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Results 251 - 300 of 1594
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Privett S E - - 2010
To investigate the regulation of blood pressure in response to an orthostatic challenge in athletes running a marathon. 10 experienced male runners (mean (SD) age 29 (4) years) were tested on the day prior to the 2004 London Marathon, and again immediately postrace (race time 210 (36) min). In addition, ...
Gemignani Tiago - - 2008
Atherosclerosis of peripheral arteries typically affects vessels of the lower limbs, suggesting that local hemodynamic stimuli play a role in this process. Our study evaluated the effects of body postural changes on carotid and popliteal blood pressure, circumferential wall tension (CWT) and arterial strain, and investigated the relationship between such ...
Peterson M - - 2008
OBJECTIVE: Intensive care unit patients are at particular risk for pressure ulcers and ventilator-associated pneumonia. Current guidelines recommend that mechanically ventilated patients be kept in a semirecumbent position with the head of bed elevated 30 degrees -45 degrees to prevent aspiration and ventilator-associated pneumonia. We tested the effects of elevating ...
Lee Jangwoen J University of California, Irvine, Beckman Laser Institute and Medical Clinic, 1002 Health Sciences Road East, Irvine, California 92612, USA. - - 2008
We demonstrate noninvasive near-infrared diffuse optical spectroscopy (DOS) measurements of tissue hemoglobin contents that can track progressive reductions in central blood volume in human volunteers. Measurements of mean arterial blood pressure (MAP), heart rate (HR), stroke volume (SV), and cardiac output (Q) are obtained in ten healthy human subjects during ...
Fan C W - - 2008
BACKGROUND: Sleeping with the head of bed tilted upwards (SHU) is recommended as a treatment of orthostatic hypotension though the supporting evidence is weak. AIM: To investigate the physiological effects of SHU amongst a group of young healthy volunteers. METHODS: Twenty-nine volunteers, mean age 22 years, underwent 1-week of SHU ...
Wong Brett J - - 2008
The "push-pull" effect denotes the reduced tolerance to +G(z) (hypergravity) when +G(z) stress is preceded by exposure to hypogravity, i.e., fractional, zero, or negative G(z). The purpose of this study was to test the hypothesis that an exaggerated, myogenically mediated rise in leg vascular conductance contributes to the push-pull effect, ...
Chi Lorne - - 2008
Orthostatic hypotension is a common condition for individuals with stroke or spinal cord injury. The inability to regulate the central nervous system will result in pooling of blood in the lower extremities leading to orthostatic intolerance. This study compared the use of functional electrical stimulation (FES) and passive leg movements ...
Vara-González Luis - - 2008
OBJECTIVE: To describe the postural changes in blood pressure and correlates among the general population of Cantabria, a region in the north of Spain. METHODS: Between 2002 and 2004 blood pressure measurements were taken in a seated position and after 1 and 3 min standing on a random sample of ...
Vogel Elizabeth R - - 2008
Blood pressure changes in response to the Valsalva maneuver (VM), which reflect the integrity of the baroreflex that regulates blood pressure. Performing this maneuver in the standard supine position often prevents adequate venous preload reduction, resulting in a rise rather than a fall in blood pressure, the "flat-top" Valsalva response. ...
Hoad A - - 2008
BACKGROUND: It has been suggested that postural orthostatic tachycardia syndrome (POTS) be considered in the differential diagnosis of those with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Currently, measurement of haemodynamic response to standing is not recommended in the UK NICE CFS/ME guidelines. OBJECTIVES: To determine prevalence of POTS in patients with ...
Stolz Erwin - - 2009
BACKGROUND: Although there exists a large body of knowledge on the regulation of arterial cerebral hemodynamics, little is known about the cerebral venous outflow (CVO). METHODS: In 19 healthy volunteers, the middle cerebral artery and the straight sinus were examined using transcranial Doppler sonography. Arterial and venous mean flow velocities ...
Ramirez-Marrero Farah A - - 2008
Orthostatic stress such as head-up tilt (HUT) elicits a wide range of heart rate (HR) and arterial pressure (AP) responses among healthy individuals. In this study, we evaluated cardiovascular dynamics in healthy subjects with different HR responses to HUT, but without autonomic dysfunction. We measured AP (brachial artery) and HR ...
Iacoviello Massimo - - 2008
AIMS: The aim of this study was to evaluate arterial baroreflex control of heart rate immediately before head-up tilt test (HUT)-induced vasovagal syncope (VVS). METHODS AND RESULTS: We enrolled 97 otherwise healthy subjects with recurrent unexplained syncope. After 10 min of rest in supine position, they underwent a passive HUT ...
Krabbendam Ineke - - 2008
Head-up tilt (HUT) induces a reduction in preload, which is thought to be restored through sympathetic venoconstriction, reducing unstressed volume (V(u)) and venous compliance (VeC). In this study, we assessed venous inflow and outflow responses and their reproducibility and determined the relation with autonomic function during HUT. Eight healthy non-pregnant ...
Krediet C T Paul - - 2008
OBJECTIVES: Squatting is a potent physical maneuver to prevent syncope; however, a major drawback is that standing up from squatting is a large hemodynamic stressor that often causes new presyncopal symptoms. We tested the hypothesis that lower body skeletal muscle tensing (LBMT) attenuates the decrease of mean arterial blood pressure ...
GOSWAMI N - - 2009
We tested whether seal location at iliac crest (IC) or upper abdomen (UA), before and during lower body negative pressure (LBNP), would affect thoracic electrical impedance, hepatic blood flow, and central cardiovascular responses to LBNP. After 30 min of supine rest, LBNP at -40 mm Hg was applied for 15 ...
Groothuis Jan T - - 2008
Leg vascular resistance is calculated as the arterial-venous pressure gradient divided by blood flow. During orthostatic challenges it is assumed that the hydrostatic pressure contributes equally to leg arterial, as well as to leg venous pressure. Because of venous valves, one may question whether, during orthostatic challenges, a continuous hydrostatic ...
Thijs Roland D - - 2008
The effects of hyperventilation (HV) on mean arterial pressure (MAP) are variable. To identify factors affecting the MAP response to HV, we dissected the effects of hypocapnic HV (HHV) and isocapnic HV (IHV) and evaluated the effects of acute vs. prolonged HHV. In 11 healthy subjects the cardio- and cerebrovascular ...
Meininger Dirk - - 2008
BACKGROUND: The present prospective study was designed to evaluate hemodynamic changes associated with head-down positioning and prolonged pneumoperitoneum during totally endoscopic robot-assisted radical prostatectomy. METHODS: Ten American Society of Anesthesiologists (ASA) physical status I-III patients undergoing totally endoscopic robot-assisted radical prostatectomy were enrolled in the study. Invasive hemodynamic parameters were ...
Krabbendam Ineke - - 2008
OBJECTIVE: Prepregnant low plasma volume (LPV) is associated with subsequent gestational hypertensive disease. It is unknown to what extent an LPV affects the venous reserve capacity (VRC). We tested the hypothesis that LPV reduces the VRC, as indicated by presyncope or altered cardiovascular changes in response to head-up tilt. STUDY ...
Yao Yong-Jie - - 2008
Thigh cuffs are used by cosmonauts to limit fluid shift during space flight, but the appropriate level of cuff pressure and the duration of application to optimize their beneficial effects require further detailed investigations. In the present study, 10 days head-down tilt (HDT) bed rest was performed to assess the ...
Rasmussen Keith G - - 2008
Falls are common in patients receiving electroconvulsive therapy (ECT) treatments. One cause of falls is orthostatic hypotension. In an effort to deduce whether modifiable anesthetic factors are associated with posttreatment hemodynamic changes, we assessed supine and standing blood pressure and pulse in 62 patients given 295 treatments approximately 2 hours ...
Taneja Indu - - 2008
Our prior studies indicated that postural fainting relates to splanchnic hypervolemia and thoracic hypovolemia during orthostasis. We hypothesized that thoracic hypovolemia causes excessive sympathetic activation, increased respiratory tidal volume, and fainting involving the pulmonary stretch reflex. We studied 18 patients 13-21 yr old, 11 who fainted within 10 min of ...
Kamiya Atsunori - - 2008
Maintenance of arterial pressure (AP) under orthostatic stress against gravitational fluid shift and pressure disturbance is of great importance. One of the mechanisms is that upright tilt resets steady-state baroreflex control to a higher sympathetic nerve activity (SNA). However, the dynamic feedback characteristics of the baroreflex system, a hallmark of ...
Sauder Charity L - - 2008
Otolith organs have been shown to activate the sympathetic nervous system in the prone position by head-down rotation (HDR) in humans. To date, otolithic stimulation by HDR has not been comprehensively studied in the upright posture. The purpose of the present study was to determine whether otolithic stimulation increases muscle ...
Gamboa Alfredo - - 2008
Approximately 50% of patients with autonomic failure (AF) suffer from supine hypertension, even those with very low plasma norepinephrine and renin. Because NO is arguably the most potent metabolic modulator of blood pressure, we hypothesized that impaired NO function contributes to supine hypertension in AF. However, we found that AF ...
Zhou Fang - - 2008
A novel method for low electroosmotic flow (EOF) rates measurement by tilting microchip which based upon the hydrostatic pressure conception and sampling zone method is described. Sampling zone could be detected in the tilting microchip but not in non-tilting one due to the hydrostatic pressure driven. The method is fulfilled ...
McManus John G - - 2008
OBJECTIVE: This study tested the hypothesis that pulmonary end-tidal CO(2) (PETCO(2)) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. METHODS: Measurements of PETCO(2), systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were ...
Jans Ø - - 2008
BACKGROUND: Based on maximisation of cardiac stroke volume (SV), peri-operative individualised goal-directed fluid therapy improves patient outcome. It remains, however, unknown how fluid therapy by this strategy relates to filling of the heart during supine rest as reference for the anaesthetised patient and whether the heart becomes distended. To answer ...
Verheyden Bart - - 2008
Tilt training is a useful therapeutic option in neurally mediated syncope (NMS). We tested the hypothesis that tilt training will restore orthostatic tolerance by increasing the degree of vasomotor reserve during sustained orthostatic stress. METHODS AND RESULTS In this follow-up study we enrolled 17 patients (age 31 +/- 22 years, ...
Robertson David - - 2008
Orthostatic Hypotension (OH) is a common manifestation of blood pressure dysregulation. OH takes a heavy toll on quality of life. It has many potential etiologies, and many effects of aging can increase susceptibility to OH. Neurological disorders are especially likely to cause severe OH. In this brief review, the pathogenesis ...
Low Phillip A - - 2008
Orthostatic hypotension (OH) is defined as a fall in blood pressure of at least 20 mmHg systolic or 10 mmHg diastolic when standing or during head-up tilt testing. The prevalence of OH increases with age, with disorders that affect autonomic nerve transmission, and with increasingly severe orthostatic stress. In normal ...
Kaufmann Horacio - - 2008
Neurogenic orthostatic hypotension results from failure to release norepinephrine, the neurotransmitter of sympathetic postganglionic neurons, appropriately upon standing. In double blind, cross over, placebo controlled trials, administration of droxidopa, a synthetic amino acid that is decarboxylated to norepinephrine by the enzyme L: -aromatic amino acid decarboxylase increases standing blood pressure, ...
Moldovanova Iryna - - 2008
Gender differences in human cardiovascular norepinephrine transporter function may be mediated through female sex hormones. We studied 16 healthy eumenorrheic women (25+/-1 years) during the early follicular phase (day 5+/-0) and midluteal phase (day 22+/-0) of the menstrual cycle. In a randomized, crossover, double-blind fashion, subjects ingested 8 mg of ...
Andersson M - - 2008
OBJECTIVES: To determine whether orthostatic hypotension (OH) is more common in patients with dementia than in older people without cognitive impairment and to identify key differences in the profile of the orthostatic response and the pulse drive during orthostatic challenge between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). ...
Galland Barbara C - - 2008
This study aimed to define cardiovascular and heart rate variability (HRV) changes following head-up tilt (HUT) in children/adolescents with chronic fatigue syndrome (CFS) in comparison to age- and gender-matched controls. Twenty-six children/adolescents with CFS (11-19 y) and controls underwent 70-degree HUT for a maximum of 30 min, but returned to ...
Gao Yunfang - - 2008
AIM: Recent results from animal experiments have shown that radix astragali (RA), a traditional Chinese herbal tonic, alleviates muscle atrophy under simulated weightlessness conditions, rendering RA a candidate for human use as a countermeasure against muscular atrophy. Possible cardiovascular side effects have not yet been investigated. We analyzed the effects ...
Chan Gregory S H - - 2008
BACKGROUND: Change in cardiac preload caused by mild hypovolemia can alter left ventricular ejection time (LVET) without noticeable change in blood pressure (BP). Previously our group has explored a novel method of LVET monitoring using a noninvasive finger photoplethysmographic pulse oximetry wave form. The current study investigated the ability of ...
Carapetian Stephanie - - 2008
The increase in orthostatic systolic blood pressure associated with the shift in posture from lying to standing requires several compensatory mechanisms to ensure adequate cerebral perfusion. Decreased efficiency in the various mechanisms controlling orthostatic blood pressure regulation can result in dizziness, lightheadedness, and syncope. The degree of effectiveness of orthostatic ...
Raffai G - - 2009
Microgravity or simulated microgravity induces acute and chronic cardiovascular responses, whose mechanism is pivotal for understanding of physiological adaptation and pathophysiological consequences. We investigated hemodynamic responses of conscious Wistar rats to 45? head-down tilt (HDT) for 7 days. Arterial blood pressure (BP) was recorded by telemetry. Heart rate (HR), spectral ...
Strempel Sebastian - - 2008
Sympathetically mediated tachycardia and vasoconstriction maintain blood pressure during hypergravitational stress, thereby preventing gravitation-induced loss of consciousness. Norepinephrine transporter (NET) inhibition prevents neurally mediated (pre)syncope during gravitational stress imposed by head-up tilt testing. Thus it seems reasonable that NET inhibition could increase tolerance to hypergravitational stress. We performed a double-blind, ...
Medow Marvin S - - 2008
Orthostatic hypotension (OH) occurs in 0.5% of individuals and as many as 7-17% of patients in acute care settings. Moreover, OH may be more prevalent in the elderly due to the increased use of vasoactive medications and the concomitant decrease in physiologic function, such as baroreceptor sensitivity. OH may result ...
Aoki Mitsuhiro - - 2008
OBJECTIVES: A number of animal studies have confirmed that the otolith organs may contribute to the maintenance of blood pressure during positional change; however, the contribution of such organs remains to be elucidated in humans. METHODS: This study investigated whether acute dizzy patients (n = 11) with an abnormal deviation ...
Soller Babs R - - 2008
OBJECTIVE: To compare the responses of noninvasively measured tissue oxygen saturation (StO2) and calculated muscle oxygen tension (PmO2) to standard hemodynamic variables for early detection of imminent hemodynamic instability during progressive central hypovolemia in humans. DESIGN: Prospective study. SETTING: Research laboratory. SUBJECTS: Sixteen healthy human volunteers. INTERVENTIONS: Progressive lower body ...
Suzuki Koji - - 2008
OBJECTIVE: Near infrared spectroscopy (NIRS) is a non-invasive optical technique to monitor cerebral tissue oxygen saturation (ScO(2)). The purpose of this study was to reveal the usefulness of ScO(2) monitoring in evaluating cerebral circulation in patients with autonomic failure. METHODS: Nineteen patients with multiple system atrophy (MSA), who had autonomic ...
Yoshida Masayoshi - - 2008
Central baroreflex failure in patients with spinal cord injury results in serious orthostatic hypotension. We examined if transcutaneous electrical stimulation regulates arterial pressure in those patients. We identified skin regions capable of increasing arterial pressure and determined respective transfer function. Using the transfer function, we designed the feedback regulator (i.e., ...
Ding Dan - - 2008
This study examined the usage of powered seating functions, including tilt-in-space, backrest recline, and seat elevation, among a group of wheelchair users during their typical daily activities. Twelve individuals who used a power wheelchair with seating functions participated in the study. They drove their own wheelchair and used the seating ...
Wyller Vegard Bruun - - 2008
The chronic fatigue syndrome (CFS) has been shown to be associated with orthostatic intolerance and cardiovascular dysregulation. We investigated the cardiovascular responses to combined orthostatic stress and isometric exercise in adolescents with CFS. We included a consecutive sample of 15 adolescents 12-18 years old with CFS diagnosed according to a ...
Ejaz A Ahsan - - 2007
The presence of orthostatic hypotension has been shown to be a significant, independent predictor of all-cause mortality. Systolic and diastolic orthostatic hypotension, reversal of the circadian pattern, and postprandial hypotension are some of the hemodynamic factors that may contribute to the increased mortality seen in patients with orthostatic hypotension. The ...
Thijs Roland D - - 2007
We evaluated the use of strain gauge plethysmography (SGP) for the assessment of orthostatic fluid shifts during head up tilt (HUT). Subjects wore a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs during HUT. 22 Healthy subjects (9 women) were tilted for 5 ...
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