The BLUE-Points: Three Points Allowing Standardization of a BLUE-Protocol

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Hôpital Ambroise Paré Service de Réanimation Médicale, Boulogne (Paris-West University), France

For exploring the most voluminous organ, three points allow standardized protocols, expedite the investigation of critically ill patients, and warrant the accuracy published in the BLUE-protocol native article.

The lung is our most voluminous organ (skin apart): about 1,500 cm² surface and 17 % of the body skin area. Where to apply the probe may appear as a quandary. We could answer simply but not efficiently “at the same places as the stethoscope.” Some experts simplify the problem but complicate the technique by advocating comprehensive scans. In critical settings, time is too precious. The 7th principle of LUCI states that the life-threatening disorders have usually an extensive projection. Apart from some small and aberrant lung consolidations (read Anecdotal Note 1), the daily profiles are extensive: pulmonary edema (even moderate), pneumothorax (even small), pleural effusion, etc. This remarkable property allows to use standardized points for expediting a BLUE-protocol. A basic empiricism associated with a long research has allowed us to define the BLUE-points [1]. We defined six BLUE-points, exactly like the 6 thoracic electrodes of standard ECG. There are three points per lung, two anterior and one semiposterior (Anecdotal Note 2).

The Concept of the BLUE-Hands

This concept allows to immediately locate the lung on any patient, from skinny to bariatric ones, from firm youngsters to old, tired ladies, and from babies to giants. The physician first compares both hand sizes (the term BLUE-hands refers to the patient). Between 1.65 and 1.85 m, the difference is insignificant. Then, the physician applies the “upper” hand, just below the clavicle, with tip of fingers at the midline (Fig. 6.1). Therefore, the upper hand is oblique. The physician then applies the “lower” hand, just below the upper one, thumbs excluded. The geometry of the hands makes the lower finger of the lower hand naturally transverse on the thorax.

Fig. 6.1

The anterior BLUE-points. The upper hand is applied with the little finger against the lower border of the clavicle (in its long axis). The finger tips touch the midline. The lower hand is applied below the first one. The thumbs do not count. The upper BLUE-point is at the root of the middle and ring fingers of the upper hand (upper cross). The lower BLUE-point is in the middle of the palm of the lower hand (lower cross). In this subject, the lower BLUE-point is near the nipple. This definition makes a symmetric analysis usually avoiding the heart. The lower edge of the lower hand roughly indicates the phrenic line (arrow), i.e., the end of the lung. Note that the shape of the hands has been studied in order to correct the obliquity of the clavicle, yielding a roughly transversal phrenic line. Figure 1.1 shows an examination at the lower BLUE-point, in a supine patient at Earth level, defining a Stage 1 examination (1’ in actual fact, since the subject is in semirecumbent)

Once this is done, the anterior lung is located, in almost all cases, exactly facing both hands. The lower finger of the lower hand indicates the lower anterior border of the lung (i.e., what we may call the phrenic line). The BLUE-points replace our previous concepts (read Anecdotal Note 3).

The BLUE-protocol was designed for exploring supine or semirecumbent patients without bothering them too much. The anterior and lateral chest walls are rather accessible. The posterior wall, of high relevance, requires more technical subtleties.

Lung Zones, Their Relevance in the BLUE-Protocol, Their Combination with the Sky-Earth Axis for Defining Stages of Investigation

The anterior zone, defined using the BLUE-hands, is of utmost relevance, defining in a few seconds half of the profiles of the BLUE-protocol.

The lateral zone, defined from the anterior to the posterior axillary line, is not used in the BLUE-protocol, for reasons of redundancy. It may be however useful on occasion (if PLAPS-point is hard to reach) (Fig. 6.2).

Fig. 6.2

Phrenic point. This figure shows a Stage 2 examination, i.e., a lateral continuation of the Stage 1. The probe here is at the intersection between the middle axillary line (vertical arrow) and the phrenic line (horizontal arrow): the phrenic point

The posterior zone, i.e., all that is behind the posterior axillary line, may appear of limited access in supine patients, a kind of twilight zone, a hidden face of the moon, etc., because the patient’s weight squashes the bed. The aim of the PLAPS-point is to make this zone accessible, precise, and easy (without searching for a help, turning difficult patients, losing time for unleashing the hands, etc.).

We define stages by considering these areas and the fact that the patient is seen in the supine position and (for most of us) at Earth level. The notion of stages specifies that the finding is done at Earth level, a kinda tribute to Scott Dulchavsky and Andrew Kirkpatrick, who investigate astronauts.

Stage 1 investigates the anterior wall in supine patients.
Stage 2 adds the lateral wall.
Stage 3 adds the external part of the posterior wall (zone “3”).
In Stage 4, the patient must be positioned laterally, or seated, in order to comprehensively study the posterior chest wall. Stage 4 also includes the apex. Only a microconvex probe can efficiently do this. With Stage 4, ultrasound is nearly as competitive as CT.

Some Technical Points for Making Lung Ultrasound an Easier Discipline

One major interest of the BLUE-points is to define points far enough from the abdomen. The advantages are as follows:

Energy for explaining what the diaphragm looks like (although not a big issue) is avoided, at least initially.
Energy for explaining how to recognize a diaphragm in challenging patients (a bigger issue) is avoided.
Energy for explaining how to distinguish a pleural from a peritoneal effusion is avoided.
Energy for explaining signs we don’t use (e.g., spinal sign) is avoided.
Energy for explaining how to distinguish a basithoracic lung consolidation from some common abdominal fat (or organ) is avoided. Without any notion of probe location, it can be a challenge (Fig. 6.3).

Fig. 6.3

Abdominal fat. Such an image given to a reader without the notion on where it was taken (here, far more podal than the lower BLUE-point or PLAPS-point) could mislead this reader for a lung consolidation. This abdominal fat may be distinguished, but this would require complicated knowledge: a waste of energy

We guess that many users would be frustrated not to see the diaphragm. Its anterior insertion is located at the lowest finger of the BLUE-hands, defining the phrenic line. One main point must be understood. Using our perpendicular approach, we do not need to see the diaphragm: its location and dynamics are much more important. The diaphragm insertion is the location where the image displays on inspiration a thoracic structure at the left of the screen (i.e., air barrier or pleural or alveolar disorders) and on expiration an image of the liver (or spleen) at the right of the screen. We then know exactly where the diaphragm is (and how it works) without any direct visualization, sparing energy.

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