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Biomedical subjects

D Hall

Publications and source records attributed to D Hall.

At least 37 records · Page 2Linked to original sources
PubMed1990

Screening for asbestos-related pleural disease with digital storage phosphor radiography.

Digital storage phosphor radiography (SR) has a wide dynamic range and unique postprocessing capabilities that may improve the performance of screening studies for asbestos-related pleural disease compared with conventional film radiography (FR). In a group of 32 asbestos-exposed and nine control subjects with established pleural data, we compared the screening performance of FR and SR obtained with a single isoexposure, dual-energy technique (system resolution 0.2 mm, 10 bits). Performance was evaluated for 7320 observations by eight readers using a paired t test (P less than .02 with Bonferroni correction) of averaged receiver operating characteristic curve (ROC) areas (Az +/- standard error). We found that SR alone and SR supplemented by dual-energy soft-tissue and calcium images (SRde) were superior to FR in the overall detection of pleural abnormalities (Az = 0.90 +/- 0.01, 0.90 +/- 0.01, and 0.88 +/- 0.01, respectively). In the specific detection of pleural calcification, SRde was superior to FR (Az = 0.91 +/- 0.01 and 0.87 +/- 0.01, respectively; P less than 0.01). Analysis of variance indicated that SRde most closely reproduced an established pleural score based on the International Labor Organization (ILO) classification of the pneumoconioses (P less than 0.05, Scheffé's multiple comparison test). We conclude that isodose SR performs at least as well as FR in screening for asbestos-related pleural disease. SR supplemented by dual-energy images might improve the specific detection of pleural calcifications compared with FR.

Asbestosis↗
PubMed1990

The diagnostic value of upper gastrointestinal radiography.

We reviewed the indications for and results of 788 consecutive upper gastrointestinal radiographs (UGIs) performed for ambulatory patients. Sixty-three percent of tests were ordered for the evaluation of abdominal pain, dyspepsia, or esophageal reflux. Of these tests, only 4.8% yielded results of major clinical importance to patient management. The yield for patients greater than 50 years of age was greater than for patients less than 50, 6.9 versus 3.0% (p = 0.04). There was a significant increase in yield with increasing age (chi trend = 11.6, p less than 0.001). Among patients with an indication of esophageal reflux alone (n = 62), there were no patients younger than age 60 with a test result that would significantly affect therapy or outcome. Among patients evaluated for fecal occult blood or weight loss (n = 120), 11.7% of tests ordered showed a finding of major clinical importance. In this group, the yield was higher in those greater than or equal to 50 years of age than in those less than 50, 14.7 versus 6.7%, (p = 0.2). These results indicate that UGIs ordered to evaluate pain or symptoms of esophageal reflux in the absence of bleeding or weight loss rarely yield results that significantly influence therapy. Such patients may be best served by an initial trial of empiric therapy or some other test. The UGI has greatest value when indications for it include bleeding or weight loss.

Age Factors↗
PubMed1990

Nitrate therapy in patients with coronary artery disease--preparations and doses with and without development of tolerance.

Rapid tolerance development with respect to hemodynamic, anti-anginal and anti-ischemic effects is a relevant clinical problem associated with any longterm treatment with nitroglycerin, isosorbide dinitrate or isosorbide 5-mononitrate. Tolerance occurs with any dosing regimen that results in nitrate accumulation in the plasma or nearly-constant plasma concentrations, as is the case with multiple daily doses of oral nitrates or continuous application of transdermal patch systems. Nitrate tolerance can be prevented by the interval treatment. This encompasses incorporation of an application-free interval which prevents meaningful nitrate accumulation such that, from a low baseline level, renewed drug administration leads to an increase in the nitrate plasma concentration greater than 2.5-fold. From controlled studies, dosing regimens for interval treatment proven to be effective have been designated for isosorbide dinitrate and isosorbide 5-mononitrate, as well as for transdermal nitroglycerin patch systems. The early attenuation of nitroglycerin, seen within the first 12 h of its use, according to the results of a recently completed study, can be counteracted through continuously increasing plasma concentrations during this period. Interval treatment does not enable 24-h therapeutic protection. Studies with ST-Holter monitoring, however, have shown that adequate coverage can be provided for the period during which the vast majority of ischemic episodes occur. Clinically-relevant rebound phenomena do not occur during interval treatment. Pharmacological approaches to prevent nitrate tolerance, on the basis of the limited and, in part, conflicting data available, do not provide an alternative to interval treatment.

Administration, Cutaneous↗
PubMed1990

[Nitrates in the treatment of heart failure].

Organic nitrates were the first peripherally-active vasodilators to be used for the treatment of heart failure. Currently, three nitrate derivatives, glycerol trinitrate, isosorbide dinitrate and isosorbide 5-mononitrate as well as the nitrate-like substance molsidomine are employed clinically. For treatment of heart failure, the decisive hemodynamic effect is a meaningful reduction in ventricular filling pressures with maintenance or even a slight increase in cardiac output. The individual response to nitrates is variable. An important indicator for the effect achievable for a certain dose or for the necessary dosage to affect a defined reduction in ventricular filling pressures, is the magnitude of right atrial pressure. It can be assumed that the latter statement is also valid for the nitrate-like substance molsidomine. An inherent problem with any long-term treatment with nitrates is the incurrence of tolerance. This can be expected with any dosing regimen which leads to nitrate cumulation in the plasma or to nearly-constant, high, plasma concentrations as rendered by multiple daily administration of orally-active nitrates or with continuous transdermal or intravenous nitrate administration. The cause of nitrate tolerance is regarded as an insufficient or absent stimulation of guanylate cyclase and, consequently, inadequate generation of cyclic GMP due to availability of thiol substrate. Since the nitrate-like substance molsidomine appears to be able to stimulate guanylate cyclase independent of thiol groups, tolerance development may not be a limiting factor with this agent. Comparable reduction of diastolic pulmonary artery pressure after acute administration and at the end of one week of treatment with 4 mg molsidomine four times daily has been reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-Response Relationship, Drug↗
PubMed1990

[Treatment of heart failure with calcium antagonists].

Vasodilators have a well-established role in the treatment of congestive heart failure. By virtue of their vasodilating properties, the calcium channel blockers have been advocated for use in the treatment of heart failure, in particular, in consideration of the fact that the left ventricular dysfunction in 60 to 70% of the patients with this condition is due to ischemic heart disease, the primary disorder for which the calcium channel blockers are intended to treat. The net hemodynamic effect of calcium channel blockade is the result of two opposing actions: negative inotropy and systemic vasodilation with reflex-induced sympathetic stimulation. The balance is dependent on the prevailing cardiovascular status prior to administration of the drug. In the presence of no or only mild-to-moderate left ventricular dysfunction and intact adrenergic reflexes, a small amount of negative inotropy is readily offset by afterload reduction and adrenergic stimulation. In the presence of severe left ventricular dysfunction sufficiently extensive to lead to heart failure, a condition in which homeostatic reflexes are already attenuated, even a slight amount of negative inotropy can lead to unequivocal deterioration of hemodynamics. Of the three conventional calcium channel blockers, verapamil exerts the most marked negative inotropic effects. Even verapamil, however, has been shown to lead to hemodynamic improvement in some patients, at least after acute administration. Apparently, the cut-off point between beneficial and adverse actions lies at an ejection fraction between 30 and 40% and a pulmonary capillary pressure of about 20 mm Hg. In patients beyond these limits, if treated with verapamil, worsening of heart failure is not uncommon.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Channel Blockers↗
PubMed1990

Associations of early childhood infections and reduced hemoglobin levels in a historic cohort of Alaska Native infants.

A retrospective study was carried out to determine the effect of common childhood infectious diseases on the hemoglobin level of a cohort of Alaskan Eskimo children born between 1960 and 1962. Hemoglobin and health records were available on 308 children between 6-11 and 12-17 months of age. Additional records were available on 187 of these children at 18-23 months of age. Episodes of chickenpox, measles, pertussis, and lower respiratory infections were reviewed. Between 38 and 50% of infants between 6 and 23 months of age had hemoglobin levels below 11.0 g/dl. The mean hemoglobin level of infants 6-11 and 12-17 months of age decreased with increasing number of total infectious episodes occurring within the 3 months before hemoglobin measurement. This trend was not apparent for infants in the 18-23 months age interval nor were low hemoglobins predictive of illness during the 3 months after the hemoglobin determination. At the 6-11 and 12-17 month age interval the number of lower respiratory infectious were most significantly associated with a decreased hemoglobin value. These observations are consistent with more recent reports that document iron deficiency anemia among children with antecedent infections and again emphasize the role of infection in the development and maintenance of anemia in children about 1 year of age.

Alaska↗
PubMed1989

Atonic pupil after cataract surgery.

A dilated, atonic pupil is a recognized but unusual complication of cataract surgery. It appears to be a more common occurrence than the paucity of previously published reports would suggest. In this article, seven cases of post-cataract extraction atonic pupil are described. All patients underwent uneventful cataract extraction with posterior chamber intraocular lens (IOL) implantation. In all except one patient, there was a delay from the time of surgery to the development of the atonic pupil. Pharmacologic testing demonstrated that the site of the lesion was the iris sphincter. Possible pathogenic mechanisms are discussed.

Aged↗
PubMed1989

Effectiveness of interval nitrate therapy in angina pectoris.

Because of rapid tolerance development, the use of multiple daily doses of oral nitrates or continuous application of transdermal nitrate systems can no longer be considered justified. Only with an interval treatment, which prevents nitrate accumulation in the plasma such that, from low baseline values, renewed administration of the drug results in a marked increase in plasma concentration, is it possible to utilize the antianginal and antiischaemic effects of nitrates for meaningful long-term treatment. For isosorbide dinitrate and isosorbide 5-mononitrate, as well as for transdermal nitroglycerin systems, interval treatment dosing regimens with maintained effectiveness documented in controlled studies have been delineated. To some degree, the principle of interval treatment can be achieved with continuously applied transdermal patches designed for discontinuous release of their content, which yield maintained though somewhat attenuated effects. Recent studies have shown that the tolerance to nitroglycerin, which develops within the first 12h of contact with currently available transdermal patches, can be prevented by gradually increasing the plasma concentration during this period of time. Evidence for clinically relevant rebound phenomena during interval treatment has not been observed.

Administration, Cutaneous↗
PubMed1989

High frequency edge enhancement in the detection of fine pulmonary lines. Parity between storage phosphor digital images and conventional chest radiography.

Fine linear structures represent a severe test of the minimum spatial resolution that is needed for digital chest imaging. We studied the comparative observer performance of storage phosphor digital imaging (1760 X 2140 pixel matrix, 10 bits deep), and conventional radiography (Lanex medium screen, Ortho C film) in the detection of simulated fine pulmonary lines superimposed on the normal chest when exposure factors were identical (20mR skin entrance dose at 141 kVp). Receiver operating characteristics analysis of 2160 observations by six readers found that high frequency edge-enhanced digital images (ROC area: 0.78 +/- 0.06) performed better than unenhanced digital images (ROC area: 0.70 +/- 0.07) (P less than 0.01 for paired t-test), and that edge enhanced digital images performed on a par with conventional radiography (ROC area: 0.78 +/- 0.09). We conclude that for the detection of fine linear structures, storage phosphor digital images can perform on a par with higher resolution conventional chest radiographs when a high frequency edge-enhancement algorithm is employed.

Adult↗
PubMed1989

Laryngeal papillomatosis: analysis of 113 patients.

Despite the low incidence of these diseases, both juvenile onset and adult onset laryngeal papillomatosis continue to concern otolaryngologists because treatment is often prolonged and unsatisfactory. Over many years various treatments have met with varied claims of success, yet no treatment today is universally accepted. We review the underlying clinical problems, the presentation, the treatment and eventual outcome of 113 patients seen at this hospital over the last 20 years with laryngeal papillomatosis. Using multivariate analysis of age at presentation, sex, smoking habits, initial site of disease, frequency of treatment and eventual outcome, two distinct patterns are revealed both between juvenile and adult onset disease and between male and female patients. Single-site lesions in adults have the best prognosis. Female children with multiple confluent lesions at presentation have the worst prognosis.

Adult↗
PubMed1989

Subtle gastric abnormalities in a canine model: detection with low-dose imaging with storage phosphors and its equivalence to conventional radiography.

The authors compared low-dose (32% of standard exposure) storage phosphor digital imaging (system resolution: 0.2-mm pixels, 10 bits) with isovoltage 75-kVp conventional radiography (standard exposure) in the detection of subtle simulated gastric abnormalities by using air contrast barium studies. Subtle simulated abnormalities (3-7-mm polyps, 4-15-mm ulcer craters, 4-11-mm-diameter edema, and 11-12-mm linear ulcers) were produced in resected canine stomachs. Receiver operating characteristic analysis of 1,800 observations by six readers indicated that the digital images with and without high-frequency edge enhancement were equivalent to conventional radiographs (mean receiver operating characteristic areas [+/- standard deviation]: 0.76 +/- 0.06, 0.78 +/- 0.04, and 0.77 +/- 0.04, respectively). The accuracy of the diagnosis was equivalent for all three modalities. The following mean accuracies of negative and positive responses, respectively, for unenhanced digital, edge-enhanced digital, and conventional images were determined: 0.71 +/- 0.05 and 0.41 +/- 0.07, 0.71 +/- 0.04 and 0.51 +/- 0.09, and 0.68 +/- 0.04 and 0.43 +/- 0.05. It was concluded that low-dose storage phosphor air-contrast barium studies were equivalent to conventional radiography in the detection of subtle gastric abnormalities.

Animals↗
PubMed1989

Temporal trends of human immunodeficiency virus type 1 (HIV-1) infection among inmates entering a statewide prison system, 1985-1987.

Acquired immune deficiency syndrome (AIDS) became the leading cause of death among Maryland State prisoners in 1985. To identify the prevalence, risk factors, and temporal trends for infection with the human immunodeficiency virus type 1 (HIV-1) in the statewide prison system, excess sera were obtained from incoming male inmates during specified periods between April and June 1985, 1986, and 1987. Correctional medical personnel also provided demographic variables of age, race, offense category, sentence, jurisidiction, and an indicator of intravenous drug use. Once rendered anonymous, specimens were assayed for antibody to HIV-1, using ELISA and Western blot techniques. For data from April to June 1985, 1986, and 1987, the crude prevalence of anti-HIV-1 was 7.1, 7.7, and 7.0%, respectively. Although one-third of incoming inmates were identified as intravenous drug users (IVDUs), the drug use variable was missing for 70% of the 1985 sample, and 40% of the 1986 sample. Several strategies were used to examined temporal trends in the context of missing data. Univariate analyses suggested no substantial change over time for either HIV-1 seroprevalence or risk of infection among IVDUs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗