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Step sign: glide sign deviates from its normal continuity. Suggests thoracic trauma, or in non- trauma patients, lung consolidation/ masses.
So in general we can say that:
Pneumothorax is ruled out if a glide sign and/or B-lines are detected;
Pneumothorax is strongly suspected when glide sign and B-lines are absent.
Pneumothorax is definitively confirmed if lung point is identified.
Emergency lung ultrasound to detect interstitial- alveolar lung injury:
BLUE (bedside lung evaluation): the key concept in this setting is the detection of B-lines that originate from
the pleural line. The proximity and number or density of B-lines correlate with extravascular lung water, and the anatomic location of B-lines with respect to lung anatomy correlates with different pathologic lung conditions. Emergency lung ultrasound may add a particular niche in differentiating underlying causes of respiratory distress in the severely dyspneic patient that is in too unstable a condition to allow thoracic radiography.
Vet Blue is performed from both sides of the chest wall with 4 points in each side.
· Caudo dorsal lung view (Cd) similar to the CTS view in TFAST
· Perihilar lung region (Ph)- caudorsal 6-7 intercostal space
· Middle lung lobe (Md)- at 4-5 intercostal space
· Cranial lung region (Cr)- 3-4 intercostal space.
What signs and lines we can see in VET BLUE;
A-lines: a result of reverberation artifact causes the pleural line to be replicated in the sonographic far field. The distance between subsequent A-lines corresponds to the same distance between the skin surface and
the parietal pleura. A-lines should be seen in the normal lungs, but also may be seen in patients with pneumothorax. A-lines should not be confused with the pleural line.
B-lines: (ring-down/ comet tail/ lung rockets) are reverberation artifacts originating from the visceral pleura lines appear as hyperechoic vertical lines extending from the pleural line to the edge of the far field image, passing through A-lines without fading. B-lines move in a to-and- fro fashion (pendulum) with inspiration and expiration, and are synchronous with the glide sign. An occasional B-line is considered normal; excessive B-lines are indicative of interstitial-alveolar lung abnormality. When B-lines are numerous they called a B-pattern.
Lung curtain- the lung artifact created by movement of the lungs at the costo-phrenic angles creates a vertical
sliding artifact similar to the opening and closing of a theater curtain, which should not be confused with the glide sign. The ultrasound probe should be moved cranially if the curtain sign is noted.
A glide sign with A lines (horizontal lines) is considered
a normal lung or “Dry Lung” only to be confounded with the pneumothorax (dry lung with absent glide sign). When B lines or so called lung rockets are presented the lung will be defined as Wet Lung meaning parenchyma lung abnormality (e.g lung edema, contusion and bleeding, pulmonary masses, lung infiltaration).
Here are some examples from Liscando et al.
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