A review of the literature describes a technique that

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only for trauma but also for many critical care fields of medicine. A review of the literature describes a technique that first identifies the pleural line. A normal ultrasound examination of the lung includes both lung sliding and comet tail artifacts. Lung sliding is the back-and-forth movement of the visceral pleura synchronized with respiration, as seen in real-time scanning. Comet tail artifacts occur when the ultrasound beam bounces back and forth between two closely spaced interfaces, causing multiple reverber- ations to merge and form a comet tail pattern or bright line (see Chapter 1 ). If a pneumothorax is present, air within the pleural space hinders the propaga- tion of ultrasound waves, thereby preventing the formation of comet tail Reference Methods Results Notes Scalea et al . 1999 [ 27 ] First consensus statement on how to use FAST in clinical algorithm. NA Has not been prospectively validated to date. Sisley, et al . 1998 [ 22 ] Results from initial chest x-ray (CXR) and chest US compared in 360 trauma patients. US more sensitive (97.5% vs. 92.5% in 360 patients with 40 effusions) and faster (1.3 vs. 14.2 min) in diagnosing traumatic hemothoraces. Comparison with gold standard showed US to be superior for hemothorax diagnosis. Rowan et al . 2002 [ 24 ] Results from chest US compared to CXR and CT scan test results. 11 pneumothoraces in 70 patients. Thoracic US detected 11/11, CXR 4/11. US as sensitive as CT, significantly more sensitive than CXR for pneumothorax diagnosis in trauma patients. Ma et al . 2008 [ 29 ] First longitudinal study looking at novice sonographer learning curve over 18 months with respect to test accuracy. Evaluated image interpretation accuracy at 6-month intervals in an emergency medicine (EM) residency training program. At 12 months (or after performing 35 examinations) novice EM residents achieved accuracy numbers consistent with published data for FAST exams. Diagnostic ultrasound 51 Focused assessment with sonography in trauma (FAST)
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artifacts and obscuring lung sliding as the visceral pleura is no longer visual- ized. Therefore, an ultrasound is positive for pneumothorax when lung sliding and comet tail artifacts are absent. One advantage of bedside ultra- sound is that each patient will have his or her own control, because compar- ing left to right thorax will often help make the diagnosis easier. A second technique uses M-mode to visually demonstrate lung sliding or absence of lung sliding (as described in the following section). Technique Using a high-frequency linear transducer (5.0–10.0 MHz), longitudinal scans of the anterior chest wall are obtained with the patient in the supine position ( Figure 2.43 ). Place the transducer over the third or fourth intercostal space anteriorly and in the third to fifth intercostal space in the anterior axillary line. The respiratory expansion of the lung (and thus the amount of sliding) may be greater in the anterior axillary-line view. It is also possible to use the same lower-frequency probe (2.5–5 MHz) that is used for FAST exams.
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