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Bedside Lung Ultrasound in Emergency - the BLUE Protocol

Acute respiratory failure requires immediate action on the part of the healthcare provider. Timely, appropriate treatment is important to change the course of the disease and improve morbidity and mortality. Thus, bedside ultrasound is an ideal tool for the evaluation of changes in lung aeration present in many life-threatening conditions.

Each disease process has its own unique ultrasound profile. The BLUE protocol is a stepwise binary analysis of three lung signs which are evaluated at six standardized points, including venous analysis as required, to then generate disease profiles. It was proposed by D. Lichtenstein in 2008 as a tool to help the clinician rapidly reach a diagnosis in patients who present with acute respiratory failure.

How do you perform the BLUE protocol?

What probes do you need for the BLUE protocol?

Microconvex probe (3.5-5MHz) OR
Phased-array probe (3.5-5MHz)

What are the six standardized BLUE points?

Four anterior BLUE points follow the anatomy of the lung while avoiding the heart as much as possible. To find these points, place two hands (approximately the patient's size) on the patient's chest with the little finger just below the clavicle and with thumbs overlapping.

BLUE Points. Image from Lichtenstein Lung Ultrasound in the Critically Ill. Curr Opin Crit Care 2014.

The Upper BLUE Point is located at the middle of the upper hand and the Lower BLUE Point is located at the middle of the lower palm. The PLAPS (posterolateral alveolar and/or pleural syndrome) Point is located at the intersection between a horizontal line drawn from the Lower BLUE Point and the posterior axillary line on each side.

What are the three lung signs used in the BLUE protocol?

1) Lung Sliding - Present or Absent

2) Artifact Analysis - A lines or B lines

3) Alveolar Consolidation and/or Pleural Effusion - Present or Absent

What are the lung profiles?

1) A-profile: normal lung sliding plus predominant A lines (horizontal hyperechoic lines that are static and appear at regular intervals).

2) B-profile: normal lung sliding plus B lines (vertical hyperechoic lines that flicker in sync with respirations).

3) C-profile: hyperechoic areas that take on the appearance of tissue structure, consistent with consolidation.

Lung Profiles. Images from Neto et al. Diagnostic Accuracy of the BLUE Protocol for the Diagnosis of Acute Respiratory Failure in spontaneously breathing patients. J Bras Pneumol 2015.

The six BLUE points are then evaluated, generating the following combinations:

A profile with normal lung sliding and without a DVT = obstructive lung disease (COPD or asthma)
A profile with normal lung sliding and with a DVT = pulmonary embolism
A profile with no lung sliding or a lung point = pneumothorax
A profile with PLAPS = pneumonia

B profile with normal lung sliding = pulmonary edema
B profile without normal lung sliding = pneumonia

C profile = pneumonia

A profile on one side with B profile on the other side = pneumonia

From D. Lichtenstein Lung Ultrasound in the Critically Ill. Curr Opin Crit Care 2014.

How good is the science?

Lichtenstein and Meziere. Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure: The BLUE Protocol. Chest 2008; 134:117-125.

Observational study, n=301. Bedside ultrasound was performed within 20 minutes of ICU admission. Healthcare providers managing the patients were blinded to ultrasound results. Official diagnoses were established by standard diagnostic practice including history, physical, and standard practice lab or imaging studies, excluding ultrasound.

Bedside ultrasound provides a correct diagnosis in <5 minutes in 90.5% of cases.

From Lichtenstein and Meziere. Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure: The BLUE Protocol. Chest 2008

Silva et al. Usefulness of Cardiothoracic Chest Ultrasound in the Management of Acute Respiratory Failure in Critical Care Practice. Chest 2013; 144(3):859-865.

Prospective randomized study, n=78. Again, bedside ultrasound was performed within 20 minutes of ICU admission and treating providers were blinded. Official diagnosis was established by chart review, excluding ultrasound.

Bedside ultrasound showed improved diagnostic accuracy compared to standard approach (83% vs 63%, p<0.02).

Neto et al. Diagnostic accuracy of the Bedside Lung Ultrasound in Emergency protocol for the diagnosis of acute respiratory failure in spontaneously breathing patients. J Bras Pneumol. 2015;41(1):58-64.

Prospective randomized study, n=42. In contrast to the previous two studies, the examiners performing the BLUE protocol were non-experts (5 hours of theoretical training and 10 supervised LUS exams). The examiners did not participate in patient management and treating providers were blinded. Official diagnosis was the ICU discharge diagnosis.

Non-experts can use bedside lung ultrasound to reach a correct diagnosis 84% of the time (k=0.81) with bedside ultrasound significantly more accurate than chest xray (84% vs 43%, p=0.01).