The BLUE Protocol
BLUE = Bedside Lung Ultrasound in Emergencies
Described by Dr David Lichtenstein
Ref: Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure. The BLUE Protocol. Lichtenstein & Meziere. Chest 2008.
Each hemithorax can be divided into 3 points (See Diagram Below):
- Upper BLUE Point
- Lower BLUE Point
- PLAPS Point – Posterior or Lateral Alveolar / Pleural Syndrome Point (+ve or -ve sign)
Image From: Application of Lung Ultrasound in Critical Care Setting. Raheja et al. Cureus. 2019
STEP 1 – Start by scanning the upper and lower BLUE points in each half of the chest. Look for the presence of lung sliding first.
STEP 2 – The next step is to look for the presence or absence of A and B Lines on both sides.
The following decision tree can then be used to make a diagnosis.
Decision Tree of BLUE Protocol – ‘ Prime Indicates Absence of Lung Sliding. Click For Larger Image
Lung sliding and bilateral B lines in a dyspneic patient likely indicates pulmonary oedema.
Absent lung sliding with B lines (B’ profile) indicates pneumonia – lung sliding is abolished because a severely consolidated lung will unlikely have ventilation. B lines in this scenario indicates the presence of fluid / pus in the alveoli.
Absent lung sliding with A lines (A’ profile) likely indicates the presence of pneumothorax – Look for a lung point which may or may not be present. Absence of a lung point may still be consistent with pneumothorax, but further imaging with other modalities may be required.
Prime – ‘ – Indicates absence of lung sliding
STEP 3 – The base of the lung – PLAPS point – is scanned next if no diagnosis has been made after scanning the anterior 2 points.
A positive PLAPS sign (presence of consolidation / effusion) likely indicates pneumonia as a cause of respiratory failure. A negative PLAPS sign may indicate COPD/Asthma or Pulmonary Embolism as a cause of dyspnea.
Sensitivity / Specificity of Lung Ultrasound for Common Causes of Dyspnea