Biomedical subjects
Publications and source records attributed to J Qvist.
The pumping rate of Alzet mini-osmotic pumps was examined in different environments by use of 125J-hippuran. There was a marked increase in pumping rate under hypobaric conditions (PB = 360 mmHg = 48kPa).
In a screening study the strength of association between individual risk factors and post-operative outcome was examined using three-dimensional variate analyses. In a study of 1016 patients, the incidence of life-threatening complications during anaesthesia was low (0.2%), whereas minor complications were seen in about 6% of the patients. Opiate overdose or residual curarization occurred in almost 2% of the cases. One hundred and eleven variables were prospectively assessed and 35 pre-operative variables were evaluated for their possible relationship to one event: post-operative mechanical ventilation (MV). The statistical method suggested that seven of the pre-operative variables seemed to be associated with post-operative MV. Eleven out of 20 patients with respiratory failure who were treated with MV died after anaesthesia (55%) compared with the overall hospital mortality of 2.7%.
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Arterial blood nitrogen tensions of free-diving Weddell seals (Leptonychotes weddelli) were measured by attaching a microprocessor-controlled blood pump and drawing samples at depth to determine how these marine mammals dive to great depths and ascend rapidly without developing decompression sickness. Forty-seven samples of arterial blood were obtained from four Weddell seals during free dives lasting up to 23 minutes to depths of 230 meters beneath the sea ice of McMurdo Sound, Antarctica. Peak arterial blood nitrogen tensions of between 2000 and 2500 millimeters of mercury were recorded at depths of 40 to 80 meters during descent, indicating that the seal's lung collapses by 25 to 50 meters. Then arterial blood nitrogen tensions slowly decreased to about 1500 millimeters of mercury at the surface. In a single dive, alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness.
243 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars with the conventional acid-etch restorative procedure and eight modifications of this technique. The teeth were extracted after 4 months and, following demineralization, the filings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity faced surface. Results showed a significant correlation between the enamel replica patterns and the marginal adaptation of the restorations while the dentin replica patterns did not influence the in vivo adaptation. Furthermore it was found that the improved adaptation obtained by low viscous resin applied as an intermediary layer in etched cavities is due to fewer porosities in the restorative material interface with enamel and dentin. Beveling of preparations prevents stress-induced fractures of unsupported enamel prisms along the cavity periphery. Treatment of etched cavities with the surface active comonomer NPG-GMA increases the general interfacial contact between resin restoratives and cavity walls, and surface coating of finished and re-etched restorations fills up spaces created along cavity margins during the filling and finishing procedure.
29 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars in cavities which after acid-etching had been treated with absolute ethanol. After extraction and demineralization of the teeth, the fillings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity-faced surface. The SEM findings were compared with previous findings concerning the replica patterns on fillings from acid-etched cavities and from cavities which after acid-etching had been treated with an ethanol solution of the surface active comonomer N-phenylglycine-glycidyl methacrylate (NPG-GMA). It was found that cavity treatment with absolute ethanol further improved the increased enamel replica patterns obtained with the NPG-GMA/ethanol comonomer solution while only the NPG-GMA/ethanol treatment improved the dentin replica patterns. Based on these results the effect of each of the two main components in the comonomer solution on replica patterns on resin restorations could be disclosed.
Plasma angiotensin II concentration gradients across the pulmonary vascular bed, plasma renin concentration and serum converting enzyme activity were measured in 19 patients. The majority of the patients were critically ill. Nine patients had septicemia with acute respiratory failure, six patients had severe chronic lung disease and four patients had other serious disorders requiring haemodynamic monitoring. Pulmonary angiotensin II generation rates were calculated as the products of the pulmonary plasma flow and the angiotensin II concentration gradient across the lung. Several patients had a highly activated renin-angiotensin system. There was a strictly linear correlation between the plasma angiotensin II concentrations in mixed venous blood and in systemic arterial blood across a wide range, the concentration in arterial blood being 1.4-1.5 times that in mixed venous blood in each of the three groups of patients. Serum converting enzyme activity was not different from the level observed in a group of control patients above 50 years of age, but lower than in younger normal individuals. The maximal angiotensin II production rates in the pulmonary vascular bed of patients with life-endangering pulmonary disease were similar to the rates previously measured in hypertensive patients with renovascular or renal parenchymal disease. In conclusion, the process of angiotensin I conversion in the lung operates without impediment in spite of severe pulmonary injury.
Three techniques for measurement of right (RVEF) and two techniques for left (LVEF) ventricular ejection fraction were evaluated in five dogs. RVEF was measured with a first-pass radionuclide technique using erythrocytes labelled in vitro with Technetium-99m methylene disphosphonate (MDP) and compared with RVEF measured with a thermodilution technique. Thermodilution-determined RVEF was compared with RVEF values measured with cine angiocardiography. LVEF was measured with a radionuclide ECG-gated equilibrium technique and compared with cine angiocardiography. Measurements were performed before and during a continuous infusion of dopamine. There was an excellent correlation between RVEF measured with the first-pass and the thermodilution technique, rs being 0.86, n = 9, P less than 0.01. When RVEF measured with the thermodilution technique was compared with cine angiocardiography rs was 0.75, n = 10, P less than 0.01. LVEF measured with the ECG-gated equilibrium technique correlated well with cine angiocardiography (rs = 0.91, n = 10, P less than 0.01).
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The NL-tracheostomy tube has a large diameter, large residual volume cuff with automatic and instant cuff pressure regulation. It has been shown in clinical studies to prevent mucosal damage; and depending on airway pressure, it should in theory prevent or delay the onset of trachea dilatation. The authors report 2 patients who developed severe tracheal dilatation with use of standard low volume cuffs during prolonged mechanical ventilation. Placement of the NL-tracheostomy tube with a special long intratracheal leg and cuff positioned below the dilatation abolished the acute problems of air leakage. Tracheal dilatation at the new cuff site did not develop in 1 patient and was slowed in onset in the 2nd patient, who needed high inflation pressures.
A study of ventricular volumes, ejection fractions and filling pressures was performed in dogs (Beagles) before and after the induction of a pulmonary insult (thrombin). The results indicate that during failure of the right ventricle the left ventricular filling pressures are increased without an increase in left ventricular enddiastolic volume and ejection fraction is unchanged. The clinical implications of this phenomenon (ventricular interference) are discussed.
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Oxygen equilibria of whole blood and hemoglobins from adult and fetal Weddell seals are reported. The maternal blood shows a lower O2 affinity than the fetal blood (halfsaturation O2 tension P50 = 26.9 +/- 1.18 and 21.4 +/- 1.25 Torr, respectively, at 37 degrees C and pH 7.4), and a greater Bohr effect (delta log P50/delta pH = -0.49 and -0.31, respectively, at pH 7.4-6.8), correlated with higher red cell 2,3-diphosphoglycerate (2,3-diphosphoglycerate (2,3-DPG) concentrations (6.45 +/- 0.81 mmol.1-1, compared to 2.65 +/- 0-42 mmol.1-1 in the fetus). Both the maternal and fetal erythrocytes contain two major and two minor hemoglobin components occurring in the same ratio and the 2,3-DPG-free whole hemolysates, as well as the isolated major components from each stage, show the same oxygenation properties, ascribing the whole-blood differences to the higher adult DPG levels. A 2,3-DPG effect also appears to account for the disparity in the Bohr effects, which will favor unloading of O2 from the maternal circulation during diving as maternal and fetal blood pH decrease in parallel.
The aim of the present study was to develop a method for quantitative evaluation of the morphology of inner surfaces of composite resin restorations. Twelve restorations made in vivo using the acid etch technique were examined in a scanning electron microscope at a magnification of x 2000. 2500 predetermined areas (6300 micron2 each) on the inner surfaces of the fillings were scored from 0 to 3 with respect to the impression of their rendering of morphologic details from the etched cavity walls. Based on all the scorings and parts of the scorings, estimates for the enamel and for the dentin relief on each of the fillings were calculated. The statistical comparison of these estimates that approximately 50 areas per filling might be scored to attain an objective and reliable quantitation of the surface morphology.
Fetal responses to normobaric diving simulated by submersion of the maternal head for 20 min were studied in four conscious Weddell seals near term. Microspheres injected into the maternal aorta were distributed to the placenta and kidneys in the ratio of 0.4 in the control period and 19.3 during diving, suggesting minimal placental vasoconstriction. Fetal heart rate fell during diving from a mean control value of 90 to 34 beats/min after 4 min. The onset of fetal bradycardia was not consistently associated with changes in blood gas tensions. Diving was associated with a fall in fetal arterial O2 tension from 24 to 9 Torr, arterial CO2 tension rose from 47 to 85 Torr, and arterial pH fell from 7.35 to 7.24. Fetal-maternal gradients for CO2 and H+ transport remained constant, whereas the gradient for O2 transport fell from 47 Torr before diving to 14 Torr at the end of diving. Blood lactate concentrations increased three- to fourfold during diving and reached peak values 10-15 min after diving ended. The similarity of the fetal and maternal heart rate responses to diving is consistent with the presence of physiological oxygen-conserving reflexes akin to the adult's.
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