I n the era of novel coronavirus disease 2019 (COVID-19), lung ultrasound (LUS) has rapidly emerged as a tool for diagnosis and monitoring of lung involvement. [1] [2] [3] Although chest computed tomography has been suggested as the preferred modality for COVID-19 lung disease investigation, it is may not be readily available in all emergency departments. 4, 5 Additionally, performing a computed tomographic examination carries the possibility of nosocomial virus spreading and increases the exposure of health care workers; in addition, the disinfection procedure for computed tomographic scanners after an examination may induce substantial delays in patients' care. 6 LUS represents a safe, quick, and noninvasive surface-imaging technique for the evaluation of several respiratory conditions, which can be performed by a single operator at the bedside. 7, 8 Importantly, in the context of the COVID-19 outbreak, the entry of portable devices protected by sterile covers can eliminate the risk of cross-contamination by preventing contact with potentially infected surfaces. 9 A diffuse B-line pattern, irregular pleural lines, and subpleural consolidations affecting mainly the lower lobe and posterior lung segments, which show a bilateral, patchy, and peripheral distribution, represent typical LUS findings in COVID-19 lung disease. 3, 10 Although the utility of LUS in COVID-19 lung involvement has been well described, there is great variability regarding the optimal technique, including the number and topography of scanned areas as well as patient positioning, with most studies suggesting the application of 8-to 28-zone protocols with the patient in a supine/sitting position. [9] [10] [11] In this regard, we recommend that a modified 18-point LUS protocol (Table 1 ) based on that proposed by Vassalou et al, 12, 13 with the patient placed in the lateral decubitus position for examining the contralateral hemithorax, is advantageous for 4 reasons:
1. Given the multifocal, peripheral, basal, and posterior distribution of COVID-19 pneumonia, the application of the proposed 18-point LUS protocol enables an extended evaluation of the lung surface, compared to more simplified protocols solely examining the anterior hemithoraxes. Additionally, the performance of this protocol has been shown exclusively in patients with idiopathic pulmonary fibrosis, in whom the lesions largely follow the distribution of COVID-19 pneumonia. 2. Lung attenuation varies according to the dependency of the lung region, being higher in the dependent areas. 14,15 A LUS examination in the lateral decubitus position ensures paramediastinal shifting of the dependent lung segments; thus, it eliminates the potential confounding effect of gravity-related changes on the number and morphologic characteristics of detected B-lines, which is of importance for a disease manifesting primarily with a diffuse B-line pattern. 3. Lung ultrasound in the decubitus position is less time-consuming and equally accurate compared to protocols in the supine/sitting position. 12,13 4. Compared to the sitting position, the lateral decubitus position is easier to achieve and maintain for patients lying in a supine or prone position. Additionally, it enables simultaneous examination of both anterior and posterior lung surfaces, without necessitating patient repositioning, thus minimizing the risk of contamination by preventing contact between the patient, the medical staff, and equipment.
We strongly recommend the use of the 18-point LUS protocol in the decubitus position for assessing lung involvement in patients with suspected or determined COVID-19 pneumonia in the emergency department or intensive care unit. 