Reliability and clinical correlations of semi-quantitative lung ultrasound on BLUE points in COVID-19 mechanically ventilated patients: The ‘BLUE-LUSS’—A feasibility clinical study

Abstract

Introduction Bedside lung ultrasound has gained a key role in each segment of the treatment chain during the COVID-19 pandemic. During the diagnostic assessment of the critically ill patients in ICUs, it is highly important to maximize the amount and quality of gathered information while minimizing unnecessary interventions (e.g. moving/rotating the patient). Another major factor is to reduce the risk of infection and the workload of the staff. Objectives To serve these significant issues we constructed a feasibility study, in which we used a single-operator technique without moving the patient, only assessing the easily achievable lung regions at conventional BLUE points. We hypothesized that calculating this ‘BLUE lung ultrasound score’ (BLUE-LUSS) is a reasonable clinical tool. Furthermore, we used both longitudinal and transverse scans to measure their reliability and assessed the interobserver variability as well. Methods University Intensive Care Unit based, single-center, prospective, observational study was performed on 24 consecutive SARS-CoV2 RT-PCR positive, mechanically ventilated critically ill patients. Altogether 400 loops were recorded, rated and assessed off-line by 4 independent intensive care specialists (each 7+ years of LUS experience). Results Intraclass correlation values indicated good reliability for transversal and longitudinal qLUSS scores, while we detected excellent interrater agreement of both cLUSS calculation methods. All of our LUS scores correlated inversely and significantly to the P/F values. Best correlation was achieved in the case of longitudinal qLUSS (r = -0.55, p = 0.0119). Conclusion Summarized score of BLUE-LUSS can be an important, easy-to-perform adjunct tool for assessing and quantifying lung pathology in critically ill ventilated patients at bedside, especially for the P/F ratio. The best agreement for the P/F ratio can be achieved with the longitudinal scans. Regarding these findings, assessing BLUE-points can be extended with the BLUE-LUSS for daily routine using both transverse and longitudinal views.

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“…As a consequence, to better estimate extravascular lung water, it is suggested to evaluate the percentage of pleural line covered by B‐lines instead of counting the number of B‐lines on each ultrasound scan. 23 Many in the medical field have adopted this type of LUSS, 4 , 21 , 24 , 25 , 26 , 27 , 28 because of its ability to semiquantify aeration loss without overestimating it, avoiding counting of every B‐line in each quadrant. Furthermore, counting B‐lines is feasible when they are singular and isolated but becomes impractical beyond a certain threshold, even with software assistance, 29 and this type of quantification could not be assigned to alveolar syndrome with a tissue‐like pattern.…”

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“…It consists of the sum of LUS score for four scans for each hemithorax (a superior point below the middle-clavicular point, a diaphragm point at the lung-liver or lung-spleen junction at mid-axillary line, an M point is at the midpoint between these two points and a posterolateral point at the intersection of posterior axillary line and the vertical line from M point). They found a significant correlation between LUS score and PaO2/FiO2 ratio but not with the inflammatory biomarkers [75]. Xue et al evaluated the interobserver variability and correlation of disease severity of M-BLUE protocol in ICU patients.…”

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“…A tüdő légtartalmának csökkenése pedig jellegzetes mintázatot követ: a B-vonalak felszaporodása, subpleuralis légtartalom-csökkenés, translobaris atelectasia. A fenti körülményeket figyelembe véve több pontrendszert is szerkesztettek, melyek a légtartalom csökkenését számszerűsítik, döntően az intenzív terápia területéről [21][22][23], újabban a COVID-19 állapotsúlyosságának jellemzésére is [6,24]. Az utóbbi területen munkacsoportunk is közölt adatokat [24].…”

“…A fenti körülményeket figyelembe véve több pontrendszert is szerkesztettek, melyek a légtartalom csökkenését számszerűsítik, döntően az intenzív terápia területéről [21][22][23], újabban a COVID-19 állapotsúlyosságának jellemzésére is [6,24]. Az utóbbi területen munkacsoportunk is közölt adatokat [24]. Kifejezetten az aneszteziológiai alkalmazásra Monastesse és mtsai adaptálták a korábbi pontrendszereket (1. táblázat) [25].…”