Accuracy of ultrasound B-lines score and E/Ea ratio to estimate extravascular lung water and its variations in patients with acute respiratory distress syndrome

Abstract

Extravascular lung water (EVLW) could increase by permeability pulmonary oedema, cardiogenic oedema, or both. Transthoracic echocardiography examination of a patient allows quantifying B-lines, originating from water-thickened interlobular septa, and the E/Ea ratio, related to pulmonary capillary wedge pressure. The aim of our study was to assess the correlation and the trending ability between EVLW measured by transpulmonary thermodilution and the B-lines score or the E/Ea ratio in patients with ARDS. Twenty-six intensive care unit patients were prospectively included. B-lines score was obtained from four ultrasound zones (anterior and lateral chest on left and right hemithorax). E/Ea was measured from the apical four-chamber view. EVLW was compared with the B-lines score and the E/Ea ratio. A linear mixed effect model was used to take account the repeated measurements. A p value<0.05 was considered significant. A total of 73 measurements were collected. The correlation coefficient between EVLW and B-lines score was 0.66 (EVLW=0.71 B-lines+7.64, R2=0.44, p=0.001), versus 0.31 for E/Ea (p=0.06). The correlation between EVLW changes and B-lines variations was significant (R2=0.26, p<0.01), with a concordance rate of 74%. A B-lines score≥6 had a sensitivity of 82% and a specificity of 77% to predict EVLW>10 ml/kg, with an AUC equal to 0.86 (0.76-0.93). The gray zone approach identified a range of B-lines between four and seven for which EVLW>10 ml/kg could not be predicted reliably. The correlation between ultrasound B-lines and EVLW was significant, but the B-lines score was not able to track EVLW changes reliably.

Lung artefacts and their use

“…BLA score ≥ 6 had a sensitivity of 82 % and a specificity of 77 % to predict EVLW >10 ml/kg. The correlation between ultrasound BLA and EVLW was significant, but the BLA score was not able to track EVLW changes reliably [26].…”

“…Scores to assess the severity of BLA have been adopted as follows: 0=none; 1=physi-ologic; 2=mild; 3=moderate; and 4=severe. In practice, a score of either 3 or 4 tends to increase the likelihood of a diagnosis of increased interstitial fluid, whereas a score of either 0 or 1 will decrease it [26]. For follow up examinations, it is necessary to use the same or similar technical equipment when counting BLA for the semiquantitative assessment of pulmonary diseases.…”

Lung Ultrasound and Static Lung Compliance during Postnatal Adaptation in Healthy Term Infants

“…Static LC increases significantly during postnatal adaptation [13]. Both B-lines in lung US and LC correlate with lung liquid measured by the thermodilution method in adults [14,15]. Our aim was to document findings of lung US and values of static LC in healthy term infants during postnatal adaptation and to study the relationship between lung US and static LC.…”

Clinical application of lung ultrasound in emergency department patients for the evaluation of pulmonary congestion: a comparison with chest X-ray

“…B-lines are defined as discrete "comet tails, laser-like" vertical hyperechoic reverberation artifacts that arise from the pleural line, which extend to the bottom of the screen without fading and move synchronously with lung sliding. Three or more B-lines between two ribs in a single scan indicates a subpleural component of the interstitial syndrome (11). There is a high correlation between the number of increased B-lines with increasing extravascular lung water and decreasing air content, but considering only Blines it is not possible to differentiate the cause (12).…”