin de journée grâce à la compression médicale. Notre hypothèse est que le port des BMC impacterait directement la dynamique de la déambulation. Pour évaluer la cinétique de la marche, nous avons conçu, développé et validé une instrumentation intégrant des capteurs accéléromètres. Des tests préliminaires ont permis de dégager des paramètres pertinents caractéristiques de la déambulation. La prochaine étape sera de conduire une campagne d’expérimentation destinée à objectiver la fatigue comportementale en fin d’après-midi mesurée avec ou sans compression médicale portée au cours de la journée. / Medical compression therapy is recognized as an essential component in the treatment of venous diseases and is indispensable in the treatment of venous diseases at different stages of the disease (heavy legs, edema and ulcers). Although the benefit is recognized by the patients themselves and by physicians, there is at present little evidence to quantify this benefit. Against this background, the aim of this thesis is to provide more understanding and objectify the benefits of compression stockings (MCS) on in terms of physiology, neurophysiology and gait dynamics. Three areas of research were identified and studied. The first line of research is the study of the effect of compression on skin microcirculatory activity in the lower limbs using the Hematron ambulatory device. The results showed an improvement in skin blood flow activity for different classes of MCS and at different positions. These results would tend to challenge the widely accepted assumption that MCS improve venous return primarily by decreasing the cross-sectional area of (superficial or deep) veins. The second line of research involves the objectification of the improvement in the quality of life resulting from the wearing of MCS, usually this is expressed subjectively by people with venous disease. Preliminary results show that the analysis of heart rate variability highlights a relationship between the indicators of sympathovagal balance activity and the use of medical compression during the day. Given the wide dispersion in the results, this study should be carried out on a larger population to draw more reliable conclusions. The last line of research relates to the impact of MCS on the behavior and, in particular, the gait of the subject. Patients report that physical fatigue in the lower limbs is less prevalent at the end of the day with compression therapy. Our hypothesis is that the wearing of MCS has a direct impact on gait. To evaluate the kinetics of walking, we have designed, developed and validated an instrumentation involving accelerometers sensors. Preliminary tests have yielded relevant parameters characteristic of gait dynamics. The next step is to conduct an experimental campaign to objectify behavioral fatigue, with or without the wearing of medical compression, at the end of the afternoon.