PLAPS and Lung Consolidation (Usually Alveolar Syndrome) and the C-profile

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

The lung consolidation is a fluid disorder, therefore easily traversed by the ultrasound each time the consolidation is subpleural, which is the case in acute settings in 98.5 % of cases [1] (Fig. 17.1). The fluid fills an alveola. Countless alveoli are contiguously filled, up to a macroscopic, visible volume. This fluid can be transudate, exudate, pus, blood, sweet or saline water, or any saline solution. The BLUE-protocol will allow to determine the kind of fluid involved.

Fig. 17.1

Shred sign on CT. This CT scan of a lung consolidation shows a large pleural contact at the posterior aspect of the left lung, a condition usual but necessary to make it accessible to ultrasound. Such a consolidation cannot be missed, even if only the PLAPS-point is investigated (note the longitudinal orientation of the microconvex probe). This consolidation is non-translobar and has the expected fractal, shredded border with the black aerated lung

As early as 1946, the father of medical ultrasound evoked the potential of detecting lung consolidations [2]. Some works arose [3–5]. Aiming at simplifying lung (and critical) ultrasound, we present here signs from CEURF which aim at being standardized.

Our 5-MHz microconvex probe is perfect for this investigation, neonate apart.

Some Terminologic Concepts

Numerous terms are used in current practice: alveolar syndrome, condensation, density, infiltrate, parenchymatous opacity, pneumonia, bronchopneumonia, pulmonary edema, atelectasis, etc. The word atelectasis in particular is often used facing any consolidation. The ill-defined radiologic term “alveolar-interstitial” just demonstrates an inability for experts (radiologists) to separate each disorder. We explain this profusion of words by the fact that “traditional” intensivists do not care too much and will not initiate a particular therapy; therefore words have less importance.

With the advent of lung ultrasound, words have much more sense. “Hepatization” is a nice ultrasound word, since the lung and the liver have similar patterns. The term “alveolar filling” implies a nonretractile cause. The term we long used, “alveolar consolidation,” has the advantage of remaining neutral, not involving a particular etiology (infectious, mechanical, hydrostatic). From Angelika Reissig’ talks, we now use the word “lung consolidation,” more logical, since the alveoli and interlobular septa are together concerned by the pathological process. By the way, the term “alveolar-interstitial syndrome” should be really reserved to these lung consolidations (see Anecdotal Note 1).

Please, the word “consolidation” does not mean “pneumonia.” Hemodynamic pulmonary edema, ARDS, pneumonia, pulmonary embolism, tumor, and even pneumothorax are causes of lung consolidation. In the BLUE-protocol (in dyspneic patients), posterior consolidations are sought for only when there is no anterior interstitial syndrome, no anterior consolidations, no abolished lung sliding, and no deep venous thrombosis. Only at this step, they indicate pneumonia.

In the BLUE-protocol, lung consolidations are not used for the diagnosis of pulmonary embolism.

Why Care at Diagnosing a Lung Consolidation, Whereas the Concept of “PLAPS” Allows Energy Saving?

It is true, in the BLUE-protocol, once a structural image is detected at the posterior thoracic area, it cannot be but a PLAPS? What else?

This is why our approach is aimed at simplifying as far as possible the sole diagnosis of lung consolidations, by providing as few signs as possible: two signs, namely, the shred sign and the tissue-like sign.

One Ultrasound Peculiarity of Lung Consolidations: Their Locations

Whereas pleural effusion, pneumothorax, and interstitial edema benefit from extensive location and therefore from standardized points of search (the BLUE-points), lung consolidations can be located in various sites and have various sizes. Where to apply the probe raises an issue.

Applying it at the PLAPS-point detects most cases (90 %) [1] and makes ultrasound already superior to bedside radiography in terms of diagnostic accuracy. We saw in Chap. 6 that if the PLAPS-point is negative, one should expect to see small or very small consolidations at the extended PLAPS-points.

Whole-lung consolidations (massive atelectasis, massive pneumonia) are visible everywhere (including the PLAPS-point).

Random consolidations should be sought for where they are. This can be apical, axillary, juxta-rachidian, trans-scapular (yet see the nice Fig. 28.3), or on anterior areas not scanned by the BLUE-points. Those who wish to increase the 90 % rate are condemned to make comprehensive, time-consuming, and chancy scanning. This option is acceptable for assessing ARDS but is questionable in critical settings; in actual fact deeply linked to the clinical question: dependent consolidations in ventilated patients after a few days (Pink-protocol) are pathologic but not surprising. Anterior (even small) consolidations, i.e., C-profile, in a patient with acute dyspnea, or a young lady with chest pain, have major relevance.

Rough correlations between BLUE-points and lobes were seen in Chap. 5 rapidly: upper BLUE-point and upper lobe, lower BLUE-point and middle lobe, and PLAPS-point at the lower lobe.

Ultrasound Diagnosis of a Lung Consolidation

Considering translobar from non-translobar forms allows deep simplification of the teaching part. Obviously, in many cases of translobar cases, the same patient can display areas of non-translobar consolidations.

Non-translobar Consolidations: The Shred (or Fractal) Sign

We use a biological fact: almost all consolidations seen in the critically ill have irregular boundaries with the underlying aerated lung (Fig. 17.1). In a longitudinal view, the upper, superficial border is the pleural line or, in the case of associated pleural effusion, the lung line (see Fig. 15.1). The deep border is almost always shredded, displaying the shred line or fractal line (Fig. 17.2) [6] (read Anecdotal Note 2). This sign usually allows immediate diagnosis, within fractions of seconds, regardless of the size (just before the step it becomes translobar; see below). Figure 17.3 is an example of a small (i.e., for sure non-translobar) consolidation. It is also distinguished from a pleural effusion with a lung line. Figure 17.4 is an extreme example of alveolar syndrome, quite alveolar miasma.