Quantitative concept mapping in pulmonary physiology: comparison of student and faculty knowledge structures.

Quantitative concept mapping, in contrast with qualitative approaches, is rigorous scientifically and permits statistical analyses of data about concept learning. This study extends past quantitative research on the structure of student concept learning in pulmonary physiology. Pathfinder scaling is used to derive concept maps for medical and veterinary students and their physiology instructors at Northwestern University and the University of Wisconsin, respectively. The concept maps are evaluated for coherence (internal consistency), student-instructor similarity, and correlation of similarity with final examination scores. Results show that student and instructor concept maps are coherent and that student concept maps become increasingly similar to instructors' concept maps from pre- to postinstruction, but that student-instructor concept map similarity does not correlate with examination performance. Research outcomes are discussed concerning possible sources of variation in student and faculty knowledge structures.

Medical and veterinary students' structural knowledge of pulmonary physiology concepts.

PURPOSE: The goal of this study was to assess quantitatively medical and veterinary students' knowledge structures of 12 pulmonary physiology concepts before and after receiving a focused instructional block. The "goodness of fit" and internal consistency reliability of the students' knowledge structures were evaluated. Indexes of the students' structural knowledge were correlated with customary measures of student learning of the same concepts. METHOD: Knowledge structures were assessed using a questionnaire that requested similarity judgments about all possible pairs of the concepts: n(n - 1)/2 = 66 pairs. The similarity judgment data were analyzed using the individual differences (INDSCAL) model of multidimensional scaling (MDS). Dimension weights for individual students were then correlated with their final examination scores. RESULTS: A four-dimensional MDS solution provided the best structural fit to the pairwise concept-similarity data. Dimension 1 ranges from control of breathing to lung gas exchange. Dimension 2 ranges from control of breathing to respiratory mechanics. Dimension 3 separates perfusion from diffusion. Dimension 4 addresses ventilatory control. Hierarchical concept clusters are located within this framework. However, indexes of structural learning did not correlate with other measures of knowledge about the same concepts. CONCLUSION: The study outcomes, in contrast to research in other fields, suggest that structural knowledge in this domain differs from knowledge assessed by standard examinations. Further research involving other basic science or clinical concept sets is needed to verify or refute this finding.

Subjectivity in decision making: common problems and limitations.

Subjectivity is an inescapable part of the diagnostic and decision making process. Limitations on memory are compensated for by invoking "diagnoses" as devices for managing information during diagnosis. Thus, large amounts of information can be stored as confirmations and departures from the diagnostic hypotheses. Well-documented limitations in probabilistic reasoning interfere with diagnosis and patient management. Uncommon diagnoses may be invoked inappropriately. Misconceptions of chance may lead to erroneous conclusions about health care. Most perplexing is that physicians attempting to incorporate patient preference in decision making are confronted with problems of subjective inconsistencies in patient valuation of outcomes of health care. The major problems of quantification and analysis are amenable to management through education, computing, and better patient data management. Problems of utility elicitation will require further research.

Women's and physicians' utilities for health outcomes in estrogen replacement therapy.

Estrogen replacement therapy (ERT) prevents fractures and relieves vasomotor symptoms, but it increases the risk of endometrial cancer. Previous studies and national prescribing patterns show that physicians are conservative in their approach to this therapy. The authors interviewed physicians and perimenopausal women to assess their utilities for the various health outcomes of estrogen replacement therapy. On all outcomes, physicians rated illness episodes followed by recovery as being closer to perfect health than did perimenopausal women. Physicians, in judging which outcomes were most important to women, estimated relief of symptoms above fracture prevention, whereas women rated fracture prevention above symptom relief. These results emphasize the need to assess patients' utilities directly, particularly when utilities for the outcome of a particular therapy may influence the choice of a therapeutic regimen.

Closure of the urinary bladder with stainless steel and absorbable staples.

Stapling is widely accepted in the field of pulmonary and gastrointestinal surgery. However, this has not been the case in urinary tract surgery, presumably because of the possibility of stone formation on the staples. In addressing the issue, both stainless steel staples and absorbable staples (PolysorbTM) were evaluated in 104 linear stapled closures of dog bladders. The mucosa to mucosa closures were performed in bladders with sterile, acutely infected, and chronically infected urine. Staple lines were resected and examined both grossly and microscopically at periods from 1 week to 4 months after the closures. No animal suffered a clinical leak or abscess formation. Four steel closures developed exposed staples, one of which developed a small amount of crystal formation. Twenty-nine absorbable closures contained exposed staples in which two closures developed crystal formation. All closures were secure and healed without difficulty. It appears that closure of the bladder with stainless or absorbable staples is safe and effective.

Comparison of physicians' decisions regarding estrogen replacement therapy for menopausal women and decisions derived from a decision analytic model.

Decisions regarding estrogen replacement therapy were obtained from 50 physicians for 12 cases representing menopausal women with systematically varying levels of cancer risk, fracture risk, and symptom severity. Their decisions were compared with a decision analytic model for which each physician provided needed quantities--subjective probabilities, utilities of various outcomes, and weightings of the importance of the outcome categories. The majority of observed decisions were not to treat. By contrast, the decision analysis based on physician-provided estimates indicated that the optimal strategy was either to treat or a toss-up. Sensitivity analysis showed that these conclusions would hold over all possible utilities, over all plausible probabilities of cancer, and so long as symptom relief and fracture prevention were also considered as treatment objectives. The increased probability of early detection of cancer by regular follow-up was systematically incorporated into the decision analysis but apparently neglected in unaided clinical judgment, which follows the principle of minimizing the most important risk, regardless of its probability.

Intersecting staple lines in intestinal anastomoses.

With the wide application of the stapling instruments in thoracic and general surgery, a number of techniques have been introduced that involve intersecting staple lines. If these simply involve two applications of the liner staplers (TA series), the problem is only one of the effect of the intersection on the circulation, particularly at the corner. With the GIA linear anastomotic instruments or the EEA circular anastomotic instrument, the question arises as to the integrity of the staple line that is cut through by the knives in these instruments. A large experience here and abroad attests to the safety of the TA intersecting lines in intestine and lung, presumably because the circulation continues through the staple line. The use of the circular anastomosing instrument, EEA, across linear staple lines has been spreading clinically with good reports. Studies were undertaken in dogs of the fate of the TA staple lines when the EEA stapler was used for rectal resection or for a Billroth I gastroduodenal reconstruction. In 20 rectal anastomoses and 10 Billroth I reconstructions, there were no leaks, dehiscences, or evidences of failure, whether the EEA transsected the linear staple line once or twice. Most frequently the knife bent the intersected staple and transferred it to the doughnut that was removed. Much less frequently a staple was cleanly transsected by the knife, and only twice did we see no evidence of damage to the staples in the TA line.

Rationale for physicians' decisions to refer obese patients.

Health care costs are an increasing burden upon American society. Referral of patients to a specialist generates additional cost. We studied the reasons behind decisions to refer patients with uncomplicated obesity to endocrinologists. Obesity may be viewed as a paradigm of diseases with relatively well-known etiology, low morbidity and mortality, chronicity, and poor outcome from standard therapy. In addition, it is a disease that is rarely curable by medical intervention, requiring behavioral change. Physicians have little direct experience in the differential diagnosis of endocrine disease, because of its low prevalence. We studied the referral decisions of 45 physicians in three medical specialties. Clinical decision making was studied using a standard set of 24 carefully structured case reports of obese women, all without obvious endocrine disease cues on history or physical. In these cases the patients' desire to be seen by endocrinologists was the major factor in the decision to refer. Referrals were not made primarily to rule out suspected endocrine disorder or because of concern for increased risk of morbidity.

Contemporary stapling instruments and basic mechanical suture techniques.

This article provides a description and demonstration of the basic linear staple closures and anastomoses, as well as of circular anastomoses. Depending on the technique used, bowel may be closed in a mucosa-to-mucosa or serosa-to-serosa fashion, and comparable results with either modality are demonstrated.