Modelflow estimates of cardiac output compared with Doppler ultrasound during acute changes in vascular resistance in women

We compared Modelflow (MF) estimates of cardiac stroke volume (SV) from the finger pressure-pulse waveform (Finometer®) with pulsed Doppler ultrasound (DU) of the ascending aorta during acute changes in total peripheral resistance (TPR) in the supine and head-up-tilt (HUT) postures. Twenty-four women were tested during intravenous infusion of 0.005 or 0.01 μg kg -1 min-1 isoprenaline, 10 or 50 ng kg-1 min-1 noradrenaline and 0.3 mg sublingual nitroglycerine. Responses to static hand-grip exercise (SHG), graded lower body negative pressure (LBNP, from -20 to -45 mmHg) and 45 deg HUT were evaluated on separate days. Bland-Altman analysis indicated that SVMF yielded lower estimates than SVDU during infusion of 0.01 μg kg-1 min -1 isoprenaline (SVMF 92.7 ± 15.5 versus SV DU 104.3 ± 22.9 ml, P = 0.03) and SHG (SVMF 78.8 ± 12.0 versus SVDU 106.1 ± 28.5 ml, P \u3c 0.01), while larger estimates were recorded with SVMF during -45 mmHg LBNP (SVMF 52.6 ± 10.7 versus SVDU 46.2 ± 14.5 ml, P = 0.04) and HUT (SVMF 59.3 ± 13.6 versus SVDU 45.2 ± 11.3 ml, P \u3c 0.01). Linear regression analysis revealed a relationship (r2 = 0.41, P \u3c 0.01) between the change in TPR from baseline and the between-methods discrepancy in SV measurements. This relationship held up under all of the experimental protocols (regression for fixed effects, P = 0.46). These results revealed a discrepancy in MF estimates of SV, in comparison with those measured by DU, during acute changes in TPR. © 2010 The Physiological Society

Temporal Artery Flow Response during the Last Minute of a Head Up Tilt Test, in Relation with Orthostatic Intolerance after a 60 Day Head-Down Bedrest

OBJECTIVE: Check if the Temporal flow response to Tilt could provide early hemodynamic pattern in the minutes preceding a syncope during the Tilt test performed after a 60-d head down bedrest (HDBR). METHOD: Twenty-one men divided into 3 groups [Control (Con), Resistive Vibration (RVE) and Chinese Herb (Herb)] underwent a 60 day HDBR. Pre and Post HDBR a 20 min Tilt identified Finishers (F) and Non Finishers (NF). Cerebral (MCA), Temporal (TEMP), Femoral (FEM) flow velocity, were measured by Doppler during the Tilt. Blood pressure (BP) was measured by arm cuff and cardiopress. RESULTS AND DISCUSSION: Four of the 21 subjects were NF at the post HDBR Tilt test (Con gr:2, RVE gr: 1, Herb gr: 1). At 1 min and 10 s before end of Tilt in NF gr, FEM flow decreased less and MCA decreased more at post HDBR Tilt compared to pre (p<0.05), while in the F gr they changed similarly as pre. In NF gr: TEMP flow decreased more at post HDBR Tilt compared to pre, but only at 10 s before the end of Tilt (P<0.05). During the last 10 s a negative TEMP diastolic component appeared which induced a drop in mean velocity until Tilt arrest. CONCLUSION: The sudden drop in TEMP flow with onset of a negative diastolic flow preceding the decrease in MCA flow confirm that the TEMP vascular resistance respond more directly than the cerebral one to the cardiac output redistribution and that this response occur several seconds before syncope

Peripheral Arterial and Venous Response to Tilt Test after a 60-Day Bedrest with and without Countermeasures (ES-IBREP)

We quantified the impact of 60-day head-down bed rest (HDBR) with countermeasures on arterial and venous response to tilt. Methods: Twenty-one males: 7 control (Con), 7 resistive vibration exercise (RVE) and 7 Chinese herb (Herb) were assessed. Subjects were identified as finisher (F) or non-finishers (NF) at the post-HDBR 20-min tilt test. The cerebral (MCA), femoral (FEM) arterial flow velocity and leg vascular resistance (FRI), the portal vein section (PV), the flow redistribution ratios (MCA/FEM; MCA/PV), the tibial (Tib), gastrocnemius (Gast), and saphenous (Saph) vein sections were measured by echography and Doppler ultrasonography. Arterial and venous parameters were measured at 3-min pre-tilt in the supine position, and at 1 min before the end of the tilt. Results: At post-HDBR tilt, MCA decreased more compared with pre-HDBR tilt in the Con, RVE, and Herb groups, the MCA/FEM tended to decrease in the Con and Herb groups (not significant) but remained stable in the RVE gr. FRI dropped in the Con gr, but remained stable in the Herb gr and increased in the RVE gr. PV decreased less in the Con and Herb groups but remained unchanged in the RVE gr. MCA/PV decreased in the Con and Herb groups, but increased to a similar extent in the RVE gr. Gast section significantly increased more in the Con gr only, whereas Tib section increased more in the Con and Herb groups but not in the RVE gr. The percent change in Saph section was similar at pre- and post-HDBR tilt. Conclusion: In the Con gr, vasoconstriction was reduced in leg and splanchnic areas. RVE and Herb contributed to prevent the loss of vasoconstriction in both areas, but the effect of RVE was higher. RVE and Herb contributed to limit Gast distension whereas only RVE had a protective effect on the Tib

Ultrasound assessments of organs and blood vessels before and after 40 days isolation in a cavern (deep time experiment 2021)

Introduction: Spaceflight simulation studies like confinement in small volume habitat with limited physical activity have reported even after 60 days an abnormal arterial wall adaptation with increase thickness or stiffness. The purpose of the current study was to determine the effects on blood vessel and organ structure of 40 days of isolation in a huge habitat with intensive physical activity.Method: Data were collected from 14 individuals (7 male) who isolated in a cavern for 40-days while performing normal daily activities without time references. Ultrasound assessments were performed pre- and post-isolation using a teleoperated system with eight different acoustic windows to obtain 19 measurements on 12 different organ/vascular structures which included the common carotid artery, femoral artery, tibial artery, jugular vein, portal vein, bile duct, kidney, pancreas, abdominal aorta, cervical and lumbar vertebral distance, and Achilles tendon.Results: Common carotid artery measures, including the intima media thickness, stiffness index, and the index of reflectivity measured from the radiofrequency signal, were not changed with isolation. Similarly, no differences were found for femoral artery measurements or measurements of any of the other organs/vessels assessed. There were no sex differences for any of the assessments.Discussion: Results from this study indicate a lack of physiological effects of 40-days of isolation in a cavern, contrary to what observed in previous 60 days confinement. This suggests a potential protective effect of sustained physical activity, or reduced environmental stress inside the huge volume of the confined facility

Paramètres vasculaires périphériques de l'intolérance orthostatique après déconditionnement cardio-vasculaire programmé (décubitus et microgravité)

Le déconditionnement cardio-vasculaire induit par une période d'alitement prolongé ou un vol spatial se traduit par une intolérance orthostatique aux mécanismes multiples. Le LBNP (Lower Body Negative Pressure) est un test adapté pour mettre en évidence ce déconditionnement Nous avons étudié à partir de la vitesse d'écoulement sanguin par Doppler les résistances vasculaires des membres inférieurs (Rf), le rapport cérébral/fémoral (CFR), le déficit cérébral de perfusion (CFD).La mesure des résistances vasculaires fémorales semble appropriée pour détecter une anomalie vasomotrice au niveau des membres inférieurs lors des tests de tolérance orthostatique. Le rapport du débit cérébral au débit des membres inférieurs (CFR) intègre les effets du déconditionnement cardio-vasculaire. Le déficit de perfusion cérébral cumulé (CFD) traduit la prédisposition du sujet à l'intolérance orthostatique . Ces paramètres permettent de quantifier et de prédire les réponses hémodynamiques aux tests.Cardiovascular deconditioning induced by spaceflight or head down Bed-Rest leads to orthostatic intolerance. Lower body negative pressure test is adapted to show cardiovascular deconditioning. We studied blood flow velocity by Doppler to assess lower limb vascular resistances, cerebral-femoral flow ratio (CFR) and cerebral flow deficit (CFD) during LBNP last level. Femoral vascular resistance assessment were appropriated for detecting lower limb vasomotor disease during orthostatic tests. CFR included cardiovascular deconditioning effects. CFD seems to be linked individual predisposition orthostatic intolerance. These parameters allow to quantify and predict hemodynamic responses during orthostatic tests.TOURS-BU Médecine (372612103) / SudocSudocFranceF

Circulation veineuse porte et intolérance orthostatique

TOURS-BU Médecine (372612103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Quantification de l'atrophie musculaire, du contenu hydrique et de la distensibilité veineuse des membres inférieurs (effet sur la tolérance orthostatique)

24 femmes ont été placées en Bed rest (60 j) pour quantifier certains éléments de l'adaptation et du déconditionnement physiologique. Le scanner à ultrasons a été validé par IRM. Après 55 j de Bed rest, la masse myocardique et le volume diastolique du ventricule gauche, le volume des muscles de la cuisse diminue, la distensibilité veineuse des membres inférieurs, évaluée au cours des tests orthostatiques, augmente dans les groupes contrôle et nutrition. La contremesure exercice limite l'altération de ces paramètres. Le contenu hydrique dans le réseau veineux et les tissus des membres inférieurs diminue. Aucune des contremesures ne limite la variation du contenu hydrique. Ces modifications étaient supérieures chez les sujets intolérants au TILT. Ces éléments sont modifiés par le Bed rest et contribuent vraisemblablement à l'intolérance orthostatique. La contremesure exercice réduit certaines de ces altérations, sans limiter complètement l'intolérance orthostatique aprè Bed rest.TOURS-BU Médecine (372612103) / SudocSudocFranceF

Ostéonécrose de la mâchoire après implantologie chez des patients traités par biphosphonates

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Adaptations du système cardio-vasculaire en microgravité réelle et simulée (influences d'une contre-mesure : les bracelets)

Le but de cette thèse est de faire la synthèse de 10 ans de missions spatiales et de simulation (HDT) pour dessiner un profil temporel de l'adaptation du système cardiovasculaire en microgravité réelle et simulée, puis d'évaluer l'efficacité d'une prophylaxie contre ce déconditionnement : les bracelets. Toutes les investigations ont été effectuées au moyen de techniques non-invasives utilisant les ultrasons (échographie et Doppler). Les mesures ont toujours été pratiquées au repos avant le vol ou l'alitement, puis à différentes durées. Au niveau cardiaque, un équilibre s'installe en 1 à 2 semaines de microgravité réelle ou simulée, caractérisé par un volume diastolique ventriculaire gauche et un volume d 'éjection cardiaques réduits, une fréquence cardiaque accélérée et un débit cardiaque maintenu entre 0 et - 5 %. Au niveau vasculaire, les paramètres cérébraux sont maintenus tandis que les résistances fémorales sont significativement réduites après 1 semaine. Du côté veineux, les jugulaires sont distendues en HDT et en vol tandis que les fémorales restent élargies en vol mais sont vidées en HDT. Hormis cette différence, le HDT reproduit convenablement les perturbations cardiovasculaires en microgravité. L'utilisation des bracelets comme contre-mesure ramène les paramètres cardiaques à leurs valeurs de base et réduit la stase veineuse cérébrale mais n'empêche pas le développement de l'intolérance orthostatique post-vol ou post-HDT.TOURS-BU Médecine (372612103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Fetal cerebrovascular response to chronic hypoxia - implications for the prevention of brain damage

Fetal hypoxia is one of the leading causes of perinatal morbidity and mortality. One of the most severe sequels of fetal hypoxic insult is the development of perinatal brain lesions resulting in a spectrum of neurological disabilities, from minor cerebral disorders to cerebral palsy. One of the most important fetal adaptive responses to hypoxia is redistribution of blood flow towards the fetal brain, known as the 'brain sparing effect'. The fetal blood flow redistribution in favor of the fetal brain can be detected and quantified by the Doppler cerebral/umbilical ratio (C/U ratio = cerebral resistance index (CRI)/umbilical resistance index (URI)). Our studies on animal models and human fetuses have demonstrated clearly that this phenomenon cannot prevent the development of perinatal brain lesions in the case of severe or prolonged hypoxia. Fetal deterioration in chronic and severe hypoxia is characterized by the disappearance of the physiological cerebral vascular variability (vasoconstriction and vasodilatation), followed by an increase in cerebral vascular resistance. However, our latest study on growth-restricted and hypoxic human fetuses has shown that perinatal brain lesions can develop even before the loss of cerebrovascular variability. The fetal exposure to hypoxia can be quantified by using a new vascular score, the hypoxia index. This parameter, which takes into account the degree as well as duration of fetal hypoxia, can be calculated by summing the daily % C/U ratio reduction from the cut-off value 1 over the period of observation. According to our results, the use of this parameter, which calculates the cumulative, relative oxygen deficit, could allow for the first time the sensitive and reliable prediction and even prevention of adverse neurological outcome in pregnancies complicated by fetal hypoxia