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Learning objectives:
Describe the basic lung ultrasound terminologies: A-lines, B-lines, lung sliding, lung pulse, lung point, PLAPS, rib shadows.
Recognize the characteristic image of consolidated lung.
Identify air artifacts suggestive of the normal aeration pattern: A-lines with sliding lung.
Identify air artifacts suggestive of alveolar interstitial pattern: number and location of B lines.
Recognize the air artifacts that allow ruling out pneumothorax: presence of sliding lung/lung point (via direct visualization of the sliding pleura or through M-mode) and presence of B-lines.
Recognize the findings that rule in pneumothorax: presence of lung point (by 2D imaging and M-mode).
Key points:
Probes used for lung exam:
Phased-array transducers (low freq.) are used for complete thoracic ultrasound exams.
Linear transducers (high freq.) should be limited to anterior thoracic exams for the presence of lung sliding and interstitial syndrome. They are also used when looking for the seashore sign (normally areated lung) vs barcode sign (pneumothorax)
An abdominal exam setting is used if the machine does not have a lung exam configuration.
The lung was classically thought to be an organ that was not conducive to US examination because of the highly reflective properties of air.
Lung ultrasound (LUS) is based on the interpretation of artifacts created by the pleural line.
Lichtenstein and others demonstrated that the artifacts are few, easily detected and they correlate strongly with pathology.
LUS has been shown to be more sensitive than CXR for:
interstitial syndromes (sensitivity 94% vs. 46%)
consolidation (sensitivity 100% vs. 38%)
pleural effusion (100% vs. 65%)
pneumothorax (88% vs. 52%)
Transducer should be placed within rib interspaces ensuring the ultrasound beam is perpendicular to the pleural surface. At least three to four interspaces in each hemithorax should be examined (The original BLUE protocol requires only 3 in each side with good accuracy). A full exam consists of 12 (6 in each hemithorax).
For this purpose the thorax can be divided as such:
3 zones: Anterior, lateral and posterior which are further divided into upper and lower zones.
Posterior zone not shown in image above
Lung ultrasound anatomy
Lung ultrasound anatomy
The "Bat Sign": The ribs represent the wings and the pleural line the body of the bat.
Normal pleural line with lung sliding imaged with a linear array transducer.
Definitions:
Definitions:
Lung sliding: Seen in healthy lungs as a shimmering visceral pleura surface moving freely with respirations. Means the two pleuras are adjacent and that the lung volume is changing.
Lung sliding or "shimmering". Also been described as "ants marching"
A-lines: Horizontal, hyperechoic lines that are equidistant repetitions of the pleural line. They are static.
A = air (when sliding lung is also present means the lung is normally aerated)
B-lines: B-lines represent a thickened interstitium such as that seen in pulmonary edema or pulmonary fibrosis. They are vertically oriented lines that:
Extend from the pleural surface to the maximum depth of the image
Move in conjunction with lung sliding
Obliterate A lines
1-2 B lines are considered normal
B = Bad IF more than 2 B-lines are present then they are called lung rockets or glass rockets (i.e. interstitial syndrome or "B-pattern")
Two types of B- lines:
Left: four or five B-lines are visible, called lung rockets.
Right: twice as many B-lines, called ground-glass rockets.
B- lines seen in pulmonary edema
Three/four B lines between two ribs are called septal-rockets, correlating with thickened subpleural interlobular septa; Five B lines or more (up to a dozen, making a white pattern), are called glass rockets, correlating with CT ground-glass opacities
Lung pulse: Analogous to lung sliding, produced when cardiac motion causes the pleuras to slide with respect to each other.
Lung point: In patients with pneumothorax is the point where visceral and parietal pleura separate. At this transition point image changes from lung signs (lung sliding+A lines) to pneumothorax signs (e.g. lack of lung sliding + A lines). 100% for pneumothorax.
Lung-Point.m4vPLAPS-point: Postero-Lateral Alveolar and Pleural Syndrome. Localized in the lower lobe. This is the lowest point of the lung and is the place you will most likely find pleural fluid. Located at the level at the level of lower BLUE point and posterior mid-axillary line. If no fluid is found here, there is likely no fluid anywhere in the thorax.
PosteroLateral = Around the back
Alveolar = Consolidation
Pleural Syndrome = Pleural fluid
Most lung consolidation cases (90%) are located at this point.
Seashore Sign
M-mode representation of lung sliding. Top part of image (above echogenic pleura) has a "wavelike" pattern (sea) while bottom part of image (below the pleura) has a speckled or "sandlike" pattern. This indicates normal lung sliding and a normal aeration pattern.
Barcode Sign
Abnormal M-mode sign pathognomonic of pneumothorax. Linear pattern is present above and below the pleura.
A seashore as seen from above
The BLUE (Bedside Lung Ultrasound in Emergency) Protocol:
Algorithm designed for evaluation of acute respiratory failure, classifies patients into "profiles" depending on the presence of lung sliding + A or B lines +/- consolidation (C-profile).
Toronto General Hospital Lung Ultrasound application:
Visit the website to access the 3D lung ultrasound application, copy and paste the link in Internet Explorer or Edge as the application requires Flash (not supported by Google Chrome).
http://pie.med.utoronto.ca/POCUS/POCUS_content/lungUS.html#instructions
Lung ultrasound videos:
Lung ultrasound videos:
Recommended reading:
BLUE protocol.pdfIntensive Care US III Lung and Pleural US Doerschug Annals ATS 2013.pdfCurrentMisconceptionsLUCI.pdfGoogle Sites
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