To investigate the effects of a short-term high altitude residence (2 weeks between 4150 m and 6885 m in the Andes) on the general and local cold responses after descent, 11 subjects were submitted both to a whole body standard cold air test (SCAT, dry bulb temperature = 1 degree ...

OBJECTIVES: To measure, with the use of suprasternal Doppler ultrasound, the hemodynamic changes in patients and volunteers during air ambulance repatriation. DESIGN: Unblinded prospective observational study. SETTING: Chartered air ambulances for the international repatriation of patients. PATIENTS AND PARTICIPANTS: Six medical crew members and seven patients transported back to hospitals ...

The systemic arterial blood pressure response to obstructive sleep apnea (OSA) in humans is usually repetitive (with each apnea) acute elevation with return to near baseline following the apnea. In addition, it is believed by most investigators that chronic diurnal elevation of systemic blood pressure may result from repetitive nightly ...

Ventilatory and cardiac responses to hypoxia, sodium cyanide (NaCN), and intra-arterial injection of atropine, noradrenaline and DL-propranolol were investigated in the neotenous axolotl (Ambystoma mexicanum). Hypoxia elicited increased gill and lung ventilation and a tachycardia. Gill ventilation and air-breathing were stimulated by NaCN infused either into the ventilatory water stream ...

1. In fetal sheep (123-129 days gestation) we investigated the effect of acute isocapnic hypoxia (Pa,O2, 12 +/- 0.6 mmHg) on the fetal heart rate (FHR), mean systemic arterial blood pressure (MAP), carotid blood flow (CBF), femoral blood flow (FBF), carotid vascular resistance (CVR) and femoral vascular resistance (FVR) with ...

BACKGROUND: Some reports claim that ventilation (VE) is greater in human subjects in normobaric hypoxia than at altitude following an equivalent drop in inspired PO2 (PIO2). It has been suggested that reduced barometric pressure (PB) may decrease chemoreceptor sensitivity and account for these results. In this pilot study we tested ...

Acute intermittent repetitive hypoxia simulating sleep apnoea syndrome is responsible for acute rises in blood pressure (BP). In the rat, the BP rises are enhanced by added hypercapnia. To investigate the role of the autonomic nervous system (ANS) in acute hypertension during repetitive hypoxia alone, FiO2 (inspiratory fractional concentration of ...

OBJECTIVES: To determine the hemodynamic responses to a wide range of specific, controlled, graded levels of hypoxic hypoxia over 120 mins in a neonatal porcine model and to identify the PaO2 threshold for altered hemodynamic homeostasis. DESIGN: Prospective, experimental, animal study. SETTING: University cardiovascular research laboratory. SUBJECTS: Three-day-old domestic swine. ...

Acute mountain sickness (AMS) strikes those in the mountains who go too high too fast. Although AMS has been long assumed to be due solely to the hypoxia of high altitude, recent evidence suggests that hypobaria may also make a significant contribution to the pathophysiology of AMS. We studied nine ...

This study tests the hypothesis that exposure of the placenta to hypobaric hypoxia at altitude results in an altered branching pattern of the villous tree. Histological material from 20 term placentae delivered at altitudes over 3000 m was compared with matched controls from 500 m. Estimates of the mean star ...

Nitric oxide synthase (NOS) blockade was used to test the cardioventilatory responses to hypercapnia and hypoxia in freely behaving animals. Chronically instrumented adult Sprague-Dawley rats were studied before and after intravenous administration of either 100 mg/kg of NG-nitro-L-arginine methyl ester (L-NAME), a nonspecific NOS blocker, or 10 mg/kg of S-methyl-L-thiocitrulline ...

The effect of hypoxic hypertension on the remodeling process of the elastic laminae of the rat hilar pulmonary arteries (PAs) was studied by electron microscopy. Rats were exposed to hypoxia (10% O2) for periods of 0.5, 2,6,12,48,96,144, and 240 h. Changes in the structure of the PA elastic laminae were ...

Lung morphometry was studied in rats between 4 and 7 weeks of age. The animals were divided into 5 groups: general controls (fed ad libitum), hypobaric normoxic, normobaric hypoxic, hypobaric hypoxic, and weight-matched controls (weight matched to the hypobaric hypoxic group). In both hypobaric and normobaric hypoxia, lung volume, alveolar ...

Cardiovascular responses (blood pressure, heart rate, stroke volume, cardiac output, and peripheral vascular resistance) to acute hypoxia (Po2 = 70 mmHg) in developing larvae of Xenopus laevis from Nieuwkoop-Faber (NF) stage 45 and up to newly metamorphosed froglets were investigated. The results revealed two distinct response patterns to acute hypoxia ...

BACKGROUND: In a previous clinical study doxapram was found to improve ventilatory efficacy postoperatively, presumably via effects on hypoxic pulmonary vasoconstriction (HPV). The present study was designed to see whether doxapram induced any changes of arterial oxygenation and pulmonary vascular resistance during normoxia or hypoxia and whether the changes were ...

Repeated, frequent hypoxic exposures may precede Sudden Infant Death. This study assessed whether such hypoxic modality, vs. continuous hypoxia, compromised compensatory cardiorespiratory responses. Following aseptic, chronic instrumentation, 10 to 20 day-old, unsedated piglets underwent measurements of arterial O2 saturation, pH and gas tensions, respiration, heart rate, physical activity, O2 consumption ...

AIM: To assess whether nitrendipine (Nit) can be used to prevent and treat the hypoxic right ventricular hypertrophy (RVH). METHODS: Rats were exposed to a simulated altitude of 5000 m (barometric pressure = 54 kPa) for 30-60 d. Nit (10-20 mg.kg-1.d-1) was administered via gavage. The therapeutic efficacy was evaluated ...

BACKGROUND AND OBJECTIVES: High concentrations of lidocaine have been found to cause pulmonary vasoconstriction and low concentrations (0.5-0.9 microgram/mL) to cause reversal of nitrous oxide-induced depression of hypoxic pulmonary vasoconstriction. This study was undertaken to examine the effects of high concentrations of lidocaine on pulmonary circulation during hyperoxic and hypoxic ...

Nitric oxide (NO) synthase inhibitors potentiate hypoxic vasoconstriction (HV), suggesting that NO production during hypoxia normally acts to attenuate HV. To begin to examine the effect of hypoxia on lung NO production, we studied four groups of isolated neonatal pig lungs. In three groups of lungs, the accumulation of nitrite/nitrate ...

Acute hypoxia in newborns of various species including humans is associated with decreased thermogenesis and a fall in body temperature. We have investigated the cardiorespiratory consequences of correcting the fall in colonic temperature (Tc) during acute hypoxia in newborn cats. Experiments were conducted on 21 unanesthetized kittens (12 +/- 1 ...

Abnormal systemic and pulmonary vascular reactivity has been demonstrated in numerous models of sepsis and pneumonia. Furthermore, the attenuated hypoxic pulmonary pressor response observed in these animals probably is responsible for the ventilation/perfusion (V/Q) mismatching and consequent arterial hypoxemia. We hypothesized that excess release of endogenous vasodilators such as calcitonin ...

The aim of the present study was to examine whether hypoxic pulmonary vasoconstriction (HPV) is preserved during one-lung ventilation combined with thoracic epidural anesthesia (TEA) in dogs. Using a separately ventilated left lower lobe (LLL) in situ, the pressure-flow (P-Q) curve was obtained. The HPV response was assessed by the ...

Regular administration of recombinant erythropoietin (EPO) is frequently complicated by a rise in arterial blood pressure. We therefore asked if prolonged stimulation of endogenous EPO production has the same effect. To this end, male Sprague-Dawley rats were placed in a hypobaric chamber (390 mm Hg) for 24 days. The control ...

To assess the effect of chronic hypoxic conditions on ventilatory, heart rate (HR), and blood pressure (BP) responses to acute progressive isocapnic hypoxia, we studied five healthy Caucasian subjects (3 men and 2 women). Each subject performed one rebreathing test at sea level (SL) and two tests at the Pyramid ...

The ATP level and the activities of hexokinase (HK), phosphofructokinase-1 (PFK-1) and pyruvate kinase (PK) in red blood cells (RBC) were measured in 50 school students 6-12 yr of age in the Jordan Valley (JV) which is the lowest region below sea level in the world (low altitude: 390 m ...

1. In 3-day-old and 3-week-old spontaneously breathing piglets anaesthetized with Saffan, we have studied ventilatory and cardiovascular responses evoked by 5 min periods of hypoxia (breathing 10 and 6% O2). 2. In 3-day-old piglets both 10 and 6% O2 evoked an increase followed by a secondary fall in ventilation, a ...

PURPOSE: To assess the effects of systemic hypoxia and hyperoxia on the volume of the subretinal space (SRS). METHODS: The authors measured the concentration of the extracellular space marker tetramethylammonium (TMA+) in the intact cat eye using double-barreled ion-selective microelectrodes. The retina was loaded with TMA+ by a single intravitreal ...

Marmots (Marmota flaviventris) are burrowing mammals that may be subjected to low levels of oxygen and high levels of carbon dioxide in their underground environment. Since marmots successfully deal with this physiological challenge, we hypothesized that the isolated perfused marmot heart would be damaged less and recover better from a ...

It has been shown that pulmonary vasodilation is sustained after discontinuation of inhaled nitric oxide (INO) during moderate hypoxic pulmonary hypertension (HPH) in swine. The present investigations demonstrated how INO dose, hypoxia duration, and endogenous NO production influence this important phenomenon. Fifteen adolescent Yorkshire swine were randomly assigned to three ...

1. In two groups of Saffan-anaesthetized rats, we studied the role of the renin-angiotensin system in mediating the antidiuresis and antinatriuresis induced by moderate systemic hypoxia. 2. In both groups, a first period of hypoxia (breathing 12% O2 for 20 min) induced a fall in arterial partial pressure of O2 ...

An isolated rat heart model of intermittent hypoxia was used to investigate the impact of exogenous supplementation of glutathione and two thiol delivery vehicles on functional recovery during reoxygenation and whether efficacy was dependent on enhanced intracellular thiol concentration. Hearts from F344 rats were perfused in the Langendorff mode and ...

A 22 year old woman with central alveolar hypoventilation (CAH) underwent repeated nocturnal polysomnographic recordings to assess the efficacy of negative pressure ventilation (NPV) administered by pneumowrap. The NPV successfully prevented hypoxia during most of the recording time; however, a sudden severe hypoxic episode not related to an apnoea occurred ...

The aim of this study was first to investigate cardio-ventilatory and haematological responses induced by intermittent acclimation and second to study de-adaptation from high altitude observed after descent. To achieve these objectives nine subjects were submitted to intermittent acclimation in a low barometric chamber (8 h daily for 5 days, ...

The rostral ventrolateral medullary surface (VMS) plays a major state-dependent role in the control of breathing; its role during hypoxia remains speculative. We therefore assessed activity within the rostral VMS by measuring reflectance of scattered light in 5 goats during normoxia, hypoxia, and hyperoxia in awake and halothane anesthetic states. ...

The effect of chronic administration of angiotensin converting enzyme inhibitor on the development of hypoxic pulmonary hypertension was studied in rats. Male Wistar rats were-exposed for 3 weeks to isobaric hypoxia (10% O2) and treated with 10 mg/kg b.w. of Ramipril daily. The haemodynamic properties of the pulmonary vasculature were ...

Propionibacterium acnes was found in the cortex of three patients with Alzheimer's disease and in one frontal cortex of an elderly patient with cardiovascular risk factors and hypoxia due to a large glioblastoma of the right frontal lobe with severely increased intracranial pressure. Propionibacterium acnes is an atypical anaerobic bacterium ...

This study investigated the human erythropoietin (EPO) response to short-term hypocapnic hypoxia, its relationship to a normoxic or hypoxic increase of the haemoglobin oxygen affinity, and its suppression by the addition of CO2 to the hypoxic gas. On separate days, eight healthy male subjects were exposed to 2 h each ...

The ventilatory and metabolic responses of lesser spear-nosed bats to hypoxia and hypercapnia were measured to determine whether these corresponded to preliminary allometries and a positive relationship between hypoxic ventilatory threshold and P50. Ventilatory responses of lesser spear-nosed bats to 3, 5 and 7% CO2 differed significantly from ventilation on ...

PURPOSE: In newborns, inhaled nitric oxide (NO) has been shown to ameliorate increased pulmonary vascular resistance (PVR) precipitated by hypoxia. The role of endogenous NO production in this response is not clear. The contribution of endogenous NO to resting PVR in normoxic newborns also has not been well studied. The ...

We hypothesized that cardiac and respiratory modulation of postganglionic peroneal activity appeared in an age-related manner. In anesthetized, paralyzed and artificially ventilated piglets, simultaneous recordings of efferent phrenic and peroneal discharges were obtained during hyperoxia (fraction of inspired oxygen, FiO2 = 1.0) and hypoxia (FiO2 = 0.1). Spectral analyses of ...

It has been hypothesized that an increased level of plasma lactate (La), the product of anaerobic glycolysis, may identify infants with anaemia and early tissue hypoxia. In the newborn piglet, a frequently used model in experimental neonatology, there is a substantial decrease in haemoglobin (Hb) during the first days of ...

A basic tenet of biology is that body temperature (Tb) has a marked effect on oxygen uptake of resting animals. For most animals, the temperature coefficient (Q10) is >> 2.5; e.g., resting oxygen uptake changes about 11% per degree C change in Tb. An important consequence of this dependence is ...

The effects of hypoxia on ventilation and cerebral activity were studied in urethane-anaesthetized newborn guinea-pigs. Ventilation was measured by a pneumotachograph, and cerebral activity by a cerebral function monitor (CFM). All animals were subjected to either 9% O2 or 6% O2 in N2 for 10 minutes or until apnoea occurred. ...

Many persons with sleep apnea are hypertensive. Forty-two subjects of similar age and weight were divided into four groups of hypertensives and normotensives with and without sleep apnea. All subjects had heart rate, blood pressure (BP), baroreflex sensitivity and pressor sensitivity to phenylephrine measured while breathing room air or 15% ...

To assess the role of diaphragmatic activity at the end of expiration (DE) in the control of end-expiratory lung volume (EELV), 1) these two parameters were correlated in anesthetized cats breathing different gas mixtures; and 2) expiratory flow volume curves in normoxia and hypoxia together with changes in esophageal pressure ...

We have studied in eight rabbits the cardiovascular effects of midazolam, propofol and alfentanil with graded hypoxia. Central blood volume was reduced progressively by gradual inflation of a thoracic vena cava cuff so that cardiac index (CI) decreased at a constant rate. Under control conditions the haemodynamic response was biphasic. ...

Hypoxia elicited a remarkable decrease in contractility and heart rate in isolated right atria from guinea pigs, a decrease which recovered partially during reoxygenation. Histamine content increased during hypoxia and decreased during reoxygenation. However, hypoxia induced a marked degranulation of mast cells. Pretreatment with alpha-methylhistamine (100-300 nM) recuperated control level ...

We hypothesized that the renal sympathetic nerve activity (RSNA) response to hypoxia is attenuated because of stimulation of pulmonary receptors by the increase in ventilation. RSNA was measured during 20 min of severe hypoxia (8% O2) in conscious New Zealand White rabbits with intact lung innervation and in rabbits with ...

1. We investigated how a continuous infusion of dopamine (DA; 5 micrograms/kg per min), which is often used clinically, would affect the ventilation and carotid chemoreceptor neural activity in anaesthetized cats. 2. In anaesthetized, spontaneously breathing cats, tidal volume (VT) and respiratory frequency (f) were continuously monitored at five levels ...

Acute hyperammonemia causes cerebral edema, elevated intracranial pressure and loss of cerebral blood flow (CBF) responsivity to CO2. Inhibition of glutamine synthetase prevents these abnormalities. If the loss of CO2 responsivity is secondary to the mechanical effects of edema, one would anticipate loss of responsivity to other physiological stimuli, such ...