Ultrasound: Lungs

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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[1]

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 [2]

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

References

  1. http://ccm.anest.ufl.edu/files/2012/08/BLUELung.pdf Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure - The BLUE Protocol
  2. Nagarsheth K, Kurek S. Ultrasound detection of pneumothorax compared with chest X-ray and computed tomography scan. Am Surg. 2011 Apr;77(4):480-4. PMID: 21679560.