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Biomedical subjects

A Gottschalk

Publications and source records attributed to A Gottschalk.

At least 235 records · Page 13Linked to original sources
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Effect of joint position and ligament tension on the MR signal intensity of the cruciate ligaments of the knee.

Six cadaveric lower extremities were imaged with T1-weighted spin-echo pulse sequences with the knees extended and flexed to 90 degrees. Magnetic resonance signal intensities of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were compared. Changing from extension to flexion resulted in decreased signal intensity in six of six ACLs and five of six PCLs. Two of the knees were then imaged with and without tension applied to the ACL. Both specimens showed a decrease in signal intensity with tension, followed by an increase in signal intensity with release of the tension. Finally, in three of the limbs the ACL was surgically reconstructed and then imaged with and without tension applied to the tendon graft. Signal intensity decreased with tension and increased with release of the tension in all three specimens. Thus, joint position and changes in ligament tension affect the signal intensity of the ACL and PCL, generally resulting in a signal intensity decrease with tension.

Aged↗
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Mechanisms of ventilatory periodicities.

The study of ventilatory periodicities is relevant to the problem of obstructive sleep apnea. Apneas occur at the nadirs of periodicities during sleep. Periodicities can be caused by chemical instability, related to unstable action of the closed loop feedback system for the chemical regulation of breathing. Such instability occurs when overall loop gain is greater than or equal to unity and the phase lag around the loop is 180 degrees. Periodic breathing during hypoxia and in patients with congestive heart failure is likely to be explained by this mechanism. Periodic breathing can also be the result of state instability. Here ventilation declines at sleep onset and the resultant changes in blood gases trigger an arousal, i.e., sudden transition to a lighter stage of sleep. With arousal, ventilation increases. Thus, periodic breathing is secondary to these changes in sleep state. These processes, chemical instability and state instability, can interact and produce complex patterns of oscillation in ventilation.

Aged↗
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Hemodynamic and morphologic evaluation of the spleen after splenic vein ligation in the dog.

The splenic vein was ligated in ten dogs in order to evaluate the time course of changes in splenic size and to relate them to splenic arterial flow, splenic pressure and development of venous collaterals. Following ligation of the splenic vein, splenic size and venous pressure immediately rose in all dogs. Arterial flow to the spleen simultaneously fell in roughly inverse proportion to the elevation of venous pressure. During the following weeks, the splenic parenchymal pressure decreased to basline levels in all but one dog, as collateral veins developed through the gastric venous network to the portal vein. Splenic size gradually decreased toward normal in eight of the ten dogs. At the time of sacrifice, 8-16 weeks after splenic vein ligation, pathologic examination demonstrated fibrosis from healed infarction. Recent hemorrhage, indicating persistence of the congestive process, we also present, although difficult to explain in view of normal splenic parenchymal pressure.

Animals↗
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1979 Memorial Award Paper. Comparison of exercise right ventricular performance in chronic obstructive pulmonary disease and coronary artery disease: noninvasive assessment by quantitative radionuclide angiocardiography.

The right ventricular (RV) response to upright bicycle exercise was assessed in 16 patients with chronic obstructive pulmonary disease (COPD), in 23 patients with coronary artery disease (CAD), and in 19 normal control subjects. Right ventricular (RV) and left ventricular (LV) ejection fractions were determined noninvasively using first-pass quantitative radionuclide angiocardiography, a technique well suited for simultaneous assessment of RV and LV systolic performance. The factors limiting exercise in COPD and CAD are distinctly different, and therefore patients with COPD were studied by means of a single-stage submaximal exercise test, while patients with CAD were studied by means of a graded maximal test. The normal response to exercise, irrespective of exercise protocol, was at least a 5% increase in RV and LV ejection fractions. In 12 of 16 patients with COPD, RV ejection fraction either decreased or remained the same with exercise (abnormal exercise RV reserve). Left ventricular exercise reserve was abnormal only in five patients, probably due to occult CAD. Isolated abnormal exercise RV reserve was present in nine patients. The severity of ventilatory impairment and resting arterial hypoxemia were major determinants of abnormal exercise RV reserve in patients with COPD. In 12 or 23 patients with CAD, RV ejection fraction either decreased or remained the same with exercise (abnormal exercise RV reserve). Left ventricular reserve was abnormal in 18 of 23 patients; RV exercise reserve was abnormal only in CAD patients with concomitant abnormal LV reserve. The presence of proximal right coronary artery stenosis (the major blood supply to the RV) was not a significant determinant of the RV response to exercise in patients with CAD. These data suggest that abnormal exercise RV reserve occurs frequently both in COPD and CAD patients. In COPD the predominant hemodynamic abnormality involves performance of the RV, while in CAD the predominant abnormality involves the LV. The common factor modulating RV exercise performance in both diseases appears to be altered RV afterload.

Angiocardiography↗
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1982 George Simon Memorial Fellowship Award. Experimental studies with 111indium-labeled platelets in pulmonary embolism.

The effects of several potential modifiers on the detection of experimental pulmonary emboli by indium-111-labeled autologous platelets were studied. Contrast material did not affect embolus visualization; heparin prevented it, but its effect was not irreversible. The addition of exogenous thrombin to the experimental thrombus was not necessary for successful detection of the resulting emboli. Indium-111-oxine detected a small number of emboli without in vitro platelet labeling. Acutely embolized thrombi up to 72 hours old were readily identified by labeled platelets, but emboli older than 24 hours were almost impossible to detect. There was evidence suggesting propagation of emboli within the pulmonary arteries.

Acute Disease↗
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Platelet kinetics and biodistribution in canine endotoxemia.

Kinetics and magnitudes of changes in Indium-labeled platelet biodistribution were studied in dogs given E. coli endotoxin. Marked, reversible, dose-dependent shifts of platelets from blood to lung and apparently irreversible shifts to liver were demonstrated. These were contemporaneous with alterations in blood gases and in pulmonary and systemic hemodynamics. Morphologic studies revealed atelectasis, sequestration of leukocytes and platelets in the lungs, and mild interstitial pulmonary edema. This study provides in vivo quantification of labeled platelet response to a specific stimulus, and illustrates a method that could be applied to more extensive study of blood element participation in acute lung injury.

Animals↗
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The influence of heparin on the in vivo distribution of IN-111 labeled platelets.

We investigated the influence of heparin (H) (bolus i.v.; 100-200 I.U./kg.) on the in vivo distribution and accumulation of autologous indium-111-platelets (In-111-P) on experimental pulmonary emboli (PE) in a canine model. Using a thrombin clot formation technique, we induced pulmonary emboli in ten dogs; three dogs were treated with heparin (H), and seven were not (NH). Of five control animals without PE, two were heparinized (H-control) and three were not (NH-control). Animals were sacrificed after 4 to 5 hours of serial blood sampling and sequential scintigraphy. We observed that heparin increased the recovery of In-111-P in the peripheral blood circulation of both control and PE dogs, and reduced the liver uptake of In-111-P in the PE dogs. No PE could be detected while the dogs were fully heparinized, but as the heparin effect dissipated over time, the deposition of In-111-P permitted the scintigraphic detection of PE.

Animals↗
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Review of criteria appropriate for a very low probability of pulmonary embolism on ventilation-perfusion lung scans: a position paper.

The "low-probability" interpretation of ventilation-perfusion lung scans has been characterized as misleading or even dangerous because of the high prevalence of pulmonary embolism associated with such an interpretation. Since the completion of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study, analyses of the PIOPED database have allowed identification of several abnormalities seen on ventilation-perfusion scans that have a positive predictive value (PPV) for pulmonary embolism of less than 10%. These include nonsegmental perfusion abnormalities (PPV = 8%), perfusion defects smaller than the corresponding areas of increased opacity at chest radiography (PPV = 8%), matched ventilation-perfusion abnormalities in two or three zones of a single lung (PPV = 3%), one to three small segmental perfusion defects (PPV = 1%), triple matched defects in the upper or middle lung zone (PPV = 4%), and the stripe sign (PPV = 7%). Use of these abnormalities as interpretative criteria constitutes "very low probability" interpretation and will reduce the number of low-probability interpretations of ventilation-perfusion lung scans, which may be considered nondiagnostic because of the unacceptably high rate of false-negative results. This will enhance the utility of the ventilation-perfusion lung scan for screening patients with suspected pulmonary embolism.

Angiography↗
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A comparison of human and machine-based predictions of successful weaning from mechanical ventilation.

PURPOSE: To evaluate the ability of an appropriately trained neural network to correctly interpret a set of weaning parameters to predict the liberation of a patient from mechanical ventilation, and to contrast these predictions with those of human experts restricted to the same limited set of physiologic data. METHODS: For each set of weaning parameters, a prediction was made by multiple realizations of a neural network and six expert volunteers. RESULTS: The percentage of correct predictions made by the neural network when the decision threshold was set to 0.5 (range 0-1) was 83.3 +/- 4.2 (mean +/- SD) and that for the experts was 83.3 +/- 4.7. Predictions by the network when the threshold was 0.5 had a sensitivity of 0.83 and a specificity of 0.84, compared with 0.90 and 0.77, respectively, for the experts. However, sensitivity and specificity comparable to those of the human experts could be obtained by adjusting the decision threshold of the network predictor so that only the most clearly ventilator-dependent patients would not be given a trial of extubation. CONCLUSION: When both are restricted to the same limited set of patient data, appropriately trained neural networks can be as effective as human experts in predicting whether weaning from mechanical ventilation will be successful.

Decision Making, Computer-Assisted↗