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Results 401 - 450 of 1560
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Richalet Jean-Paul - - 2008
A 24-year-old adult with a Down syndrome was admitted in December 2006 at the Moutiers hospital in the French Alps for an acute inaugural episode of high altitude pulmonary edema (HAPE) that occurred in the early morning of day 3 after his arrival to La Plagne (2000 m). This patient ...
Wilson Mark H - - 2008
Gross pupil dynamics are used as an indirect measure of brain function. Changes in hypoxia and intracranial pressure are thought to alter pupil responses to light. This study assessed a portable handheld pupil measuring device (pupillometer) in the field investigating the changes in pupil size, speed of reaction, and rate ...
Sangkatumvong Suvimol S Biomedical Engineering Department, University of Southern California, Los Angeles, CA 90089, USA. - - 2008
Abnormalities in autonomic control in sickle cell anemia (SCA) patients have been reported by multiple researchers. However their potential causal association with sickle cell crisis remains unknown. We employed hypoxia, a known trigger to sickle cell crisis, to perturb the autonomic systems of the subjects. Cardiac autonomic control was non-invasively ...
Petersen Bodil - - 2008
Endogenous endothelin (ET)-1 modulates hypoxic pulmonary vasoconstriction (HPV). Accordingly, intravenously applied ET(A) receptor antagonists reduce HPV, but this is accompanied by systemic vasodilation. We hypothesized that inhalation of an ET(A) receptor antagonist might act selectively on the pulmonary vasculature and investigated the effects of aerosolized LU-135252 in an experimental model ...
Steinback Craig D - - 2008
We examined the cardiovascular and cerebrovascular responses to acute isocapnic (IH) and poikilocapnic hypoxia (PH) in 10 men (25.7 +/- 4.2 yr, mean +/- SD). Heart rate (HR), mean arterial pressure (MAP), and mean peak middle cerebral artery blood flow velocity (Vp) were measured continuously during two randomized protocols of ...
Cheung Po-Yin - - 2008
OBJECTIVES: The increase in oxidative stress following neonatal hypoxia-reoxygenation can be related to subsequent cardiovascular deficits. We compared the acute systemic, pulmonary and regional hemodynamic recovery in hypoxic newborn pigs reoxygenated by low (18%) or high (100%) concentration of oxygen with that by 21% oxygen. STUDY DESIGN: Pigs (1-3 days, ...
Querido Jordan S - - 2008
The purpose of this study was to determine the changes in human cerebrovascular function associated with intermittent poikilocapnic hypoxia (IH). Healthy men (n=8; 24+/-1 years) were exposed to IH for 10 days (12% O(2) for 5min followed by 5min of normoxia for 1h). During the hypoxic exposures, oxyhemoglobin saturation (SaO(2)) ...
Burtscher Martin - - 2008
When hypoxia increases during ascending in the mountains, ventilatory control and the related oxygenation may be challenged. The pre-treatment by intermittent hypoxia will elevate ventilation and offset hypoxemia and acetazolamide may inhibit peripheral chemosensitivity and act through central mechanisms. To study these effects in the field, one well-trained male mountaineer ...
Holt Timothy N - - 2007
High mountain or brisket disease is an economically costly disease of cattle raised at elevations greater than 1500 m (5000 ft). It appears that no one breed is resistant to the effects of high-altitude hypoxia. Some breeds, and pedigrees within breeds, appear to be more naturally resistant to the effects ...
Siekierka M - - 2007
Daily changes in reflex ventilatory responses to hypoxia were studied in 56 young healthy men participated. A rebreathing technique--progressive isocapnic hypoxia--was used to measure hypoxic chemoreflex reactivity. The measurements were repeated every 3 hours during a 24-hour period. The ventilatory response to hypoxia--analyzed as the relationships (slope) MV/SaO2 (minute ventilation/arterial ...
Dematteis Maurice - - 2008
RATIONALE: Intermittent hypoxia, a hallmark of sleep apnea, is a major factor for hypertension and impaired vasoreactivity. OBJECTIVES: To examine the temporal occurrence of these two outcomes in order to provide insight into mechanisms and early cardiovascular disease identification. METHODS: Functional and structural cardiovascular alterations were assessed in C57BL6 mice ...
Liu Chun - - 2008
This study sought: (1) to clarify the effects of hydralazine on both the pulmonary vasculature and respiratory control in euoxia and hypoxia in healthy humans; and (2) to determine whether hydralazine alters the expression of genes regulated by hypoxia-inducible factor 1 (HIF-1). Ten volunteers participated in two 2 day protocols. ...
Wan Chidang - - 2007
In order to explore the method to prepare hypoxia UW solution and the stability and preservation of hypoxia UW solution, UW solution was purged by argon or air for 15 min or 60 at a flow rate of 0.8 or 2 L/min, and the oxygen partial pressure of UW solution ...
He Chuanjiu - - 2007
The objectives of this research were to determine the influence of hypobaria (reduced atmospheric pressure) and reduced partial pressure of oxygen (pO2) [hypoxia] on carbon dioxide (CO2) assimilation (C(A)), dark-period respiration (DPR) and growth of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce plants were grown under variable total gas pressures ...
Spöhr Fabian - - 2007
BACKGROUND: Hypoxic pulmonary vasoconstriction (HPV) is impaired during inflammatory lung processes such as pneumonia or the acute respiratory distress syndrome. Voltage-gated potassium channels play a central role in mediating HPV. The aim of this study was to determine whether 4-aminopyridine (4-AP), a known voltage-gated potassium channel inhibitor, may restore HPV ...
Cheung Po-Yin - - 2007
Shock and poor regional perfusion are common in asphyxiated neonates. We compared the systemic and regional hemodynamic effects of high-dose epinephrine (E) with those of dopamine combined with low-dose epinephrine (DE) infusions in a neonatal model of hypoxia-reoxygenation. Neonatal piglets (1-3 days, 1.5-2.5 kg) were acutely instrumented to continuously monitor ...
Tamisier Renaud - - 2007
Hemodynamics, muscle sympathetic nerve activity (MSNA), and forearm blood flow were evaluated in 12 normal subjects before, during (1 and 7 h), and after ventilatory acclimatization to hypoxia achieved with 8 h of continuous poikilocapnic hypoxia. All results are means +/- SD. Subjects experienced mean oxygen saturation of 84.3 +/- ...
Al-Salam Zakariya - - 2007
Asphyxiated neonates usually have myocardial stunning and hypotension and require inotropic support. A randomized controlled study was designed to examine the dose-response effect of dobutamine (5-20 microg x kg(-1) x min(-1)) on systemic and regional circulations and oxygen metabolism in a neonatal swine model of hypoxia/reoxygenation. Thirty-eight anesthetized newborn piglets ...
Reichenberger Frank - - 2007
Hypoxia leads to pulmonary vasoconstriction in healthy men. However, the consequences on right ventricular function are not known. The effects of hypoxia on systolic pulmonary artery pressure (sPAP) and right ventricular function index (TEI) were assessed by Doppler echocardiography. Fourteen members of a Mount Everest expedition were monitored during acute ...
Wibbens Bert - - 2007
There is limited information about whether preexisting fetal hypoxia alters hemodynamic responses and changes in T/QRS ratio and ST waveform shape during subsequent severe asphyxia. Chronically instrumented near-term sheep fetuses (124 +/- 1 days) were identified as either normoxic Pa(O(2)) > 17 mmHg (n = 9) or hypoxic Pa(O(2)) < ...
Mittal Manish - - 2007
Nonphagocytic NADPH oxidases have recently been suggested to play a major role in the regulation of physiological and pathophysiological processes, in particular, hypertrophy, remodeling, and angiogenesis in the systemic circulation. Moreover, NADPH oxidases have been suggested to serve as oxygen sensors in the lung. Chronic hypoxia induces vascular remodeling with ...
Lamm Wayne J E - - 2007
Studies in whole animals, isolated lungs and pulmonary tissue strips have shown that the pulmonary vascular resistance (PVR) to hypoxia is temporally biphasic in nature. We studied the regional temporal response to hypoxia in prone pigs. The animals were ventilated with an FIO2 of 0.21 (control), followed by an FIO2 ...
Leuenberger Urs A UA Division of Cardiology, MC H047, Heart & Vascular Institute, The Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, P.O. Box 850, Hershey, PA 17033, USA. - - 2007
Short-term intermittent hypoxia leads to sustained sympathetic activation and a small increase in blood pressure in healthy humans. Because obstructive sleep apnea, a condition associated with intermittent hypoxia, is accompanied by elevated sympathetic activity and enhanced sympathetic chemoreflex responses to acute hypoxia, we sought to determine whether intermittent hypoxia also ...
Choi K - - 2007
Inadequate dissolved oxygen in the aquatic environment is a well-established cause of fish morbidity and mortality. The specific effects of hypoxia on immune function in fish, however, are not well characterized. In this study, the effects of acute hypoxia followed by reoxygenation (rapid tissue reperfusion) as a source of immunocompromise ...
Osinaike B B - - 2007
To determine the changes in oxygen saturation, blood pressure and heart rate during various endoscopic procedures and to find out the risk factors for these changes. Forty patients without cardiorespiratory disorders were recruited. Oxygen saturation, blood pressure and pulse rate were monitored during endoscopy using pulse oximeter and automated blood ...
Hainsworth Roger - - 2007
The effects of hypobaric hypoxia in visitors depend not only on the actual elevation but also on the rate of ascent. There are increases in sympathetic activity resulting in increases in systemic vascular resistance, blood pressure and heart rate. Pulmonary vasoconstriction leads to pulmonary hypertension, particularly during exercise. The sympathetic ...
Simmons Grant H - - 2007
Hypoxia and hypercapnia represent special challenges to homeostasis because of their effects on sympathetic outflow and vascular smooth muscle. In the cutaneous vasculature, even small changes in perfusion can shift considerable blood volume to the periphery and thereby impact both blood pressure regulation and thermoregulation. However, little is known about ...
Farrell A P - - 2007
The sensing and processing of hypoxic signals, the responses to these signals and the modulation of these responses by other physical and physiological factors are an immense topic filled with numerous novel and exciting discoveries. Nestled among these discoveries, and in contrast to mammals, is the unusual cardiac response of ...
Julian R J - - 2007
The pulmonary arterioles react to hypoxia by contraction and to increased pressure and volume by hypertrophy of the muscular wall, referred to as pulmonary vascular remodeling, both of which increase vascular resistance and result in increased pulmonary arterial pressure. Heart muscle reacts to increased pressure by hypertrophy of cardiac myocytes ...
Kilgore Delbert L DL - - 2008
We measured ventilation, oxygen consumption and blood gases in burrowing owls (Athene cunicularia) breathing moderate and extreme hypoxic gas mixtures to determine their hypoxic ventilatory threshold (HVT) and to assess if they, like other birds and mammals, exhibit a relationship between HVT and hemoglobin O2 affinity (P(50)) of their blood. ...
Hlavac Michael C - - 2007
Inspiratory load compensation is impaired in patients with obstructive sleep apnea (OSA), a condition characterized by hypoxia during sleep. We sought to compare the effects of sustained hypoxia on ventilation during inspiratory resistive loading in OSA patients and matched controls. Ten OSA patients and 10 controls received 30 min of ...
Yang Bo - - 2007
OBJECTIVE: To investigate the anti-hypoxia and anti-oxidation effects of aminophylline on human with acute high-altitude exposure. METHODS: Totally 100 young male army members newly recruited from Sichuan province (400 meters above sea level) were enrolled. They were randomly divided into two groups: 50 in aminophylline group (A group) and 50 ...
Hainsworth Roger - - 2007
The effects of hypobaric hypoxia in visitors depend not only on the actual elevation but also on the rate of ascent. Sympathetic activity increases and there are increases in blood pressure and heart rate. Pulmonary vasoconstriction leads to pulmonary hypertension, particularly during exercise. The sympathetic excitation results from hypoxia, partly ...
Powell Frank L FL Department of Medicine and White Mountain Research Station, University of California, San Diego, La Jolla, CA 92093-0623, USA. - - 2007
Carotid body chemoreceptors are essential for time-dependent changes in ventilatory control during chronic hypoxia. Early theories of ventilatory acclimatization to hypoxia focused on time-dependent changes in known ventilatory stimuli, such as small changes in arterial pH that may play a significant role in some species. However, plasticity in the cellular ...
Ainslie Philip N - - 2007
We tested the hypothesis that intermittent hypoxia (IH) and/or continuous hypoxia (CH) would enhance the ventilatory response to acute hypoxia (HVR), thereby altering blood pressure (BP) and cerebral perfusion. Seven healthy volunteers were randomly selected to complete 10-12 days of IH (5-min hypoxia to 5-min normoxia repeated for 90 min) ...
Fu Qi - - 2007
Intermittent hypoxia (IH), which refers to the discontinuous use of hypoxia to reproduce some key features of altitude acclimatization, is commonly used in athletes to improve their performance. However, variations of IH are also used as a model for sleep apnea, causing sustained sympathoexcitation and hypertension in animals and, thus, ...
Wagner Peter D - - 2007
The amount of O(2) available to tissues is essentially the product of cardiac output, [Hb], and O(2) saturation. Saturation depends on P(O2) and the O(2)Hb dissociation curve. With altitude, increased [2,3-DPG] shifts the dissociation curve rightward, but hypocapnia and alkalosis move it leftward. We determined both standard and in vivo ...
Morgan Barbara J - - 2007
In patients with obstructive sleep apnea (OSA), nocturnal exposure to intermittent hypoxia causes elevations in arterial pressure that persist throughout the day. Animal models have shown that this hypertensive effect requires an intact sympathetic nervous system and an intact carotid chemoreceptor reflex. The renin-angiotensin system contributes importantly to hypertension in ...
Dubowitz Gerald - - 2007
OBJECTIVE: Acute hypoxia causes vasoconstriction in the pulmonary arteries. This hypoxic pulmonary vasoconstriction (HPV) has been reported to be common in subjects exposed to high altitude. In the past, it has been difficult to directly measure this HPV because of the invasive nature of tests, but the recent availability of ...
Brito Julio - - 2007
The aim of this cross-sectional study was to assess the health status of subjects weekly commuting between sea level and 3550-m altitude for at least 12 yr (average 22.1 +/- 5.8). We studied 50 healthy army men (aged 48.7 +/- 2.0) working 4 days in Putre at 3550-m altitude, with ...
Ciulla Michele M - - 2007
Circulating Endothelial Precursors (PB-EPCs) are involved in the maintenance of the endothelial compartment being promptly mobilized after injuries of the vascular endothelium, but the effects of a brief normobaric hypoxia on PB-EPCs in healthy subjects are scarcely studied. Clinical and molecular parameters were investigated in healthy subjects (n = 8) ...
Mayock Dennis E - - 2007
Dopamine is used clinically to stabilize mean arterial blood pressure (MAP) in sick infants. One goal of this therapeutic intervention is to maintain adequate cerebral blood flow (CBF) and perfusion pressure. High-dose intravenous dopamine has been previously demonstrated to increase cerebrovascular resistance (CVR) in near-term fetal sheep. We hypothesized that ...
Saiki Chikako - - 2007
This study was designed to examine how systemic administration of an N-methyl-d-aspartate (NMDA) receptor antagonist, MK-801, altered respiratory timing in unanesthetized rats under normoxia and hypoxia. To detect fine changes in inspiratory time (TI) and expiratory time (TE), and cycle duration (TTOT), we prepared a diaphragmatic electromyogram (EMGdia). Diaphragm electrodes ...
Teppema Luc J - - 2007
RATIONALE: Acute mountain sickness (AMS) may affect individuals who (rapidly) ascend to altitudes higher than 2,000-3,000 m. A more serious consequence of rapid ascent may be high-altitude pulmonary edema, a hydrostatic edema associated with increased pulmonary capillary pressures. Acetazolamide is effective against AMS, possibly by increasing ventilation and cerebral blood ...
Zaar Morten - - 2007
The heart of Python regius is functionally divided so that systemic blood pressure is much higher than pulmonary pressure (6.6+/-1.0 and 0.7+/-0.1 kPa, respectively). The present study shows that force production of cardiac strips from the cavum arteriosum and cavum pulmonale exhibits similar force production when stimulated in vitro. The ...
Plaza Vicente - - 2006
Several studies have demonstrated impaired control of ventilation in some patients with near-fatal asthma (NFA). The objective of our study was to determine a possible relationship between alexithymia (a cognitive processing disorder), control of ventilation, and breathlessness perception in patients who had an NFA attack. We analyzed data from 100 ...
Gat Yigal - - 2006
Varicocele is considered a predominantly unilateral left-sided disease. However, since male fertility is preserved with only one healthy testis, infertility perforce represents bilateral testicular dysfunction. It was hypothesized that: (i) right varicocele cannot be diagnosed by palpation and therefore has not been treated in the past by the traditional treatment, ...
Modesti Pietro Amedeo - - 2006
The degree of pulmonary hypertension in healthy subjects exposed to acute hypobaric hypoxia at high altitude was found to be related to increased plasma endothelin (ET)-1. The aim of the present study was to investigate the effects of ET-1 antagonism on pulmonary hypertension, renal water, and sodium balance under acute ...
Fox W Christopher - - 2006
BACKGROUND: We postulated that acute hypoxemia increases susceptibility to orthostatic hypotension by increasing the sensitivity of cardiovascular baroreceptors. METHODS: Hemodynamics were measured noninvasively in 17 healthy, normotensive subjects while being subjected to decreasing venous return by exposure to lower body negative pressure (LBNP) and breathing either a normobaric normoxic (21% ...
Thomson Alastair J - - 2006
Both hypoxia and hyperoxia have major effects on cardiovascular function. However, both states affect ventilation and many previous studies have not controlled CO(2) tension. We investigated whether hemodynamic effects previously attributed to modified O(2) tension were still apparent under isocapnic conditions. In eight healthy men, we studied blood pressure (BP), ...
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