II. Indications

  1. Severe Acute Dyspnea evaluation in critical care patients (Acute Respiratory Failure)
  2. Distinguish acute Dyspnea Causes in a critical care patient
    1. Pneumothorax
    2. Pneumonia
    3. Acute cardiogenic pulmonary edema
    4. Pulmonary Embolism
    5. Obstructive Lung Disease (COPD, Asthma)

III. Background: Zones

  1. Zone 1: Anterior chest
    1. Mid-clavicular line at 2nd to 3rd intercostal space
    2. Assess for Sliding Lung Sign and artifacts (A-Lines and B-Lines)
  2. Zone 2: Lateral chest above nipple line
    1. Anterior axillary line lateral and slightly superior to nipple
    2. Assess for Lung Point and artifacts (A-Lines and B-Lines)
  3. Zone 3: Posterior chest
    1. Posterior axillary line at most inferior point above diaphragm
    2. Assess for PLAPS (Pleural Effusion or consolidation)
  4. Images
    1. ultrasoundProbePositionLungBlueZones.jpg

IV. Background: Lung artifact categories

  1. See Lung Ultrasound
  2. See Lung Ultrasound for Pneumothorax
  3. Pneumothorax findings
    1. Sliding Lung Sign
    2. Lung Point
  4. Lung edema
    1. B+ Lines (3 or more B Lines in a single view)
  5. PLAPS (Posterolateral alveolar and/or pleural syndrome)
    1. Pleural Effusion (hypoechoic region)
    2. Consolidation (lung with Ultrasound appearance of liver without the sinusoids)
  6. Profiles
    1. A Profile
      1. A lines predominate in both hemithoraces (Zones 1 and 2)
    2. B Profile
      1. B+ lines predominate in both hemithoraces (Zones 1 and 2)
    3. AB Profile (C profile)
      1. A lines predominate in one hemithorax (Zones 1 and 2)
      2. B lines predominate in the other hemithorax (Zones 1 and 2)

V. Technique

  1. Cardiac or Linear high frequency Ultrasound probe (Lichtenstein used 5 MHz micro-convex probe)
  2. Ultrasound probe directed longitudinally (indicator toward 12:00)
  3. Turn off all Ultrasound machine automatic features that reduce artifact (technique depends on maximizing artifact)
    1. Tissue harmonic imaging (THI) off
    2. Multi-Beam Imaging (Sono MB) off

VI. Interpretation

  1. Lung Sliding present
    1. A Profile
      1. Perform DVT Ultrasound and Lung Ultrasound of Zone 3
      2. DVT Ultrasound positive
        1. Venous Thromboembolism
      3. PLAPS positive (Pleural Effusion or consolidation)
        1. Pneumonia
      4. PLAPS negative
        1. Obstructive Lung Disease (Asthma or COPD)
    2. B Profile
      1. Pulmonary edema
    3. AB Profile (C Profile)
      1. Pneumonia
  2. Lung sliding absent
    1. A Profile
      1. Lung Point present
        1. Pneumothorax
      2. Lung Point absent
        1. Obtain additional studies to evaluate
    2. B Profile
      1. Pneumonia
    3. AB Profile (C Profile)
      1. Pneumonia

VII. Efficacy

  1. Protocol delivered diagnosis in 90.5% of Acute Respiratory Failure cases

VIII. Pitfalls

  1. Operator dependent (learning curve)
  2. Pulmonary Embolism
    1. High False Negative Rate (approaches 20%)
    2. Use protocol as rule-in (not rule-out)
  3. Diaphragm paralysis
    1. Results in False Positive study
    2. khosla (2010) Chest 137(6):1487-8 [PubMed]

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