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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Crayfish, Astacus leptodactylus, for several hours breathed water equilibrated either with a hypoxic gas mixture, or air, or oxygen. The hydrostatic pressure in the right epibranchial cavity was recorded and the left epibranchial water sempled from time to time. The higher the water oxygenation, the less the duration of ventilation, the frequency of the scaphognathite beats which ensure water convection, the negative of the water hydrostatic pressure relative to ambient water pressure, and the respired water flow. The water convection per unit quantity of oxygen consumed decreased by a factor of about 20 when the animal passed from hypoxic water at PO2 of 72 torr to hyperoxic water at PO2 of 697 torr. Prolonged hyperoxia, up to 100 days, results in a hypercapnic acidosis of the prebranchial blood. pH decreased about 0.2 unit, PCO2 increased from 2.5 torr to a value of 6 torr, and [HCO-3] from 6 to a value of 9 meq-L-1. This hypercapnic acidosis remained uncompensated during several weeks exposure to hyperoxia. Observations on the fresh water crayfish, a marine crab, and several species of fish, suggest that in aquatic animals (1) the ventilatory activity depends greatly on the degree of water oxygenation: the higher the water oxygenation, the lower the ventilation; (2) the change of ventilation may be accompanied by a new equilibrium of the blood acid-base status, quite different from that observed in normoxia.
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PMID:Crayfish respiration as a function of water oxygenation. 1 99

A review of anatomical and biochemical responses of the lung to high concentrations of oxygen leads us to postulate a biphasic adaptive response. The early phase entails a defense against life-threatening pulmonary edema engendered by destruction of oxygen susceptible cells forming most of the air-blood interface. This defense is brought about by type II alveolar cell replication to reform a continuous epithelial layer in the alveoli; its success would depend upon the rapidly with which this continuity can be reestablished. Factors favoring a successful defense would include an initial large population of type II cells or the ability of type II cells to divide fast enough to reestablish continuity before of oxygen-sensitive cells (type 1 alveolar epithelial and endothelial cells) proceeds to fatal pulmonary edema; both conditions probably exist in young animals, which are known to be more resistant to hyperoxia than old animals. The second phase of adaptation would require the development of increased tolerance of previously susceptible cells to continued exposure to high oxygen concentrations to prevent their total destruction. We postulate that here the development of new biochemical defenses or the augmentation of those previously present would play a major role.
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PMID:Biochemical and anatomical adaptation of the lung to oxygen-induced injury. 2 61

In cats air embolism of the brain was produced by injecting 0.6 ml blood foam into the innominate artery proximal to the origin of both common carotid arteries. Air embolism caused transient ischemia of the brain, reaching a maximum within 1 min after injection. Resolution of the air embolism began a few minutes later and was completed within 15 min in the center and within 30 min in the border zone of the main supplying arteries. During this phase tissue perfusion was inhomogenous with reduced flow rates in some areas and reactive hyperemia up to 300% in others. This resulted in venous hyperoxia and a decrease of arteriovenous oxygen difference to as low as 2 ml/100 ml blood. Reactive hyperemia was accompanied by brain swelling and an increase in intracranial pressure from 3.6 +/- 1.2 to 12.3 +/- 2.0 mm Hg. The reason for hyperemia was a decrease of cortical pH which fell from 7.33 +/- 0.03 to 7.03 +/- 0.05, and which caused a dilation of pial arteries up to 260%. Immediately after embolism, the EEG flattened and oxygen consumption decreased. After normalization of flow, oxygen consumption returned to normal, but EEG only partially recovered. Air embolism had little effect on the water and electrolyte content of the brain, and produced very little damage to the blood-brain barrier.
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PMID:Arterial air embolism in the cat brain. 4 47

To investigate the influence of variations in arterial oxygen tensions (PaO2), arterial carbon dioxide tensions (PaCO2), and arterial pH on long bone medullary pressures, seven anaesthetized dogs were investigated. Comparing the control medullary pressures, i.e. the mean medullary pressures obtained at the normal range of PaO2 (75--110 mmHg) with the mean medullary pressures corresponding to the range of PaO2 of less than 75 mmHg, statistically significant (P less than 0.05) decreases were seen in both epiphyseal, metaphyseal and diaphyseal medullary pressures, from 27.6 +/- 5.0 to 15.5 +/- 3.6 mmHg, from 23.5 +/- 2.9 to 13.9 +/- 2.3 mmHg and from 27.7 +/- 3.9 to 18.3 +/- 2.5 mmHg (all mean values +/- s.e. mean), respectively. Hyperoxia, hypocapnia, hypercapnia or metabolic acidosis had no effect on medullary pressures in any of the regions studied.
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PMID:Observations on long bone medullary pressures in relation to arterial PO2, PCO2 and pH in the anaesthetized dog. 4 59

To investigate the oxygen transport capacity of solutions for blood replacement the oxygen solubility coefficients (ml/ml atm) at 37 degrees C of 12 solutions for volume replacement were determined and compared with those of 12 solutions for parenteral nutrition, 4 electrolyte solutions and 5 solutions for osmotherapy. All solutions for volume replacement have lower values for oxygen solubility than human plasma which shows a very constant oxygen solubility value even under extreme conditions. For clinical use of volume replacement solutions it is recommended that the oxygen solubility of the substitute be considered when any of the following conditions presents: a) large amounts are infused (hemodilution), b) isobar of hyperbar oxygen therapy is employed (hyperoxia), c) the body temperature is lowered (hypothermia). This is valid especially in the case of any impairment of the microcirculation.
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PMID:[Oxygen transport by solutions for blood replacement in comparison with other infusion solutions (author's transl)]. 9 98

Four male and four female, fully conscious, M. mulatta were exposed twice each to diphasic accelerations of 3 or 4 +Gz (3 min) with a 10-min, 1-G intersession. One polarographic electrode was inserted intracortically and another one into neck subcutaneous tissue. With the first of two 3 or 4 +Gz exposures, cerebral PO2 fell from 15.11 to 5.73 and 2.92 torr, respectively; subcutaneous PO2 fell from 27.6 to 7.72 and 4.8 torr, respectively. Cerebral tissue exhibits post-G hyperoxia, related to initial stress intensity; even after the 10-min intersession, it is capable of mitigating the O2 desaturation effect of the second stress. Cerebral and subcutaneous tissue oxygen desaturation with G onset are comparable, but re-oxygenation in the latter tissue is apparently inertia-ridden and a simple relationship between the overall responses of cerebral and subcutaneous PO2 to +Gz acceleration could not be demonstrated.
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PMID:Determination of cerebral and neck subcutaneous tissue PO2 with 3 and 4 +Gz in M. mulatta. 11 59

The ratio vascular volume to total volume was quantitatively analyzed in the cat's carotid body in dependence on the oxygen content of respired air and arterial pO2, respectively. Under hypoxia the vascular volume was 50% higher than under hyperoxia. This connection was ascertained after both perfusion fixation and immersion fixation.
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PMID:[Quantitative determination of the vascular volume of the cat carotid body under normoxia, hyperoxia, hypoxia and hypercapnia (author's transl)]. 12 Apr 83

The effects of normobaric and hyperbaric hyperoxia (short and long time) have been studied on the pyloric antrum motility of the rabbit. The results show the absence of effect of normobaric oxygen in short application (twenty to thirty minutes), but its inhibiting effect on the pyloric antrum motility in long time application. The hyperbaric hyperoxia slows down the frequency of the pyloric antrum contractions so much more the pression is higher. This effect is independant of the speed to which the pression is set up, and also of the moment of day where the experiment is done.
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PMID:[Effects of normebaric and hyperbaric hyperoxia on digestive motricity of the awake rabbit. I Antropyloric motricity]. 13 44

Ventilation versus alveolar PCO2 relationships were determined by the steady-state method in 6 normal male subjects at rest and during positive and negative work at one load in both normoxic and hyperoxic condition. In 5 subjects the slopes of the VE-PACO2 lines during positive and negative work increased in normoxia as compared with rest. This effect was less evident in hyperoxia. It was also found that the slopes of the VE-PACO2 lines in positive and in negative work were about the same in both normoxic and hyperoxic conditions. Oxygen uptake and CO2 production during positive work is higher than during negative work. These results suggest that: 1) the disagreement between various authors on the change of the slope of the VE-PACO2 line may be due to the differences in the method of calculation of the slope or the method of the determination of VE-PACO2 lines; 2) the stimuli from the muscle spindles in the working muscle during exercise probably do not contribute to the increase in ventilatory response to CO2; 3) the increased slope of the normoxic VE-PACO2 line during exercise may be due to the interaction of several factors such as impulses from working muscles, chemosensitivity of central or peripheral chemoreceptors, adrenal-sympathetic pathways or temperature; 4) respiratory oscilations of PAO2 or PACO2 do not seem to influence the respiratory response to CO2.
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PMID:Ventilatory response to CO2 at rest and during positive and negative work in normoxia and hyperoxia. 13 51

The total Mg2+-ATPase and Na+, K+-ATPase activity was studied in the fractions of "400 g X for 20 min" and "900 g X for 30 min" conditionally called the fraction of the external cellular membranes and total fraction of mitochondria. The subcellular fractions were isolated from great hemispheres and stem part of the rat brain. The brain of control animals and those during a severe spasmodic attact induced by the oxygen action at a pressure of 6 ati was studied. The total ATPase activity is established to be practically the same in the studied brain areas and unchanged with hyperoxia. Hyperoxia accompanying by convulsions results in an increase in the activity of Mg2+-ATPase and in a decrease in that of Na+, K+-ATPase both in the cerebral cortex and the stem part. The authors suppose that the decrease in the enzyme activity may occur due to an inhibitory effect on it of the lipids reoxidation products formed in the brain with hyperoxia.
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PMID:[ATPase activity of subcellular rat brain fractions following hyperoxia]. 13 79


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