Biomedical subjects
Publications and source records attributed to W R Webb.
We report details of a neonate with cranial bone dysplasia, broad nasal bridge, microphthalmia, optic and olfactory nerve anomalies, pulmonary segmentation defects, polydactyly, abnormally positioned and shaped thumbs, absent mesentery to the gut and streak gonads. Review of the literature and relevant databases does not identify a likely diagnosis.
Although high-resolution CT scan has proved most useful in the diagnosis of infiltrative lung disease, its use in the diagnosis of airway and obstructive lung diseases has recently been emphasized. In particular, the use of dynamic expiratory or postexpiratory CT scans, usually in combination with an inspiratory high-resolution CT scan study, has proved useful in the diagnosis and assessment of obstructive lung diseases. This article reviews the use of expiratory CT scan in the diagnosis of lung disease, including the various CT scan techniques that can be used, normal and abnormal expiratory CT scan findings, and the use of expiratory CT scan in a variety of obstructive diseases.
Expandable metallic stents offer advantages over previously available techniques for treating benign tracheobronchial stenosis or obstruction. Endoluminal stent placement offers a rapid and effective means of opening up narrowed airways, and results in excellent relief of symptoms and improvement in pulmonary function. Because they are delivered in a nonexpanded state using flexible over-wire systems, they can be placed using a flexible bronchoscope and can be located in second-order bronchial branches. Metallic stents have been used to treat benign airway obstruction caused by anastomotic narrowing after lung transplantation, infection, congenital lesions, tracheobronchial malacia, inflammatory conditions including relapsing polychondritis, Wegener granulomatosis, and acquired immunodeficiency syndrome, and external compression from benign mediastinal masses or fibrosis. The stents become epithelialized, which prevents migration and permits ciliary activity to continue. Significant complications can occur, including airway inflammation, stent migration, airway erosion, and stent fracture and collapse, but more serious complications are uncommon. Computed tomography is essential in imaging patients being considered for stent placement, as it allows 1) accurate representation of airway anatomy in three dimensions. 2) measurement of airway diameter, 3) evaluation of airway anatomy distal to a narrowed segment and invisible to bronchoscopy, 4) demonstration of dynamic changes in airway morphologic features during forced exhalation in patients with airway malacia, and 5) demonstration of focal or diffuse air trapping in lung peripheral to the abnormal airway. In patients who have had stent placement, computed tomography is valuable in assessing airway morphologic features and dynamics distal to the stent, and can be valuable in assessing stent dysfunction.
The authors assess the utility of postexpiratory high-resolution computed tomography (HRCT) scans in the evaluation of air trapping in patients with obstructive lung disease. Thirteen healthy volunteers and 14 patients with obstructive lung disease (OLD) were examined using inspiratory and postexpiratory HRCT scans. All had pulmonary function tests. Lung attenuation was measured on both inspiration and expiration, and the extent of air trapping on postexpiratory scans was visually assessed. The results of the healthy volunteers were compared with those of patients with OLD, and HRCT findings were correlated with pulmonary function tests. Lung attenuation on expiration, its change from inspiration to expiration, and air-trapping scores of patients with OLD were significantly different from those of the healthy volunteers. When the healthy participants and patients with OLD were combined and analyzed as one group, the lung attenuation change and air-trapping score both significantly correlated with pulmonary function tests (p < 0.001) and correlation values were similar (r = 0.61-0.89). Air trapping was found in 61% of healthy participants and all the patients with OLD, although the extent was significantly greater in the patients with OLD. Inspiratory and postexpiratory HRCT can be used to evaluate air trapping in patients with OLD. Measurements of lung attenuation and estimates of air-trapping extent are both valuable methods of analysis.
PURPOSE: To determine the utility of expiratory scans for diagnosis of inhomogeneous attenuation on thin-section computed tomographic (CT) scans. MATERIALS AND METHODS: On the basis of clinical information and pulmonary function test results, disease in 53 patients with inhomogeneous attenuation on inspiratory scans was classified into four groups--infiltrative, airway, vascular, or mixed. Without knowledge of the diagnosis, inhomogeneous attenuation was classified as (a) ground-glass opacity due to infiltrative disease, (b) mosaic perfusion due to airway disease, or (c) mosaic perfusion due to vascular disease, and the degree of confidence was indicated. Each case was reclassified if necessary on the basis of expiratory scan findings. RESULTS: A correct diagnosis was made more often on the basis of both inspiratory and expiratory scans than on the basis of inspiratory scans alone (92% [49 of 53 patients] vs 79% [42 of 53], respectively [P < .05]). Accuracy increased from 81% (21 of 26) to 89% (23 of 26) in cases of infiltrative disease and from 84% (16 of 19) to 100% (19 of 19) in cases of airway disease. A correct interpretation with high confidence level was reached more often with expiratory scans than on the basis of inspiratory scans alone (92% [49 of 53] vs 45% [24 of 53], respectively [P < .0001]). The extent of air trapping correlated significantly with pulmonary function test results. With expiratory scans, the classification of inhomogeneous attenuation was changed in 15% (eight of 53) of cases and the confidence level was improved in 51% (27 of 53) (P < .0001). CONCLUSION: Expiratory scans significantly improved diagnostic accuracy in patients with inhomogeneous attenuation on inspiratory scans, and they helped in the diagnosis of diffuse lung disease.
OBJECTIVE: We wish to describe the differential diagnosis and pulmonary function correlates of patients with normal findings on inspiratory high-resolution CT (HRCT) scans who showed air trapping on expiratory scans. MATERIALS AND METHODS: HRCT scans in 273 consecutive patients with suspected diffuse lung disease were reviewed. HRCT consisted of inspiratory scans at 1- to 2-cm intervals and expiratory scans at three levels. Studies considered to show expiratory air trapping were divided into two groups, one having normal findings on inspiratory scans and one having abnormal findings on inspiratory scans. Pulmonary function test results in these groups were compared with a group of patients who had normal findings on inspiratory and expiratory HRCT scans. RESULTS: Forty-five patients showed air trapping on expiratory HRCT scans. Of these 45 patients, inspiratory high-resolution CT scans showed abnormal findings in 36 (bronchiectasis, bronchiolitis obliterans, asthma, chronic bronchitis, and cystic fibrosis). In the remaining nine patients, inspiratory HRCT had normal findings; conditions in these nine patients included bronchiolitis obliterans (n = 5), asthma (n = 3), and chronic bronchitis (n = 1). Results of pulmonary function tests in patients with air trapping and normal findings on inspiratory scans were intermediate, falling between those of patients with normal findings on inspiratory and expiratory HRCT scans and those of patients with air trapping and abnormal findings on inspiratory scans. CONCLUSION: Air trapping on expiratory HRCT scans in patients with normal findings on inspiratory scans is most often associated with bronchiolitis obliterans and asthma. Obtaining expiratory scans in patients who may have one of these diseases is recommended.
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Transesophageal echocardiographic studies were used to monitor the presence of air bubbles in the heart after open heart operations. After cardiac valvular procedures all 22 patients managed with careful deairing procedures had persistence of air bubbles for at least 30 minutes and usually for 45 minutes. In 56 patients with CO2 field flooding, all foam disappeared in less than 1 minute in 48 patients and the remaining 8 had complete disappearance in 1 to 24 minutes. These observations demonstrate the ineffectiveness of the usual deairing maneuvers and the effectiveness of CO2 field flooding in displacing air.
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STUDY OBJECTIVE: To determine whether a correlation exists between pulmonary function and both frontal chest radiographs and high-resolution chest CT findings in patients with pulmonary alveolar proteinosis (PAP). DESIGN: Retrospective review of radiographic and clinical data. SETTING: Tertiary referral hospital. PATIENTS: Seven patients with PAP were studied on 25 occasions using high-resolution chest CT (n=21), frontal chest radiographs (n=19), and pulmonary function tests (PFTs) (n=25). MEASUREMENTS AND RESULTS: Visual estimates of the extent, degree, and overall severity of parenchymal abnormalities were determined for plain radiographs and high-resolution chest CT, and were correlated with PFTs. With high-resolution CT, the extent and severity of ground-glass opacity correlated significantly with the presence of a restrictive ventilatory defect, reduced diffusing capacity, and hypoxemia. Chest radiographic findings also correlated significantly with restrictive ventilatory defect, diffusing capacity, and hypoxemia. CONCLUSION: In patients with PAP, although high-resolution CT correlates more closely with pulmonary function, plain radiographs should be sufficient for follow-up.
OBJECTIVE: We assessed the usefulness of chest radiographs for predicting whether high-resolution CT scans obtained with the patient prone would be valuable in assessing suspected diffuse lung disease. MATERIALS AND METHODS: In 100 consecutive patients undergoing high-resolution CT, findings on plain chest radiographs were classified as normal, possibly abnormal, or abnormal. CT scans obtained with the patient supine were assessed for the presence and distribution of lung abnormalities without knowledge of the plain radiographic classification. A second review of the CT scans was done with equal numbers of scans obtained with the patient prone and with the patient supine. The usefulness of the CT scans obtained with the patient prone for detecting lung disease was determined and related to the plain radiographic classifications. RESULTS: High-resolution CT scans obtained with patients prone were helpful in excluding or confirming posterior lung abnormalities in 10 (28%) of 36 patients who had normal findings on chest radiographs, five (28%) of 18 patients who had possibly abnormal findings on chest radiographs, and only two (4%) of 46 patients who had abnormal findings on chest radiographs. The proportion of patients who benefited from high-resolution CT scans obtained with the patient prone was significantly lower among the patients with abnormal findings on chest radiographs than among the patients with normal (p = .008) or possibly abnormal (p = .02) findings on chest radiographs. The two patients with abnormal findings on radiographs in whom CT scans obtained with the patient prone were helpful had minimal radiographic abnormalities. CONCLUSION: In patients with suspected diffuse lung disease, obtaining high-resolution CT scans with the patient prone may be useful when chest radiographs show normal findings, possibly abnormal findings, or minimal abnormalities indicative of diffuse lung disease. However, such scans are of little value in patients whose radiographs show abnormalities indicative of diffuse lung disease.
Obstructive lung diseases may be associated with a variety of pathologic findings, including emphysema, large airways abnormalities, and small airways abnormalities. The usefulness of plain radiographs for showing these findings is limited, although the presence of obstructive lung disease can often be inferred in the presence of increased lung volumes, gross lung destruction (emphysema) or large airways abnormalities. Furthermore, radiographs may not provide useful information in many patients with a known disease who experience an exacerbation of their symptoms. Nonetheless, chest radiographs are commonly obtained in this setting to assess the presence or absence of disease complications. HRCT can reveal morphologic abnormalities associated with obstructive lung disease with a greater accuracy than plain radiographs. HRCT is more sensitive than radiographs in showing emphysema, large airways abnormalities such as bronchiectasis, and small airways abnormalities such as bronchiolectasis and the tree-in-bud appearance. Furthermore, findings associated with abnormal ventilation, including mosaic perfusion, can also be seen on HRCT, as can findings of air trapping on expiratory scans. These latter findings are particularly helpful in diagnosing obstructive disease in the absence of other morphologic abnormalities. Although the indications for use of HRCT vary with the specific disease, HRCT can be valuable in patients in whom the diagnosis is, on the basis of clinical and plain radiographic findings, in question or for whom specific therapy is being contemplated.
OBJECTIVE: We prospectively studied AIDS patients with a high clinical pretest probability of Pneumocystis carinii pneumonia (PCP) in whom chest radiographic findings were normal, equivocal, or nonspecific with high-resolution CT (HRCT) to determine the incidence of PCP in these patients, to assess the diagnostic accuracy of HRCT for the presence or absence of PCP, to evaluate the role of HRCT in patient management, and to determine the clinical outcome of all patients 1 month after evaluation. SUBJECTS AND METHODS: All patients were referred to the Division of Pulmonary and Critical Care Medicine for diagnosis of clinically suspected PCP. Thirty-three patients were prospectively evaluated with HRCT within 24 hr of diagnostic bronchoalveolar lavage; 18 other patients who underwent HRCT were managed according to the HRCT interpretation and followed up clinically. All HRCT scans were independently reviewed by three chest radiologists; patchy or nodular ground-glass attenuation was considered to indicate "possible PCP." RESULTS: The incidence of PCP was 12% (6/51). The sensitivity of HRCT was 100%; specificity, 89%; and accuracy, 90% (p < .005). We had five false-positive and no false-negative interpretations. Some form of "airways disease" (n = 23) was the single most common HRCT interpretation. CONCLUSION: HRCT may allow exclusion of PCP in patients with findings that are normal, equivocal, or nonspecific on chest radiographs. Empiric therapy or immediate bronchoscopy can be avoided in many patients on the basis of the HRCT findings.
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Clinical and radiologic findings in a 73-year-old man who developed a systemic illness while receiving intravesical bacillus Calmette-Guérin (BCG) immunotherapy for bladder cancer are presented. Thin-section chest computed tomographic findings included a diffuse pattern of small nodules consistent with miliary disease. Potential mechanisms explaining the pulmonary disease resulting from intravesical BCG treatment include a hypersensitivity reaction or actual BCG infection of the lungs.
The Findlay centrifugal pump is unique in its two-stage pumping mechanisms and in its complementary interrelationship of the stages to each other and to the exit system, and it forms an extremely efficient unit. The first stage is a lift force pump as an inlet. The second and major stage is a shear force pump. Twenty-six prototypes, many multiply modified, have been hand fabricated, and most have had classic pump function analyses. Six pumps have demonstrated minimal hemolysis (3.5-5 h). At modest rotation speeds, it pumps water up to 10 L/min. Forty-four acute studies in normal dogs have been performed with the Findlay pump in a ventricular assist system. Blood flows through the pump ranged from 1.2 to 4.5 L/min. The conclusion is that the Findlay pump has the ability to operate with low blood damage, performs at acceptable rotational speed with reasonable hydraulic and mechanical efficiency, and is small and implantable.
Abnormal findings on high-resolution CT that are localized to the centrilobular region imply primary disease of the small airways or primary peribronchiolar or perivascular pathology. We review methods of localizing abnormal opacity to the centrilobular region and discuss differential diagnostic considerations for centrilobular disease. Straightforward ways to differentiate between primary small-airways disease and peribronchiolar or perivascular conditions are also emphasized. Although perilymphatic disorders can also be associated with centrilobular opacities, these conditions have a distinctive appearance that warrants separate categorization; distinguishing characteristics of perilymphatic disorders with respect to the centrilobular conditions are discussed.
RATIONALE AND OBJECTIVES: We determined whether a limited number of high-resolution computed tomography (HRCT) scans will effectively screen for interstitial lung disease (ILD) in a population of individuals exposed to asbestos. METHODS: We retrospectively reviewed the computed tomography studies of 49 patients exposed to asbestos. HRCT in the supine and prone positions had been performed at specifically preselected levels. Two teams of thoracic radiologists evaluated, on separate occasions: (1) all images, (2) prone images only, and (3) a single prone image through the lung bases for the presence of diffuse ILD. RESULTS: A relatively high level of accuracy was obtained with a single prone scan. However, improvement to 95% or better was found when additional prone images were used. CONCLUSION: A screening study for ILD, in this case patients exposed to asbestos, may be performed by preselected prone HRCT images only. The ease and decreased time of performing the procedure make screening relatively large patient groups for ILD more feasible.