Lung Ultrasound for Pneumothorax

Aka: Lung Ultrasound for Pneumothorax, Sliding Lung Sign, Lung Point

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II. Indications

  1. FAST Exam
  2. Pneumothorax Evaluation

III. Technique: Bilateral lung apices (part of Extended FAST Exam or eFAST)

  1. Transducer
    1. Linear probe (preferred) or
    2. Cardiac phased array probe (more convenient during eFAST Exam)
  2. Transducer positioning
    1. Placement: Lung Apex (3rd intercostal space in a supine patient), mid-clavicular line
    2. Axis: Long axis with indicator at 12:00
    3. Direction: Perpendicular to chest
  3. Landmarks
    1. Third rib (with shadowing)
    2. Third Interspace
      1. Chest wall
      2. Pleural line
      3. Sliding Lung Sign present (normal findings)
        1. Marching-ants appearance
          1. More prominent with color power doppler mode
        2. Changes on M-mode
          1. Top: Bar code pattern (skin to pleura)
          2. Bottom
            1. Normal: Seashore granular appearance (lung)
            2. Pneumothorax: Bar code throughout (known as stratosphere sign)
      4. Artfacts
        1. A-Lines: Pleural line reverberation artfacts (horizontal lines at regular intervals)
        2. B-Lines: Comet tail artifacts (vertical wedges)
    3. Fourth rib (with shadowing)
  4. Images
    1. ultrasoundProbePositionLungPneumothoraxLt.jpg
    2. ultrasoundProbePositionLungPneumothoraxRt.jpg

IV. Interpretation: Pneumothorax

  1. B-Lines (ray artifacts) absent
  2. A-Lines present
    1. Typically present in Pneumothorax (and increases Test Specificity)
  3. Sliding-lung sign absent
    1. No marching ants appearance
    2. Sliding Lung Sign is lost with even a 1 mm gap between parietal and visceral pleura
    3. Image
      1. ultrasoundBMP_lungPtxEvalSliding.jpg
  4. Lung pulse absent
    1. Cardiac pulsation may normally be present when parietal and visceral pleura are directly opposed
  5. M-Mode with bar code appearance continuously from top to bottom
    1. Confirm by having patient hold their breath
    2. ultrasoundBMP_lungPtxEvalMModeWNL.jpg
    3. ultrasoundBMP_lungPtxEvalMModeWNL2.jpg
    4. ultrasoundBMP_lungPtxEvalMModeAbnl.jpg
  6. Distinguish from heart motion artifact which can appear similar to sliding-lung sign
    1. Staying high in the chest (2nd intercostal space) avoids this potential False Negative finding
  7. Differential diagnosis of absent sliding lung sound includes apnea and shallow respirations
    1. Treat absence of Sliding Lung Sign with Chest Tube in a crashing patient with suspicion for Tension Pneumothorax
    2. May confirm absent Sliding Lung Sign by identifying the Lung Point
    3. Reasonable to obtain additional imaging to confirm Pneumothorax if patient stable without Tension Pneumothorax
      1. However, chest XRay Test Sensitivity for Pneumothorax is lower, especially in a supine patient
  8. Lung Point
    1. Can be used to estimate size of Pneumothorax
    2. Transition between normal lung and Pneumothorax
    3. Transition between Ultrasound seashore appearance and continuous bar code throughout

V. Diagnosis: Pneumothorax

  1. Sliding Lung Sign absent
      1. Test Sensitivity: 100%
      2. Test Specificity: 78% (see differential diagnosis below)
  2. Sliding Lung Signs absent AND A-Lines present
      1. Test Sensitivity: 95%
      2. Test Specificity: 94%
  3. References
    1. Lichtenstein (2005) Crit Care Med 33(6): 1231-8 [PubMed]

VI. Differential Diagnosis: Loss of Sliding Lung Sign

  1. Pneumothorax
  2. Mainstem intubation (esp. loss of left sided lung sliding)
  3. Pleural adhesions
  4. Pulmonary fibrosis
  5. Lung Contusion
  6. Acute Respiratory Distress Syndrome (ARDS)
  7. Pneumonia
  8. Atelectasis

VII. Efficacy

  1. Single view (third interspace) for Sliding Lung Sign is equivalent to four view on each side (each 93% Test Sensitivity)
    1. Helland (2016) Acad Emerg Med 23(10): 1170-5 +PMID: 27428394 [PubMed]

VIII. Resources

  1. FAST Exam - Pneumothorax (SonoSite)
    1. http://www.youtube.com/watch?v=26RQyxk5vGc
  2. Pneumothorax (Dr. Perera, SonoSite)
    1. http://www.youtube.com/watch?v=Xxdedx1HtHo

IX. References

  1. Reardon (2016) Lung Ultrasound, Stabroom.com online video, accessed 4/1/2016
  2. Reardon (2013) Emergency Ultrasound Course, 3rd Rock Ultrasound, Minneapolis, MN
  3. Alameda County Trauma Service FAST Exam
    1. http://eastbay.surgery.ucsf.edu/eastbaytrauma/Protocols/ER%20protocol%20pages/FAST-files/FAST.htm
  4. Mateer (2012) Introduction to Trauma Ultrasound Video, GulfCoast Ultrasound, VL-95-T
    1. https://www.gcus.com/products/about.asp?product=338/Introduction-to-Trauma-Ultrasound
  5. HCMC FAST Exam
    1. http://vimeo.com/1044031

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