II. Technique

  1. 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
  2. Landmarks
    1. Rib (with shadowing)
    2. Lung Interspace
      1. Chest wall
      2. Pleural line
      3. Rib (with shadowing)
  3. Artfacts
    1. A-Lines: Pleural line reverberation artfacts (horizontal lines at regular intervals)
      1. Normal finding
    2. B-Lines: Lung rockets (vertical wedges)
      1. Indicates Interstitial Edema
      2. Significant findings consistent with B-Lines
        1. Three or more rays in a single intercostal view (known as B+ lines)
        2. B-Lines start at the pleural line (not in the soft tissue)
        3. B-Lines descend the entire length of the screen
        4. B-Lines obscure A-Lines which are not typically visible
        5. B-Lines move with respiration
      3. Distinguish from similar artifacts
        1. Comet tail artifacts
          1. Partial rays that do not descend the length of the screen
          2. A-Lines typically still visible
        2. Superficial artifacts
          1. Rays start superficial to the pleural line
      4. Generalized B-Lines
        1. Volume overload (e.g. CHF)
        2. ARDS
      5. Localized B-Lines
        1. Pneumonia
        2. Pulmonary Contusion
  4. Sliding Lung Sign present (normal findings)
    1. Marching-ants appearance
    2. Changes on M-mode
      1. Top: Bar code pattern (skin to pleura)
      2. Bottom: Seashore granular appearance (lung)
  5. Miscellaneous Findings
    1. Pleural Effusion
      1. Anechoic (black space) surrounds a triangle of well-defined lung
      2. Exudative fluid may appear hyperechoic (white)
    2. Consolidation
      1. Consolidated lung tissue appears similar to liver tissue on Ultrasound
      2. Pulmonary Edema
      3. Pneumonia
      4. Lung Contusion
      5. Lung Neoplasm
    3. PLAPS (Posterolateral alveolar and/or pleural syndrome)
      1. Best seen at the most posterior and inferior accessible point above the diaphragm in a supine patient
      2. Positive if Pleural Effusion or consolidation

III. Interpretation

  1. Pneumothorax
    1. See Lung Ultrasound for Pneumothorax (Sliding Lung Sign, Lung Point)
  2. Pneumonia
    1. Focal or unilateral B-Lines (fluid in alveoli)
    2. Subpleural consolidation
      1. Consolidated lung tissue appears similar to liver tissue on Ultrasound
    3. Parapneumonic Effusion
  3. Interstitial Syndrome
    1. Excessive alveolar fluid as seen in CHF exacerbation
    2. Prominent B-Lines obscure other findings (and A-Lines disappear)
  4. Negative Lung Ultrasound
    1. Dyspnea due to COPD/Asthma, Pulmonary Embolism or non-respiratory cause (e.g. Anemia)
  5. Pleural Effusion
    1. See Pleural Effusion
    2. More accurate than Chest XRay in detecting a Pleural Effusion (operator dependent)
      1. Detects Pleural Effusion volumes as small as 5 ml
      2. Test Sensitivity 94%, Test Specificity 98% (varies with operator experience)
    3. Identifies Pleural Fluid septations more accurately than CT
    4. Recommended for guiding Thoracentesis

IV. Efficacy

  1. Limited by shadowing from bullae (COPD), subcutaneous air, and tight rib spaces
  2. POCUS in Acute Dyspnea speeds time to correct diagnosis
    1. Also increases the accuracy of CHF, Pneumonia, PE and Pleural Effusion diagnosis
    2. Does not appear to reduce mortality, hospital length of stay or readmission rates
    3. (2021) Ann Intern Med 147(7): 985-93 [PubMed]

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