Biomedical subjects
Publications and source records attributed to P A Farrer.
Patients having lobar airway obstruction or consolidation usually have decreases of both ventilation and perfusion on lung scans. We report three patients in whom hypoxic vasoconstriction was apparently incomplete, resulting in a "reversed" ventilation-perfusion mismatch. Perfusion of the hypoxic lobe on the radionuclide scan was associated with metabolic alkalosis, pulmonary venous and pulmonary arterial hypertension in these patients.
Using serial perfusion lung scans, we have documented the opening up and closure of right-to-left intrapulmonary arteriovenous shunts over a period of several weeks in a patient with chronic alcoholic liver disease. The presence of the shunts correlates well with the severity of hypoxemia and the presence of nodular mottling on chest radiographs. The time course of these changes with clinical status suggests lability and the functional nature of these shunts.
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In the presence of multiple tandem arteriosclerotic stenoses of the distal aorta, iliac, and lower extremity arteries, it may be difficult to ascertain which lesions are clinically and surgically important. Usually the history, physical examination, and arteriogram will resolve this issue. However, a recent report has stated that the rapid transit time of isotope from the distal aorta to the femoral arteries may be helpful. The relevance of this technique in surgical candidates with different clinical stages of vascular disease has yet to be demonstrated. We compared the use of this technique in surgical candidates with their clinical state and assessment of vascular disease by standard angiographic and directional transcutaneous Doppler techniques. Only modest benefit from the isotope transit was found, particularly when compared with the patient's clinical status of asymptomatic, claudicating, or limb salvage categories. We conclude that isotope transit times as currently measured are not as clinically important as previously reported. With further development, some trends may prove to be useful.
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The interobserver and intraobserver variability in lung scan reading and interpretation was tested using a consecutive series of 96 lung scans done for patients clinically suspected to have pulmonary embolism. Lung scans were also done on 37 reference patients who were matched to a suspect case and consented to the procedure. Two experienced readers blindly read all films twice. Intraobserver agreement was low, especially for lung scans showing minor defects. Kappa, a measure of agreement beyond chance, was consistently less than .500. Interobserver agreement was lower. Only 4.3% of the suspect cases had lobar defects on the lung scan. The distribution of abnormalities in suspect and reference cases was similar. The results indicate that the reproducibility of lung scan readings is probably to low to be clinically useful, for readings involving defects that are segmental or smaller. The reproducibility for lobar defects could not be determined adequately because of their low frequency in this study.
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A simple method is described for assessing the patency of LeVeen peritoneo-venous shunts. Following the intraperitoneal injection of 5 mCi of Tc-99m-MAA pulmonary radioactivity is monitored using a gamma scintillation camera. Lung visualization indicates shunt patency, while lack of lung uptake implies shunt obstruction.
A case report is presented on the use of intravenous radioisotope angiocardiography in the diagnosis of an atherosclerotic aneurysm of the ascending aorta in a 44-year-old man who presented with mild superior vena cava obstruction. In addition to outlining the site and extent of the aneurysm, intravenous Tc-99m-albumin radioisotope angiocardiography and blood pool imaging permitted demonstration of the site of obstruction of the cava, indicated the presence of venous collateral channels bringing about delayed filling of the right heart, and also detected obstruction of the right pulmonary artery by the aneurysm. The procedure is simple, rapid, and entirely noninvasive and permits both anatomic and hemodynamic evaluation of the abnormality.
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A simple method for labeling human lymphocytes with Hg-197 is described. Lymphocytes were isolated from human blood and purified by the Ficoll-Hypaque method. Labeling was carried out by incubating viable cells suspended in saline with Hg-197 for different time intervals and at different temperatures. The labeling yield varied from 48% for 1 million cells to about 70% for 10 million cells after incubation with 2 muCi of Hg-197 for 2 hr at 37 degrees C. The temperature and incubation period beyond 1 hr had no appreciable effect on the labeling yield. The yield increased by a factor of 1.5 when the cells were stimulated by phytohemagglutinin. Subcellular distribution studies showed that 60% of the tracer localized in the nucleus and cell membrane, while the remaining portion concentrated in the mitochondrial and microsomal fractions.
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