Evaluation of the upper airway in patients with obstructive sleep apnea.

Multiple methods have been used to study the structure and physiological behavior of the upper airway (UA) in patients with obstructive sleep apnea (OSA). Valuable information may be obtained from the physiologic measurement of pressure and resistance along the UA, as well as from imaging techniques that include: direct or fiberoptic visualization, cephalometric roentgenograms, fluoroscopy, acoustic reflection, computerized tomography, and magnetic resonance imaging. This review summarizes the information that each of these methods has contributed to our understanding of the UA. The results obtained with these different methodologies have generally been complementary with structural narrowing being identified in the majority of patients with OSA. This narrowing is usually focal and located in the velopharyngeal or retropalatal segment of the UA. This is also the predominant site of initial UA collapse. Although obesity with enlargement of soft tissue structures is considered the predominant mechanism leading to UA narrowing, abnormal craniofacial development on a genetic or developmental basis plays an important contributory role.

Acute pulmonary edema induced by overdosage of phenothiazines.

Three schizophrenic adults with previous histories of using phenothiazine derivatives developed acute pulmonary edema after taking large amounts of these drugs. The clinical manifestations included coma (three), hypothermia (two), tachycardia (two), miosis (two) and hypotension (one). All three patients underwent gastric lavage and were treated supportively. The fulminant pulmonary edema in the three cases resolved within 18 to 40 h. The etiology of pulmonary edema following overdosage of phenothiazines remains unknown. The authors hypothesize that the most likely pathogenesis is a drug-induced neurogenic pulmonary edema resulting from a disturbance of hypothalamic function.

Recent advances in pulmonary imaging.

Recent years have witnessed an explosion in imaging technology applicable to chest medicine. These include CT and magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, and high-resolution CT for the detection and characterization of diffuse lung diseases and the quantification of emphysema. Newly developed approaches to pulmonary functional imaging using CT and MRI have been applied to the evaluation of pulmonary ventilation and perfusion and to the detection of small airways disease. Volumetric CT imaging techniques together with advanced image processing have made possible "virtual bronchoscopy." Positron emission tomography provides an important new approach to the accurate detection and staging of chest malignancies and to the evaluation of pulmonary nodules. Finally, new digital imaging techniques, which are rapidly replacing conventional x-ray film, offer the possibility of computer-aided diagnosis.

Pulmonary aspergillosis in patients with AIDS. Clinical and radiographic correlations.

OBJECTIVE: To evaluate the clinical and radiographic features of pulmonary aspergillosis as they present in AIDS patients; in particular, to determine similarities and differences between Aspergillus infection in patients with AIDS vs those without AIDS. SUBJECTS AND METHODS: Six new cases of confirmed or probable pulmonary aspergillosis were discovered during a search of hospital records. These are reviewed with 30 previously reported cases with special attention to radiographic appearance of disease and how radiographic appearance influences clinical outcome. RESULTS: Symptoms of pulmonary aspergillosis in AIDS were nonspecific, most often including fever, cough, and dyspnea, and less commonly, chest pain or hemoptysis. Major risk factors for the development of pulmonary aspergillosis in patients with AIDS were steroid administration and neutropenia. Neutropenia was often a complication of therapies for AIDS, in particular, ganciclovir and zidovudine. Radiographic appearance of disease could be divided into three general categories. One third of the patients (13/36) presented with cavitary upper lobe disease resembling noninvasive or chronic necrotizing aspergillosis. Fatal hemoptysis occurred in 42 percent of patients with this form of disease. Twenty-two percent (8/36) of the cases presented as a nondescript focal alveolar opacity similar to invasive aspergillosis. In several patients, the focal infiltrate remained stable for several months, a feature that is unusual for aspergillosis in non-AIDS patients. The air crescent sign was present in none of the 36 reported cases. Patients with only focal disease had the best prognosis of patients with pulmonary aspergillosis. Bilateral alveolar or interstitial disease similar to invasive aspergillosis was present in 23 percent (9/36) of the patients. Bilateral disease appears to be a marker for disseminated infection and was associated with a high mortality due to aspergillosis. Two new forms of bronchial aspergillosis (5/36 cases) have been described previously. These patients presented with either obstructing fungal casts or bronchial pseudomembranes demonstrated bronchoscopically. In some patients with the bronchial forms of aspergillosis, transient alveolar opacities were seen on chest radiographs. These opacities may represent regions of atelectasis due to airway obstruction. One patient who had bilateral pneumothoraces without parenchymal opacities did not correspond to any of the three previously mentioned categories. Mortality due to aspergillosis was greater than 50 percent among AIDS patients. Death was subsequent to fatal hemoptysis or widespread pulmonary or systemic infection. CONCLUSION: Unlike other risk groups that tend to contract only one form of pulmonary aspergillosis, AIDS patients can develop the whole spectrum of aspergillosis-related pulmonary disorders, including chronic cavitary, invasive, and bronchial forms of aspergillosis. Clinical symptoms are nonspecific and major risk factors include neutropenia, which is often a side effect of various therapies for AIDS, and steroid administration. Patients with the chronic cavitary form of disease have an unusually high mortality due to fatal hemoptysis. Patients with bilateral pulmonary infiltrates and aspergillosis have a high mortality due to disseminated infection.

Dynamic imaging of the upper airway during respiration in normal subjects.

The present study was conducted to determine the effects of quiet respiration on upper airway caliber in 15 normal subjects by using cine computed tomography. The cine computed tomography (Imatron) scanner was programmed to obtain 8-mm-thick axial slices every 0.4 s during inspiration and expiration at four anatomic levels, from the nasopharynx to the retroglossal region. Airflow (pneumotachograph) was measured, and tidal volume was obtained by integration. Upper airway area, determined by an objective edge detection algorithm, was plotted as a function of tidal volume to generate a loop describing upper airway area changes at each level during a respiratory cycle. The results demonstrate a 17% change in airway size across all anatomic levels during respiration. The maximum upper airway cross-sectional area at all four anatomic levels was significantly greater during expiration than during inspiration. Other major findings include 1) upper airway cross-sectional area decreases slightly during early inspiration, enlarges toward end inspiration, and is larger at end inspiration than at the beginning of inspiration; 2) upper airway cross-sectional area enlarges from end inspiration to the first point in expiration; the airway enlarges further, reaching its maximum early in expiration, and then narrows toward end expiration; and 3) the changes in upper airway dimensions during resting tidal breathing are greater in the lateral than in the anteroposterior direction. The data suggest that during inspiration, the action of negative intraluminal pressure may be largely balanced by the action of the upper airway dilator muscles, whereas during expiration, positive intraluminal pressure produces expansion of the upper airway.

MRI study of regional variations of pharyngeal wall compliance in cats.

Upper airway compliance indicates the potential of the airway to collapse and is relevant to the pathogenesis of obstructive sleep apnea. We hypothesized that compliance would vary over the rostral-to-caudal extent of the pharyngeal airway. In a paralyzed isolated upper airway preparation in cats, we controlled static upper airway pressure during magnetic resonance imaging (MRI, 0.391-mm resolution). We measured cross-sectional area and anteroposterior and lateral dimensions from three-dimensional reconstructed MRIs in axial slices orthogonal to the airway centerline. High-retropalatal (HRP), midretropalatal (MRP), and hypopharyngeal (HYP) regions were defined. Regional compliance was significantly increased from rostral to caudal regions as follows: HRP < MRP < HYP (P < 0.0001), and compliance differences among regions were directly related to collapsibility. Thus our findings in the isolated upper airway of the cat support the hypothesis that regional differences in pharyngeal compliance exist and suggest that baseline regional variations in compliance and collapsibility may be an important factor in the pathogenesis and treatment of obstructive sleep apnea.

Prolonged dense nephrograms in battered children. Suspect rhabdomyolysis and myoglobinuria.

Prolonged, dense nephrograms were seen on intravenous urography in 5 cases of child abuse presenting with possible renal injury. Each child had oliguria, elevated muscle enzymes, and pigmented urine positive for blood, but without red cells on microscopic examination. These findings are suggestive of myoglobinuria. The abnormalities resolved with appropriate fluid and electrolyte management. This complication of child abuse, not previously emphasized, may be suggested by the urographic findings. Possible factors contributing to the dense nephrograms are presented.

Chest applications of magnetic resonance imaging: an update.

Accumulated experience with MR applications in the chest has helped to define its role relative to other modalities. Technical advances improving image quality, newer fast scans, and cine methods are expanding the information available from MR. This discussion reviews the useful applications and limitations of MR in evaluating thoracic disorders. Physicians should be knowledgeable and selective in their utilization of this modality.

MRI of the upper aerodigestive tract and neck.

The application of new technology has improved the ability of MR to image the upper aerodigestive tract and neck. Improved resolution along with inherent high tissue contrast and multiplanar capability now allow clear definition of detailed anatomic and pathologic tissue planes. MR currently rivals other imaging modalities in this region. At present, it is often better in demonstrating the depth of tumor infiltration and the presence of nodal metastasis. Initial studies also suggest that MR can effectively image postoperative sites and discriminate chronic fibrosis from recurrent tumor. Localization of abnormal parathyroid glands, particularly for re-exploration, is a promising technique. If the present limitations are recognized, such as identification of soft tissue calcification, MR can play an important role in the evaluation of the face and neck. With additional investigation and continued technologic improvements it is likely that this role will continue to increase.

Electron beam computed tomography for the quantification of aortic valvular calcification.

BACKGROUND AND AIM OF THE STUDY: Calcific aortic stenosis is common in the elderly; indeed, 30-60% of patients with mild 'senile' aortic stenosis will progress to severe obstruction. Nonetheless, predictors of progression are incompletely defined, and non-invasive technologies capable of quantifying aortic valve calcium are needed. The reliability of electron beam computed tomography (EBCT) was evaluated for quantification of aortic valve calcium content. METHODS: Nineteen patients with and without restrictive valve calcification underwent EBCT scanning. Separate calcium scores, 30 s apart, were obtained in all patients, and the Spearman correlation coefficient was calculated between measurements. The relationship between dichotomized mean calcium score and aortic valve area was also investigated. RESULTS: There was excellent correlation between calcium scores (R = 0.99, p = 0.0001), as well as a significant inverse relationship between calcium scores in the upper and lower ranges and aortic valve area (p = 0.002). CONCLUSION: EBCT can be used for reproducible quantitation of aortic valve calcification. While at their extremes, calcium scores are inversely related to aortic valve area, further evaluation is needed to define the precise nature of this relationship throughout the spectrum of stenosis severity. EBCT holds promise in the longitudinal assessment of valvular calcification progression and its response to potential medical therapies.

Accuracy of CT angiography versus pulmonary angiography in the diagnosis of acute pulmonary embolism: evaluation of the literature with summary ROC curve analysis.

RATIONALE AND OBJECTIVES: The authors performed this study to estimate, by using published data, the sensitivity and specificity of computed tomographic (CT) angiography in the evaluation of suspected acute pulmonary embolism (PE). MATERIALS AND METHODS: Summary receiver operating characteristic (ROC) curve analysis was used to determine the sensitivity and specificity of CT angiography in the diagnosis of acute PE. Pulmonary angiography was used as the diagnostic standard of reference. The authors reviewed the results of 11 independent studies published in the English-language literature between January 1992 and June 1999. RESULTS: The sensitivity of CT angiography in the diagnosis or exclusion of PE in the central pulmonary arteries (to the level of the segmental pulmonary arteries) ranged from 0.74 to 0.81 on the basis of specificities of 0.89-0.91. The sensitivity of CT angiography in the diagnosis or exclusion of PE in all pulmonary arteries (to the level of the subsegmental pulmonary arteries) was 0.68 on the basis of a specificity of 0.91. CONCLUSION: On the basis of the studies in the current literature, most of which used 5.0-mm collimation and single-detector CT, CT angiography may be less accurate in the diagnosis of PE than previously reported. With improvements in data acquisition, particularly the use of thinner section collimation and multidetector CT, and in the increased use of workstations for data analysis, the accuracy and utility of CT angiography will require continued investigation.

Fast magnetic resonance imaging of the lung.

The impact of fast MR techniques developed for MR imaging of the lung will soon be recognized as equivalent to the high-resolution technique in chest CT imaging. In this article, the difficulties in MR imaging posed by lung morphology and its physiological motion are briefly introduced. Then, fast MR imaging techniques to overcome the problems of lung imaging and recent applications of the fast MR techniques including pulmonary perfusion and ventilation imaging are discussed. Fast MR imaging opens a new exciting window to multi-functional MR imaging of the lung. We believe that fast MR functional imaging will play an important role in the assessment of pulmonary function and disease process.

T2* and proton density measurement of normal human lung parenchyma using submillisecond echo time gradient echo magnetic resonance imaging.

OBJECTIVE: To obtain T2* and proton density measurements of normal human lung parenchyma in vivo using submillisecond echo time (TE) gradient echo (GRE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Six normal volunteers were scanned using a 1.5-T system equipped with a prototype enhanced gradient (GE Signa, Waukausha, WI). Images were obtained during breath-holding with acquisition times of 7-16 s. Multiple TEs ranging from 0.7 to 2.5 ms were tested. Linear regression was performed on the logarithmic plots of signal intensity versus TE, yielding measurements of T2* and proton density relative to chest wall muscle. Measurements in supine and prone position were compared, and effects of the level of lung inflation on lung signal were also evaluated. RESULTS: The signal from the lung parenchyma diminished exponentially with prolongation of TE. The measured T2* in six normal volunteers ranged from 0.89 to 2.18 ms (1.43 +/- 0.41 ms, mean +/- S.D.). The measured relative proton density values ranged between 0.21 and 0.45 (0.29 +/- 0.08, mean +/- S.D.). Calculated T2* values of 1.46 +/- 0.50, 1.01 +/- 0.29 and 1.52 +/- 0.18 ms, and calculated relative proton densities of 0.20 +/- 0.03, 0.32 +/- 0.13 and 0.35 +/- 0.10 were obtained from the anterior, middle and posterior portions of the supine right lung, respectively. The anterior-posterior proton density gradient was reversed in the prone position. There was a pronounced increase in signal from lung parenchyma at maximum expiration compared with maximum inspiration. The ultrashort TE GRE technique yielded images demonstrating signal from lung parenchyma with minimal motion-induced noise. CONCLUSION: Quantitative in vivo measurements of lung T2* and relative proton density in conjunction with high-signal parenchymal images can be obtained using a set of very rapid breath-hold images with a recently developed ultrashort TE GRE sequence.

The spectrum of pulmonary aspergillosis.

Aspergillus species can produce a wide range of pulmonary disorders. Classically, pulmonary aspergillosis has been categorized into invasive, saprophytic, and allergic forms, all of which differ in their manifestations and therapy. More recently, however, other types of infection by this fungus have been recognized that do not fit into these traditional categories; an example is semi-invasive (chronic necrotizing) aspergillosis. In fact, these forms have features that are intermediate between those of the invasive and saprophytic types. The various types of aspergillosis can be regarded as constituting a continuous spectrum, ranging from invasive disease in the severely immunosuppressed patient to hypersensitivity reactions such as allergic bronchopulmonary aspergillosis (and bronchocentric granulomatosis) in the hyperreactive patient. Between these extremes are chronic necrotizing disease seen in midly immunocompromised hosts, and the noninvasive aspergilloma, which is due to saprophytic growth within a previously diseased area of lung in an otherwise normal host. Other intermediate forms may be encountered, their behavior being determined by the host immune status in combination with the underlying lung morphology. The radiographic and clinical features of these various forms of pulmonary aspergillosis are reviewed, including the more recently reported forms of infection such as Aspergillus tracheobronchitis and aspergillosis associated with acquired immunodeficiency syndrome and cystic fibrosis. The proposed concept of a disease spectrum is emphasized.

Drug-induced pulmonary disease: an update.

The review provides an update of drug-induced pulmonary disorders, focusing on newer agents whose effects on the lung have been studied recently. Included among these drugs are cyclosporine, cytosine arabinoside (Ara-C), amiodarone, interleukin-2 (IL-2), OKT3, tricyclic antidepressants, and bromocriptine. A brief review of the most common cytotoxic and noncytotoxic agents causing pulmonary toxicity is also included.

Issues and controversies in the plain-film diagnosis of asbestos-related disorders in the chest.

This article reviews the chest radiographic manifestations of asbestos exposure. While the chest radiograph (CXR) is a highly valuable tool in the evaluation of asbestos-related disease, there are ongoing controversies regarding the sensitivity and specificity of the plain film in diagnosing asbestos-related disorders. Autopsy series indicate that at least 60% of pleural plaques may be overlooked. Conversely, such series indicate that up to 20% of plaques are falsely diagnosed. The significance of visceral pleural thickening and the definition and positive predictive value of diffuse pleural thickening as they relate to asbestos exposure are unresolved issues. Data suggest that the CXR may fail to reflect significant asbestosis in 10% to 20% of cases. On the other hand, the presence of overlying pleural abnormalities as well as technical factors may contribute to overreading of interstitial disease. Data on the rate of false positive readings for asbestosis are limited. Considered alone, the CXR can support but not specifically establish nor exclude the diagnosis of asbestosis. In practice, an ILO grade of less than 1/0 implies that the diagnosis is unlikely. A constellation of positive CXR findings may increase specificity, although the diagnosis rests on a combination of multiple clinical criteria.

Evaluation of pulmonary vascular anatomy and blood flow by magnetic resonance.

Rapidly evolving magnetic resonance (MR) imaging techniques provide noninvasive approaches to evaluating morphology and quantitative physiologic information about blood flow in the pulmonary circulation. Important clinical applications currently include the preoperative and postoperative evaluation of congenital abnormalities, assessment of vascular involvement by extrinsic and intrinsic tumors, identification of central thromboemboli, and diagnosis of vascular lung lesions. Ongoing refinements in pulmonary MR angiography may make it possible to use the technique for the noninvasive detection of acute pulmonary emboli in the near future. Quantitative measurements based upon MR flow-encoding sequences are promising for the evaluation of patients with abnormal degrees or distributions of pulmonary blood flow, for example, those with unilateral lung transplants or pulmonary arterial stenoses. MR contrast agents currently under development also show promise for quantitative measurements of regional pulmonary ventilation and perfusion. The coupling of high-resolution anatomic and functional images renders MR a uniquely attractive and powerful method for evaluating the pulmonary vasculature.

Spontaneous tension pneumopericardium complicating staphylococcal pneumonia.

The authors describe a patient with spontaneous pneumopericardium complicating staphylococcal pneumonia and empyema that resulted in cardiac tamponade. Spontaneous pneumopericardium is an unusual disorder. The causes and clinical findings of pneumopericardium are reviewed, as are the radiographic features that differentiate this condition from pneumomediastinum. Early recognition of pneumopericardium is important, because emergent pericardiocentesis may be required if there is clinical evidence of tamponade.

Utility of high resolution computed tomography in predicting bronchiolitis obliterans syndrome following lung transplantation: preliminary findings.

This study was undertaken to evaluate the efficacy of high resolution computed tomography (HRCT) in predicting the development of bronchiolitis obliterans syndrome (BOS) in lung transplant recipients. Fifty lung transplant patients who were clinically stable and without evidence of BOS were evaluated for the presence of four HRCT features reported to be associated with bronchiolitis obliterans: mosaic attenuation on inspiratory CT (mosaic perfusion), mosaic attenuation on expiratory CT (air trapping), bronchiectasis, and tree-in-bud opacities. CT exams were part of an annual surveillance process with the hope of predicting subsequent development of BOS. Diagnosis of BOS was made in 9 of 50 patients as indicated by a fall in FEV1 of greater than 20% of a stable baseline. None of the radiographic features associated with clinically established BOS were both sensitive and specific in the prediction of BOS. Air trapping demonstrated moderate sensitivity (56%, 5/9) and moderate specificity (76%, 35/46) for prediction of BOS in the year following the CT exam. Bronchiectasis, the most reliable indicator of the presence of BOS was a poor predictor of subsequent BOS with an 11% (1/9) sensitivity but had high specificity (96%, 44/46). No high resolution CT features accurately predicted the development of BOS.

Pulmonary MR angiography.

Recent technical improvements have made pulmonary MR angiography (MRA) feasible. The technique is attractive because it is noninvasive, provides a full three-dimensional (3D) display of the pulmonary vasculature, and potentially can be combined with MR venography of the lower extremities and pelvis for the comprehensive diagnosis of thromboembolism. Approaches to acquiring pulmonary MR angiograms are currently being developed and include both two-dimensional and 3D time-of-flight methods, breath-hold and non-breath-hold techniques, and the use of gadolinium-based contrast enhancement. The results of initial studies using pulmonary MRA for the detection of pulmonary embolism are encouraging, but they must be evaluated in conjunction with newly developed fast CT scanning techniques. This article reviews the state of development of pulmonary MRA, the current clinical applications of the technique, and the prospects for future development.