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

Scanning (SEM) and transmission electron microscopy (TEM) were used to examine the effect of dietary copper deficiency and hyperbaric hyperoxia, alone and in combination, on lung structure. Male, weanling Sprague-Dawley rats were fed a copper-deficient (CuD, 0.2 microgram/g) or copper-adequate diet (CuA, 5.1 micrograms/g). After 35-41 d on their respective diets, rats from each group were placed inside a pressure vessel kept at 27 degrees C under one of two pressure protocols. Air controls were maintained at 1 atm for 75 min. Rats exposed to oxygen were maintained at 1 atm of air plus 3 atm of oxygen for 1 h and then decompressed for 15 min. Under SEM, none of the treated lungs (CuD, CuA-O2 exposed, or CuD-O2 exposed) showed abnormal lung morphology from the conducting bronchioles down to the alveoli. Copper-deficient red blood cells were abnormally shaped. Under TEM, CuA-O2-exposed lungs showed thicker respiratory membranes, especially basement membranes and endothelial cells, and alveolar Type II cells having more than the usual number of surfactant vacuoles. CuD lungs also showed thicker endothelial and basement membrane components of the respiratory membrane, but normal looking Type II cells. CuD-O2-exposed lungs showed greatly thickened respiratory membranes and severe disruption of both endothelium and basement membrane and, judging by the increased number of nuclei per field, an increase in the number of both Type I and Type II cells. We conclude that copper deficiency enhances the damage caused by O2 toxicity, an effect that may be caused by reduced antioxidant status.
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PMID:Hyperbaric hyperoxia exaggerates respiratory membrane defects in the copper-deficient rat lung. 750 51

This study was performed to determine the occurrence and time course of airway hyperreactivity following exposure to normobaric hyperoxia. Twenty-six rabbits were studied. Twelve served as control (group 1), and 14 were exposed to normobaric hyperoxia (FiO2 > or = 95%) for 48 h: 9 rabbits (group 2) were studied after 1 day of recovery in room air and 5 (group 3) after 7 days. The rabbits were anesthetized, curarized and artificially ventilated. Respiratory resistance (Rrs) and elastance (Ers) and their respective changes induced by cumulative doses of aerosolized methacholine were assessed by the multiple linear regression analysis of airway pressure, tidal flow and volume. Weight-specific Rrs and Ers were significantly higher in group 2 (respectively, 87.7 +/- 6.5 cmH2O.L-1.sec.kg and 1100.2 +/- 87.1 cmH2O.L-1.kg, mean +/- SEM) than in group 1 (respectively, 65.2 +/- 3.2 cmH2O.L-1.sec.kg and 904.4 +/- 49.7 cmH2O.L-1.kg (P < 0.05)), but were not different from group 3 (79.4 +/- 7.9 cmH2O.L-1.sec.kg and 952.3 +/- 125.0 cmH2O.L-1.kg, respectively). The dose of methacholine required to increase Rrs by 50% (PDRrs50) was significantly lower in both treated groups: 0.37 +/- 0.11 mg in group 2 and 0.51 +/- 0.19 mg in group 3 vs 2.07 +/- 0.51 mg in group 1 (P < 0.05)). PDErs50 was significantly lower in group 2 (0.45 +/- 0.15 mg) and 3 (0.75 +/- 0.43 mg) compared with controls (1.11 +/- 0.26 mg (P < 0.05)). These results show that hyperoxia induces an increase in Rrs and Ers, and airway hyperreactivity in the rabbit. The latter is prolonged beyond the immediate post-exposure period.
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PMID:Persistent increased lung response to methacholine after normobaric hyperoxia in rabbits. 777 2

Hypotension is known to affect the rate of carotid chemosensory activity in the adult cat, but the relationship between arterial blood pressure and carotid sinus nerve discharge has not been established in the kitten. The purpose of this study was to determine the response of carotid chemosensory afferents to hypotension induced in normoxia and in hyperoxia in eight kittens aged 1 to 25 days. Hypotension was obtained by a gradual decrease in blood volume. The activity of a few chemosensory fibres was recorded from one carotid sinus nerve. Baseline steady-state mean arterial blood pressure and carotid chemosensory activity were, respectively, 70.0 +/- 4.3 mmHg and 7.6 +/- 1.9 impulse/s (mean +/- SEM) in normoxia and 56.3 +/- 6.7 mmHg and 0.58 +/- 0.2 impulse/s in hyperoxia. Lowering arterial blood pressure below 37.5 +/- 3.5 mmHg in normoxia and 26.8 +/- 2.3 mmHg in hyperoxia was associated with a consistent increase in the rate of chemosensory discharge. Above this threshold, blood pressure variations had little effect on carotid chemoreceptor activity. These data are qualitatively similar to those of adult cats and provide evidence that, in newborn kittens, changes in arterial blood pressure will not influence carotid chemosensory discharge unless these changes are out of the physiological range.
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PMID:Effects of haemorrhagic hypotension on carotid chemosensory discharge in the kitten. 803 20

In a previous study, it has been shown that bolus injections of dopamine could either stimulate or inhibit the carotid chemosensory discharge in the kitten (Marchal et al., 1992a). To further characterize dopaminergic mechanisms in the carotid body during development, the effects of a continuous infusion of dopamine on carotid chemosensory activity in air, hypoxia (8% O2 in N2) and hyperoxia (100% O2) were studied in ten anesthetized, paralyzed and artificially ventilated kittens, aged 1 to 21 days and in three adult cats. One carotid sinus nerve was prepared for recording the activity of a single or a few chemosensory afferents. In the kittens, the immediate effect of dopamine at the onset of infusion (10 micrograms/kg/min) was an inhibition of the discharge in five kittens, a progressive excitation in four and no change in one. Four minutes after the onset of dopamine infusion, there was a significant increase in chemosensory activity both in room air (from 4.5 +/- 0.8 impulse/sec to 8.8 +/- 1.4 impulse/sec, mean +/- SEM, P < 0.05) and in hypoxia (from 24.6 +/- 3.7 impulse/sec to 33.4 +/- 5.3 impulse/sec, P < 0.05) but not in hyperoxia (0.5 +/- 0.2 impulse/sec vs 0.7 +/- 0.3 impulse/sec). The adult cats received four successive dopamine infusions at the rate of 2.5, 5, 7.5 and 10 micrograms/kg/min, in an attempt to establish a dose-response relationship. The effects of dopamine infusions were consistent within, but variable between, cats. The onset of dopamine infusion was associated with an inhibition of the discharge in two cats, at all infusion rates. In one of them, chemosensory activity returned quickly to control and the response to hypoxia was enhanced. In the other cat, the inhibition of the discharge persisted for the duration of the infusion, and the response to hypoxia was inhibited. In the third cat, dopamine had no effect on the chemosensory discharge. The patterns of chemosensory responses evoked by dopamine are qualitatively similar in kittens and cats, but the excitatory type of response appear to be more readily elicited in the kitten.
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PMID:Effects of dopamine on the carotid chemosensory response to hypoxia in newborn kittens. 810 8

We analyzed the spatial structure of contact radiographs of barium-filled pulmonary arteries of rats raised in room air and in two environments that induce pulmonary arterial hypertension (PAH)--hypoxia and hyperoxia. We found that the spatial structure of the pulmonary arteries was fractal in both the control and the hypertensive lungs. The fractal dimension of the pulmonary arteries of the control lungs was 1.62 +/- 0.01 (mean +/- SEM), which is greater than that of both the hypoxic lungs 1.50 +/- 0.03 (p < 0.01) and the hyperoxic lungs 1.44 +/- 0.01 (p < 0.01). There was no significant difference between the hypoxic and hyperoxic lungs. The fractal dimension may be a useful clinical index to quantify pathologic changes in the pulmonary arterial tree.
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PMID:Fractal analysis of pulmonary arteries: the fractal dimension is lower in pulmonary hypertension. 811 70

A high resolution optical mapping procedure was developed to visualize oxygen concentration levels topographically within the tissue of the inner retina in vivo. The novel optical mapping procedure has the potential for describing oxygen metabolism in retinal and other body tissues and elucidating the coupling of metabolism to function. The method is based upon the fluorescence quenching by molecular oxygen of a lipid soluble probe substance which accumulates within the lipid bilayers of tissue cells. The optical mapping system can provide more than 300,000 values of tissue PO2 in space with millisecond time resolution. Optical maps of inner retinal tissue PO2 were imaged under conditions of normoxia, hyperoxia, and for a retina which received restricted panretinal photocoagulation. Moreover, the effects of transient increases in intraocular pressure were also investigated. An O2 consumption rate of 5.48 +/- 0.50 (SEM) x 10(-3) ml O2/ml tissue/min for the light-adapted rat inner retina was estimated from the application of a Krogh cylinder diffusion model to tissue PO2 gradients measured in the capillary-free zone around arterioles. Similarly, arterioles oxygenated a surrounding cylinder of tissue with a mean radius of 144.73 +/- 5.52 (SEM) microns. Histograms of PO2 values within inner retinal tissue (mean PO2 = 25.03 mm Hg, median = 24.58 mm Hg) showed remarkable correspondence to those determined invasively in brain by others, using O2 microcathodes, possibly suggesting a similarity in the underlying capillary architectures of the two neural tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Optical mapping of inner retinal tissue PO2. 826 93

The effects of hypoxia (95% N2/5% CO2) followed by hyperoxia (95% O2/5% CO2) were determined in isolated lungs of premature (gestational age 128 to 135 d) and full-term (postnatal age 0 to 5 d) lambs perfused with autologous blood (100 mL.min-1.kg body weight-1). In full-term lungs, hypoxia-hyperoxia compared with hypoxia alone decreased pulmonary artery pressure and increased weight gain and extravascular lung water. In premature lungs, the increase in weight gain was greater and was associated with hemorrhage and increased pulmonary arterial and peak airway pressures. Papaverine eliminated reoxygenation-induced differences in pulmonary artery pressure, peak airway pressure, and weight gain in both age groups. Osmotic reflection coefficients for total protein and albumin, measured by a modification of the filtered volume technique, averaged 0.591 +/- 0.054 (SEM) and 0.465 +/- 0.054 (SEM), respectively, and were not altered by reoxygenation or age. Catalase activity in lung tissue and erythrocytes was lower in premature lambs, but there were no age-related differences in superoxide dismutase or glutathione peroxidase activities. These results demonstrate that hypoxia-hyperoxia in isolated lamb lungs increased lung weight due to edema formation in full-term lamb lungs and hemorrhage in premature lamb lungs and that this increase was greater in premature lamb lungs. We speculate that the weight gain caused by reoxygenation was due to a vasodilation-induced increase in surface area in full-term lamb lungs and a vasoconstriction-induced increase in vascular pressure in premature lamb lungs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Developmental differences in catalase activity and hypoxic-hyperoxic effects on fluid balance in isolated lamb lungs. 851 Oct 27

The mechanisms of exertional dyspnea relief in response to supplemental oxygen (O2) in chronic airflow limitation (CAL) are not precisely known and are likely multifactorial. To explore factors contributing to the relief of dyspnea after oxygen administration, 11 patients with severe CAL (FEV1.0 = 39 +/- 3% predicted, mean +/- SEM) and mild hypoxemia (resting PaO2 = 74 +/- 2 mm Hg) breathed room air (RA) and 60% O2 during exercise at approximately 50% of their maximal incremental exercise capacity. Breathlessness ratings (Borg scale), endurance time, respiratory drive (change in mouth occlusion pressure over the first 0.1 s of inspiration, P0.1), ventilation (VE), breathing pattern, operational lung volumes, gas exchange, and metabolic parameters were compared during RA and 60% O2. PaO2 at exercise cessation during RA and 60% O2 was 65 +/- 3 mm Hg and 226 +/- 12 mm Hg, respectively (p < 0.001). With 60% O2, the mean of individual Borg/time slopes fell significantly (p < 0.05) by 23 +/- 12% and was associated with a 35 +/- 11% increase (p < 0.01) in endurance time (r = -0.64, p < 0.05). During 60% O2, slopes of P0.1 and lactate over time also fell significantly (p < 0.05), whereas delta PaCO2/time did not change significantly. At a standardized time near end-exercise, Borg, VE, and P0.1 changed during 60% O2 by -0.8 +/- 0.3 (p < 0.05), -4.1 +/- 2.0 L/min (p = 0.07), and -1.3 +/- 0.5 cm H2O/s (p < 0.05), respectively. Slopes of Borg/VE, Borg/lactate, and VE/lactate were essentially superimposable during tests on RA and O2: Borg, lactate, and VE all fell proportionally during hyperoxia. In patients with CAL and mild exercise hypoxemia, relief of exertional breathlessness during hyperoxia is explained by reduced ventilatory demand in association with reduced blood lactate levels.
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PMID:Factors contributing to relief of exertional breathlessness during hyperoxia in chronic airflow limitation. 903 90

The aim of the study was to evaluate whether the Heidelberg retina flowmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after breathing 5% carbogen, (2) at baseline and after breathing 100% oxygen and (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The changes in the value of the HRF parameter 'flow' were analyzed by means of a paired Student's t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7+/-2.5% (mean+/-SEM) in HR parameter 'flow' (p < 0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3+/-2.6% in HRF parameter 'flow' (p = 0.024). Increasing IOP to 20 mm Hg did not result in a statistically significant change in HRF parameter 'flow' (-9.6+/-7.4%; p = 0.13). Increasing IOP from 20 to 50 mm Hg, however, resulted in a statistically significant decrease of 40.1+/-6.6% in HRF parameter 'flow' (p = 0.003). With the applied stimuli, the HRF parameter 'flow' changed in the expected direction, i.e. an increase with hypercapnia and a decrease with hyperoxia or high IOP. The simplicity of use of the HRF instrument suggests that it might be well suited for a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.
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PMID:Effect of carbogen, oxygen and intraocular pressure on Heidelberg retina flowmeter parameter 'flow' measured at the papilla. 956 85

We studied interrelationships between exercise endurance, ventilatory demand, operational lung volumes, and dyspnea during acute hyperoxia in ventilatory-limited patients with advanced chronic obstructive pulmonary disease (COPD). Eleven patients with COPD (FEV(1.0) = 31 +/- 3% predicted, mean +/- SEM) and chronic respiratory failure (Pa(O(2)) 52 +/- 2 mm Hg, Pa(CO(2 ))48 +/- 2 mm Hg) breathed room air (RA) or 60% O(2) during two cycle exercise tests at 50% of their maximal exercise capacity, in randomized order. Endurance time (T(lim)), dyspnea intensity (Borg Scale), ventilation (V E), breathing pattern, dynamic inspiratory capacity (IC(dyn)), and gas exchange were compared. Pa(O(2)) at end-exercise was 46 +/- 3 and 245 +/- 10 mm Hg during RA and O(2), respectively. During O(2), T(lim) increased 4.7 +/- 1.4 min (p < 0.001); slopes of Borg, V E, V CO(2), and lactate over time fell (p < 0.05); slopes of Borg-V E, V E-V CO(2), V E-lactate were unchanged. At a standardized time near end-exercise, O(2) reduced dyspnea 2.0 +/- 0.5 Borg units, V CO(2) 0.06 +/- 0.03 L/min, V E 2.8 +/- 1.0 L/min, and breathing frequency 4.4 +/- 1.1 breaths/min (p < 0.05 each). IC(dyn) and inspiratory reserve volume (IRV) increased throughout exercise with O(2) (p < 0.05). Increased IC(dyn) was explained by the combination of increased resting IRV and decreased exercise breathing frequency (r(2) = 0.83, p < 0.0005). In conclusion, improved exercise endurance during hyperoxia was explained, in part, by a combination of reduced ventilatory demand, improved operational lung volumes, and dyspnea alleviation.
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PMID:Effects of hyperoxia on ventilatory limitation during exercise in advanced chronic obstructive pulmonary disease. 1128 62


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