BLUE protocol

Not to be confused with Blue Protocol.

The BLUE (Bedside Lung Ultrasound in Emergency) protocol is a standardized method for using lung ultrasound in emergency and critical care settings.^[1] In 2008, it was introduced by Daniel Lichtenstein and Gilbert Mezière and has been used to diagnose acute respiratory failure in critically ill patients.^[1] It was first proposed in 1996 and rejected repeatedly until being accepted twelve years later.^[2] Lung ultrasound has been shown to provide timely diagnosis of acute respiratory failure in about 90% of cases.^[1] It can be performed under 3 minutes.^[3]

BLUE Protocol. Adapted from Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008 Jul;134(1):117-25.

Overview

The BLUE protocol is a systematic approach to evaluating lung pathology through ultrasound, allowing for rapid differentiation of conditions such as COPD or asthma, pneumothorax, pulmonary edema, pneumonia, and pulmonary embolism.^[1] By assessing specific lung zones and identifying characteristic ultrasound patterns, clinicians can quickly determine the cause of respiratory failure at the bedside.^[1] In the emergency department setting, the BLUE protocol can be modified for assessment of pericardial and pleural effusions.^[4]

Methodology

The protocol involves scanning specific areas of the thorax using a bedside ultrasound machine.^[1] There are three standardized points to scan: upper BLUE-point, lower BLUE-point and PLAPS (posterolateral alveolar and/or pleural syndrome)-point.^[3][5] The interpretation of lung ultrasound findings follows established patterns, including A-lines, B-lines, lung sliding, and pleural effusions.^[1] Based on the appearance of the images, it is identified as one of the following profiles: A (A lines in all 4 BLUE points), A' (A profile without lung sliding), B (3 or more B-lines in all 4 BLUE points), B' (B profile without lung sliding), and A/B (various findings of A lines and B lines) or C (consolidation in one of the BLUE points).^[1]

Advantages and limitations

The protocol offers several advantages over traditional imaging methods such as chest X-ray and CT scans.^[1] It is rapid, radiation-free, and cost-effective.^[1]

It can be limited due to operator dependence, variability in interpretation, and need for the right equipment.^[1]