Biomedical subjects
L Oppenheimer
Publications and source records attributed to L Oppenheimer.
Critical closure in the canine pulmonary vasculature.
The vascular pressure-flow (P-Q) relationships in zone II (West et al.) were studied in isolated canine left lower lobes, in order to characterize the total resistance in the pulmonary vascular bed with respect to incremental or flow resistance and critical closure. At each of five levels of static lung inflation, the P-Q relationship was curvilinear at low flow and rectilinear at higher flows. The slope of the linear portion was not significantly different at alveolar pressures (PA) = 5, 7, or 9 cm H2O, but decreased significantly at PA = 11 and 15 cm H2O ((P less than 0.05), indicating an increase in flow resistance. The pulmonary artery pressure (Ppa) fell to the same value at zero flow regardless of inflation level [10.1 +/- 1.0 (SD) cm H2O at PA = 5 cm H2O to 10.9 +/- 2.7 (SD) at PA = 15 cm H2O]. The Ppa intercept (Ppai), extrapolated from the linear portion of the P-Q curve and representing the average closing pressure for the vascular bed, increased from 16.0 +/- 1.8 (SD) cm H2O at PA = 5.0 to 26.5 +/- 4.4 (SD) cm H2O at PA = 15 (P less than 0.05) in a direct one-to-one relationship with the increase in PA. Since this results in a constant transmural gradient at the alveolar vessel level, these vessels must be the major fraction which undergo critical closure. Operationally defined vascular compliance, determined from the slope of a simultaneously obtained pressure-volume (P-V) curve, decreased significantly from 1.51 +/- 0.62 (SD) ml/cm H2O at PA = 5.0 H2O to 0.87 +/- 0.27 ml/cm H2O at PA = 15 cm H2O (P less than 0.05).
Application of jackknife procedures to inter-experiment comparisons of parameter estimates for the Michaelis-Menten equation.
The jackknife procedure is introduced as a means of making comparisons among Michaelis-Menten parameter estimates for six different experimental conditions. In addition to providing a solution to the general inter-experimental comparison problem, the jackknife procedure will provide valid parameter estimates even when some of the assumptions usually required for statistical analysis are violated, e.g., the random errors are not normally distributed and the variances are not homogeneous. Other recent variations of the jackknife have also been introduced and briefly investigated: (i) the linear jackknife, which is more efficient computationally, and (ii) the weighted jackknife, which reduces the influence of design points (substrate concentrations) that have an excessive influence on the precision of parameter estimates.
Effect of positive end-expiratory pressure on left ventricular mechanics in patients with hypoxemic respiratory failure.
When positive end-expiratory pressure (PEEP) is added to intermittent positive pressure ventilation, cardiac output and stroke volume frequently fall despite unchanged or increased transmural left ventricular end-diastolic pressure. To determine whether a part of the fall in stroke volume with PEEP is explained by depressed left ventricular systolic function (increased end-systolic volume at a given end-systolic pressure on PEEP) the authors measured left ventricular end-diastolic volume (EDV), end-systolic volume (ESV), and the corresponding pressures in nine patients with acute hypoxemic respiratory failure. Measurements were made before and after 10 cm H2O PEEP was added to the ventilator. PEEP reduced mean stroke volume from 71 to 62 ml and this was explained entirely by a reduction in end-diastolic volume from 135 to 112 ml (P less than 0.005). Despite reduced EDV, pulmonary wedge pressure increased from 12 to 14 torr on PEEP, indicating reduced diastolic compliance or unstressed volume of the left ventricle in these patients similar to that reported in dogs. The authors conclude that PEEP reduces venous return and cardiac output without depressing left ventricular pumping function because end-systolic volume decreased from 64 to 49 ml on PEEP despite identical blood pressures (78 torr). They speculate that PEEP might improve ventricular performance by increasing intrathoracic pressure and left ventricular pressure relative to systemic blood pressure in extrathoracic vessels.
Epidemiology of trauma deaths.
The records of all 437 persons who died from trauma in San Francisco in 1977 were examined. Sixty-five percent of the sample (285 younger than 50 years, and 119 were between ages 21 and 30. Gunshot wounds (140 or 32 percent) and falls (122 or 28 percent) were the most common causes of injury. Fifty-three percent of the sample were dead at the scene of injury before transport could be accomplished, 7.5 percent died in the emergency room, and 39.5 percent died in the hospital. Fifty-five percent of the 359 patients who died within the first 2 days died from brain injury, while 78 percent of the 55 late deaths were due to sepsis and multiple organ failure. In 10 cases (2 percent), death was due to delayed transport or to errors in diagnosis and treatment and was deemed preventable. The key areas in which advances are necessary in order to reduce the number of trauma deaths are prevention of trauma, more rapid and skilled transport of injured victims, better early management of primary brain injuries, and more effective treatment of the late complications of sepsis and multiple organ failure.
Glutathione synthetase. Purification from rat kidney and mapping of the substrate binding sites.
Explore the source record for details and available documents.
Thermal-dye lung water measurements: effects of edema and embolization.
Explore the source record for details and available documents.
Pathophysiology of pulmonary contusion in dogs.
We produced a localized right lower lobe (RLL) contusion in 14 anesthetized ventilated dogs, 7 of which were treated with positive end-expiratory pressure (PEEP group). We measured gas exchange, pulmonary mechanics, and regional function before and 5 h after the contusion. Arterial PO2 decreased by 20 Torr and venous admixture doubled in both groups during air breathing. The shunt fraction (Qs/Qt) was minimally increased, despite a large lobar Qs/Qt (0.43) in the contused RLL. These results were explained by reduced ventilation per unit volume (VA/V), and ventilation-to-perfusion ratios of the contused RLL measured with 133Xe technique. We conclude that pulmonary contusion causes a leak of blood and plasma, flooding 25% of the air spaces of the RLL at FRC, reducing the compliance of adjacent air spaces, and resulting in a reduced VA/V and a large RLL Qs/Qt. These results are consistent with the observed reduction in regional volume and perfusion in the contused RLL, and suggest that Qs/Qt was not increased because blood flow was markedly reduced to flooded air spaces. PEEP reduced the hypoxemia, but increased the contusion.
Effects of contusion and flail chest on pulmonary perfusion and oxygen exchange.
Localized pulmonary contusions were produced in the right lower lobes (RLL) of 12 anesthetized ventilated dogs, 6 of which had a flail segment in the chest wall over the RLL. Pulmonary oxygen exchange during ventilation with air and oxygen, and the lobar distribution of pulmonary perfusion by radioactive microsphere techniques were measured before and 3 h after contusion, and again after thoracotomy. These were compared to 12 noncontused dogs, 6 of which had a flail segment. Contusion produced an average decrease of 20 Torr in Pao2 during air breathing and an average increase in Qs/Qt of less than 5%, surprisingly small given the doubled weight and average 44% shunt calculated in the contused lobe after thoracotomy. No significant effect of flail or thoracotomy was found, indicating that the presence of an intact chest wall and lung-chest wall interdependence was not a major factor preventing a larger increase in intact whole-animal shunt of contused dogs. Rather, the small effect of this severe lobar injury on whole-animal shunt was due to a 30% decrease in RLL relative perfusion. This reduction was demonstrated to be localized to a smaller hemorrhagic subsection of the contused lobe.
Controlled trial of low-dose heparin and sulfinpyrazone to prevent venous thromboembolism after operation on the hip.
A randomized, double-blind controlled trial of low-dose heparin combined with sulfinpyrazone to prevent deep-vein thrombosis after operation on the hip was carried out. In a group of seventy-three patients after arthroplasty, postoperative thrombosis of the veins of the lower limbs occurred in 51 per cent of the control patients and in 36 per cent of the treated patients. In a fracture group of thirty patients, thrombosis occurred in 75 per cent of the control patients and in 36 per cent of the treated patients. These differences are of borderline statistical significance in the fracture group and are of no statistical significance in the arthroplasty group. However, a 36 per cent incidence of venous thrombosis in the drug-treated patients is too high to justify recommendation of the regimen tested without careful monitoring of patients by tests designed to detect thrombosis. Then, appropriate anticoagulant therapy can be instituted if necessary.
Thrombocytopenia in severe bacterial infections.
Explore the source record for details and available documents.
Effect of different training methods on perceptual learning in impulsive children.
The effectiveness of different training and transfer test conditions in promoting perceptual learning in impulsive kindergarten children was investigated. Interproblem variability was found to be more effective than intraproblem variability, and a differentiation training procedure was found to be more effective than a matching training procedure. The results provide guidelines for designing effective training methods for improving discrimination learning and problem solving in impulsive children.
Ultrasonic relaxation evaluation of the thermodynamics of syn-anti glycosidic isomerization in adenosine.
Explore the source record for details and available documents.
Spectroscopic approach to capillary-alveolar membrane damage induced acute lung injury.
BACKGROUND: Acute (or adult) respiratory distress syndrome (ARDS) is often associated with a high mortality rate in the critical care population. The term acute lung injury (ALI), a primitive phase of ARDS, was introduced by the European and American consensus groups to provide early diagnoses of ARDS. The pathophysiological characterization of ALI/ARDS - an increased pulmonary capillary-alveolar membrane barrier permeability - is generally not included in current intensive care unit diagnosis criteria. OBJECTIVES: To apply the infrared (IR) spectroscopic technique, in combination with the administration of hydroxyethyl starch (HES), to patients with ALI and ARDS. PATIENTS AND METHODS: This retrospective study involved 67 patients from the intensive care unit at the Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba. The methodology was based on the IR spectroscopic determination of HES in patient's bronchial washing fluid. Exaggerated infiltration of HES into the alveolar space was taken as evidence of damage to the pulmonary capillary-alveolar membrane, which in turn provided a diagnosis of ALI/ARDS. RESULTS: The accuracy of determining pulmonary HES leakage in severe lung injury (Partial pressure of arterial oxygen/fraction of inspired oxygen [PaO2/FiO2] less than 100 mmHg [n=10]), was 100%. The subgroups with PaO2/FiO2 between 100 and 200 mmHg (n=23), and PaO2/FiO2 between 200 and 300 mmHg (n=22), 56.5% and 77.3%, respectively, showed IR positive for HES leakage. CONCLUSIONS: The proposed IR bronchial washing assay is very sensitive in determining the pulmonary HES leakage in severe lung injury. It is also suitable for evaluating pulmonary leakage at an early phase of the injury, a fact that is particularly important for supportive treatment. The method is advantageous because no radioactive tracers are employed, little sample preparation is required, and it is rapid and minimally invasive, making it convenient to use in the critical care environment.
[Pulmonary vascular reactivity and the development of edema in the presence of prostaglandin inhibitors in the isolated canine lobe].
UNLABELLED: Alveolar hypoxia is the most powerful pulmonary vasoconstrictor. In a previous work, we did not demonstrate significant changes in vascular reactivity and edema formation in an isolated canine lobe model during alveolar hypoxia. The purpose of this study is to define vascular pulmonary reactivity and edema formation after induction of pulmonary vasoconstriction using a prostaglandin inhibitor like tiaprofenic acid and alveolar hypoxia. Six isolated canine pulmonary lobules were instrumented and studied, all of them under two conditions (normoxia FIO2 21% and hypoxia FIO2 5%) four starting in normoxia condition and 2 starting in hypoxia condition. RESULTS: No significant changes in filtration rate were found, normoxia 0.42 +/- 0.41, hypoxia 0.37 +/- 0.51 ml/min/100 g pulmonary tissue P = NS. The arterial pressure in basal conditions was 25.1 +/- 6.21, and during hypoxia increased to 37 +/- 7.19 cm H2O (Delta 12.0 +/- 1.2 cm H2O). P < 0.001. CONCLUSION: Hypoxia vascular reactivity was significantly increased in tiaprofenic acid pretreated isolated canine lobes, no changes in pulmonary permeability was found nor increased rate in edema formation.
[Continuous spectrophotometry as a method to study pulmonary edema in isolated canine pulmonary lobe].
The aim of this paper is to introduce the spectrophotometric method to the study of pulmonary edema in isolated ex-vivo canine pulmonary lobe preparation. This spectrophotometric method is based on the on-line measure of light transmission in a column of blood, that is proportional to hematocrit. A second light is used to follow Evans blue dyed proteins. With this method we were able to measure the amount of edema in 10 isolated canine lobes. Both the filtration and reflection coefficient of the membrane as well as the characteristics of the filtrate could be calculated. The filtration coefficient was 0.6 +/- 0.4 ml/min (1.3 +/- 0.9 ml/min/100 g pulmonary, tissue) at maximum capillary pressure and the reflection coefficient was 0.53 +/- 0.07. With the spectrophotometric method we have the capability to study different aspects of lung edema formation. This method has the advantage of being exact and independent from pressure and volume induced vascular changes. It also allows the measurement of solute transport.