Lung Ultrasound: Just B Lines?
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* Pablo Blanco
* Gabriela Bello

*To the Editor:*

We enjoyed reading the interesting article by Antonio et al1 regarding the use of lung ultrasound to predict extubation in critical care subjects. Studies with neutral or negative results like this one are extremely important, in the same tenor as those with positive findings. In this era, in which point-of-care ultrasound seems to be a panacea, this article teaches us that we are treating patients, not images, and this is a concept we should always keep in mind. As a matter of fact, point-of-care ultrasound should be never used in isolation in any application related to patients in need of critical care. However, we would like to make some constructive comments about this work.

First, the assertion that lung ultrasound is not helpful prior to a spontaneous breathing trial (SBT) seems to be imprudent, primarily because this article does not study the direct effects of other alterations detected by lung ultrasound prior to SBT, such as large pleural effusions, consolidations, or diaphragmatic dysfunction, regardless of the presence or absence of B lines.2

Second, while the 4-zone lung-study protocol allows rapid scanning as noted by the authors, this is not representative of the whole picture of the lungs, especially in the case of B-line assessments, as described by Lichtenstein and Mezière.3 Exploring the lateral and posterior regions aids in recognizing other important lung findings that may contribute to a failed SBT, and this is not necessarily time-consuming in trained hands.

Third, given the alterations in systolic and diastolic function intrinsically related to the critically ill patient and the fact that the echocardiographic data were collected at an excessively distant time for the subjects enrolled in this study, an actual cardiac mechanism could not be entirely ruled out in failed SBT cases.

The take-home message is that we, as practitioners, need to consider lung ultrasound in all the ways it contributes to deterioration, not only interstitial syndrome. Even more importantly, we need to point out the relevance of always integrating lung ultrasound into a multimodality approach and avoiding its use in isolation.

## Footnotes

*   The authors have disclosed no conflicts of interest.

*   Copyright © 2019 by Daedalus Enterprises

## References

1.  1.Antonio ACP, Knorst MM, Teixeira C. Lung ultrasound prior to spontaneous breathing trial is not helpful in weaning the decision making process. Respir Care 2018;63(7):873–878.
    
    [Abstract/FREE Full Text](http://rc.rcjournal.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6ODoicmVzcGNhcmUiO3M6NToicmVzaWQiO3M6ODoiNjMvNy84NzMiO3M6NDoiYXRvbSI7czoyNToiL3Jlc3BjYXJlLzY0LzEvMTE0LjIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

2.  2.Blumhof S, Wheeler D, Thomas K, McCool FD, Mora J. Change in diaphragmatic thickness during the respiratory cycle predicts extubation success at various levels of pressure support ventilation. Lung 2016;194(4):519–525.
    
    

3.  3.Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest 2008;134(1):117–125.
    
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