Lung Ultrasound & the BLUE Protocol: The New "Visual" Stethoscope for Anesthesiologists
In the high-stakes environment of the OR and the ICU, time is the ultimate variable. When a patient develops acute respiratory failure, waiting for a portable X-ray or transporting a hemodynamically unstable patient to CT can be risky, if not impossible.
Enter the BLUE Protocol (Bedside Lung Ultrasound in Emergency). Developed by Professor Daniel Lichtenstein, this diagnostic algorithm allows an anesthesiologist to identify the cause of dyspnea with over 90% accuracy in under 3 minutes.
What is the BLUE Protocol?
The BLUE Protocol is a standardized ultrasound algorithm designed for the rapid differential diagnosis of acute respiratory distress. By focusing on specific artifacts rather than traditional imaging, it provides immediate clinical answers.
Standardized Scanning: The BLUE-Points
To ensure reproducibility—much like the six leads of an ECG—the BLUE-protocol utilizes six standardized points (three on each side) that maximize lung coverage while avoiding the heart:- Upper & Lower BLUE-points: These are located using a "two-hand" technique tailored to the patient’s size. With the upper little finger placed just below the clavicle and fingertips at the midline (excluding thumbs), the Upper BLUE-point is at the center of the upper hand. The Lower BLUE-point is located at the center of the lower palm.
- The PLAPS-point: Essential for detecting Posterolateral Alveolar and/or Pleural Syndrome, this point is found at the intersection of a horizontal line from the lower BLUE-point and the vertical posterior axillary line.
- Dynamic Scanning: From the PLAPS-point, the clinician can adjust the probe in two directions: (1) as posteriorly as possible to gather data from supine, sedated patients, or (2) downward if no pathology is immediately detected.
Scanning these six spots is sufficient to achieve the protocol’s documented 90.5% diagnostic accuracy
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- Upper & Lower BLUE-points: These are located using a "two-hand" technique tailored to the patient’s size. With the upper little finger placed just below the clavicle and fingertips at the midline (excluding thumbs), the Upper BLUE-point is at the center of the upper hand. The Lower BLUE-point is located at the center of the lower palm.
- The PLAPS-point: Essential for detecting Posterolateral Alveolar and/or Pleural Syndrome, this point is found at the intersection of a horizontal line from the lower BLUE-point and the vertical posterior axillary line.
- Dynamic Scanning: From the PLAPS-point, the clinician can adjust the probe in two directions: (1) as posteriorly as possible to gather data from supine, sedated patients, or (2) downward if no pathology is immediately detected.
The Ultrasound Alphabet: Lung Signs and Artifacts
To master the BLUE Protocol, one must recognize these essential sonographic markers:
Lung Sliding: The back-and-forth movement of the visceral pleura against the parietal pleura. Its presence rules out pneumothorax at that specific point.
A-lines: Horizontal, hyperechoic "reverberation" artifacts indicating a normally aerated lung.
Longitudinal ultrasound scan of the second intercostal space in the mid-clavicular line on anterior chest wall depicting sonographic appearance of normal lung, identified by the landmarks forming the “bat sign”: two ribs (R) with posterior acoustic shadowing representing the wings of the bat, and the hyperechoic pleural line (asterisk), its body. A-lines (arrowheads) can be seen parallel to the pleural line:The A-profile is defined by the presence of both lung sliding and A-lines on anterior scans, bilaterally. Sometimes one or two B-lines with lung sliding may also be seen and are also included under A-profile:
B-lines: Vertical, laser-like "comet-tail" artifacts. Three or more B-lines in one view suggest interstitial edema.
Lung Point: The specific transition zone where lung sliding disappears and reappears—the "gold standard" ultrasound sign for pneumothorax.
Diagnostic Profiles: From Artifacts to Diagnosis
The protocol categorizes findings into specific "profiles" that correlate with clinical pathologies:
| Profile | Sonographic Findings | Likely Diagnosis |
| A-Profile | Lung sliding + A-lines | COPD or Asthma (Rule out PE via leg veins) |
| B-Profile | Lung sliding + Diffuse B-lines | Pulmonary Edema (Cardiogenic) |
| A' Profile | Absent sliding + Lung Point | Pneumothorax |
| B' Profile | Absent sliding + B-lines | Pneumonia |
| A/B Profile | Asymmetrical findings (A one side, B other) | Pneumonia |
| C-Profile | Anterior alveolar consolidation | Pneumonia |
Why Anesthesiologists Need This Tool Today
Immediate Decision Making: Instantly decide whether to intubate, administer diuretics, or insert a chest tube.
Radiation-Free: Eliminates unnecessary X-ray exposure for patients and staff, especially critical in pediatrics and pregnancy.
Dynamic Monitoring: Assess the effectiveness of recruitment maneuvers or fluid resuscitation in real-time.
Superior Sensitivity: Ultrasound is significantly more sensitive than supine chest X-rays for detecting small pneumothoraces and pleural effusions.
Conclusion
Lung ultrasound is no longer an "optional" skill; it is the evolution of physical examination. For the modern anesthesiologist, the BLUE Protocol transforms the ultrasound probe into a powerful diagnostic extension of our clinical intuition.
Pro-Tip for Colleagues: Start by scanning your stable, pre-operative patients. Familiarizing yourself with "normal" lung sliding and A-lines will make identifying pathology in a crisis second nature.
