Ultrasound: Lungs

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Lobes of the lung with related anatomy.
  • 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
  • Landmark study by a French intensivist that described various profiles of specific pulmonary disease found on US[2]
  • Ultrasound approaches include anterior zones and PLAPS (posterior or lateral alveolar and/or pleural syndrome) point, which is located at the posterior axillary line similar to FAST view
  • Predominant A lines anteriorly + lung sliding = Asthma/COPD
  • Multiple predominant B lines anteriorly + lung sliding = Pulmonary Edema
  • Predominant A lines anteriorly + lung sliding + positive DVT = PE
  • Absent anterior lung sliding + anterior A lines + positive lung point = Pneumothorax (PTX)
  • PLAPS findings +/- A or B lines +/- abolished lung sliding = Pneumonia
    • PLAPS describes changes at the PLAPS point, usually related to consolidations and pleural effusions[3]
    • Consolidations may include lung hepatization, shred sign, air bronchograms
      • Note that mirroring (normal) may appear similar to hepatization, but mirroring only shows in specific spots due to specific echogenic windows
    • Pleural effusions are visualized as anechoic/hypoechoic areas with possible spine sign or floating lung sign (sinusoid sign on M-mode)
  • A suggested BLUE protocol guides diagnosis of dyspnea; this should be modified as needed based on clinical presentation
    • Check lung sliding in anterior lung fields ---> check for A and B lines ---> check for PLAPS findings

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 [4]

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


  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. Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008 Jul;134(1):117-25. doi: 10.1378/chest.07-2800. Epub 2008 Apr 10. Erratum in: Chest. 2013 Aug;144(2):721. PMID: 18403664; PMCID: PMC3734893.
  3. Lichtenstein DA. Lung ultrasound in the critically ill. Ann Intensive Care. 2014 Jan 9;4(1):1. doi: 10.1186/2110-5820-4-1. PMID: 24401163; PMCID: PMC3895677.
  4. 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.