Restrictive lung function and asbestos-induced pleural fibrosis. A quantitative approach.

To assess further the clinical significance of asbestos-induced pleural fibrosis, we used a computer algorithm to reconstruct images three dimensionally from the high-resolution computerized tomography (HRCT) scan of the chest in 60 asbestos-exposed subjects. Pulmonary function tests, chest radiographs, and HRCT scans were performed on all study subjects. The volume of asbestos-induced pleural fibrosis was computed from the three-dimensional reconstruction of the HRCT scan. Among those with pleural fibrosis identified on the HRCT scan (n = 29), the volume of the pleural lesion varied from 0.01% (0.5 ml) and 7.11% (260.4 ml) of the total chest cavity. To investigate the relationship between asbestos-induced pleural fibrosis and restrictive lung function, we compared the computer-derived estimate of pleural fibrosis to the total lung capacity and found that these measures were inversely related (r = -0.40; P = 0.002). After controlling for age, height, pack-years of cigarette smoking, and the presence of interstitial fibrosis on the chest radiograph, the volume of pleural fibrosis identified on the three-dimensional reconstructed image from the HRCT scan was inversely associated with the total lung capacity (P = 0.03) and independently accounted for 9.5% of the variance of this measure of lung volume. These findings further extend the scientific data supporting an independent association between pleural fibrosis and restrictive lung function.

Normal diffusing capacity in patients with PiZ alpha(1)-antitrypsin deficiency, severe airflow obstruction, and significant radiographic emphysema.

alpha(1)-Antitrypsin deficiency is usually suspected clinically in young adults with irreversible airflow obstruction that is out of proportion to their smoking history. Many patients with alpha(1)-antitrypsin deficiency receive an initial diagnosis of asthma or chronic bronchitis. Measurement of the diffusing capacity of the lung for carbon monoxide (DLCO) has been recommended as a way to help distinguish emphysema from asthma and chronic bronchitis. In this article, we describe four patients with severe alpha(1)-antitrypsin deficiency, each of whom had a repeatedly normal DLCO despite having a significant component of fixed airway obstruction and prominent panacinar emphysema on high-resolution CT scan (HRCT). Each patient also demonstrated significant bronchodilator responsiveness, and two patients received an initial diagnosis of asthma. Potential explanations for these findings are discussed. We report these findings to illustrate the limitations of DLCO in this setting. alpha(1)-Antitrypsin deficiency should be considered in patients with fixed airway obstruction that is out of proportion to their age and smoking history, regardless of their diffusing capacity and response to bronchodilators.

Pulmonary embolization and infarction. An iatrogenic complication of transcatheter embolization of a cerebral arteriovenous malformation with polyvinyl alcohol sponge.

Transcatheter embolization therapy of vascular abnormalities is a well-accepted technique. It is particularly useful in the preoperative management of cerebral arteriovenous malformations, in which the risk of significant hemorrhage at surgery would otherwise be unacceptably high. A patient developed symptomatic pulmonary emboli and infarction following an uneventful embolization using polyvinyl alcohol particles. The authors believe this to be the first reported case of this complication of embolic therapy using polyvinyl alcohol.

High-resolution ultrafast chest CT in the clinical management of febrile bone marrow transplant patients with normal or nonspecific chest roentgenograms.

Plain chest roentgenograms may be normal or show nonspecific abnormalities during the frequent febrile episodes that occur in patients after bone marrow transplantation. In this group, ultrafast 10-mm and 3-mm high-resolution CT scans were prospectively performed in 33 patients to determine if useful information was provided that either changed the patient's clinical management or added confidence to the clinical diagnosis. The 36 symptomatic episodes that occurred in 33 patients included fever in 20 episodes and fever combined with cough, dyspnea, chest pain, or rales in 16. Fourteen chest roentgenograms were interpreted as normal, and 22 were interpreted as demonstrating nonspecific changes; however, none of the roentgenograms was considered helpful in that they did not provide sufficient information for further management. In 2 of 14 episodes in patients with normal chest roentgenograms and in 9 of 22 episodes in patients with nonspecific chest roentgenograms, CT scanning resulted in a change in clinical management that included performing bronchoscopy, increasing or changing antibiotic coverage, starting white blood cell transfusions, requesting surgical biopsy, or a combination of these. In 1 of 14 episodes in patients with normal chest roentgenograms and in 8 of 22 episodes in patients with nonspecific roentgenograms, CT added confidence to the diagnosis. In the remaining 16 episodes, CT scans provided no additional information. We conclude that in many instances, noncontrast ultrafast chest CT scans can provide information that may either change a patient's clinical management or more clearly establish the extent of pulmonary disease.

Realizing the promise: delivering pulmonary continuing medical education over the Internet.

STUDY OBJECTIVES: Continuing medical education (CME) is meant to bridge the gap between new scientific observations and clinical practice. However, traditional CME has not been effective at altering the behaviors of physicians. One reason for this failure of traditional CME programs may be their inflexibility. In traditional CME, the clinician does not choose the topic, the pace of the program, or the place of learning, and the CME material cannot be easily delivered to the point of care where the clinician needs the information. Computers and computer networks have the potential to accomplish these goals. CME has begun to appear on the Internet; however, there have been few evaluations of its usefulness, acceptance, and effectiveness. Over the last 18 months, we have developed three on-line pulmonary CME programs, and we have delivered them on the Virtual Hospital, the University of Iowa's digital health sciences library on the Internet. We report our initial experience with this CME material. DESIGN: We measured the frequency with which the Internet-delivered CME is accessed by monitoring page accessions and by using a log file analysis program (Analog 1.2.3; University of Cambridge Statistical Laboratory; Cambridge, UK). In addition, we collected all completed CME examinations and evaluation forms submitted by registered users. MEASUREMENTS AND RESULTS: We have found that the frequency with which the Internet-delivered CME is accessed has continued to increase with time (2.3-fold increase over 18 months), that evaluations of technical and content issues are strongly favorable, and that some clinicians have been willing to pay to receive CME through the medium of the Internet. CONCLUSIONS: We feel that with adequate peer review and quality control, physicians will use the Internet-delivered CME. However, several obstacles to wide use remain. These obstacles include issues regarding training in using the Internet for physicians, reluctance of physicians to participate in on-line commerce, and the current unavailability of CME to be delivered in small-grained quantities to the point of care. As these issues are addressed, we feel that on-line CME will represent an increasingly important CME medium for clinicians.

Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population.

To further define the relationship between asbestos-induced pleural fibrosis and restrictive lung function, we investigated the pleural determinants of respiratory symptoms and restrictive physiology in 1,211 sheet metal workers. We evaluated the relationship between specific components of pleural fibrosis (costophrenic angle involvement, diaphragmatic plaques, width and length of pleural fibrosis, pleural calcification, and the type of fibrosis-circumscribed plaque or diffuse pleural thickening) and both forced vital capacity and respiratory symptoms. We found that costophrenic angle involvement, the width and length of pleural fibrosis, and the presence of either circumscribed plaque or diffuse pleural thickening were each significantly associated with a lower FVC. No consistent relationship was observed between FVC and either diaphragmatic plaques or pleural calcification. However, since the pleural abnormalities were highly collinear, none of these abnormalities alone or in combination predicted the reduction in FVC significantly better than a model that included circumscribed plaques and diffuse pleural thickening. We also investigated the relationship of each component of pleural fibrosis with cough, dyspnea, and chest pain. After controlling for appropriate confounders, a trend toward significance was observed between increased width and length of fibrosis and dyspnea with exertion. Otherwise, these pleural abnormalities were not consistently related to any of the three respiratory symptoms. Our results indicate that although pleural plaques and diffuse pleural thickening and their components are independently associated with a lower FVC, these components of pleural fibrosis do not substantially improve the previously defined relationship between FVC and both circumscribed plaques and diffuse pleural thickening. In addition, a trend toward significance was observed between the width and length of the pleural abnormality and dyspnea while hurrying.

The relationship between HLA-A, B, DQ, and DR antigens and asbestos-induced lung disease.

To evaluate the relationship between human leukocyte antigen (HLA) and both asbestos-induced pulmonary fibrosis and pleural fibrosis, we obtained HLA-A, B, C, DQ, and DR phenotypes in 42 long-term asbestos-exposed workers. Among these exposed workers, 15 had asbestosis (ILO > or = 1/0) on the chest radiograph and 18 had asbestos-induced pleural fibrosis. We found that there was an increased percentage of HLA-A29, HLA-B44, and HLA-Bw4 in the subjects with asbestosis. In addition, we observed a marginally positive relationship between HLA-A29 and the severity of pulmonary fibrosis. Similarly, there was a higher prevalence of HLA-DRw53 and DQ2 in the subjects with asbestos-induced pleural fibrosis. The presence of HLA-DQ2 was significantly related to the extent and type of asbestos-induced pleural fibrosis while HLA-DRw53 was not consistently related to the type or extent of pleural disease. Importantly, we observed that HLA-A29, HLA-B44, HLA-Bw4, HLA-DRw53, and HLA-DQ2 do not have a significantly shorter duration or latency of asbestos exposure. Moreover, none of the HLA haplotypes (A29, B44, Bw4, DRw53, and DQ2) that we found to be associated with radiographic manifestations of asbestos-induced lung disease were associated with the physiologic abnormalities that have been traditionally associated with asbestos-induced lung disease. The only exception was an isolated decrease in the residual volume associated with the presence of HLA-A29. These results suggest that the HLA-A29 phenotype may be associated with the development of asbestosis and the HLA-DQ2 phenotype may be associated with the development of asbestos-induced pleural fibrosis. However, these associations are not particularly strong, physiologic correlation is lacking, and previous studies do not support our findings.

Asbestos-induced pleural fibrosis and impaired exercise physiology.

To further assess the clinical significance of asbestos-induced pleural fibrosis, we performed cardiopulmonary exercise testing in 90 subjects who were exposed to asbestos. Of the 82 subjects without an abnormal resperate exercise, 35 had normal pleura, 33 had circumscribed pleural plaques, and 14 had diffuse pleural thickening. Interstitial fibrosis (International Labor Organization [ILO]. > or = 1/10) was present in 14 of 35 subjects with normal pleura, 13 of 33 subjects with circumscribed pleural plaques, and 2 of 14 subjects with diffuse pleural thickening. Although pleural fibrosis did not appear to be related to impaired respiratory function with exercise in our entire cohort, this finding was confounded by a higher proportion of interstitial fibrosis in subjects with normal pleura. In fact, among study subjects without asbestosis, significant decreases in gas exchange (higher VD/VT and increased alveolar-arterial oxygen pressure difference) were observed at maximal exercise among subjects with pleural fibrosis. Interestingly, neither a higher respiratory rate nor a lower VT/FVC ratio was observed among those with pleural fibrosis, suggesting that the mechanical effects of pleural fibrosis on the chest wall do not explain the increased VD/VT. Using multivariate analyses to control for potential confounders, regression models showed that pleural plaques (p = 0.04) and diffuse pleural thickening (p = 0.03) were independently associated with significant increases in dead space ventilation (VD/VT) with maximal exercise. These findings indicate that asbestos-induced pleural fibrosis is independently associated with decrements in gas exchange with maximal exercise and suggest that interstitial lung disease, not detected on the routine chest x-ray film, may be responsible for this abnormal response to exercise.

Ultrafast computed tomography in experimental pulmonary embolism.

Computed tomography (CT) has proven useful in the diagnosis of central pulmonary embolism; however, its ability to detect peripheral emboli has not been established. The authors evaluate the usefulness of ultrafast CT (UFCT) in detecting experimental peripheral pulmonary emboli. Three Gelfoam emboli measuring 0.7 x 1.5 cm were introduced into the pulmonary arteries of each of seven dogs, and contiguous, 3-mm, axial UFCT images from the lung apex to the base were obtained after the administration of a contrast bolus. After scanning, the dogs were killed, and the locations of the emboli were determined by a pulmonary pathologist blinded to the imaging results. Concomitantly, the locations of the emboli on the UFCT images were determined by consensus of three chest radiologists blinded to the autopsy results. All 21 emboli were identified on UFCT images; the locations of the emboli corresponded exactly with the autopsy findings. The authors conclude that UFCT can reliably detect Gelfoam emboli in second- to fourth-division pulmonary vessels. Further studies are needed to determine if in vivo blood clots can be similarly visualized.

Contrast-enhanced thin slice ultrafast computed tomography for the detection of small pulmonary emboli. Studies using autologous emboli in the pig.

RATIONALE AND OBJECTIVES: Ultrafast computed tomography (UFCT) has proven useful, but is of limited practical application in the diagnosis of central pulmonary embolism; however, its ability to detect more peripheral emboli has not been established. In this study, the use of contrast-enhanced UFCT images for the detection of autologous peripheral pulmonary emboli in the pig is evaluated. METHODS: A single autologous embolus measuring 0.7 x 1.5 cm was introduced into the superior vena cava of eight pigs. Contiguous, 3-mm axial UFCT images from the lung apex to the base were obtained before and after the introduction of the embolus. After scanning, the pigs were killed, and the thorax was removed intact and was frozen in a dry ice-alcohol mixture. Later, the thorax was sliced at 10-mm thicknesses, and the locations of the emboli were determined by a pulmonary pathologist blinded to the imaging results. Concomitantly, the locations of the emboli were determined by consensus of three chest radiologists blinded to the autopsy results. RESULTS: In 6 of 8 animals with emboli, the embolus location correlated exactly with the autopsy findings. In one, the embolus was on the same side, but 1.6 cm further distal. In the other, a marking suture was identified, but no clot was identified on the pathologic or UFCT examination. In the eight animals scanned before the introduction of the embolus, no embolus was found. Interobserver agreement was 100%. CONCLUSIONS: Ultrafast computed tomography has the potential to detect autologous emboli in second- to fourth-division pulmonary vessels. Further studies are needed to determine if in vivo emboli can be similarly visualized.

The instructional effectiveness of a radiology multimedia textbook (HyperLung) versus a standard lecture.

RATIONALE AND OBJECTIVES: Information overload is a significant problem for the modern radiologist. This prospective study compares the instructional effectiveness of a multimedia textbook (HyperLung) with a lecture. HyperLung is a radiologic multimedia textbook about imaging diffuse lung disease created using a multimedia authoring tool, the Annotator (the University of Iowa Second Look Computing, Iowa City, IA), on the Apple Macintosh computer (Apple Computer, Cupertino, CA). METHODS: Forty-nine staff physicians and residents in the Department of Radiology were randomized to receive instruction either by HyperLung or by a lecture. The instructional content was the same in both groups, and both groups were tested before and after instruction. The actual time spent in each instructional situation was recorded. RESULTS: The instructional effectiveness of the multimedia textbook and lecture was equal. The instructional efficiency of HyperLung was only 60% of the lecture. Users of the multimedia textbook found it enjoyable and straightforward to use. CONCLUSIONS: Multimedia textbooks have a promising future in radiology education.

Time course of satisfaction of search.

"Satisfaction of search" (SOS) refers to the effect in which a second lesion remains undetected after detection of another lesion on the same radiograph. The objective of this study was to clarify our understanding of SOS by relating it to total time of inspection and time intervals before, between, and after discovery of lesions. Detection accuracy of native lesions in chest radiographs, before and after the addition of a simulated nodular lesion, was measured for ten observers. Analysis of data from this and a previous experiment showed that average perceptual accuracy of individual receiver operating characteristic curves was significantly reduced with the addition of the nodules. Plots and analyses of search time revealed that, on average, during a typical 46-second inspection of a case, simulated nodules were found at 18 seconds, native abnormalities at 25 seconds, and false positives occurred at 33 seconds. Time needed to find nodules did not depend on whether native lesions were present; time to find native lesions did not change with addition of nodules; and total search time was the same for images with one, two, or no lesions. The detection results show that the SOS effect was obtained, but that interrupting search in order to measure it also diminishes accuracy. Analysis of the time course data relates SOS to perceptual capture and strategic halting of search.

The multimedia textbook. A revolutionary tool for pediatric education.

Textbooks are now available via computers. These new electronic or multimedia textbooks appears similar to conventional books but differ in function. In addition to text and images, they contain video and audio clips and allow readers to interact with the content. Multimedia textbooks contain digital media, can be quickly and inexpensively updated and repurposed for lectures and handouts, and are available on-line via computer networks for distance learning. We present the concept of computer-generated multimedia text-books; describe their creation by an easy-to-use, sophisticated authoring system; and describe the underlying instructional design approach to guide future authors of multimedia textbooks.

A comparison of educational interventions. Multimedia textbook, standard lecture, and printed textbook.

OBJECTIVE: To compare the instructional effectiveness and efficiency of a pediatric multimedia textbook (MMTB) with that of a standard lecture and of a printed textbook in a prospective, interinstitutional study. DESIGN: Randomized, prospective cohort. SETTINGS: An urban and a rural medical school affiliated with tertiary care hospitals. POPULATION: Third- and fourth-year medical students from June 1992 to June 1993. INTERVENTIONS/OUTCOME MEASURES: Students were randomized to one of four treatment groups: (1) computer-aided instruction with MMTBs (n = 39), (2) traditional lecture (n = 39), (3) printed textbook (n = 39), or (4) a control group (n = 62). Only the control group was pretested. Following their randomized instruction, all groups were tested via a 26-question multiple-choice test. Statistical analysis was accomplished by analysis of variance of mean post-test scores. The amount of time that students spent with each educational intervention was recorded. RESULTS: Three hundred two students were eligible for the study, 267 entered the study, and 179 completed the study. The instructional effectiveness of the MMTB was greater than that of the lecture (P < .05), and it was the same as that of the printed textbook. All instructional methods were more effective than the control group (P < .05). The instructional efficiency of the MMTB was equal to that of the lecture and of the printed textbook. The subjective response to the MMTB instruction was positive. CONCLUSION: The MMTBs constitute an educationally sound alternative instructional method and have a promising future in medical education.

Solutions to challenges facing a university digital library and press.

During the creation of a university digital library and press intended to serve as a medical reference and education tool for health care providers and their patients, six distinct and complex digital publishing challenges were encountered. Over nine years, through a multidisciplinary approach, solutions were devised to the challenges of digital content ownership, management, mirroring, translation, interactions with users, and archiving. The result is a unique, author-owned, internationally mirrored, university digital library and press that serves as an authoritative medical reference and education tool for users around the world. The purpose of this paper is to share the valuable digital publishing lessons learned and outline the challenges facing university digital libraries and presses.

High-resolution CT-derived measures of lung density are valid indexes of interstitial lung disease.

To assess the validity of computer-assisted methods in analyzing the lung parenchyma imaged with high-resolution computed tomography (HRCT), we compared computer-derived estimates of lung density to other, more traditional, measures of parenchymal injury in 24 subjects with idiopathic pulmonary fibrosis (IPF) and 60 subjects with extensive occupational exposure to asbestos. Gray scale density histograms were constructed from the HRCT images. The gray scale histogram of both study groups was of a skewed unimodal distribution. However, compared with the asbestos-exposed subjects, the patients with IPF had a gray scale distribution that was significantly shifted to the right (greater density) and flatter. In a multivariate analysis, after controlling for age and cigarette smoking, we found that the mean and median gray scale densities were independently associated with the presence of moderate-to-severe dyspnea, a higher International Labour Office chest X-ray category, a lower forced vital capacity, and a higher concentration of macrophages and eosinophils in the bronchoalveolar lavage fluid. These factors accounted for > 70% of the variance of the mean and median gray scale densities. Interestingly, no differences in gray scale density measures were noted between patients with IPF and patients with asbestosis when these other factors were taken into account. Our results suggest that computer-derived density analysis of the lung parenchyma on the HRCT scan is a valid, clinically meaningful, and objective measure of interstitial lung disease.

Determinants of restrictive lung function in asbestos-induced pleural fibrosis.

We evaluated whether restrictive lung function among asbestos-exposed individuals with pleural fibrosis was caused by radiographically inapparent parenchymal inflammation and/or parenchymal fibrosis. All 24 study participants were sheet metal workers who were nonsmokers with normal parenchyma on posteroanterior chest radiograph. These subjects had either normal pleura (n = 7), circumscribed plaques (n = 9), or diffuse pleural thickening (n = 8). After controlling for age, years in the trade, and pack-years of smoking, we found that sheet metal workers with diffuse pleural thickening had a lower forced vital capacity (P less than 0.001), total lung capacity (P less than 0.01), and CO-diffusing capacity of the lung (P less than 0.05) than those with normal pleura. Similarly, sheet metal workers with circumscribed plaques were found to have a reduced forced vital capacity; however, because of the small number of study subjects, this difference (regression coefficient = -11.0) was only marginally significant (P = 0.06). Although circumscribed plaque and diffuse pleural thickening were both associated with a lymphocytic alveolitis and a higher prevalence of parenchymal fibrosis on high-resolution computerized tomography (HRCT) scan, neither a lymphocytic alveolitis nor the finding of parenchymal fibrosis on HRCT scan influenced the relationship between pleural fibrosis and restrictive lung function. We conclude that pleural fibrosis is associated with restrictive lung function and abnormally low diffusion that appears to be independent of our measures of parenchymal injury (chest X-ray, bronchoalveolar lavage, and HRCT scan).(ABSTRACT TRUNCATED AT 250 WORDS)

Electron beam computed tomography: use in pulmonary embolectomy.

Proximal chronic pulmonary emboli with severe pulmonary hypertension were diagnosed by electron-beam computed tomography and Doppler echocardiography. After successful embolectomy, repeat examinations showed normal pulmonary artery pressures and patency. Electron beam computed tomography can noninvasively identify surgically treatable pulmonary emboli.

Ultrafast computed tomography of the chest.

Improvements in scan speed and resolution are changing the role of the pulmonary imager. An understanding of airway mechanics and blood flow physiology is required to take full advantage of the new technology. Assessment of regional airflow and blood flow provides information that is currently unavailable from clinical tools.

The diagnosis of bronchiectasis.

Antibiotics and childhood immunizations have made bronchiectasis a relatively rare disease. The diagnostic imaging modality of choice is computerized tomography using 4-mm sections and 5-mm intervals. Bronchography is only indicated in cases where surgical resection is contemplated. Utilizing these imaging modalities, the pulmonary internist should have little difficulty in diagnosing bronchiectasis and initiating appropriate treatment.