Ultrasound - Lung
To assess and exclude or confirm the presence of:
Interstitial lung fluid (heart failure)
Consolidation (pneumonia or atelectasis)
Consider in the following presentations:
Contraindications (absolute in bold)
Tension pneumothorax requiring emergency decompression
Consent is not required if the patient lacks capacity or is unable to consent
Brief verbal discussion is recommended if the situation allows
Less complex non-emergency procedure with low risk of complications
Failure to visualise structures (excess tissue, gas in tissue, pain)
Failure of image interpretation (false negative or positive)
PPE: non-sterile gloves
Ultrasound machine and gel
Linear ultrasound probe (focused at pleural line)
Phased array ultrasound probe or curvilinear ultrasound probe (depth set to 15cm)
Semi-recumbent or supine (trauma)
Place linear probe longitudinally at the midclavicular just inferior to the clavicle
Identify the pleural line beneath the ribs
Evaluate for pleural sliding, shimmering (indicating pleural opposition)
Reassess proximally and distally
Consider using M-mode evaluation over time (seashore sign excludes pneumothorax)
Scanning (pleural effusion)
Select phased array ultrasound probe or curvilinear ultrasound probe (depth set to 15cm)
Oblique placement between ribs 8-11 at right mid-axillary line (marker to patient’s head)
Identify kidney, liver and diaphragm then rock probe to evaluate above the diaphragm
Oblique placement between ribs 6-9 at left posterior axillary line (marker to patient’s head)
Identify spleen, liver and diaphragm then rock probe to evaluate above the diaphragm
Free fluid in the hemithorax will be identified as an anechoic area above the diaphragm
If an effusion is seen, assess for consolidated lung visualised within a large effusion
If no fluid is seen, look for mirror image artefact and the spine sign to exclude pleural fluids (see below)
Scanning (interstitial lung fluid and pneumonia)
Select the phased array ultrasound probe with depth set to 15cm (or curvilinear ultrasound probe)
Using the anterior axillary line and the nipple line, divide each hemithorax into four zones
Orienting the transducer longitudinally in each zone identify two ribs and the pleural line beneath
Assess for multiple B lines indicating interstitial fluid (reverberation artefacts extending to the far field)
Assess for hepatisation of the lung indicating consolidation (lung appears similar to the liver)
Clean ultrasound gel from patient
Initiate further management if required
Document (indication, structures identified, interpretation)
Avoid confusing movement of the pericardium with pleural sliding in the left chest
Anterior two regions scan can exclude severe interstitial syndrome or pneumothorax in the critically ill
Subtle pathology requires multiple scanning positions (early pneumonia, apical pneumothorax or mild CCF)
Use lung pre-set (or turn off filter settings and image enhancing features) when looking for B lines
Pleural opposition excludes pneumothorax and can be confirmed by observing sliding or shimmering of the visceral on parietal pleura. The absence of pleural sliding is not 100% specific for pneumothorax. Other causes include immobility of the pleural or lung in conditions such as pleurodesis, pleural scarring, lung contusions, bronchial obstruction, and advanced bullous emphysema. Comet tails (reverberation artefact similar to B lines) and B lines (see below) also help confirm the absence of pneumothorax.
When scanning for pleural effusions, free fluid in the hemithorax is confirmed by anechoic area above the diaphragm. If this is not present pleural fluid is excluded by confirming a mirror image artefact of the diaphragm and the loss of visualisation of the spine and vertebral bodies during inspiration (spine sign). Both features demonstrate that the thoracic cavity is full of air.
If there is fluid in the interstitial tissue the lung begins to reflect ultrasound waves which would normally be scattered. This is seen as vertical, bright, torch like white ‘B lines’ which originate at the pleura and are transmitted the full length of the screen. These B lines move back and forth with respiration as the pleura move. A normal lung may have occasional B lines (maximum three on screen in any window), but increased B lines indicates increased pleural fluid. As interstitial fluid increases to severe levels, these lines start to coalesce and become wedge-shaped. Bilateral extensive B lines suggest volume overload, heart failure or acute respiratory distress syndrome. Unilateral or localised B lines suggest focal pneumonitis which may progress to lung consolidation, demonstrated by increased lung density and the appearance of lung changing to that of liver (hepatisation).
This guideline has been reviewed and approved by the following expert groups:
Emergency Care Institute
Please direct feedback for this procedure to ACI-ECIs@health.nsw.gov.au.
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