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Biomedical subjects

J R Clarke

Publications and source records attributed to J R Clarke.

At least 109 records · Page 6Linked to original sources
PubMed1985

A comparison of decision analysis and second opinions for surgical decisions.

Second opinions and decision analysis, a mathematical process the decision maker can use to represent and solve problems, were compared in hypothetical surgical situations. Fifty expert surgeons gave opinions and provided the information necessary to solve the problems by decision analyses. Each surgeon's opinion was randomly selected again as a second opinion. In six difficult cases, 59% of the individual opinions were correct when compared with previously determined answers. For two surgical second-opinion protocols, the accuracies were 54% and 60%. The accuracy of the decision analyses was 69%. Improvement from second-opinion protocols can be predicted mathematically and is limited. Improvement from decision analysis is not limited by mathematical constraints. Decision analysis may be preferable to second opinions in verifying surgical decisions.

Decision Making↗
PubMed1985

The identification of experimentally induced appendicitis using in vitro nuclear magnetic resonance.

Appendicitis was induced in six New Zealand white rabbits. The appendices from these animals had significantly higher spin-lattice relaxation times, T1, as determined in vitro by nuclear magnetic resonance (NMR) (10 controls vs 6 experimentals, 413 +/- 23 vs 455 +/- 41, X +/- SD, P less than (0.02). T1 correlated significantly with the water content of the appendiceal tissue (P less than 0.001). These findings suggest that in vivo NMR imaging techniques weighted on T1 might be able to identify human appendicitis noninvasively by detecting localized edema.

Animals↗
PubMed1984

Improving the varicella-zoster virus: IgG radioimmunoassay procedure by the use of purified antigen.

The indirect radioimmunoassay (RIA) for detecting and assaying IgG class antibodies against varicella-zoster virus (VZV) can be improved by simple purification of the viral antigen. This is achieved by reducing binding to cellular components present in crude antigens. The purified antigen is particularly useful for testing sera that either bind excessively to normal control antigen or give equivocal results when crude antigens are used.

Antibodies, Viral↗
PubMed1984

A concise model for the management of possible appendicitis.

A conventional decision tree model for the management of patients with possible appendicitis requires at least 15 pieces of information. It makes three assumptions. A more concise decision tree model of the problem is presented here. It requires six pieces of information and prevents unintended mathematical shifts between disease states. It makes an additional five assumptions. The concise decision tree model was compared with the larger original model. Expert surgeons gave opinions on the management of a theoretical patient with possible appendicitis and the information necessary to solve the problem by decision analysis. Information from 25 surgeons whose opinions were consistent with analyses of their information using the original large decision tree was used to reanalyze the problem using the concise decision tree. The concise decision tree agreed with the original analysis in 24 of 25 cases (96%), despite violation of the five additional assumptions in 103 of 125 possible instances. The surgeon's decision can be shown by this model to be a function of the probability of appendicitis, the probability of perforation during observation, and the relative differences in outcomes between avoidable perforation and unnecessary operation.

Abdomen, Acute↗
PubMed1984

Development of an objective rating system for residency applications.

A method was developed to include the opinions of all full-time surgical faculty in reproducible ratings of surgical residency applications according to five attributes: knowledge, judgment, technical skills, work habits, and interpersonal skills. Criteria for classifying each attribute on a scale of five intervals from deans' letters, recommendations, and interviews were developed and used to describe 25 theoretic applications. The applications were rated by each of 14 faculty members on a scale of 1 to 100. The value for each interval of each attribute was determined by conjoint measurement and verified with a second set of theoretic applications. The variation in the second set from faculty opinion was less than 1% (r2 greater than 0.99). The 56 applications for the four positions in our 5-year surgical training program were stripped of identifying information and rated objectively according to the criteria for classification and the values generated. The objective ratings correlated significantly (p less than 0.001) with the interview ratings of seven of the eight faculty interviewers. Variation of the objective ratings from the consensus of all full-time faculty was less than 1% (r2 greater than 0.99). Variation between the actual rank submitted to the National Resident Matching Program and that from the objective rating system was less than 1% (r2 greater than 0.99). As a result of our experience, we will be using this reproducible rating system for the preliminary ranking of our applicants next year.

Educational Measurement↗
PubMed1983

Epidemiology of coronavirus respiratory infections.

Human coronaviruses were found by enzyme linked immunosorbent assay in upper respiratory tract secretions taken during 30% of 108 acute respiratory infections experienced by 30 children under age 6 years with recurrent respiratory infections (index group), and during 29% of 51 acute infections experienced by their siblings. Lower respiratory tract infection--predominantly wheezy bronchitis--occurred in 30% of the index children's coronavirus positive infections but in none of their siblings' infections. Reinfections were common. Two peaks of infection were seen each year in the late autumn/early winter and in the early summer.

Acute Disease↗
PubMed1983

Fertility of the post-partum bank vole (Clethrionomys glareolus).

Analysis of records of a bank vole breeding colony suggests that fertility is high immediately post partum, declines during established lactation and rises after weaning of young. Mating tests with lactating females and females whose young had been removed at birth showed that receptivity is reduced during lactation, although amongst the females which did mate there was no difference between lactating and non-lactating animals in the proportion which produced litters. However, average size of litters at birth was significantly larger for the lactating than for the non-lactating females. There is some evidence suggesting that this difference may arise after ovulation has occurred. Virgin females were no more receptive or fertile than lactating females.

Animals↗
PubMed1982

Selective infection of lower respiratory tract by respiratory viruses in children with recurrent respiratory tract infections.

Thirty preschool children presenting with recurrent respiratory infections and their unaffected siblings were observed prospectively for a year. The index children experienced more episodes of acute respiratory infection than their siblings. Respiratory viruses were the major cause of respiratory infections. The index children had lower respiratory tract disease, predominantly wheeze, during 34% of proved respiratory virus infections compared with 11% of such infections experienced by the control children (p less than 0.02). Atopic children had an increased tendency to wheeze that did not reach significance, but atopy was not associated with increased susceptibility to respiratory infections.

Adenoviridae↗
PubMed1982

Prothrombin and partial thromboplastin times as preoperative screening tests.

Preoperative tests of coagulation function have been suggested to detect patients who are likely to have abnormal bleeding during and after surgery. A study was designed to determine the yield of prothrombin time (PT) and partial thromboplastin time (PTT), both in discovering patients who are at risk for abnormal bleeding and in inducing changes in patient care or outcome. Of 750 patients on three surgical services, 611 (81%) patients had no indication of a bleeding disorder on history or physical examination. Of the 139 patients who had clinical indications, 25 (18.0%) patients had an abnormal PT or PTT. Of the 611 patients without clinical indications, 480 patients had the PT or PTT determined, and 13 (2.7%) patients had abnormal results. One (0.2%) of the 480 patients might have benefited from the test result (this patient required a second operation to control arterial bleeding). The prolonged PT or PTT was of no apparent clinical importance in the remaining 12 patients without indications of bleeding disorders preoperatively. The low yield of the PT and PTT in detecting unsuspected bleeding disorders preoperatively was further obscured by the larger number of apparently false-positive results.

Blood Coagulation Tests↗
PubMed1982

Respiratory resistance from 1 to 46 ATA measured with the interrupter technique.

Measurements of respiratory resistance by an interrupter technique were made in six subjects during a Navy saturation dive to 457 m. Repeated measurements were made at five depths with complete pulmonary function testing after the dive. Increase in resistance was about linear with gas density (rho). Three smokers exhibited a significantly steeper slope of the respiratory resistance versus rho relationship than three nonsmokers. The disparity in resistance among the divers became considerable only at great pressure. Likewise, the predictions of two contradictory fluid dynamic theories agreed fairly well with our data and with each other over the densities explored and disagreed greatly with our data only at higher pressures.

Adult↗
PubMed1982

Gonadotrophin levels in male voles (Microtus agrestis) reared in long and short photoperiods.

Male voles were reared from birth to the age of 56 days in photoperiods of 16L:8D or 6L:18D. In 16L:8D testes increased 10-fold in size between the age of 14 and 56 days, and there were concomitant increases in diameter of seminiferous tubules and seminal vesicle weight. Spermatozoa were present in tubules by 35 days. In 6L:18D no significant changes with age occurred in testis size, diameter of seminiferous tubules or seminal vesicle weight. LH secretion increased with age in 16L:8D, but not in 6L:18D, and pituitary and plasma levels were higher in the former than in the latter by 35 days. Pituitary levels of FSH were high up to 21 days in 16L:8D, and up to 35 days in 6L:18D. At 35 days the mean pituitary level was significantly higher in the 6L:18D than in 16L:8D. Plasma levels of FSH were significantly higher in 16L:8D at 14 and 21 days, and then gradually declined. In 6L:18D plasma FSH rose to a maximum at 35 days, but did not reach the levels occurring at an earlier age in voles in 16L:8D. The relationship between pituitary and plasma levels of FSH in the two photoperiods is compatible with the idea of a storage and a readily releasable pool of the hormone within the pituitary gland. In 16L:8D changing levels of LH and FSH seem to be due to the onset of testicular activity with consequent feedback effects of testicular hormones upon the anterior pituitary gland.

Age Factors↗
PubMed1982

Barotrauma susceptibility in hamster lungs following elastase exposure.

The hypothesis that reduced lung compliance increases barotrauma susceptibility was tested in isolated hamster lungs. Elastase, instilled intratracheally in some hamsters from 4 h up to 8 days prior to testing, caused a patchy distribution of acute suppurative bronchiolitis and pneumonia. Airway blockage and decreased compliance were the anticipated results. For testing, anesthetized animals were ventilated with positive end-expiratory pressure prior to opening of the chest wall; this minimum pressure was maintained throughout testing. Transpulmonary pressure and lung volume changes, determined plethysmographically, were used to calculate quasi-static (C) and dynamic compliance (Cdyn) over a 2-ml tidal volume at frequencies up to 120 breaths/min. Some lungs were exposed, airway open, to a vacuum to stimulate a rapid ascent to the surface. All lungs were eventually pressurized through the trachea to determine rupture pressure (Pr). Rupture pressure exhibited an unexpected dichotomy apparently unrelated to elastase exposure. Statistically C did not differ between the elastase-treated and nontreated animals. Compliance correlated with Pr in a well-defined group (elastase-treated, nonevacuated lungs), but compliance had no value in predicting Pr for the group as a whole.

Animals↗
PubMed1982

The role of decision skills and medical knowledge in the clinical judgment of surgical residents.

Five surgical management problems amenable to solution by decision analysis were developed to test the decision-making skills, or surgical judgment, of residents in three university-based surgical training programs. Incorporated within the problems were indicators of textbook knowledge, basic computational ability and the ability to integrate probabilistic information in a logical decision-making process. Seventy-two residents representing 65% of those in the 5-year programs participated. Correct answers were determined by 50 senior surgeons and independently supported by the surgical literature and decision analyses. The percentage of correct surgical decisions averaged 72 +/- 3% until after the chief residency year, when it rose to 87 +/- 6%. Among the residents still in training, correct clinical decisions were associated with more accurate estimates of textbook information. The clinical recommendations of senior surgeons were consistent with the solutions of the problems by formal decision analysis in 92 +/- 2% of cases; the clinical recommendations of residents were consistent in 77 +/- 2% of cases. Decision analyses with appropriate use of textbook information could improve the accuracy of the residents' clinical recommendations. Decision analysis without accurate information resulted in inferior decision making for one of the management problems. Decision analysis can supplement, but not replace, the acquisition of scientific knowledge in the education of surgical residents.

Academic Medical Centers↗
PubMed1981

Neutrophil function in coeliac disease.

Neutrophil function of 23 patients with coeliac disease, consisting of 13 untreated and 10 on treatment with a gluten-free diet, was examined. The results obtained were compared with those from health volunteers. No significant differences were observed between the coeliac subjects and the control group in respect of the bactericidal ability of the polymorphs and the opsonic capacity of the serum.

Celiac Disease↗