key: cord-0793411-nr0akd7k authors: Aziz, R.; Kaminstein, D. title: Essential notes: The use of Lung Ultrasound for COVID-19 in the intensive care unit date: 2020-09-26 journal: BJA Educ DOI: 10.1016/j.bjae.2020.09.001 sha: ddd1ecccf5d69b510c7e0c3355c6502c56f105b1 doc_id: 793411 cord_uid: nr0akd7k nan Thoracic imaging is a key component of managing respiratory failure in patients with . Timely access to routine chest X-rays (CXR) and computed tomography (CT) scans can however be challenging in a pandemic. Furthermore, resource utilisation is critical, and the safety of the patient and staff must be balanced carefully with the necessity of obtaining images. Point-of-care lung ultrasound (LUS) is a dynamic technique routinely used in intensive care to answer targeted questions and aid in practical procedures. 1 Whilst LUS has its limitations, and in isolation cannot provide a definitive diagnosis, it can be useful where resources are scarce. In this article we explore the use of LUS specifically in critically ill patients with COVID -19, outlining both essential aspects for new practitioners of LUS and points of high diagnostic yield. When using any imaging technology in the face of an infectious disease the equipment itself must not be allowed to become a vector for further spread. Ideally a dedicated ultrasound machine is required for the "red zone", as was the case during the Ebola virus outbreak in 2014. 2, 3 Basic principles of hygiene to minimise contamination include: the removal of organic debris from the probe and machine; disinfection with probe-compatible material; the use of sachets rather than bottled ultrasound gel; and clear documentation of the cleaning process. 4 Portable handheld machines are preferable, being easier both to cover during scanning and to clean. J o u r n a l P r e -p r o o f There is currently no validated systematic approach for performing LUS in patients with COVID-19 pneumonitis, although the Intensive Care Society has made some recommendations. 5 There are several different techniques and choices of probe, including the Blue protocol. 6 The optimal approach where resources are limited must balance the following: • The need to answering the clinical question; • The workload in ICU; • The risks of disturbing the patient's position, particularly when there is cardiovascular instability. LUS protocols for ICU assume users have a degree of expertise, time and appropriate resources. During a pandemic, providers may find themselves in temporary hospital structures with large numbers of critically ill patients. Protocols designed for normal working conditions may not address the context of a strained and overwhelmed system. We believe the following key points determine the highest yield approach to LUS in patients with COVID-19: • The changes seen are not homogenous, with normal areas interspaced between areas of abnormality (in contrast to bilateral, homogenous changes seen with cardiogenic pulmonary oedema). • Abnormal lung findings predominate in the posterolateral aspect of the chest. We therefore recommend the following approach for those new to thoracic ultrasound. • Begin with a "survey" of the lungs in general using a probe that offers a wide field of view and maximises tissue penetration. The curvilinear (abdominal) probe allows a rapid survey of the lung fields but shadowing from the ribs can obscure much of the image. The cardiac probe provides superior views between ribs, and evaluation of cardiac function, but the narrower field of view prolongs the duration of the scan. Either is suitable, with the aim being to gain a rapid sense of the extent of disease. • Start at the lung bases as posteriorly as possible, accounting for the patient's position and severity of illness. This allows identification of a dependent pleural effusion, and any involvement of the lower lung zones. • Then move systematically to the apex anteriorly, looking for any abnormalities at the pleural interface suggestive of a large pneumothorax, and reviewing as much of each lung as possible as you scan to gauge the extent of lung involvement. If any abnormalities are detected the higher resolution linear probe (8-12 MHz) should be used to examine these areas in more detail for characteristic findings. LUS does not rely primarily on visualising actual pathology but instead uses artefacts generated by density changes at air/water or air/tissue interfaces. 8 Terminology and definitions are important. B-line patterns are frequently referred to in patients with COVID-19. By definition B-lines must arise from the pleura and erase A-lines. 9 In COVID-19 the vertical lines often originate however from subpleural consolidations and not from the pleura itself. Whilst similar, these are not strictly B-lines but instead C-lines, which are defined as originating below the pleura from consolidations or defects on the pleural surface 9 (Figure 1 ; Supplementary Videos 1 and 2). The 'light-beam artefact' that has also been described may be a confluence of C lines leading to a different appearance than that seen in pulmonary oedema or bacterial pneumonia. 10 The key difference between C-lines and B-lines is that Clines are artefacts caused by viral-induced irregularities of the pleural surface and not caused by alveolar oedema, which gives rise to B-lines. This is similar to the ring-down pattern in tuberculosis, which affects the pleural interface causing defects and artefacts that arise from the pleura itself ( Supervised practice during the early stages of learning may not be possible during a pandemic setting. During the Ebola pandemic physicians were trained to obtain images which were reviewed remotely by an expert for detailed analysis and quality assurance. This 'telemedicine' approach is used extensively in providing ultrasound training to front-line providers throughout the world and could also be used for patients with COVID-19. Both images are taken with the same ultrasound machine using phased array probe with similar settings. Probe in both cases is positioned in the mid axillary line at the base of the lung in the lower lung zone just above the diaphragm. Figure 1A is from a patient with known COVID-19 pulmonary disease. Ring-down artefacts are seen as C-lines (solid arrow) originating from a thickened pleura (thin arrow) and do not erase the underlying A-lines (hollow arrow). Figure 1B demonstrates Lung ultrasound in the critically ill Isolation Unit : The Emory University Hospital Experience Imaging an Outbreak -Ultrasound in an Ebola Treatment Unit Prevention of pathogen transmission during ultrasound use in the Intensive Care Unit: Recommendations from the College of Intensive Care Society. Guidance for lung ultrasound during COVID-19 Practical approach to lung ultrasound Chest CT manifestations of new coronavirus disease 2019 (COVID-19): a pictorial review Findings of lung ultrasonography of novel corona virus pneumonia during the 2019-2020 epidemic Lung Ultrasound in the Critically Ill Sonographic signs and patterns of COVID-19 pneumonia Lung ultrasonography in pulmonary