Olfactory sensitivity of rats with transection of the lateral olfactory tract.

Rats with discrete transection of the lateral olfactory tract (LOT) were tested using operant conditioning and psychophysical methods for their amyl acetate intensity difference threshold and absolute detection threshold. Experimental rats performed as well as controls on the easiest problems of both threshold series but their intensity difference threshold was approximately 2.5 times as high as controls and their absolute detection threshold was approximately 2.25 orders of magnitude higher than controls. The deficit in sensitivity in both tests was related to the frontal level at which the tract was cut; rats with the most rostral transection had the greatest increase in threshold. The absolute detection threshold of rats with transection of the LOT was increased to that of normal human subjects tested with the same apparatus.

Olfactory pathways and the sense of smell.

Rats were trained using operant conditioning to detect isoamyl acetate vapor generated by an olfactometer. They received lesions of olfactory pathways and were tested for retention of the odor detection task and trained on two-odor tasks. Deficits in odor detection and two-odor discrimination were related to the extent to which lesions disconnected the olfactory bulb from the forebrain. Transection of only the lateral olfactory tract, only the anterior limb of the anterior commissure, or lesions of the olfactory tubercle had little effect but combined lesions of these structures produced severe deficits in both odor detection and discrimination. Only rats with almost complete transection of the olfactory peduncle or cortex were anosmic; those with transections that spared a small segment of tissue between the olfactory bulb and olfactory cortex had detectable olfactory function. The results are discussed with regard to efferent connections of the olfactory bulb.

Suspected pulmonary embolism and lung scan interpretation: trial of a Bayesian reporting method.

OBJECTIVE: To determine whether a Bayesian method of lung scan (LS) reporting could influence the management of patients with suspected pulmonary embolism (PE). DESIGN: 1) A descriptive study of the diagnostic process for suspected PE using the new reporting method; 2) a non-experimental evaluation of the reporting method comparing prospective patients and historical controls; and 3) a survey of physicians' reactions to the reporting innovation. SETTING: University of Virginia Hospital. PATIENTS: Of 148 consecutive patients enrolled at the time of LS, 129 were completely evaluated; 75 patients scanned the previous year served as controls. INTERVENTION: The LS results of patients with suspected PE were reported as posttest probabilities of PE calculated from physician-provided pretest probabilities and the likelihood ratios for PE of LS interpretations. RESULTS: Despite the Bayesian intervention, the confirmation or exclusion of PE was often based on inconclusive evidence. PE was considered by the clinician to be ruled out in 98% of patients with posttest probabilities less than 25% and ruled in for 95% of patients with posttest probabilities greater than 75%. Prospective patients and historical controls were similar in terms of tests ordered after the LS (e.g., pulmonary angiography). Patients with intermediate or indeterminate lung scan results had the highest proportion of subsequent testing. Most physicians (80%) found the reporting innovation to be helpful, either because it confirmed clinical judgement (94 cases) or because it led to additional testing (7 cases). CONCLUSIONS: Despite the probabilistic guidance provided by the study, the diagnosis of PE was often neither clearly established nor excluded. While physicians appreciated the innovation and were not confused by the terminology, their clinical decision making was not clearly enhanced.

Plasma DNA. A simple, rapid test for aiding the diagnosis of pulmonary embolism.

Previously, we reported that the sensitivity of plasma DNA for patients with pulmonary emboli was 83 to 88 percent. To confirm these findings in a more comprehensive study, we collected plasma samples from 137 consecutive patients undergoing 148 ventilation-perfusion lung scans for pulmonary embolism. DNA was measured using a counter-immunoelectrophoresis technique that used high titer precipitating double-stranded DNA antibody from a patient with systemic lupus erythematosus. In addition to 17 patients (17 lung scans) excluded for not having plasma collected, 32 patients (37 lung scans) were excluded for having either a condition other than pulmonary embolism that could be associated with plasma DNA or for having nonacute symptoms. Eighteen of 22 patients with a diagnosis of pulmonary embolism (defined by either a high probability lung scan or abnormal pulmonary angiogram) had detectable plasma DNA. Only four of 27 patients without pulmonary embolism (defined by either a normal lung scan or normal pulmonary angiogram) had plasma DNA detected. Based on these results, plasma DNA had a sensitivity of 82 percent and a specificity of 85 percent for this condition. Plasma DNA is a promising test for pulmonary embolism and could help physicians interpret equivocal lung scan findings and thereby clarify difficult decisions such as the need for pulmonary angiography.

Incidence of 24-hour faculty coverage in teaching EDs.

There is growing concern in academic emergency medicine as to the appropriateness of 24-hour faculty coverage in the teaching emergency department. We surveyed 170 teaching emergency departments, 49 of which had approved emergency medicine residencies, asking for information regarding 24-hour faculty coverage. We were able to separate each department into one of 15 profiles based on the two variables of average ED yearly census and hospital type. Seventy-three percent of university teaching hospital EDs and 65% of those with emergency medicine residencies have 24-hour faculty coverage; 83% of private teaching hospital EDs and 100% of those with emergency medicine residencies have 24-hour faculty coverage; and 79% of city/county teaching hospital EDs and 80% of those with emergency medicine residencies have 24-hour faculty coverage.