Restricted and controlled drug delivery to the heart remains a challenge giving frequent off-target effects as well as limited retention of drugs in the heart. There is a need to develop and optimize tools to allow for improved design of... more
Restricted and controlled drug delivery to the heart remains a challenge giving frequent off-target effects as well as limited retention of drugs in the heart. There is a need to develop and optimize tools to allow for improved design of drug candidates for treatment of heart diseases. Over the last decade, novel drug platforms and nanomaterials were designed to confine bioactive materials to the heart. Yet, the research remains in its infancy, not only in the development of tools but also in the understanding of effects of these materials on cardiac function and tissue integrity. Upconverting nanoparticles are nanomaterials that recently accelerated interest in theranostic nanomedicine technologies. Their unique photophysical properties allow for sensitive in vivo imaging that can be combined with spatio-temporal control for targeted release of encapsulated drugs. Here we synthesized upconverting NaYF4:Yb,Tm nanoparticles and show for the first time their innocuity in the heart, wh...
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Dry immersion (DI) is used to simulate weightlessness. We investigated in healthy volunteers if DI induces changes in ONSD, as a surrogate marker of intracranial pressure (ICP) and how these changes could affect cerebral autoregulation... more
Dry immersion (DI) is used to simulate weightlessness. We investigated in healthy volunteers if DI induces changes in ONSD, as a surrogate marker of intracranial pressure (ICP) and how these changes could affect cerebral autoregulation (CA). Changes in ICP were indirectly measured by changes in optic nerve sheath diameter (ONSD). 12 healthy male volunteers underwent 3 days of DI. ONSD was indirectly assessed by ocular ultrasonography. Cerebral blood flow velocity (CBFV) of the middle cerebral artery was gauged using transcranial Doppler ultrasonography. CA was evaluated by two methods: (1) transfer function analysis was calculated to determine the relationship between mean CBFV and mean arterial blood pressure (ABP) and (2) correlation index Mxa between mean CBFV and mean ABP.ONSD increased significantly during the first day, the third day and the first day of recovery of DI ( < 0.001).DI induced a reduction in Mxa index ( < 0.001) and an elevation in phase shift in low freque...
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Publisher Summary This chapter discusses the cardiovascular deconditioning syndrome that occurs after spaceflight and after long-term inactivity. During long-term confinement in a hyperbaric chamber, decreased physical activity is... more
Publisher Summary This chapter discusses the cardiovascular deconditioning syndrome that occurs after spaceflight and after long-term inactivity. During long-term confinement in a hyperbaric chamber, decreased physical activity is commonly observed, as it is in space. Because confinement in a limited space for 28 days was the principal characteristic of the Isolation Study for European Manned Space Infrastructure (ISEMSI) experiment, there was to be expected a considerable decrease in the physical activity of the subjects. Hence, there was the possibility of the occurrence of a certain degree of cardiac deconditioning. To investigate this, a lower body negative pressure (LBNP) experiment was carried out as part of the ISEMSI program. From the LBNP experiment carried out during the ISEMSI project, it can be concluded that there was no indication of the cardiac deconditioning syndrome in any of the subjects. The absence of such effects can probably be ascribed to two conditions: the subjects were not in inactive conditions and there was only a slight overpressure in the hyperbaric chamber.
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Background and Purpose —Asymptomatic microembolic signals (MES) can be demonstrated in patients with cerebral ischemia using transcranial Doppler (TCD) ultrasonographic monitoring of the middle cerebral artery. However, the clinical... more
Background and Purpose —Asymptomatic microembolic signals (MES) can be demonstrated in patients with cerebral ischemia using transcranial Doppler (TCD) ultrasonographic monitoring of the middle cerebral artery. However, the clinical relevance of MES remains uncertain. The purpose of this study was to estimate the independent contribution of microembolism to the risk of early ischemic recurrence (EIR) in patients with stroke or transient ischemic attack (TIA) of presumed arterial origin. Methods —We studied the incidence of EIR in 73 consecutive patients with carotid stroke or TIA in whom TCD scanning of the symptomatic middle cerebral artery was performed within 7 days from the onset of symptoms. Patients with a potential cardiac source of embolism were excluded from the study. Results —Eight patients had EIR during a mean±SD follow-up of 10±8 days. The incidence of EIR was 4.3 per 100 patient-days in patients with MES and only 0.5 per 100 patient-days in patients without MES. The p...
Research Interests: Cardiology, Humans, Internal Medicine, Female, Male, and 15 moreIncidence, Clinical Sciences, Aged, Adult, Cerebral Ischemia, Antiplatelet Therapy, Asymptomatic, Cerebrovascular Disorders, Embolism, Confidence Interval, Carotid Stenosis, Aortic arch, Cardiovascular medicine and haematology, Intracranial Embolism and Thrombosis, and cerebral arteries
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This paper summarizes what has been learned from studies of the effects of artificial gravity generated by centrifugation in actual and simulated weightless conditions. The experience of artificial gravity during actual space flight in... more
This paper summarizes what has been learned from studies of the effects of artificial gravity generated by centrifugation in actual and simulated weightless conditions. The experience of artificial gravity during actual space flight in animals and humans are discussed. Studies using intermittent centrifugation during bed rest and water immersion, as a way to maintain orthostatic tolerance and exercise capacity, are reviewed; their results indicate that intermittent centrifugation is a potential countermeasure for maintaining the integrity of these physiological functions in extended space missions. These results can help set guidelines for future experiments aimed at validating the regimes of centrifugation as a countermeasure for space missions. Current and future research projects using artificial gravity conditions in humans are discussed.
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Multimodal MRI approach is based on a combination of MRI parameters sensitive to different tissue characteristics (eg, volume atrophy, iron deposition, and microstructural damage). The main objective of the present study was to use a... more
Multimodal MRI approach is based on a combination of MRI parameters sensitive to different tissue characteristics (eg, volume atrophy, iron deposition, and microstructural damage). The main objective of the present study was to use a multimodal MRI approach to identify brain differences that could discriminate between matched groups of patients with multiple system atrophy, Parkinson's disease, and healthy controls. We assessed the 2 different MSA variants, namely, MSA-P, with predominant parkinsonism, and MSA-C, with more prominent cerebellar symptoms. Twenty-six PD patients, 29 MSA patients (16 MSA-P, 13 MSA-C), and 26 controls underwent 3-T MRI comprising T2*-weighted, T1-weighted, and diffusion tensor imaging scans. Using whole-brain voxel-based MRI, we combined gray-matter density, T2* relaxation rates, and diffusion tensor imaging scalars to compare and discriminate PD, MSA-P, MSA-C, and healthy controls. Our main results showed that this approach reveals multiparametric m...
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Patients with cardiovascular disease show autonomic dysfunction, including sympathetic activation and vagal withdrawal, which leads to fatal events. This review aims to place sympathovagal balance as an essential element to be considered... more
Patients with cardiovascular disease show autonomic dysfunction, including sympathetic activation and vagal withdrawal, which leads to fatal events. This review aims to place sympathovagal balance as an essential element to be considered in management for cardiovascular disease patients who benefit from a cardiac rehabilitation program. Many studies showed that exercise training, as non-pharmacologic treatment, plays an important role in enhancing sympathovagal balance and could normalize levels of markers of sympathetic flow measured by microneurography, heart rate variability or plasma catecholamine levels. This alteration positively affects prognosis with cardiovascular disease. In general, cardiac rehabilitation programs include moderate-intensity and continuous aerobic exercise. Other forms of activities such as high-intensity interval training, breathing exercises, relaxation and transcutaneous electrical stimulation can improve sympathovagal balance and should be implemented in cardiac rehabilitation programs. Currently, the exercise training programs in cardiac rehabilitation are individualized to optimize health outcomes. The sports science concept of the heart rate variability (HRV)-vagal index used to manage exercise sessions (for a goal of performance) could be implemented in cardiac rehabilitation to improve cardiovascular fitness and autonomic nervous system function.
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Simulated microgravity produces sustained inhibition of sympathoneural release, turnover, and synthesis of norepinephrine (NE) and hypersensitization of beta-adrenergic pathways. These changes may explain the orthostatic intolerance... more
Simulated microgravity produces sustained inhibition of sympathoneural release, turnover, and synthesis of norepinephrine (NE) and hypersensitization of beta-adrenergic pathways. These changes may explain the orthostatic intolerance experienced by astronauts returning from spaceflights. Chronic administration of yohimbine would prevent the increase of beta-adrenergic hypersensitivity to epinephrine (Epi) induced by simulated microgravity. Eight healthy young subjects received 8 mg of yohimbine (an antagonist of alpha2adrenoceptors) orally twice a day during the simulated microgravity achieved through -6 degrees head-down bed rest (HDBR). The catecholamine-induced lipolysis was studied on isolated fat cells from subcutaneous adipose tissue before HDBR and on the fifth day of HDBR. Epi was infused at three graded rates (0.01, 0.02, and 0.03 microg x kg(-1) x min(-1) for 40 min each) before and at the end of the HDBR period. The effects of Epi on the sympathetic nervous system (SNS) ac...
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ABSTRACT Introduction: l-threo-3,4-dihydroxyphenylserine (droxidopa) is a pro-drug that is metabolized to norepinephrine in nerve endings and in other tissues. It has been commercialized in Japan since 1989 for treatment of orthostatic... more
ABSTRACT Introduction: l-threo-3,4-dihydroxyphenylserine (droxidopa) is a pro-drug that is metabolized to norepinephrine in nerve endings and in other tissues. It has been commercialized in Japan since 1989 for treatment of orthostatic hypotension (OH) symptoms in Parkinson&#39;s disease (PD) with Hoehn &amp; Yahr stage III, Shy-Drager syndrome, familial amyloid polyneuropathy and hemodialytic patients. It has also been recently approved by the FDA for symptomatic neurogenic OH. Areas covered: In this review, clinical uses of droxidopa in neurogenic OH and other neurodegenerative disorders will be reviewed. Results from a MEDLINE search with the keywords ‘droxidopa&#39; or ‘l-threo-3,4-dihydroxyphenylserine&#39; or ‘L-DOPS&#39; will be discussed. Abstracts from international congresses will also be explored. Expert opinion: Results from a few small and short placebo-controlled trials and clinical studies in neurogenic OH showed significant reductions in the manometric drop of blood pressure after posture changes or meals. Larger Phase III studies suggest a positive effect of the drug on dizziness, which has only been shown in the short term (i.e., Keywords: Parkinson&#39;s disease; droxidopa; multiple system atrophy; norepinephrine; orthostatic hypotension; pure autonomic failure; sympathetic autonomic nervous system; synucleinopathies; treatment Document Type: Research Article DOI: http://dx.doi.org/10.1517/21678707.2014.901167 Affiliations: 1 University of Toulouse III and INSERM, University Hospital, Departments of Clinical Pharmacology and Neurosciences, Toulouse, France Publication date: May 1, 2014 More about this publication? Information for Authors Subscribe to this Title Terms &amp; Conditions ingentaconnect is not responsible for the content or availability of external websites $(document).ready(function() { var shortdescription = $(&quot;.originaldescription&quot;).text().replace(/\\&amp;/g, &#39;&amp;&#39;).replace(/\\, &#39;&lt;&#39;).replace(/\\&gt;/g, &#39;&gt;&#39;).replace(/\\t/g, &#39; &#39;).replace(/\\n/g, &#39;&#39;); if (shortdescription.length &gt; 350){ shortdescription = &quot;&quot; + shortdescription.substring(0,250) + &quot;... more&quot;; } $(&quot;.descriptionitem&quot;).prepend(shortdescription); $(&quot;.shortdescription a&quot;).click(function() { $(&quot;.shortdescription&quot;).hide(); $(&quot;.originaldescription&quot;).slideDown(); return false; }); }); Related content In this: publication By this: publisher By this author: Perez-Lloret, Santiago ; Rey, María Verónica ; Pavy-Le Traon, Anne ; Rascol, Olivier GA_googleFillSlot(&quot;Horizontal_banner_bottom&quot;);
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ABSTRACT Since more than 40 years, manned Space flights have shown that sleep in space is possible. However, in-flight studies have reported reduced sleep duration and sleep disturbances which may lead to performance impairment. The... more
ABSTRACT Since more than 40 years, manned Space flights have shown that sleep in space is possible. However, in-flight studies have reported reduced sleep duration and sleep disturbances which may lead to performance impairment. The causes of these changes are not well known. These disturbances have been particularly reported in case of abnormal work-rest schedule due to operational constraints. But space environment factors as microgravity and changes in light/dark cycle may also induce changes in sleep and circadian rhythms. This review discusses how different factors may influence sleep and biological rhythms in space flight and simulation experiments.
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1 University of Udine, Italy 2 Centre National de la Recherche Scientifique, Toulouse, France 3 Ohio University, Athens, Ohio, USA 4 University of Brescia, Italy 5 University Medical Center, Geneva, Switzerland 6 Karolinska ...
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Autonomic failure is a key feature of multiple system atrophy (MSA). Moreover, early autonomic failure is an independent predictive factor for rapid disease progression and shorter survival. The assessment of autonomic failure is... more
Autonomic failure is a key feature of multiple system atrophy (MSA). Moreover, early autonomic failure is an independent predictive factor for rapid disease progression and shorter survival. The assessment of autonomic failure is therefore important for both, the diagnosis and prognosis of MSA. Here, we evaluate autonomic dysfunction in MSA patients by the Scopa-Aut questionnaire. Potential associations between the Scopa-Aut questionnaire and established markers of disease progression - that is the Unified MSA Rating Scale (UMSARS) - were further assessed. The results confirm early and prominent autonomic failure in MSA patients. Relative scores were highest for the sexual and urinary subdomains. Surprisingly, relative scores in the cardiovascular subdomain were lowest suggesting that the Scopa-Aut questionnaire is suboptimal for the screening and evaluation of cardiovascular symptoms in MSA. A multivariate regression showed an association between total Scopa-Aut and UMSARS I scores. No significant changes in Scopa-Aut scores were observed during follow-up except for the urinary subdomain, while UMSARS I, II and IV scores significantly increased over time. In conclusion, Scopa-Aut can be used as a simple auto-questionnaire for the screening of autonomic symptoms in multiple system atrophy. It seems not useful as endpoint for disease-modification or neuroprotection trials.
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Orthostatic hypotension (OH), a frequent feature of... more
Orthostatic hypotension (OH), a frequent feature of Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD) can contribute to falls and is usually related to the disease itself and/or to drugs. To explore factors related to OH and to assess the concordance between abnormal blood pressure (BP) fall after standing and the presence of orthostatic symptoms. Non-demented, non-operated idiopathic PD out-patients were questioned about the presence of orthostatic symptoms. Afterward, BP was measured 5-min after lying down and for 3-min after standing up. OH was defined as systolic and/or diastolic BP fall ≥ 20 and/or 10 mmHg after standing. Patients were further evaluated by the Unified PD Rating Scale (UPDRS) and their medications were recorded. 103 patients were included in this study (mean age = 66 ± 1 years, mean disease duration = 9 ± 1 years; mean UPDRS II+III in ON-state = 37 ± 2 points). Forty-one subjects (40%) reported the presence of orthostatic symptoms during the previous week and 38 (37%) had OH according to manometric definition. Independent factors related to OH, as assessed by logistic regression were age &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;68 years (OR, 95% CI=3.61, 1.31-9.95), polypharmacy (defined as intake of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;5 medications, OR = 3.59, 1.33-9.69), amantadine (7.45, 1.91-29.07) or diuretics (5.48, 1.10-54.76), whereas the consumption of entacapone was protective (0.20, 0.05-0.76). The agreement between abnormal BP fall and presence of orthostatic symptoms was poor (kappa = 0.12 ± 0.1, p = 0.23). OH was significantly related to older age, polypharmacy and amantadine or diuretics intake, while entacapone exposure appeared to reduce the risk of OH. Low concordance between OH and orthostatic symptoms was observed.
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Research Interests: Cognitive Science, Nonlinear dynamics, Multiple System Atrophy, Movement disorders, Humans, and 14 moreMovement, Blood Pressure, Female, Male, Heart rate, Clinical Sciences, Aged, Middle Aged, Transcranial Doppler, Homeostasis, Spectrum analysis, Blood Flow Velocity, Middle Cerebral Artery, and Cerebral autoregulation
Autonomic dysfunction, including orthostatic hypotension (OH), sialorrhea, sexual dysfunction, urinary dysfunction and constipation is a common feature of... more
Autonomic dysfunction, including orthostatic hypotension (OH), sialorrhea, sexual dysfunction, urinary dysfunction and constipation is a common feature of Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD). Even though its treatment has been recognized as a major unmet need in PD, there is a paucity of clinical trials to assess their treatment. Evidence about the efficacy and safety of available treatments for autonomic dysfunction is summarized. Potential targets for upcoming therapies are then discussed in light of what is currently known about the physiopathology of each disorder in PD. Proof-of-concept trials and circumstantial evidence about treatments for autonomic dysfunction as well as upcoming clinical trials are discussed. Finally, critical aspects of clinical trials design are considered. Botulinum toxin (BTX) or glycopyrrolate might be used for sialorrhea whereas macrogol could be useful in constipation. There is preliminary evidence suggesting that fludrocortisone, domperidone, droxidopa or fipamezole may be effective for the treatment of OH. Tropicamide, clonidine or radiotherapy are under development for sialorrhea. Sildenafil may be effective for the treatment of erectile dysfunction; BTX or behavioral therapy for urinary incontinence and lubiprostone and probiotics for constipation. Sound clinical trials are needed in order to allow firm evidence-based recommendations about these treatments.
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Aneurysmal subarachnoid hemorrhage (SAH) is characterized by important changes in the autonomic nervous system with potentially adverse consequences. The baroreflex has a key role in regulating the autonomic nervous system. Its role in... more
Aneurysmal subarachnoid hemorrhage (SAH) is characterized by important changes in the autonomic nervous system with potentially adverse consequences. The baroreflex has a key role in regulating the autonomic nervous system. Its role in SAH outcome is not known. The purpose of this study was to evaluate the association between the baroreflex and the functional 3-month outcome in SAH. The study used a prospective database of 101 patients hospitalized for SAH. We excluded patients receiving β-blockers or noradrenaline. Baroreflex sensitivity (BRS) was measured using the cross-correlation method. A good outcome was defined by a Glasgow Outcome Scale score at 4 or 5 at 3 months. Forty-eight patients were included. Median age was 58 years old (36-76 years); women/men: 34/14. The World Federation of Neurosurgery clinical severity score on admission was 1 or 2 for 73% of patients. In the univariate analysis, BRS (=0.007), sedation (=0.001), World Federation of Neurosurgery score (=0.001), G...
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PURPOSE: To determine the change in intraocular pressure (IOP) due to postural changes in young healthy volunteers.MATERIALS AND METHODS: Intraocular pressure was measured using a calibrated Pulsair noncontact tonometer in both eyes of 25... more
PURPOSE: To determine the change in intraocular pressure (IOP) due to postural changes in young healthy volunteers.MATERIALS AND METHODS: Intraocular pressure was measured using a calibrated Pulsair noncontact tonometer in both eyes of 25 female volunteers in a sitting position and after 1, 3, and 10 minutes in a supine position. In the second part of the experiment (a 7-day -6 degrees head-down tilt [HDT]), IOP (at 8 am, 12 am and 6 pm) and corneal thickness (12 am) were monitored in 8 female volunteers before, during, and after the HDT period. Blood pressure, hematocrit, plasma volume and osmolality, and plasma catecholamines concentrations were also measured.RESULTS: Intraocular pressure was significantly higher in the supine position (16.1 +/- 3.6 mm Hg) than in the sitting position, with a mean pressure difference of 2.23 +/- 2.9 mm Hg after 1 minute, 0.9 +/- 3 mm Hg after 3 minutes, and 1.9 +/- 3.8 mm Hg after 10 minutes in a supine position (P < 0.001). During the period of HDT, IOP values decreased significantly on the fifth day (13.3 +/- 1.6 mm Hg, P = 0.03) and the seventh day (12.7 +/- 1.7 mm Hg, P = 0.02) when compared with IOP in the supine position (14.26 +/- 2 mm Hg). The corneal thickness increased significantly (P < 0.0001) at day 5 (549.25 +/- 48.7 microm) and day 7 (540.31 +/- 46.9 microm) compared with baseline (532.45 +/- 38.6 microm). Two days after the end of the HDT bedrest, the mean supine IOP significantly increased (14.1 +/- 1.8 mm Hg, P = 0.003) and corneal thickness was similar to that found at baseline. The mean decrease of IOP was positively correlated with that of the plasma volume (-10%, r = 0.61, P = 0.02) and negatively correlated with the mean rise of hematocrit (r = -0.5, P = 0.07), variables that are considered to be indirect measures of plasma dehydration.CONCLUSIONS: During a 7-day HDT bedrest experiment in healthy women, eyes seemed to compensate the moderate rise of IOP described between a sitting and a supine position, and exhibited a slight and progressive average decrease of 1.3 mm Hg. These physiological modifications could be related to an ocular dehydration or to systemic cardiovascular and hormonal variations during bedrest.
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Research Interests: Carbon Dioxide, Humans, Obstructive sleep apnea, Blood Pressure, Female, and 14 moreMale, Regression Analysis, Clinical Sciences, Polysomnography, Pressure, Wakefulness, Middle Aged, Homeostasis, Blood Flow Velocity, Neurosciences, Middle Cerebral Artery, Cerebral autoregulation, Obstructive Sleep Apnea Syndrome, and Cerebrum
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The relative stability of cerebral blood flow is maintained by the baroreflex and cerebral autoregulation (CA). We assessed the relationship between baroreflex sensitivity (BRS) and CA in patients with atherosclerotic carotid stenosis or... more
The relative stability of cerebral blood flow is maintained by the baroreflex and cerebral autoregulation (CA). We assessed the relationship between baroreflex sensitivity (BRS) and CA in patients with atherosclerotic carotid stenosis or occlusion. Patients referred for assessment of atherosclerotic unilateral >50% carotid stenosis or occlusion were included. Ten healthy volunteers served as a reference group. BRS was measured using the sequence method. CA was quantified by the correlation coefficient (Mx) between slow oscillations in mean arterial blood pressure and mean cerebral blood flow velocities from transcranial Doppler. Forty-five patients (M/F: 36/9), with a median age of 68 years (IQR:17) were included. Thirty-four patients had carotid stenosis, and 11 patients had carotid occlusion (asymptomatic: 31 patients; symptomatic: 14 patients). The median degree of carotid steno-occlusive disease was 90% (IQR:18). Both CA (P=0.02) and BRS (P<0.001) were impaired in patients...
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Besides microgravity, inactivity is likely to play a role in the cardiovascular deconditioning after space flights and weightlessness simulations. The aim of the study was to compare the effects of a 4-day head-down bed rest (HDBR) (-6... more
Besides microgravity, inactivity is likely to play a role in the cardiovascular deconditioning after space flights and weightlessness simulations. The aim of the study was to compare the effects of a 4-day head-down bed rest (HDBR) (-6 degrees) and a 4-day confinement (C) on cardiovascular responses to orthostatic stress. Eight male subjects underwent head-up tilt (HUT) (+60 degrees) and lower-body negative pressure (LBNP) (-20, -30, -40 and -50 mmHg) before (D-1) and at the end (R1) of each situation. Blood pressure, heart rate variability (HRV) and spontaneous baroreflex slope (SBS) were determined. The HDBR reduced orthostatic tolerance, as five subjects presented orthostatic hypotension during the HUT at R1, compared with two subjects at D-1. These same two subjects presented orthostatic hypotension after confinement. The main findings, after HDBR, included reductions in RR interval and total spectral power and a decrease in the parasympathetic indicator (PNS) in favour of a dec...
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Research Interests: Kinetics, Ultrasound, High Frequency, Humans, Space flight, and 15 moreTibia, Ultrasonography, Male, Skin, Forehead, European, Pressure, High Resolution, Body water, Adult, Edema, Bed Rest, Skin Disease, Thigh, and Control Group
Various factors may contribute to orthostatic intolerance (OI) observed after space flights or simulated weightlessness such as bed rest experiments: individual physical and physiological factors (arterial blood pressure (BP), height),... more
Various factors may contribute to orthostatic intolerance (OI) observed after space flights or simulated weightlessness such as bed rest experiments: individual physical and physiological factors (arterial blood pressure (BP), height), physiological changes induced by real or simulated weightlessness (hypovolaemia, increase in venous distensibility), and space flight or simulation conditions (duration and counter-measure application). Our purpose was to test which of these factors were dominant in contributing to the OI. This was assessed in 47 healthy men participating in bed rest experiments of 4, 14, 28, 30 and 42 days, with or without counter-measures (medical stockings, lower-body negative pressure (LBNP), LBNP + muscular exercise). Nineteen subjects did not finish the orthostatic test (60 degrees head-up tilt or stand test) after bed rest. The occurrence of OI was associated with greater height, low resting BP, greater changes in resting lower-limb venous distensibility throughout the bed rest, and absence of counter-measures.