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Volumetric analysis of aeration in the lungs during general anaesthesia.

Spiral computed tomography (CT) allows volumetric analysis of formation of atelectasis and aeration of the lungs during anaesthesia. We studied 26 premedicated patients undergoing elective surgery allocated to group 1 (conscious, spontaneous breathing, investigating inspiration and expiration), group 2 (general anaesthesia with mechanical ventilation, investigating inspiration and expiration) or group 3 (general anaesthesia with mechanical ventilation, investigating changes over time). Using spiral CT, the lungs were studied either before or during general anaesthesia. CT scans were grouped into the following areas: overaeration, normal aeration, reduced aeration, poor aeration and atelectasis. The mechanism of atelectasis appeared to be both gravitational forces and a diaphragm-related force that acts regionally in caudal lung regions. Mean atelectasis formation and poorly aerated regions comprised approximately 4% of the total lung volume between the diaphragm and carina, giving a mean value of 16-20% of the normal aerated lung tissue being either collapsed or poorly aerated. The vertical ventilation distribution was more even during anaesthesia than in the awake state.

Anesthesia, General↗

Lung collapse and gas exchange during general anesthesia: effects of spontaneous breathing, muscle paralysis, and positive end-expiratory pressure.

Lung densities (atelectasis) and pulmonary gas exchange were studied in 13 supine patients with no apparent lung disease, the former by transverse computerized tomography (CT) and the latter by a multiple inert gas elimination technique for assessment of the distribution of ventilation/perfusion ratios. In the awake state no patient had clear signs of atelectasis on the CT scan. Lung ventilation and perfusion were well matched in most of the patients. Three patients had shunts corresponding to 2-5% of cardiac output, and in one patient there was low perfusion of poorly ventilated regions. CT scans after 15 min of halothane anesthesia and mechanical ventilation showed densities in dependent lung regions in 11 patients. A shunt was present in all patients, ranging from 1% in two patients (unchanged from the awake state) to 17%. Ventilation of poorly perfused regions was noted in nine patients, ranging from 1-19% of total ventilation. The magnitude of the shunt significantly correlated to the size of dependent densities (r = 0.84, P less than 0.001). Five patients studied during spontaneous breathing under anesthesia displayed both densities in dependent regions and a shunt, although of fairly small magnitude (1.8% and 3.7%, respectively). Both the density area and the shunt increased after muscle paralysis. PEEP reduced the density area in all patients but did not consistently alter the shunt. It is concluded that the development of atelectasis in dependent lung regions is a major cause of gas exchange impairment during halothane anesthesia, during both spontaneous breathing and mechanical ventilation, and that PEEP diminishes the atelectasis, but not necessarily the shunt.

Adult↗

Effect of patient-controlled analgesia on pulmonary complications after coronary artery bypass grafting.

OBJECTIVE: To determine whether treatment with patient-controlled analgesia (PCA) alone or in combination with nonsteroidal anti-inflammatory drugs can prevent postoperative pulmonary complications after cardiac surgery, when compared with conventional nurse-controlled analgesia. DESIGN: Randomized controlled trial. SETTING: University Medical Center. PATIENTS: A total of 120 patients undergoing elective coronary artery bypass grafting. INTERVENTIONS: After extubation of the trachea, 120 patients were randomly allocated to three different methods of postoperative pain relief for 72 hrs. In group 1, patients received PCA with a bolus of 1.5 mg piritramide combined with a 10-min lockout interval. Group 2 patients were treated with a combination of PCA and administration of nonsteroidal anti-inflammatory drugs prescribed three times per day. Patients of group 3 received conventional nurse-controlled analgesia. Postoperative assessment included daily visual analog pain scoring (VAS) and chest radiographs. All chest radiographs were graded for the extent of atelectasis by a radiologist blinded as to treatment using a scale from 0 to 9 for each of the three lung fields of the right and left lungs. MEASUREMENTS AND MAIN RESULTS: Chest radiograph atelectasis scores and VAS values were similar among the three groups on the first and second days. On the third day, the chest radiograph atelectasis scores of the left lower and the right middle lung field were significantly better in the groups treated with PCA alone (4.7 +/- 3.0; 0.3 +/- 1.0) and in combination with nonsteroidal anti-inflammatory drugs (3.9 +/- 1.1; 0.4 +/- 1.2) than in the control group (5.5 +/- 3.1; 0.8 +/- 1.8). Furthermore, on the third day, the VAS values for maximum pain were higher in the control group (42.6 +/- 19.7) compared with the VAS values in the two groups with PCA (32.2 +/- 17.9 and 34.5 +/- 21.0). CONCLUSIONS: PCA significantly decreases postoperative pulmonary atelectasis in patients after coronary artery bypass grafting when compared with nurse-controlled analgesia. In addition, patients treated with PCA experienced a higher quality of analgesia. We therefore conclude that treatment with PCA may reduce respiratory complications after coronary artery bypass grafting.

Academic Medical Centers↗

Lung aeration. The effect of pre-oxygenation and hyperoxygenation during total intravenous anaesthesia.

We have investigated the effect of pre-oxygenation and hyperoxygenation (an increase in inspired oxygen fraction from 0.4 to 1.0 after induction of general anaesthesia) on aeration and atelectasis formation in the lungs during total intravenous anaesthesia. Twenty-seven consecutive patients were randomly allocated to group 1 (with pre-oxygenation), group 2 (without pre-oxygenation), or group 3 (hyperoxygenation). Lung aeration was investigated by means of spiral computed tomography. The aeration of lung regions identified by computed tomography scans was divided into five categories: over-aeration, normal aeration, reduced aeration, poor aeration, and atelectasis formation. In group 1 larger areas of atelectasis were found in the basal parts of the lungs compared to group 2. In group 3 a significant increase in atelectatic areas with a corresponding reduction in areas with reduced aeration occurred at the bases of the lungs. The considerable increase in atelectasis associated with pre-oxygenation and its rapid appearance during hyperoxygenation suggest that these procedures should be used with caution.

Adult↗

Echocardiographic tissue characterization and range-gated Doppler ultrasound for the diagnosis of pulmonary embolism.

We evaluated reflection and absorption indexes of ultrasound as well as Doppler estimates of intrapulmonary blood flow for diagnosing pulmonary embolism. The pulmonary reflection coefficient (PRC), coefficient of tissue attenuation (alpha R) and range-gated blood Doppler signals were studied in 25 patients with pulmonary embolism, 19 with pneumonia, nine with atelectasis, 20 with congestive heart failure, 20 with chronic obstructive lung disease and 10 normal subjects. The PRC was significantly diminished in pulmonary embolism, pneumonia and atelectasis, but was not altered by underlying chronic obstructive lung disease or congestive heart failure. The alpha R in pulmonary embolism was 1.03 +/- 0.04 db/MHz cm, significantly lower than that for pneumonia, 1.48 +/- 0.03 db/MHz cm (p less than 0.001), but not significantly different from that for atelectasis, 0.95 +/- 0.05 db/MHz cm. Doppler signals indicating blood flow in the affected area of lung were present in only two of 25 patients with pulmonary embolism, compared with seven of nine with atelectasis and 17 of 19 with pneumonia. The combined use of PRC, alpha R and blood Doppler signals correctly diagnosed pulmonary embolism in 23 of 25 patients. Thus, ultrasound offers a reliable noninvasive method for diagnosis of pulmonary embolism.

Echocardiography↗

A computed tomographic scan assessment of endotracheal suctioning-induced bronchoconstriction in ventilated sheep.

This study was directed at assessing changes in bronchial cross-sectional surface areas (BCSA) and in respiratory resistance induced by endotracheal suctioning in nine anesthetized sheep. Cardiorespiratory parameters (Swan-Ganz catheter), respiratory resistance (inspiratory occlusion technique), BCSA, and lung aeration (computed tomography) were studied at baseline, during endotracheal suctioning, and after 20 consecutive hyperinflations. Measurements performed initially at an inspired oxygen fraction (FI(O(2))) of 0.3 were repeated at an FI(O(2)) of 1.0. At an FI(O(2)) of 0.3, endotracheal suctioning resulted in atelectasis, a reduction in BCSA of 29 +/- 23% (mean +/- SD), a decrease in arterial oxygen saturation from 95 +/- 3% to 87 +/- 12% (p = 0.02), an increase in venous admixture from 19 +/- 10% to 31 +/- 19% (p = 0. 006), and an increase in lung tissue resistance (DR(rs)) (p = 0. 0003). At an FI(O(2)) of 1.0, despite an extension of atelectasis and an increase in pulmonary shunt from 19 +/- 5% to 36 +/- 2% (p < 0.0001), arterial O(2) desaturation was prevented and BCSA decreased by only 7 +/- 32%. A recruitment maneuver after endotracheal suctioning entirely reversed the suctioning-induced increase in DR(rs) and atelectasis. In three lidocaine-pretreated sheep, the endotracheal suctioning-induced reduction of BCSA was entirely prevented. These data suggest that the endotracheal suctioning-induced decrease in BCSA is related to atelectasis and bronchoconstriction. Both effects can be reversed by hyperoxygenation maneuver before suctioning in combination with recruitment maneuver after suctioning.

Airway Resistance↗

Time to reconsider the pre-oxygenation during induction of anaesthesia.

Atelectasis is a frequent finding in paralysed and mechanically ventilated patients. Atelectasis, causing shunt, impairs oxygenation and could contribute to postoperative pulmonary complications. Pre-oxygenation used during anaesthesia induction causes atelectasis. A lowering of oxygen fraction from 100% to 80% does not shorten the safety time of apnoea period, particularly useful for a difficult intubation, but it reduces drastically the atelectasis incidence.

Anesthesia↗

[A case of mucoid impaction of bronchi (MIB) due to Schizophyllum commune].

A 51-year-old woman was admitted because of a productive cough. Atelectasis of the left upper lobe and eosinophilia were noted. The atelectasis was resolved after bronchoscopic removal of the mucous plug. Pathologically, it consisted of eosinophil accumulation with hyphae. Cultures of sputum samples revealed Schizophyllum commune. We diagnosed this case as mucoid impaction of bronchi due to S. commune. Eight months later, a productive cough developed again. Chest radiography showed atelectasis of the right middle lobe. Cultures of bronchial washings yielded S. commune and Aspergillus niger. The atelectasis was resolved by four months of administration of itraconazole (200 mg daily).

Aspergillosis, Allergic Bronchopulmonary↗

[Thoraco-abdominal binding in the treatment of overdistention of the lung bases in children].

In the patient with homogeneously or inhomogeneously distributed atelectasis, localized primarily in the apices, overdistension of the non-dependent portion of the lung bases, only partially surrounded by the rib cage, is generally observed during mechanical ventilation. This phenomenon is even more pronounced in the neonate and in the infant because their rib cage compliance is almost infinite. In order to protect the lung bases in the event of their overdistension and/or to reexpand the atelectasis of the upper lobes we apply an external resistance, in form of thoracoabdominal binding, to limit the movement of the diaphragm. The degree of the binding's tension is regulated according to the degree of the distension of the lung bases detected on chest x-ray. This restriction was so far applied in 12 children using elastic bandages. We have used the thoraco-abdominal binding with good result in the treatment of atelectasis of the upper lobes, in extensive atelectasis as well as in the treatment of primitive lung bases overdistension, as described in 3 cases reports. We suggest this technique in order to obtain an homogeneous ventilation along the longitudinal axis of the lung. This method does not interfere with prone-supine postural changes, systematically applied in our department, and therefore, the homogeneous ventilation along the vertical axis is also provided.

Abdomen↗

Wegener's Granulomatosis: CT evolution of pulmonary parenchymal findings in treated disease.

OBJECTIVE: To determine the computed tomography (CT) evolution of various pulmonary manifestations of Wegener's Granulomatosis (WG) following appropriate pharmacologic treatment of the disease. METHODS: Eleven patients with WG were identified, each of whom had had at least two CT examinations. CTs were reviewed retrospectively to identify pulmonary lesions of WG. Lesions were categorized as nodules, cavities, lobar atelectasis, pulmonary bands, or infiltrates. To determine the evolution of each individual lesion following pharmacologic treatment, the authors compared the lesions at presentation to their appearances on follow-up CT examinations. RESULTS: A total of 112 lesions were identified (nodules = 70, cavities = 25, lobar atelectasis = 7, pulmonary bands = 6, infiltrates = 4). The mean time interval between CT examinations was 34 weeks (range: 3-248 weeks). Treated nodules tended to become smaller (33/70, 47%), to resolve (14/70, 20%), or to remain unchanged (8/70, 11%). However, the nodules became larger or cavitated in a substantial minority of cases (13/70, 19% and 2/70, 3%, respectively). Although more than half of the treated cavities became smaller (13/25, 52%) or resolved (1/25, 4%), many evolved into nodules (6/25, 24%) or enlarged (5/25, 20%). All cases of lobar atelectasis (14/14, 100%) and transpulmonary bands (6/6, 100%) were unchanged at follow-up. All infiltrates were either resolved (3/4, 75%) or substantially improved (1/4, 25%). CONCLUSION: WG has a wide spectrum of pulmonary manifestations. Nodules, cavities, and infiltrates are among the most common lesions seen on CT. Although these findings tend to improve with treatment, mixed responses are not uncommon. Lobar atelectasis and transpulmonary bands tend not to improve, even with the occurrence of clinical disease remission.

Adult↗

Effects of pleurotomy on respiratory sequelae after internal mammary artery harvesting.

The preservation of pleural integrity during mammary artery harvesting may decrease atelectasis and pleural effusion during the postoperative period. We designed this retrospective study to evaluate the effects on postoperative pulmonary function of pleural integrity versus opened pleura, in patients who receive a left internal mammary artery graft. The study group consisted of 1141 patients who underwent elective coronary artery bypass grafting. The patients were retrospectively evaluated and divided into 2 groups: those who underwent internal mammary artery harvesting with opened pleura (n=873) or with pleural integrity (n=268). To monitor pleural effusion and atelectasis, chest radiography was performed routinely 1 day before operation and on the 2nd, 5th, and 7th postoperative days. The preoperative, after extubation, and 1st postoperative day values of partial oxygen pressure (PaO2), partial carbon dioxide pressure (PaCO2), and oxygen (O2) saturation were recorded for comparison, as was the hematocrit. The mean age of the patients was 574 +/- 8.81 years. There were no significant differences between the groups in mean values of PaO2, PaCO2, O2 saturation, and hematocrit after extubation or on the 1st postoperative day. Atelectasis on the 5th and 7th postoperative days, pleural effusion on the 2nd, 5th, and 7th days, and postoperative bleeding were significantly less in the group with preserved pleural integrity. We showed that preservation of pleural integrity during internal mammary artery harvesting decreases postoperative bleeding, pleural effusion, and atelectasis. We conclude that preservation of pleural integrity, when possible, can decrease these postoperative complications of coronary artery bypass grafting.

Aged↗

Roentgenographic findings in infants with meconium aspiration syndrome.

Aspiration of meconium produces respiratory distress of various severity and outcome. To evaluate whether the initial chest roentgenogram (0 to 8 hours of age) can be used to predict the outcome, an analysis of 80 cases with clinical and roentgenographic features of aspiration syndrome was undertaken. Infiltration was seen in 62, consolidation or atelectasis in 44, hyperinflation in 37, air leak in 25, pleural effusion in 16, and increased cardiothymic shadow in 16. Consolidation or atelectasis, most commonly associated with thick meconium aspiration, appeared to be the most significant determinant of poor outcome. Infants who had consolidation or atelectasis were more ill, had lower pH, higher fraction of inspired oxygen, higher alveolar-arterial oxygen gradients, and required longer duration of oxygen intake than those infants who had no consolidation or atelectasis. Thus, the initial chest roentgenogram can be used for predicting outcome in infants with meconium aspiration syndrome.

Humans↗

Pulmonary function in the early postoperative period.

To the author's knowledge, an intensive investigation of pulmonary function during the first 2 postoperative days has not previously been reported. Consequently, in this study the effect of regional surgery on respiratory function, monitored every 4 h during the first 2 postoperative days, was analyzed. Hypoxaemia was a constant finding in all patients undergoing general anaesthesia. The degree and duration of hypoxaemia and spirometry changes were related to the site of surgical incision. Clinical signs of atelectasis were commonly observed during the first postoperative day and occurred after the change in PO2 and spirometry. Atelectasis was more common in patients having upper abdominal surgery. The current investigation reveals that the earliest postoperative change indicative of atelectasis is the fall in PO2; that auscultatory changes do not always occur in the presence of postoperative hypoxaemia; that auscultatory signs are not indicative of the extent of the PO2 fall; and that radiology represents a crude method of assessing postoperative atelectasis.

Adolescent↗

Middle lobe syndrome: a clinicopathological study of 21 patients.

Middle lobe syndrome (MLS) is an uncommon lung disorder involving the right middle lobe and/or lingula and is characterized by a spectrum of clinical and pathological lesions ranging from recurrent atelectasis or pneumonias to bronchiectasis. Despite several series reporting the clinical features of MLS, histopathological descriptions are rare. We reviewed the clinical characteristics and pathological findings in 21 patients with MLS who underwent surgical resections. Six male and 15 female patients between the ages of 5 and 80 years (mean, 47 years) were studied. All patients were symptomatic and complained of chronic cough (8), hemoptysis (6), chest pain (4), dyspnea (3), or fever (2). The right middle lobe was involved in 11 patients, the lingula in four patients, and both right middle lobe and lingula in six patients. Chest radiographs, bronchograms, and/or computed tomography scans were available for review in 19 patients and showed consolidation (8), bronchiectasis (9), patchy infiltrates (5), and atelectasis (4) in various combinations. Pathological findings included bronchiectasis in 10 patients, chronic bronchitis/bronchiolitis with lymphoid hyperplasia in seven, patchy organizing pneumonia in six, atelectasis in five, granulomatous inflammation in five, and abscess formation in four. Three patients with granulomatous inflammation had associated atypical mycobacterial infection. Broncholithiasis was confirmed by pathological examination in one patient. No pathological cause for bronchial obstruction was identified in the remaining 20 patients, although one was thought to have had broncholithiasis on the basis of preoperative bronchoscopy. The presence of bronchiectasis, bronchitis or bronchiolitis, organizing pneumonia, or atelectasis in specimens from the right middle lobe or of lingula in the absence of an identifiable cause of bronchial obstruction should suggest a diagnosis of MLS.

Adolescent↗

Hyperectasis: the hyperinflated tympanic membrane: the middle ear as an actively controlled system.

OBJECTIVE: To describe and analyze a middle ear condition in which the steady state of the middle ear pressure is elevated above the atmospheric pressure. SETTING AND STUDY DESIGN: This is a long-term survey of 59 patients from a private clinic who were observed on routine examination to have a ballooned out (hyperinflated) tympanic membrane. INTERVENTION: All patients underwent hearing tests, tympanometry, and Shullers (lateral) mastoid radiography. MAIN OUTCOME MEASURES: A hyperinflated tympanic membrane indicates a middle ear pressure that is higher than atmospheric pressure. The ballooned tympanic membrane returns to its physiological level after being punctured. This pressure situation is the reverse or opposite of atelectasis and is therefore termed hyperectasis. Hyperectasis, like atelectasis, is associated with a poorly pneumatized mastoid. RESULTS: Fifty-nine hyperectatic ears persisted in their hyperinflated state for weeks, months, or even years. The hyperectasis was preceded by atelectasis, and both conditions occasionally changed one into the other. The ballooned part of the tympanic membrane is usually thin and "scarred." Hyperectasis is not a rare situation and, once recognized, can be readily encountered in an otologic clinic. CONCLUSIONS: Like most biologic systems (e.g., blood pressure, temperature), the middle ear's central feature, i.e., pressure, also has a dynamic character vacillating up and down. It is conceivable that middle ear pressure is also actively regulated and controlled with the aid of a feedback mechanism. Passage of gas through the eustachian tube or absorption by diffusion-perfusion is also at least partly an active process. The up and down middle ear pressure vacillations are usually clinically benign and do not lead to any pathologic features as long as they are buffered by an accompanying normal mastoid pneumatization. It is the ear with a nonpneumatized mastoid that has limited ability to buffer pressure changes and that will present as an atelectasis, a retraction pocket, or (eventually a cholesteatoma) or their reverse, a hyperectatic tympanic membrane.

Acoustic Impedance Tests↗

Hydroxyapatite prosthesis extrusion.

OBJECTIVE: To examine the mechanism of prosthesis extrusion and evaluate preoperative and postoperative variables associated with extrusion of hydroxyapatite prostheses for ossicular reconstruction. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral, university medical center. PATIENTS: Patients undergoing ossiculoplasty with a hydroxyapatite prosthesis and having at least six months follow-up. MAIN OUTCOME MEASURE: Prosthesis extrusion, defined as loss of the tympanic membrane resulting in exposure of the prosthesis. Extrusion is further classified into early (< 2 months) and late (> 6 months). RESULTS: Early extrusion or tympanoplasty graft failure occurred in 15/195 cases (8%). Late extrusion was seen in 17/125 cases (14%). Cases exhibiting late extrusion had a significantly greater incidence of postoperative atelectasis (p < 0.0001), recurrent otitis media (p < 0.0001), and myringitis (p = 0.003) than those with retention of the prosthesis. Regression analysis found an abnormal contralateral ear increased the risk of postoperative recurrent otitis media, while staged surgery reduced the risk, odds ratios of 3.56 (95% confidence interval 2.20-9.37) and 6.84 (95% CI 4.24-17.76) respectively. There were no preoperative variables that predicted postoperative atelectasis or myringitis. CONCLUSIONS: Recurrent otitis media, myringitis, and atelectasis developing after ossiculoplasty are associated with a greater risk of prosthesis extrusion. Predicting postoperative complications from preoperative and intraoperative findings proved difficult. Measures to prevent atelectasis, such as covering the prosthesis with cartilage, are recommended at the time of ossiculoplasty.

Cartilage↗

Obliquely oriented superior accessory fissure of the lower lobe of the lung: CT evaluation of the normal appearance and effect on the distribution of parenchymal and pleural opacities.

PURPOSE: To review computed tomographic (CT) and radiographic features of an oblique superior accessory fissure in the lower lobe of the lung. MATERIALS AND METHODS: CT scans in 34 patients with a prospectively identified accessory fissure of the lower lobe were reviewed and correlated with chest radiographs (31 patients). The fissure and its relationship to segmental bronchovascular structures were evaluated on transverse scans. Three-dimensional (3D) shaded surface display (SSD) reconstructions were obtained from spiral volume data (six patients). RESULTS: Thirty-four patients had 36 accessory fissures (26 right, 10 left). Four of the 36 accessory fissures were manifested by a normal fissure line; two, by slight thickening or minimal linear atelectasis; 16, by thicker linear or subsegmental atelectasis; two, by contiguous tumor infiltration; one, by adjacent consolidation; and 11, by intrafissural extension of pleural fluid. Analysis of bronchovascular structures revealed that this fissure was the superior accessory fissure. The 3D SSD reconstructions demonstrated an oblique orientation. On frontal radiographs, presence of this fissure correlated with a curvilinear band of atelectasis coursing inferomedially and obliquely from its intersection with the lateral aspect of the major fissure toward the infrahilar region on the right and the heart border on the left. Chest radiographs also showed intrafissural extension of pleural fluid. CONCLUSION: A superior accessory fissure of the lower lobe, more common on the right than on the left, can be identified at transverse CT. Contrary to previous descriptions, it may be oblique, as findings on transverse images suggest and 3D SSD reconstructions confirm. Its presence correlates with characteristic patterns of atelectasis and pleural fluid collection on conventional radiographs.

Adult↗

Asbestosis, pleural plaques and diffuse pleural thickening: three distinct benign responses to asbestos exposure.

The aim of this study was to investigate by computed tomography (CT) whether asbestosis, diffuse pleural thickening and/or pleural plaques are statistically associated. We also tried to find criteria to differentiate between diffuse and circumscribed pleural thickening. From 231 exposed workers, only those subjects whose radiograph showed neither bilateral calcified pleural plaques nor small pulmonary opacities higher than 1/1 grade according to the 1980 International Labour Office (ILO) Classification were considered. Scans were assessed for the presence of subpleural curvilinear lines, septal and intralobular lines, parenchymal bands, honeycombing, rounded atelectasis, pleural plaques and diffuse pleural thickening. CT scans revealed pleural and/or lung abnormalities in 99 workers. Pleural plaques were unilateral in one-third of cases with plaques. Diffuse pleural thickening, parenchymal bands and rounded atelectasis were unilateral in, respectively, 62 and 69 and 75% of cases with the abnormality. Septal and intralobular lines, and honeycombing were always bilateral. CT signs could be grouped into three patterns: 1) septal and intralobular lines, and honeycombing corresponding to pulmonary fibrosis; 2) pleural plaques corresponding to parietal pleural fibrosis; and 3) diffuse pleural thickening, rounded atelectasis and parenchymal bands corresponding to visceral pleural fibrosis. In these workers with a normal or near-normal radiograph, three groups of subjects with different responses were distinguished. Crow's feet and rounded atelectasis help to differentiate plaques from diffuse thickening.

Adult↗