PoCUS LUNG in ASSESSMENT for RISK STRATIFICATION and THERAPY in COVID-19 PATIENTS

 

ABSTRACT

Background: Lung ultrasound (LUS) is feasible for assessing lung injury caused by COVID19. However, the prognostic meaning and time-line changes of lung injury assessed by LUS in COVID-19 hospitalized patients, is unknown. 

Methods: Prospective cohort study designed to analyze prognostic value of LUS in COVID-19 patients by using a quantitative scale (LUZ-score) during the first 72 hours after admission. Primary endpoint was in-hospital death and / or admission to the intensive care unit. Total length of hospital stay, increase of oxygen flow or escalate medical treatment during the first 72 hours, were secondary endpoints.

  Results: 130 patients were included in the final analysis; mean age was 56.7 ± 13.5 years. Time since the beginning of symptoms until admission was 6 days (4 - 9). Lung injury assessed by LUZ-score did not differ during the first 72 hours (21 points [16-26] at admission vs 20 points [16-27] at 72 hours; p = 0.183). In univariable logistic regression analysis estimated PaO2/FiO2 (HR 0.99 [0.98 – 0.99]; p=0.027) and LUZ-score > 22 points (5.45 (1.42 – 20.90); p=0.013) were predictors for the primary endpoint. 

Conclusions: LUZ-score is an easy, simple and fast point of care ultrasound tool to identify patients with severe lung injury due to COVID-19, upon admission. Baseline score is predictive of severity along the whole period of hospitalization. The score facilitates early implementation or intensification of treatment for COVID-19 infection. LUZ-score may be combined with clinical variables (as estimated PAFI) to further refine risk stratification. 

Lung ultrasound 

Lung US examinations were performed with the UPROBE-C5PL wireless ultrasound device (Leleman ©), convex probe of 3.5 to 5 MHz, with a gain between 80-100 dB, and a maximum depth of between 160 and 220 mm. Images and videos were stored (Ipad 10.2. Apple ©). Researchers responsible for LUS were Internal Medicine specialists, with extensive experience in clinical ultrasound (more than two years and more than 180 thoracic LUS explorations)[11– 13]. 

In each examination, 12 areas were analyzed according to previous studies[14] (2 anterior, 2 lateral and 2 posterior for each lung). 

Given the progressive nature of ultrasound changes in COVID-19, a score between 0 and 4 points was assigned to each quadrant according to the pattern of observed findings, resulting in a total score between 0 and 48 points

(0 point: A lines and normal pleural line; 

1 point: A lines coexist with isolated and small "B "lines; 

2 points: A lines disappear and multiple "B" lines are seen alternating with preserved lung parenchymal spaces. Pleural line thickens and small "bites" may be seen; 

3 points: "B" lines merge and form a giant "B" line that fills the entire intercostal space. Pleural line is blurred, "bites" appear more frequently; 

4 points: Pleural line is broken and subpleural consolidations (1 to 1,5 cm deep) are observed. ―Sun rays and ―Waterfall‖ patterns coexists.) 

(Figure 1,supplementary figure 5 and supplementary multimedia)

 -we called this protocol ―Lung Ultrasound Zaragoza Score‖ (LUZScore).

 In case of multiple patterns coexisting in the same lung quadrant (according to the intercostal space analyzed), the finding with highest score was annotated. Number of affected areas, presence of sub-pleural consolidations and presence of pleural effusion were also recorded.

Limitations The study was carried out in a single center, so their results cannot be generalizable. We did not analyzed correlations between LUS and CT due to the study design. The sample size was designed based on the collection of samples for biomarkers analysis, which could have underestimated power of multivariable logistic regression analysis. Finally, although all physicians who took LUS images had a large previous experience in LUS, this technique is operator-dependent, and could have influenced final results. 

Lung ultrasound and LUZ-Score allow quantifying degree of pulmonary involvement in patients with COVID-19. There are no changes in the score during the first 72 hours of admission, which reinforces the importance of the very first ultrasound assessment, which should be performed soon after admission. 

A baseline admission LUZ-Score > 22 is a predictor of ICU admission or in-hospital death. Despite the improvement in clinical condition, ultrasound lung artifacts remain at discharge in a proportion of patients. This particular finding has not been previously reported and its significance is not clear.