Specificity np negative predictive value pp positive

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specificity; NP, negative predictive value; PP, positive predictive value; CT, computed tomography; CXR, chest x-ray. Figure 2.46 Presence of color ( left ) indicates movement or sliding and thus normal lung when using power Doppler. Its absence ( right ) indicates pneumothorax. 54 Diagnostic ultrasound Focused assessment with sonography in trauma (FAST)
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a rougher, grainier image. The interface between the smooth lines of the chest wall and the rough texture of the moving lung has been described as a “waves on a beach” or “seashore” image ( Figure 2.47A ). In the case of pneumothorax, no motion will be visible in the chest wall or lung. Thus the lines will be uniformly straight and smooth. This has been called the “barcode” sign ( Figure 2.47B ) [ 34 ]. One of the most specific signs for pneumo- thorax has been described as the “lung point” sign. This is where the area of pleural reattachment can be seen, represented on ultrasound by an image which is half no lung sliding and half lung sliding [ 34 ]. M-mode demonstrates (A) (B) Figure 2.47 ( A ) The “seashore” or normal lung: the pleural line marks a difference in texture above and below (moving lung below the pleura). ( B ) The “barcode sign,” with the same texture seen above and below the pleural line. Diagnostic ultrasound 55 Focused assessment with sonography in trauma (FAST)
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this in a still image by showing half the image as “seashore” and half as “barcode” ( Fig 2.48 ). One of the most important things to remember when evaluating the thoracic cavity for pneumothorax is that the probe can only interrogate the area of pleura directly beneath the probe footprint. Therefore, if the patient is upright, the most important place to look for a pneumothorax is the apices bilaterally. If a patient is supine, the most important place to look for a pneumothorax is the anterior chest wall. If a patient has penetrating trauma or has just had a procedure, the most important place to look for lung sliding is directly below the point of penetration. Obviously looking in more places increases the sensitivity and specificity of the exam. New directions As promised, most chapters will try to stimulate creative thinking about new diagnostic applications for bedside ultrasound. One interesting idea is the concept of using M-mode to diagnose diaphragmatic injury. Diaphragmatic injuries are notoriously difficult to diagnose; even CT scans can be fooled. The gold standard is usually laparoscopy or laparotomy to directly visualize the diaphragm. Blaivas et al . [35 ] describe using M-mode to show whether the diaphragm maintains its respiratory movement/contraction or whether it becomes fixed after injury. Cases where fixed M-mode images correlate with diaphragmatic injury are reported ( Figure 2.49 ). Another area for research is the evaluation of trauma ultrasound applica- tions in the prehospital setting. Could identifying intraperitoneal fluid in a Figure 2.48 M-mode imaging demonstrating the “lung point” sign (half “seashore,” half “barcode”).
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