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Results 701 - 750 of 1553
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Kanstrup I L - - 1999
This study measured the pressor and plasma catecholamine response to local hypothermia during adaptation to hypobaric hypoxia. Eight healthy men were studied at rest and after 10 and 45 min of local cooling of one hand and forearm as well as after 30 min of rewarming at sea level and ...
Sharma G D - - 1999
OBJECTIVES: To study the effects of fiberoptic bronchoscopy (FOB) at an altitude of 2250 m on arterial blood gases (ABG) and cardiac rhythm abnormality. METHODS: Fifty consecutive patients undergoing fiberoptic bronchoscopy were evaluated for the arterial blood gases and cardiac rhythm changes at Shimla (a moderate altitude of 2250 m), ...
Herman JK - - 1999
The ventilatory responses of chelonian reptiles to hypoxic and hypercapnic stress have been fairly well described. As turtles are capable of large cardiac shunts, changes in pulmonary perfusion may be an equally viable and potent response to these stressors. To test this hypothesis, conscious unrestrained turtles were unidirectionally ventilated while ...
Crapo R O - - 1999
Blood gas measurements were collected on healthy lifetime nonsmokers at sea level (n = 96) and at an altitude of 1,400 meters (n = 243) to establish reference equations. At each study site, arterial blood samples were analyzed in duplicate on two separate blood gas analyzers and CO-oximeters. Arterial blood ...
Pearl J M - - 1999
Acute hypoxia results in increased pulmonary vascular resistance. Despite reoxygenation, pulmonary vascular resistance remains elevated and pulmonary function is altered. Endothelin-1 might contribute to hypoxia-reoxygenation-induced pulmonary hypertension and to reoxygenation injury by stimulating leukocytes. This study was carried out using an established model of hypoxia and reoxygenation to determine whether ...
Asemu G - - 1999
The aim was to determine whether adaptation to chronic hypoxia protects the heart against ischemic arrhythmias and whether ATP-dependent potassium channels (K(ATP)) play a role in the antiarrhythmic mechanism. Adult male rats were adapted to intermittent high altitude hypoxia (5000 m, 4 h/day) and susceptibility to ischemia-induced ventricular arrhythmias was ...
Wolfram G - - 1999
A model to investigate the functional capacity (psychomental performance) under stressful conditions was developed. Twenty eight patients with mild hypertension receiving Nitrendipine (20 mg) for 30 days were tested under hypoxic (16% oxygen) and/or orthostatic (-30 mmHg lower body negative pressure) conditions using a subset of the AGARD battery. The ...
Remsburg S - - 1999
Patients with obstructive sleep apnea (OSA) have been reported to have an augmented pressor response to hypoxic rebreathing. To assess the contribution of the peripheral vasculature to this hemodynamic response, we measured heart rate, mean arterial pressure (MAP), and forearm blood flow by venous occlusion plethysmography in 13 patients with ...
Arabi Y - - 1999
The purpose of this study was to investigate whether nocturnal hypoxia causes daytime blood pressure (BP) elevation. We hypothesized that overnight exposure to hypoxia leads the next morning to elevation in BP that outlasts the hypoxia stimulus. We studied the effect on BP of two consecutive night exposures to hypobaric ...
Ostadal B - - 1999
Hypoxic states of the cardiovascular system are undoubtedly associated with the most frequent diseases of modern times. They originate as a result of disproportion between the amount of oxygen supplied to the cardiac cell and the amount actually required by the cell. The degree of hypoxic injury depends not only ...
Matsuoka T - - 1999
We asked whether repeated hypoxic exposures during the early neonatal periods could affect the ventilatory control, such as the lung volume-dependent ventilatory inhibition (HBR), pulmonary ventilation (VE), and CO2 production (VCO2). Within each litter of rats, one group of pups (experimental group H) was exposed to 6% O2 (30-min duration ...
Krebs M O - - 1999
Acute hypoxic pulmonary vasoconstriction (HPV) may be mediated by vasoactive peptides. We studied eight conscious, chronically tracheostomized dogs kept on a standardized dietary sodium intake. Normoxia (40 min) was followed by hypoxia (40 min, breathing 10% oxygen, arterial oxygen pressures 36 +/- 1 Torr) during both control (Con) and losartan ...
Gillessen S - - 1999
The effect of perfusion with elevated glucose concentrations on hypoxic myocardium was investigated in isolated Langendorff guinea pig hearts. For that purpose, mechanical (heart rate, systolic peak pressure and coronary flow) and electrophysiological (monophasic action potential duration=MAP, ectopic beats) data were evaluated. At the end of the experiments the hearts ...
Brimioulle S - - 1999
OBJECTIVE: Flow-pressure curves and vascular impedance are commonly used to investigate pulmonary circulation, but they may be affected at low flow by reflex neurohumoral activation. We therefore investigated the mechanical effects and the reflex effects of decreased flow on pulmonary vascular resistance and impedance. METHODS: In ten anaesthetized dogs, we ...
Yu B H - - 1999
An increased sympathetic nervous response to hypoxia and reduced beta-adrenergic receptor function have been reported in hypertension. This study examines the relationship between hypoxia and beta-adrenergic receptor function in sixteen normotensive and eight hypertensive subjects. We measured the average arterial oxygen saturation and the end tidal carbon dioxide partial pressure ...
Narkiewicz K - - 1999
BACKGROUND: The chemoreflexes are an important mechanism for regulation of both breathing and autonomic cardiovascular function. Abnormalities in chemoreflex mechanisms may be implicated in increased cardiovascular stress in patients with obstructive sleep apnea (OSA). We tested the hypothesis that chemoreflex function is altered in patients with OSA. METHODS AND RESULTS: ...
Thürich T - - 1999
Excessive right heart hypertrophy was investigated under additional acute hypoxic stress to find out a possible contribution of mitochondrial dysfunction to sudden heart failure. Severe right heart hypertrophy in rats was induced by exposure to hypobaric pressure (46,663 Pa) for 4 weeks. Heart rate, isovolumic pressure and coronary flow were ...
Guery B P - - 1999
OBJECTIVE: Multiwavelength near infrared (NIR) spectrophotometry can monitor the redox state of cytochrome a,a3 (cyt a,a3) in vivo. Because cyt a,a3 is the most immediate reductant of oxygen, this technique has been proposed to evaluate tissue oxygenation. The purpose of this study was to examine the relationship between cyt a,a3 ...
West J B - - 1999
Barometric pressures (PB) near the summit of Mt. Everest (altitude 8, 848 m) are of great physiological interest because the partial pressure of oxygen is very near the limit for human survival. Until recently, the only direct measurement on the summit was 253 Torr, which was obtained in October 1981, ...
Penn D - - 1999
Sepsis and hypoxia are important stressors for the neonate. Newborn infants receiving total parenteral nutrition are routinely deprived of carnitine and develop low carnitine plasma and tissue levels. Because of its high metabolic rate and dependence on fatty acids for energy, the newborn heart may be particularly vulnerable to stress ...
Ren X - - 1999
1. Acute exposure to hypoxia stimulates ventilation and induces hypocapnia. Long-term exposure to hypoxia generates changes in respiratory control known as ventilatory acclimatization to hypoxia. The object of this study was to investigate the degree to which the hyperventilation and hypocapnia can induce the changes known as ventilatory acclimatization to ...
Yang T D - - 1999
Cabin emergent depressurization (CED) may occur in spacecraft during manned space flight. The purpose of this paper was to study the combined effects of simulated weightlessness (SW) and CED factors on humans and animals. It was found that the amplitude of T wave of human electrocardiograms (ECG) significantly decreased in ...
Sahin G - - 1999
The branch of the cranial superior thyroid artery that supplies the larynx was perfused unilaterally at a constant flow rate in dogs anesthetized with pentobarbitone sodium (30 mg.kg-1, i.v.). Laryngeal vascular resistance (RLv) was calculated. Intraluminal laryngeal pressure (PL) was determined. Asphyxia caused a diminution in PL (-27.7 +/- 4.2%) ...
West J B - - 1999
There have been recent advances in the physiology of extreme altitude, especially on the barometric pressure-altitude relationship, and pulmonary gas exchange. Until recently, the only direct measurement of barometric pressure on the summit of Mt. Everest was the value of 253 Torr obtained in October 1981. During the 1997 NOVA ...
Perry SF - - 1999
Adult freshwater rainbow trout (Oncorhynchus mykiss) were exposed acutely (approximately 20 min) in a stepwise manner to increasing levels of environmental carbon dioxide ranging between 1.7 and 9.0 mmHg (0.23-1.2 kPa). Experiments were performed to examine, for the first time, the influence of hypercapnic acidosis on aspects of cardiovascular physiology ...
Kaloyianni M - - 1999
The effect of normoxia, hypoxia and hypercapnia on the extracellular pH, partial pressure carbon dioxide (pCO2), partial pressure oxygen (pO2) and HCO3- levels after noradrenaline treatment of Rana balcanica erythrocytes, was investigated. Noradrenaline caused a significant reduction of the extracellular pH which may have been due to the activation of ...
Alexander J K - - 1999
To evaluate the effects of aging on cardiac rhythm at high altitude, I wore a Holter monitor at age 75 during a climb to 5,100 m on Mt. Kilimanjaro, then compared findings with those from my climb to 5,895 m at age 65. Holter leads were placed to identify left ...
Richalet J P - - 1999
Exposure to high altitude induces physiological or pathological modifications that are not always clearly attributable to a specific environmental factor: hypoxia, cold, stress, inadequate food. The principal goal of hypobaric chamber studies is to determine the specific effect of hypoxia. Eight male volunteers ("altinauts"), aged 23 to 37 were selected. ...
Sakai H - - 1999
We measured the change in total lung resistance (RL) and that in total lung elastance (EL) induced by hypoxia (n = 7) and compared the results with those by intravenous histamine bolus (n = 5) at three different positive end-expiratory pressure (PEEP) levels (2, 5, and 8 hPa) in open-chest ...
Venteicher A - - 1998
Because pial artery dilation during a 20- or 40-min hypoxic exposure was less than that observed during a 5- or 10-min exposure, stimulus duration determines the vascular response to hypoxia. Dynorphin (Dyn) modulates hypoxic pial dilation and contributes to decremented dilation during longer hypoxic exposures. This study was designed to ...
Sand T - - 1998
OBJECTIVES: To investigate if the EEG response at moderate altitude may predict a person's tolerance to acute mountain sickness (AMS). MATERIALS AND METHODS: Frequency analysis (QEEG) of tape-recorded ambulatory EEG was performed in 6 climbers during a mountaineering expedition to 7546 m above sea level. The QEEG response in climbers, ...
Tansley J G - - 1998
Ventilatory acclimatization to hypoxia is associated with an increase in ventilation under conditions of acute hyperoxia (VEhyperoxia) and an increase in acute hypoxic ventilatory response (AHVR). This study compares 48-h exposures to isocapnic hypoxia (protocol I) with 48-h exposures to poikilocapnic hypoxia (protocol P) in 10 subjects to assess the ...
Lai Y L - - 1998
Because chronic hypoxia increases the production of oxygen radicals, we hypothesized that antioxidants attenuate chronic hypoxic pulmonary hypertension. In part 1, we examined the temporal progress in chronic hypoxic pulmonary hypertension in 46 Wistar rats exposed to hypoxia from 0-3 weeks. In part 2, we tested whether antioxidants attenuated chronic ...
Xi S - - 1998
OBJECTIVE: To observe the inhibitory effects of Radix Astragali (RA) on hypoxic structural remodeling of intraacinar pulmonary arteries (IAPA) and pulmonary hypertension (PHT). METHODS: Sixty rats were divided into three groups: hypoxia group, hypoxia + RA group and normal control group. The rats of hypoxia group and hypoxia + RA ...
García-Río F - - 1998
STUDY OBJECTIVE: We analyze the within-subject variation of mouth occlusion pressure (P0.1) response to progressive isocapnic hypoxic stimulation over long time periods in normal subjects. PATIENTS AND INTERVENTIONS: We studied 21 healthy subjects (14 male and 7 female; aged 40+/-12 yrs) (mean+/-SD). Lung volumes, basal P0.1, and P0.1 response to ...
Pino-García J M - - 1998
We sought to examine the breathing pattern, inspiratory drive and chemosensitivity of hyperthyroid patients and to explore the interactions between their thyroid hormones, basal metabolism and chemosensitivity. We studied 15 hyperthyroid patients and 15 sex- and age-matched controls. Thyroid hormone levels, arterial blood gas tensions, lung volumes, diffusing capacity for ...
Albertini M - - 1998
This study investigated the mechanisms that may contribute to the hypoxic pulmonary vasoconstriction and compared the effects of hypoxia on pulmonary and systemic vascular beds. Six anesthetized spontaneously breathing pigs inhaled a hypoxic mixture (10% O2 in air) in control conditions and after pre-treatment with Indomethacin (3 mg kg(-1) i.v.) ...
van de Borne P - - 1998
BACKGROUND: Low-dose dopamine is frequently used in patients in the intensive care setting. Dopamine may inhibit chemoreceptor afferents and hence decrease chemoreflex sensitivity to hypoxia. METHODS AND RESULTS: In a double-blind, randomized, crossover study, we determined the effects of dopamine (5 microg x kg(-1) x min(-1)) and placebo infusion on ...
Ni Z - - 1998
BACKGROUND: We have recently demonstrated that prolonged hypobaric hypoxia can lead to a hematocrit-independent sustained arterial hypertension (HTN) in genetically normotensive Sprague-Dawley rats. The rise in blood pressure in the hypoxic animals was accompanied by a marked but transient increase in plasma endothelin level. In addition, hypoxia has been shown ...
Derrick J L - - 1998
OBJECTIVE: To define the longest sampling interval which will faithfully record the time course of episodes of severe hypotension and hypoxia in anesthetised patients. METHODS: Electronic anesthetic records of 1501 patients were analyzed retrospectively for hypotension where measured systolic blood pressure fell to 60 mmHg or less, and for hypoxia ...
Zanzinger J - - 1998
The role of nitric oxide (NO) in the regulation of sympathetic activity during hypoxia was studied in anesthetized pigs (n = 21). Hypoxia (fractional concentration of O2 in inspired air = 0.1) increased pulmonary arterial pressure and decreased arterial blood pressure and peripheral vascular resistance. Renal sympathetic nerve activity (RSNA) ...
Huang C C - - 1998
Perinatal asphyxia is an important cause of neonatal mortality and subsequent sequelae. Striatum, richly innervated by nigrostriatal dopaminergic projections, is susceptible to perinatal insults. Measuring the cerebral cortical oxygen pressure and striatal extracellular dopamine in the striatum in piglets under different kinds and degrees of hypoxia/ischemia insult, the changes of ...
Mulder A L - - 1998
1. The fetus develops cardiovascular adaptations to protect vital organs in situations such as hypoxia and asphyxia. These include bradycardia, increased systemic blood pressure and redistribution of the cardiac output. The extent to which they involve maternal or placenta influences is not known. The objective of the present work was ...
Mazzeo R S - - 1998
We have previously demonstrated that acclimatization to high altitude elicits increased sympathetic nerve activity in men. The purpose of this investigation was to determine 1) whether women respond in a similar manner as found previously in men and 2) the extent to which menstrual cycle phase influences this response. Sixteen ...
Green L R - - 1998
1. In six intact and nine carotid sinus denervated (CSD) fetal sheep (125-128 days gestation) we measured heart rate (FHR), mean systemic arterial blood pressure (MAP), femoral and carotid blood flows (FBF and CBF), and femoral and carotid vascular resistances (FVR and CVR). Three experiments were conducted on successive days: ...
Bak M I - - 1998
To test the hypotheses that aged myocardium has lower ATP concentration and that a greater ATP hydrolysis during hypoxia exaggerates diastolic dysfunction in aged myocardium, we used 31P NMR spectroscopy to measure ATP and phosphocreatine (PCr) contents combined with heart function at baseline and during hypoxia and reoxygenation in perfused ...
Hogan Q H - - 1998
BACKGROUND: Although pulmonary function is minimally changed by neuraxial blockade in most cases, ventilatory arrest may ensue in rare cases. The authors examined the mechanism of apnea in a rabbit model of sudden ventilatory arrest during the combination of epidural anesthesia and hypoxia. METHODS: Rabbits were studied during alpha-chloralose sedation ...
McCormick A - - 1998
To evaluate whether changes in extracellular glutamate (Glu) levels in the central nervous system could explain the depressed hypoxic ventilatory response in hypothermic neonates, 12 anesthetized, paralyzed, and mechanically ventilated piglets <7 days old were studied. The Glu levels in the nucleus tractus solitarius obtained by microdialysis, minute phrenic output ...
Maggiorini M - - 1998
The pig has been reported to present with a stronger hypoxic pulmonary vasoconstriction than many other species, including the dog, but it is not known whether this is associated with a different longitudinal partitioning of pulmonary vascular resistance (PVR). We investigated the relationships between cardiac output (Q) and mean pulmonary ...
Wassmann H - - 1998
An in vitro human neocortical and rodent hippocampus brain slice technique was used under repeated hypoxia to investigate the cerebroprotective effect of hypothermia. As a hallmark of the neuronal hypoxic reaction anoxic terminal negativity (ATN) was registered to test whether hypothermia delays the onset of ATN. The experiments clearly confirm ...
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