From the Critical Care Unit, Inserm U825, CHU Purpan.
CORRESPONDENCE TO: Stein Silva, MD, PhD, Critical Care Unit, Inserm U825, CHU Purpan, 31059 Toulouse Cedex 3, France; e-mail: firstname.lastname@example.org
FINANCIAL/NONFINANCIAL DISCLOSURES: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
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I thank Dr Volpicelli for his insights on our article published in CHEST1 and agree with the fact that we probably are on the verge of a paradigm shift in this field. Pioneering studies that have described thoracic ultrasonography semiotics2 must now be followed by research aiming to integrate the totality of physiologic data at our disposal in a comprehensive and clinically relevant way. We could expect from this not only to improve the diagnosis accuracy of ultrasound tools but also to allow patient bedside study of interorgan interactions, an indispensable step to further expand our understanding and potentially lead to the design and monitoring of new individually tailored treatment strategies.3
Dr Volpicelli’s pertinent comments converge to the moot issue of the potential utility of lung ultrasonography, not only to detect but also to quantify extravascular lung water. We completely agree with the idea that B-lines are nothing more than reverberation artifacts through edematous interlobular septa within the lung (a phenomenon also observed in physiologic conditions).4 Nevertheless, it remains to be shown to what extent this pattern could be used to accurately explore pulmonary edema topography and, additionally, to track the impact of therapeutic interventions across time.
In the current study,1 we used supervised machine-learning methods to integrate lung ultrasound and echocardiography data as independent variables in a predictive mathematical model. Remarkably, we identified several cases of lung consolidation (C and posterolateral alveolar and/or pleural syndrome profiles),2 but their detection was not significantly correlated with any component of the model (e-Fig 1, e-Table 1 in our article1). In other words, we confirm that we observed several cases of lung consolidation in patients without pneumonia. We interpret these data relative to the value of such ultrasound patterns in patients on mechanical ventilation in the ICU and highlight the interest of concomitant echocardiography recordings in this setting.
Regarding cardiogenic edema and its spatial and temporal dynamics, it is worth noting that we used previously well-described lung ultrasound criteria, which do not take into account B-line spatial distribution.2 Furthermore, we note that both thoracic and lung ultrasound recordings were performed during reproducible clinical conditions at the time of ICU admission, aiming to avoid confounding factors.
Overall, we suggest that B-lines seem to be sensitive markers of extravascular lung water per se, regardless of its etiology. The technical revolution in which we are now immersed does not make us forget to integrate such valuable information in a broader medical reasoning. Substantial progress has been made in the description of a standardized lung ultrasound semiotics. We can speculate that further advances will come from the complementary study of thoracic ultrasonography, alongside described methods for the assessment of pulmonary edema in human5 and animal6 models. For thoracic ultrasonography, it is time to move beyond the lines.
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