W. Richard Webb

Helical CT pulmonary angiography predictors of in-hospital morbidity and mortality in patients with acute pulmonary embolism.

Purpose To determine if CT variables predict in-hospital morbidity and mortality in patients with pulmonary embolism (PE). Materials and Methods CT scans and charts of 173 patients with CT scans positive for PE were reviewed. CT scans were reviewed for leftward ventricular septal bowing, increased right ventricle (RV) to left ventricle (LV) diameter ratio, clot burden, increased pulmonary artery to aorta diameter ratio, and oligemia. Charts were reviewed for severe morbidity and mortality outcomes: death from pulmonary emboli or any cause, and cardiac arrest. Charts were also reviewed for milder morbidity outcomes: intubation, vasopressor use, or admission to an intensive care unit (ICU) and for multiple comorbidities. Results No CT predictor was significantly associated with severe morbidity or mortality outcomes. Ventricular septal bowing and increased RV/LV diameter ratio were both associated with subsequent admission to an ICU (P = 0.004 and P = 0.025, respectively). Oligemia (either lung) was associated with subsequent intubation; right lung oligemia was associated with the subsequent use of vasopressors. After controlling for history of congestive heart failure, ischemic heart disease, and pulmonary disease, both septal bowing and an increased RV/LV diameter ratio remained associated with admission to an ICU. Conclusion No CT variables predicted severe in-hospital morbidity and mortality (death from pulmonary embolism, death from any cause, or cardiac arrest) in patients with PE. However, ventricular septal bowing and increased RV/LV diameter ratio were both strongly predictive of less severe morbidity, namely, subsequent ICU admission, and oligemia was associated with subsequent intubation and vasopressor use.

Ct of a Bronchial Phantom: Factors Affecting Appearance and Size Measurements

In order to determine the most appropriate window settings for viewing CT of the bronchial tree, we performed CT of a bronchial phantom consisting of air-filled tubes measuring from 3.1 to 12.7 mm, oriented at varying angles relative to the scan plane, surrounded by water or air, and with scan collimation of 10 mm, 5 mm, and 1.5 mm. Using a computer program to graphically display CT number relative to the distance across the tubes lumen, it was found that a window mean of -150 H accurately estimated the internal diameter of tubes surrounded by water, at all angles, when collimation was 5 mm or 1.5 mm. With 10-mm collimation, tube diameter was slightly underestimated for tubes 9.5 mm or less when oriented 30 degrees or more from perpendicular to the plane of scan. At lower window settings and window widths of 500 H or less, all tubes diameters were significantly underestimated. At -150 H, with tubes parallel to and centered in the scan plane, 5-mm and 1.5-mm collimation were most accurate; with decentering of 4 mm, 10-mm collimation better showed the tubes lumen. When surrounded by air, tube wall thickness was best estimated using a window mean of -450 H.

Ventilator-Related Extra-Alveolar Air in Adults

Extra-alveolar air (EAA) developed in 38 patients during mechanical ventilation. High ventilatory pressures and destructive lung disease predispose to EAA. Pneumoretroperitoneum and pneumoperitoneum are more common forms of ventilator-induced EAA in adults than generally realized; an associated pneumomediastinum was always identified when one of the two disorders above resulted from ventilation. Retroperitoneal air was located laterally along the liver and in the flanks, and changed little with change in patient position. Early detection of EAA may allow life-saving changes in therapy to be implemented.

Fibrosing Alveolitis in Patients with Neurofibromatosis

Fibrosing alveolitis, or interstitial pulmonary fibrosis, is a common manifestation of neurofibromatosis, and was observed in 7 of 70 patients with the disease. Though neurofibromatosis is congenital, fibrosing alveolitis does not appear until adulthood, and occurs in 20% of patients with the disease who are over 30 years old. Characteristic radiographic findings include linear, interstitial density, and large upper lobe bullae; this combination limits the differential diagnosis. Pathological examination demonstrates alveolar wall thickening progressing to fibrosis and lung destruction. Pulmonary function tests can show obstructive or restrictive lung disease.

Increased mortality of ventilated patients with endotracheal Pseudomonas aeruginosa without clinical signs of infection.

Objective:To investigate the frequency and outcomes of ventilated patients with newly acquired large burdens of Pseudomonas aeruginosa and to test the hypothesis that large quantities of bacteria are associated with adverse patient outcomes. Design:A prospective, single-center, observational, cohort study. Setting:Medical-surgical intensive care units in a tertiary care university hospital. Patients:All adult patients requiring ≥48 hrs of mechanical ventilation and identified as having newly acquired P. aeruginosa in their lower respiratory tracts between October 2002 and April 2006. Interventions:None. Measurements and Main Results:Daily surveillance cultures of endotracheal aspirates were performed on patients intubated ≥48 hrs; 69 patients with newly acquired P. aeruginosa were enrolled. Daily P. aeruginosa quantification of endotracheal aspirates was performed; clinical signs of infection were noted. Of 45 patients with high P. aeruginosa burdens (≥1,000,000 colony-forming units/mL in endotracheal aspirates; ≥10,000 colony-forming units/mL in bronchoalveolar-lavage), 17 (37.8%) patients did not meet clinical criteria for ventilator-associated pneumonia and had a statistically significant higher risk of death (adjusted hazard ratio, 37.53; 95% confidence interval, 3.79–371.96; p = 0.002) when compared with the patients who had P. aeruginosa ventilator-associated pneumonia. When excluding the ten patients who had ventilator-associated pneumonia attributed to bacteria other than P. aeruginosa or attributed to multiple bacteria including P. aeruginosa, the risk of death remained statistically significant (adjusted hazard ratio, 23.98; 95% confidence interval: 2.49–230.53; p = 0.006). Furthermore, more patients with high P. aeruginosa burdens secreted the type III secretion facilitator protein, PcrV (p = 0.01). Conclusions:A group of patients with large burdens of P. aeruginosa who did not meet clinical criteria for ventilator-associated pneumonia had an increased risk of death when compared with patients who had high P. aeruginosa burdens and met ventilator-associated pneumonia criteria. Patients with high P. aeruginosa burden seemed to possess more virulent strains.

Hypersensitivity pneumonitis: patterns on high-resolution CT.

Hypersensitivity pneumonitis, also known as extrinsic allergic alveolitis, is caused by inhalation of specific environmental organic antigens. This disease may have typical high-resolution CT findings that, in the appropriate clinical setting, can be sufficiently characteristic to allow a confident diagnosis without the need for a lung biopsy. In this pictorial essay, the high-resolution CT patterns of hypersensitivity pneumonitis are illustrated. The authors emphasize the correlation among the radiologic presentation, functional abnormalities, and pathologic findings.

EXPIRATORY HIGH-RESOLUTION CT SCAN

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.

Low-dose, dynamic, expiratory thin-section CT of the lungs using a spiral CT scanner.

Seventeen patients with lung transplants were evaluated with inspiratory, postexpiratory, and low-dose, dynamic expiratory thin-section computed tomography (CT). Region of interest measurements were performed on inspiration and expiration images with both techniques, and mean lung attenuation changes between inspiration and expiration images were calculated and compared. Dynamic expiratory thin-section CT resulted in a significantly greater increase in lung attenuation than postexpiratory thin-section CT. Dynamic expiratory thin-section CT may prove useful in the evaluation of patients with lung diseases characterized by air flow obstruction with little increase in patient radiation dose.

The radiologic spectrum of pulmonary Aspergillus infections.

Aspergillus infections may be categorized by specific radiographic patterns, the patients immunologic status, and the presence or absence of preexisting structural lung disease. General patterns include invasive aspergillosis (both vascular and airway invasive varieties and acute tracheobronchitis), semiinvasive aspergillosis (including allergic bronchopulmonary aspergillosis and hypersensitivity pneumonitis), mycetoma, allergic aspergillosis, and obstructing bronchial aspergillosis. Knowledge of these various radiographic patterns as well as the immune derangements that accompany these infections may allow proper diagnosis.

Clinical and radiographic predictors of the etiology of computed tomography-diagnosed intrathoracic lymphadenopathy in HIV-infected patients.

&NA; In HIV‐infected patients with intrathoracic lymphadenopathy, it is not known whether clinical and radiographic findings are useful in predicting a specific diagnosis. We determined the etiology and predictors of the etiology of computed tomography (CT)‐diagnosed intrathoracic lymphadenopathy in HIV‐infected patients evaluated from June 1993 through April 1999. Multivariate analyses were performed to determine clinical and radiographic predictors of the three most common diagnoses. Of 318 patients, 110 (35%) had lymphadenopathy on chest CT. Among these 110 patients, tuberculosis/nontuberculous mycobacterial disease (n = 31), bacterial pneumonia (n = 26), and lymphoma (n = 21) were the most common diagnoses. Multivariate analysis identified cough and necrosis of lymph nodes on chest CT as independent predictors of tuberculosis/nontuberculous mycobacterial disease. African‐American race, symptoms for 1 to 7 days, dyspnea, and presence of airways disease on chest CT were independent predictors of bacterial pneumonia; symptoms for >7 days, absence of cough, and absence of pulmonary nodules on CT independently predicted lymphoma. Intrathoracic lymphadenopathy is a frequent chest CT finding in HIV‐infected patients. Opportunistic infections and lymphoma are the most common causes, and specific clinical and radiographic features can suggest these particular diagnoses.