Ultrasound: Lungs

Technique

• Use linear probe
  • Can use curvilinear or phased array probe, but will need to decrease depth
• Place the probe vertically (marker toward head) over the 2nd intercostal space at the midclavicular line
• Adjust your view in order to see a rib on each side of the screen (designated by rib shadow)
• Look between the ribs for "lung sliding"
  • To document sliding on a single image, use M mode ("waves on a beach")
• Can continue to evaluate each intercostal space for sliding if needed

Specific Indications

Bedside Lung Ultrasound in Emergency (BLUE) Protocol

Algorithm for the Use of Ultrasound in the Evaluation of Dyspnea

• Predominant A lines + lung sliding = Asthma/COPD
• Multiple predominant B lines anteriorly with lung sliding = Pulmonary Edema
• Normal anterior profile + DVT= PE
• Anterior absent lung sliding + A lines + lung point = Pneumothorax (PTX)
• Anterior alveolar consolidations, anterior diffuse B lines with abolished lung sliding, anterior asymmetric interstitial patterns, posterior consolidations or effusions with out anterior diffuse B lines = Pneumonia

Lung ultrasound of pneumothorax

• No lung sliding seen (not specific for pneumothorax)
• May also identify "lung point": distinct point where you no longer see lung sliding (pathognomonic)
• Absence of lung sliding WITHOUT lung point could represent apnea or right mainstem intubation
• Evaluate other intercostal spaces because pneumothorax may only be seen in least dependent area of thorax
  • NO comet tail artifact
  • Bar Code appearance/"Stratosphere" sign on M-mode (absence of "seashore" waves)
• Ultrasound has greater sensitivity than chest x-ray for pneumothorax in trauma patients

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Lung ultrasound of pulmonary edema

Lung ultrasound showing pulmonary edema.

• A lines and B lines
  • A lines:
    • Appear as horizontal lines
    • Indicate dry interlobular septa.
    • Predominance of A lines has 90% sensitivity, 67% specificity for pulmonary artery wedge pressure <= 13mm Hg
    • A line predominance suggests that intravenous fluids may be safely given without concern for pulmonary edema
  • B lines ("comets"):
    • White lines from the pleura to the bottom of the screen
    • Highly sensitive for pulmonary edema, but can be present at low wedge pressures

Further Reading

• Ultrasound (Main)