The correlation of subcarinal density visualized on plain chest roentgenograms with computed tomographic scans.

A prospective evaluation of 212 paired chest roentgenograms and computed tomographic (CT) scans was performed to determine the predictive value of detecting subcarinal adenopathy by finding increased subcarinal density on routine roentgenograms. Based on CT criteria for subcarinal lymphadenopathy, 37 true-positive and 124 true-negative cases of subcarinal adenopathy were found in 161 patients. Evaluation of density in the subcarinal area on the routine posteroanterior (PA) chest roentgenograms in these patients demonstrated a sensitivity of 72 percent and specificity of 96 percent for the detection of adenopathy when compared with established CT criteria. False-positive and false-negative appraisals of central mediastinal density on routine roentgenograms appear to be due to the super-imposition of other masses, bullae, or lack of appropriate roentgenographic contrast. The accuracy of predicting the presence or absence of subcarinal adenopathy from routine chest roentgenograms suggests that this observation is clinically useful and should be routinely evaluated.

Tissue release of adenosine triphosphate degradation products during shock in dogs.

Clinical monitoring of cellular metabolism during shock, based largely on traditional metabolic indicators, remains unsatisfactory. The purpose of this study was to compare venous oxygen tension and blood lactate gradients with blood gradients of purine nucleotide degradation products which are derived from tissue ATP catabolism during hypovolemic shock. Sixteen dogs were instrumented to sample arterial and venous blood. Measurements of arteriovenous lactate and PNDP gradients during spontaneous respiration were examined at four tissue sites: gut, kidney, hindlimb, and diaphragm. Hypovolemic shock (mean arterial blood pressure 35 to 40 mm Hg) was induced and maintained for one hour. The above parameters were remeasured at 30 and 60 minutes after induction of shock. Hypoxanthine gradients were greater than that of other PNDP, and so were used as the primary indicator of tissue ATP metabolism. In the hindlimb, the mean AV gradients for hypoxanthine (1 +/- 1 microM) were not significantly greater than baseline, while the lactate gradient (700 +/- 300 microM) rose markedly. In contrast, across the kidney there was a significantly greater AV hypoxanthine gradient (16 +/- 3 microM, p less than 0.002) but no lactate gradient (-400 +/- 200 microM). Both the hypoxanthine and lactate AV gradients were significantly elevated across the diaphragm and gut. Venous PO2 values less than 35 mm Hg predicted an increased hypoxanthine gradient across the kidney, but not across the hindlimb. We conclude that the metabolic response to hypovolemic shock as assessed by PNDP gradients, lactate gradients, and venous PO2 differs among tissues. Although resting muscle such as the hindlimb may be an important source of blood lactate, the viscera and working skeletal muscle (the diaphragm) are major contributors to circulating PNDP.

Transbronchial biopsy during mechanical ventilation.

The value and risk of transbronchial biopsy (TBB) was assessed in 15 cases requiring mechanical ventilation for progressive pulmonary infiltrates. TBB was diagnostic in five patients, and in two additional cases a diagnosis was made from the accompanying bronchial secretions. TBB results significantly altered the therapeutic management in seven cases. The alveolar-arterial gradient P(A-a)O2, widened by a mean of 110 mm Hg in nine patients; however, this change was transient and clinically insignificant. Three instances of reversible hypercapnia (mean of 15 mm Hg) occurred. Complications included self-limited bleeding in three cases and one tension pneumothorax. No fatalities were attributable to TBB. In these hemodynamically stable patients requiring mechanical ventilation for diffuse lung disease, TBB was performed safely and provided important data.

Spirometry and chest roentgenographic appearance in adults with cystic fibrosis.

The pathophysiologic manifestations of cystic fibrosis are continually evolving as more patients survive into their adult years. Although the correlation between chest roentgenographic appearance and pulmonary function testing is well described in children with cystic fibrosis, to our knowledge, there are no data that evaluate this relationship in adults. We analyzed 66 paired studies of chest roentgenographic appearance (Brasfield score) and spirometry in 27 adults with cystic fibrosis between the ages of 18 and 40 years. There was a very good correlation between spirometry and the Brasfield score in adults with cystic fibrosis. The strongest correlation was between the percent predicted FEV1 and the Brasfield score (r = 0.68, p less than 0.001). These correlations were found to remain significant in the patients in whom longitudinal data were available. The FEV1 declined 104 +/- 26 ml/yr in 11 patients who were followed up for a mean duration of 5.8 +/- 0.5 years. The decline in FEV1 per year in adults with cystic fibrosis was significantly greater than in nonsmoking or smoking adults of similar age.

Evidence for adenosine triphosphate degradation in critically-ill patients.

Alterations of cellular energy metabolism may provide important markers during the clinical course of critically ill patients. To determine whether adenosine triphosphate (ATP) degradation occurs in critically ill patients, we measured levels of adenosine, inosine, hypoxanthine, and xanthine in 18 patients and seven control subjects. The mean concentration of hypoxanthine (3.8 microM) in the critically ill patients was elevated (p less than 0.01) compared to that of our control population (0.1 microM). A subgroup of seven critically ill patients had levels of hypoxanthine, xanthine, or inosine higher than those of any member of the control group. This subgroup was characterized by a lower systolic blood pressure, an increased requirement for vasopressors, and a markedly decreased survival rate when compared to the other critically ill patients. Arterial and mixed venous blood gas values were not helpful in predicting survival and did not correlate with levels of ATP degradation products. In two patients who showed subsequent clinical improvement, the initially elevated levels of hypoxanthine and xanthine returned to normal. This study indicates that critically ill patients have elevated levels of ATP degradation products. These increased levels may indicate cellular hypoxia.

Training students in education of the hypertensive patient: enhanced performance after a simulated patient instructor (SPI)-based exercise.

The process whereby a physician explains to the ill patient what has gone wrong and what can be done about it can be taught and evaluated by simulated patients (SPIs). This study was designed to determine whether a training experience in educating a diabetic SPI improves subsequent performance with a hypertensive SPI. Competence in educating a hypertensive SPI by students who had no prior training experience (n = 26) was compared to that of an experimental group (n = 20) that had a prior training session. Performance was assessed with a counseling skills scale and a case-specific content checklist (1 = poor to 5 = excellent). Students in the experimental group performed better than controls in both counseling skills (4.46 v 3.86, P < .01) and completeness of coverage of content (3.28 v 2.65, P < .01). Students in both groups focused more on clinical features and treatment than on laboratory testing and follow-up. The ability to counsel "patients" with hypertension can be enhanced by a prior learning experience with a diabetic SPI. Clinical application of knowledge about hypertension can be assessed by SPIs.

Hypothermia or continuous ventilation decreases ischemia-reperfusion injury in an ex vivo rat lung model.

The susceptibility of lung tissue to ischemia-reperfusion injury has made distant procurement of heart-lung allografts difficult. The effects of hypothermia, ventilation without perfusion, and various reperfusion solutions (PSS/Ficoll or whole blood) on the development of ischemia-reperfusion lung injury were investigated. Use of an ex vivo rat lung model in which the above variables were individually varied permitted a direct approach for these studies. Normothermic ischemia for 1 hour caused significant damage, documented by increased iodine 125 bovine serum albumin (125I-BSA) in alveolar lavage fluid and lung parenchyma compared with nonischemic controls. Hypothermic (4 degrees C) ischemia for 4 hours in lungs reperfused with salt solution and for as many as 12 hours in lungs reperfused with whole blood caused no significant increase in 125I-BSA in alveolar lavage fluid and lung parenchyma compared with nonischemic controls. Lungs ventilated without perfusion showed no increase in 125I-BSA leakage compared with controls. The ex vivo rat lung model is excellent for studying ischemia-reperfusion injury. It is reproducible, allows for variance of reperfusion solutions, and permits change in temperature and ventilation easily.

Neutrophils are not necessary for induction of ischemia-reperfusion lung injury.

Ischemia-reperfusion lung injury limits lung transplantation. Neutrophil activation and/or xanthine oxidase-mediated purine degradation may cause toxic oxygen metabolite production and lung injury. We investigated whether circulating blood elements are involved in the pathogenesis of ischemia-reperfusion lung injury. Isolated rat lungs were perfused with physiological salt solution (PSS) stabilized with Ficoll until circulating blood elements were not detected in the lung effluent. Lungs were then rendered ischemic by stopping ventilation and perfusion for 45 min at room temperature. Lung injury occurred and was quantitated by the accumulation of 125I-bovine serum albumin into lung parenchyma and alveolar lavage fluid during reperfusion. Lung injury occurred, in the absence of circulating blood elements, when ischemic lungs were reperfused with PSS-Ficoll solution alone. Reperfusion with whole blood or PSS-Ficoll supplemented with human or rat neutrophils did not increase lung injury. Furthermore, during lung ischemia, the presence of neutrophils did not enhance injury. Experiments using PSS-albumin perfusate and quantitating lung injury by permeability-surface area product yielded similar results. Microvascular pressures were not different and could not account for the results. Toxic O2 metabolites were involved in the injury because addition of erythrocytes or catalase to the perfusate attenuated the injury. Thus reperfusion after lung ischemia causes injury that is dependent on a nonneutrophil source of toxic O2 metabolites.

Conventional mechanical ventilation.

Mechanical ventilation has become a very common and well-accepted practice in modern intensive care units. The use of the mechanical ventilator has progressed from being a support system during surgery and for acutely ill patients to being used in both moderate and long-term life support in patients with inadequate ventilation. The sophistication of modern ventilators and the ability of trained respiratory therapists and nursing personnel have permitted this technology to explode. This is occurring at a time when there are still many controversies about the relative benefits and modes of action of conventional ventilation. As newer techniques are developed, it is mandatory that the application of these techniques be tempered with controlled clinical trials, documenting their effectiveness. The beneficial effects of new modalities must be documented as mechanical ventilation expands from use in the intensive care unit to use in standard medical wards and the patient's home. In these latter two settings, the vigilance of an intensive care unit is absent and the simplest method will be preferable. The requirement to demonstrate efficacy of new techniques with adequate studies is especially necessary now as the economics of health delivery have come under increasing scrutiny. Even more important than new technologies may be the efficacy of prolonged mechanical ventilation. A recent study by Spicher and White evaluated the outcome in 250 patients ventilated for 10 days or more at the Hershey Medical Center (Pennsylvania State University). The mortality, morbidity, and disability in patients in this study population requiring prolonged ventilation were extremely high. As these studies have pointed out, further evaluations of predictors of meaningful survival are necessary to avoid unnecessary human suffering and to best use limited resources.

Assessing medical students' awareness of and sensitivity to diverse health beliefs using a standardized patient station.

PURPOSE: To assess students' performances on a health-beliefs communication OSCE station to determine whether there were differences in cultural competence based on the students' ethnic backgrounds. METHOD: A total of 71 students completed a health-beliefs communication OSCE station in which they were required to address the health beliefs and cultural concerns of a standardized patient (SP) portraying an African American woman with diabetes. The SPs rated students' performances on a ten-item interview assessment checklist. Scores on the station were standardized within SPs to adjust for differences in their use of the rating scale. A factor analysis was performed to determine conceptual constructs on the interview assessment checklist. Subscale means were computed for each student. T-tests of these subscale scores were conducted to investigate gender and ethnic differences between subgroups of students. The underrepresented minority (URM) students (five African Americans and three Mexican Americans) were compared with all other students, and the white students were compared with all others. To assess the magnitudes of the differences between subgroups, effect sizes (ES(m)) were computed for means comparisons. RESULTS: Factor analysis formed two factors: Disease Beliefs and Management, and Cultural Concerns. Two remaining items loaded on a third factor that had reliability too low to support further analysis. Meaningful differences were found in cultural sensitivity based on students' ethnic backgrounds. The URM students performed better than did all other students in addressing the patient's concerns about altering culturally-based dietary behaviors for diabetes self-care [URM students' mean standardized score (SD) = 0.42 (0.15); all others = -0.01 (0.67); ES(m) = 1.05]. White students performed better than did all other students in assessing the patient's concerns about using insulin to control her blood sugar levels [white students' mean standardized score (SD) = 0.13 (0.40); all others = -0.10 (0.64); ES(m) = 0.4]. CONCLUSION: Cultural competency deficits and differences were measurable using a health-beliefs communications station, and these differences were meaningful enough to warrant faculty discussion and research about how to ensure that students master this competency.

Medical students' self-assessments and their allocations of learning time.

PURPOSE: To investigate the impact of self-assessed diagnostic strengths and weaknesses on medical students' allocation of learning time (one indicator of self-directed learning) during a third-year internal medicine clerkship. METHOD: In 1997-98, 107 students at the University of Michigan Medical School self-assessed their diagnostic skills in 14 clinical areas before and after the clerkship and reported the relative amounts of time spent learning about these topics during the clerkship. RESULTS: Individual-level analyses indicated that, for the average student, self-assessed strengths and weaknesses did not correlate with allocation of educational time, but that time allocation was positively related to changes in self-assessed skill. Considerable variations in these relationships, however, suggest a need for closer study. CONCLUSION: Although individual students evidenced different levels of self-directed learning, this study suggests overall that students at this level of training are neophytes in applying both information generated through self-assessment and principles of self-directed learning in their clinical education. Attempts to advance students beyond this level depend on many factors, including the extent to which the learning environment encourages or even permits self-directed learning, the progression and time frame through which students become self-directed practitioners, and the impact of educational interventions to promote this development.

Is there a relationship between attending physicians' and residents' teaching skills and students' examination scores?

PURPOSE: Faculty development programs and faculty incentive systems have heightened the need to validate a connection between the quality of teaching and students' learning. This study was designed to determine the association between attending physicians' and residents' teacher ratings and their students' examination scores. METHOD: From a database of 362 students, 138 faculty, and 107 residents in internal medicine, student-faculty (n = 476) and student-resident (n = 474) pairs were identified. All students were in their third year, rotating on inpatient general medicine and cardiology services, July 1994 through June 1996, at a single institution. The outcome measure for students' knowledge was the NBME Subject Examination in internal medicine. To control for students' baseline knowledge, the predictors were scores on the USMLE Step 1 and a sequential examination (a clinically-based pre- and post-clerkship examination). Teaching abilities of faculty and residents were rated by a global item on the post-clerkship evaluation. Faculty's ratings used only scores from prior to the study period; residents' ratings included those scores students gave during the study period. RESULTS: Multivariate analyses showed faculty's teaching ratings were a small but significant predictor of the increase in students' knowledge. Residents' teaching ratings did not predict an increase in students' knowledge. CONCLUSION: Attending faculty's clinical teaching ability has a positive and significant effect on medical students' learning.

Educational interventions for asthma in children.

BACKGROUND: Self-management education programs have been developed for children with asthma, but it is unclear whether such programs improve outcomes. OBJECTIVES: To determine the efficacy of asthma self-management education on health outcomes in children. SEARCH STRATEGY: Systematic search of the Cochrane Airways Group's and Cochrane Schizophrenia Group's Special Registers of Controlled Trials and hand searches of the reference lists of relevant review articles. SELECTION CRITERIA: Randomized and controlled clinical trials of asthma self-management education programs in children and adolescents aged 2 -18 years. DATA COLLECTION AND ANALYSIS: All studies were assessed independently by two reviewers. Disagreements were settled by consensus. Study authors were contacted for missing data or to verify methods. Subgroup analyses examined the impact of type and intensity of educational intervention, self-management strategy, trial type, asthma severity, adequacy of follow-up, and study quality. MAIN RESULTS: Of 45 trials identified, 32 studies involving 3706 patients were eligible. Asthma education programs were associated with moderate improvement in measures of airflow (standardized mean difference [SMD] 0.50, 95% confidence interval [CI] 0.25 to 0.75) and self-efficacy scales (SMD 0.36, 95% CI 0.15 to 0.57). Education programs were associated with modest reductions in days of school absence (SMD -0.14, 95% CI -0.23 to -0.04), days of restricted activity (SMD -0.29, 95% CI -0.49 to -0.08), and emergency room visits (SMD -0.21, 95% CI -0.33 to -0.09). There was a reduction in nights disturbed by asthma when pooled using a fixed-effects but not a random-effects model. Effects of education were greater for most outcomes in moderate-severe, compared with mild-moderate asthma, and among studies employing peak flow versus symptom-based strategies. Effects were evident within the first 6 months, but for measures of morbidity and health care utilization, were more evident by 12 months. REVIEWER'S CONCLUSIONS: Asthma self-management education programs in children improve a wide range of measures of outcome. Self-management education directed to prevention and management of attacks should be be incorporated into routine asthma care. Conclusions about the relative effectiveness of the various components are limited by the lack of direct comparisons. Future trials of asthma education programs should focus on morbidity and functional status outcomes, including quality of life, and involve direct comparisons of the various components of interventions.

Comparison of resident and medical student evaluation of faculty teaching.

Recognizing and rewarding teaching faculty are increasingly important to medical schools and are often hampered by low perceived reliability and validity of measures of teaching ability. The purpose of this study was to cross-validate two independently generated measures of teaching from medical students and residents. A total of 2,318 medical student and 4,425 resident scores for single-item measures of teaching ability for 129 teaching faculty members of a department of internal medicine over a 6-year period were compared. Results showed that average teaching scores were higher for medical students than residents. Rank order of faculty were within 2 quintiles for the two groups for over 90% of faculty. Highly discordant evaluations were seen for only 8% of faculty. The authors conclude the general concordance of two independent measures of teaching ability adds evidence to the existing literature of the validity of single-item measures of teaching ability from two different types of learners.