key: cord-0969370-7nh5zxsu authors: Kiamanesh, Omid; Harper, Lea; Wiskar, Katie; Luksun, Warren; McDonald, Michael; Ross, Heather; Woo, Anna; Granton, John title: Lung Ultrasound for Cardiologists in the Time of COVID-19 date: 2020-05-19 journal: Can J Cardiol DOI: 10.1016/j.cjca.2020.05.008 sha: a8a55a248998b9bf2a81103d677b2ca44e1afb01 doc_id: 969370 cord_uid: 7nh5zxsu Lung ultrasound (LUS) is a point-of-care ultrasound (POCUS) technique used for its portability, widespread availability, and ability to provide real-time diagnostic information procedural guidance. LUS outperforms lung auscultation and chest X-ray, and is an alternative to chest computed tomography in select cases. Cardiologists may enhance their physical and echocardiographic examination with the addition of LUS. We present a practical guide to LUS, including device selection, scanning, findings, and interpretation. We outline a 3-point scanning protocol using 2D and M-mode imaging to evaluate the pleural line, pleural space, and parenchyma. We describe LUS findings and interpretation for common causes of respiratory failure. We provide guidance specific of COVID-19, which at the time of writing is responsible for a global pandemic. In this context, LUS emerges as a particularly useful tool for the diagnosis and management of patients with cardiopulmonary disease. Lung ultrasound (LUS) is a useful point-of-care ultrasound (POCUS) technique that outperforms lung auscultation and chest X-ray, and nears the diagnostic accuracy of chest computed tomography (CT) for common causes of acute respiratory failure. LUS offers the advantage of portability, availability, and the avoidance of radiation exposure. It provides real-time diagnostic information and procedural guidance. Cardiologists can use LUS to enhance their physical and echocardiographic examination. We provide a practical overview of LUS for cardiologists. We perform LUS with widely available cart-based and handheld devices (Online Supplement Table 1 ). The optimal patient position for LUS depends on the suspected pathology. If a pneumothorax is suspected, we prefer the supine position to allow pleural air to collect at the anterior chest wall. If a simple pleural effusion is suspected, we prefer the semi-recumbent or supine position to allow pleural fluid to collect at the posterior costophrenic angle. If a person is prone, pleural air will collect dorsally, and pleural fluid will collect ventrally. If an interstitial syndrome or lung consolidation is suspected, patient positioning is less critical, as all lung zones must be examined. We base probe selection on availability, pathology, and area of interest. High-frequency probes (8) (9) (10) (11) (12) MHz) provide excellent visualization of superficial structures (e.g. pleural line) but have a narrow sector width and poor visualization of deeper structures. Curvilinear probes (3) (4) (5) provide good visualization of both superficial and deep structures but have a larger footprint and may require angulation when scanning to avoid rib shadows. Phased array probes can show all lung findings and have a smaller footprint, making the avoidance of rib shadows easier, but provide less adequate visualization of the pleural line. We disable features that decrease artifact production because LUS relies on interpreting artifacts. We optimize gain, focus, and depth for the structure of interest. Several LUS protocols provide instructions on the systematic scanning of lung zones to identify the causes of respiratory failure. We describe the 6-zone (3 zones per lung) for speed and simplicity; however, more comprehensive 8-and 12-zone protocols exist. 1, 2 Six-zone LUS can provide a rapid and accurate assessment in most cases of acute respiratory failure. 1 We examine the anterior, lateral, and posterior basal chest wall by two-dimensional (2D) and M-mode imaging ( Figure 1 ). The angle of insonation must be perpendicular to the pleural line. Because the contour of the chest wall may differ from the underlying pleura, techniques such as sliding and fanning are essential to ensure ultrasound beam alignment. Failing to do so may cause false positive (e.g., impression of an abnormal pleural line) or false negative (e.g., failing to see A-or B-lines) findings. LUS clips should capture an entire respiratory cycle and should be stored for documentation. As with any imaging modality, the accuracy of LUS depends on operator skill. Learners may save and review images with experienced operators for supervised interpretation. All handheld devices discussed have this ability (Online Supplement Table 1 ). Refer to the Online Supplement. LUS interpretation relies on characteristic normal and abnormal artifacts, as ultrasound waves do not transmit through gas-filled structures such as normal lung parenchyma. Normal. The parietal pleura appears as a horizontal hyperechoic line one-half centimetre below the rib line (Online Supplement Figure 1) . A-lines are reverberation artifacts produced by the interface between pleura and aerated lung. A-lines appear as echogenic horizontal lines spaced at equidistant multiples of the transducer-pleural line (Online Supplement Figure 2 , Video 1). Lung sliding is the normal respirophasic horizontal to-and-fro movement of the parietal and visceral pleural sliding against each other (Online Supplement Video 2). M-mode imaging will show a stratified pattern of fixed subcutaneous tissue and parietal pleura with a heterogeneous 'sandy pattern' below, termed the seashore sign (Online Supplement Figure 2 ). The lung pulse is the rhythmic movement of the visceral pleural along the parietal pleural with cardiac contraction and is a useful finding to rule out pneumothorax (Online Supplement Video 3). Abnormal. Abnormal pleural line findings include an irregular pleural line and the absence or impairment of lung sliding (Online Supplement Figure 1 , Videos 4-5). A lung point is an abrupt cessation of lung sliding that is pathognomonic of pneumothorax (Online Supplement Video 6). It defines the margin of a pneumothorax, where pleural air transitions to parenchymal air. Mmode imaging of a pneumothorax will show a stratified pattern of all structures, termed the barcode sign (Online Supplement Figure 2 ). Normal. The pleural space is a potential space between the parietal and visceral pleura. It is normally not seen. Normal. Normal lung shows lung sliding with A-lines, as described above. A-lines are produced by the interface of the pleura with air and may therefore be present in normal or abnormal lung that remains aerated (e.g. pneumothorax, obstructive lung disease, pulmonary embolism) (Online Supplement Figure 2 ). Abnormal. An interstitial pattern is characterized by multiple B-lines. The B-line is a welldefined respirophasic vertical artifact that arises from the pleural line, extends to the bottom of the screen without fading in a hyperechoic comet-tail appearance, and erases A-lines (Online Supplement Figure 4 ). Two or fewer B-lines per intercostal space may be normal (particularly in dependent areas). More than 2 B-lines per intercostal space is abnormal and defines an interstitial process, which correlates with an interstitial pattern on a chest X-ray (Online Supplement Video 9). Coalescent B-lines reflect a higher burden of disease and correlate with ground-glass opacities on chest CT (Online Supplement Figure 4 , Video 10). An alveolar pattern is characterized by consolidated, isoechoic lung. Consolidations and atelectasis can appear the same echotexture as the liver, termed hepatization (Online Supplement Cardiac POCUS can complement LUS to enhance the diagnostic accuracy of causes of respiratory failure and to screen for concurrent cardiovascular conditions. Cardiac POCUS provides a real-time assessment of ventricular function, pericardial abnormalities, and gross valvular abnormalities. In patients with hypoxemic respiratory failure and normal LUS findings, vascular POCUS using a 2-point compression test may be useful to exclude venous thromboembolism. 3 LUS interpretation is quick and >90% accurate for common causes of acute respiratory failure (Online Supplement Table 2 ). A few concepts are of great value to the clinician. Pleural line abnormalities and impaired lung sliding are present in pneumothorax, inflammatory conditions (ARDS, pneumonia), and fibrotic disease, but absent in heart failure ( Table 1) Figure 6 ). Refer to Online Supplement for background, indications, findings, and infection precautions for LUS during the COVID-19 pandemic. LUS enhances the physical and echocardiographic examination to improve the diagnosis of the causes of respiratory failure. LUS has a clear advantage over chest X-ray as a point-of-care test that is portable, safe, accurate, and provides immediate feedback. Cardiologists may learn LUS to improve their diagnosis and management of cardiopulmonary disease. Table 1 Lung abnormalities in COVID-19 may develop prior symptoms and nucleic acid detection. 2, 3 In one series, the sensitivity of chest computed tomography (CT) and initial real-time polymerase chain reaction (RT-PCR) was 98% and 71%, respectively, for detection of SARS-CoV-2. 2 In patients with a negative initial RT-PCR, the sensitivity of chest CT is 75%, leading to the suggestion by some for the use of screening chest CT in patients suspected of COVID-19. 2, 4 However, this practice has significant implications for resource utilization and infection control and is discouraged by North American radiological societies. 5, 6 Lung ultrasound (LUS) therefore emerges as an important imaging modality. LUS outperforms chest x-ray and approaches the accuracy of chest CT in the evaluation of pneumonia and acute respiratory distress syndrome (ARDS). 7 LUS can identify disease, detect complications, and guide therapy. LUS offers the advantage of a point-of-care test without radiation exposure and may reduce the risk of nosocomial spread of infection. We provide a practical overview of LUS for clinicians involved in the care of patients with suspected or confirmed COVID-19. The benefits of LUS compared with CT include portability, avoidance of moving isolated patients to the radiology suite, immediate feedback, and the provision of an alternate diagnosis, particularly if coupled with cardiac POCUS. LUS also has the potential for increased risk to the clinician as it requires additional clinician-patient contact. Therefore, we only use LUS when it may change management. Examples in a hospitalized patient include to aid in the diagnosis when RT-PCR is negative or pending, to exclude alternative diagnoses, to detect progressive disease or complications (e.g. development of ARDS, pneumothorax), to guide therapy (e.g. Figure 7) . We avoid LUS when it will not impact clinical care, such as for a patient with confirmed COVID-19 who is clinically stable. We avoid LUS for training purposes in patients with suspected or confirmed COVID-19. LUS findings of COVID-19 relate to the stage and severity of disease and can range from a mild interstitial pattern, to severe bilateral interstitial pattern, to dense lung consolidations. [8] [9] [10] Findings include a thickened and irregular pleural line; B-lines in focal, multifocal, or confluent patterns; consolidations in a variety of patterns including multifocal small, non-translobar, and translobar with occasional dynamic air bronchograms; and A-lines during the recovery phase. 10 Pleural effusions are uncommon but may be present with concurrent heart failure. 10 These findings are not specific to COVID-19 and instead reflect findings broadly observed in pneumonia and ARDS. Point-of-care ultrasound (POCUS) devices must be properly cleaned and disinfected to prevent Table 2 . Diagnostic accuracy of lung ultrasound and chest x-ray for common causes of respiratory failure. Lung Ultrasound Chest X-ray Lung Ultrasound for the Cardiologist International evidence-based recommendations for point-of-care lung ultrasound ASE Statement on Point-of-Care Ultrasound (POCUS) During the 2019 Novel Coronavirus Pandemic Online Supplement References Sensitivity of Chest CT for COVID-19: Comparison to RT-PCR. Radiology Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study Correlation of Chest CT and RT-PCR Testing in Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases ACR Recommendations for the use of Chest Radiography and Computed Tomography (CT) for Suspected COVID-19 Infection | American College of Radiology Canadian Society of Thoracic Radiology and the Canadian Association of Radiologists' Statement on COVID -19 -CAR -Canadian Association of Radiologists Thoracic ultrasonography: a narrative review Can Lung US Help Critical Care Clinicians in the Early Diagnosis of Novel Coronavirus (COVID-19) Pneumonia? Radiology A Preliminary Study on the Ultrasonic Manifestations of Peripulmonary Lesions of Non-Critical Novel Coronavirus Pneumonia (COVID-19). SSRN Electron J Findings of lung ultrasonography of novel coronavirus pneumonia during the 2019-2020 epidemic Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 List of hard-surface disinfectants for use against coronavirus (COVID-19) -Canada.ca Clean your Pixel phone -Pixel Phone Help Galaxy Note 8: How to clean dirty glass/screen? | Samsung Support NZ Accuracy of lung ultrasonography versus chest radiography for the diagnosis of adult community-acquired pneumonia: Review of the literature and meta-analysis Diagnostic Accuracy of Point-of-Care Lung Ultrasonography and Chest Radiography in Adults With Symptoms Suggestive of Acute Decompensated Heart Failure: A Systematic Review and Meta-analysis Screening Performance Characteristic of Ultrasonography and Radiography in Detection of Pleural Effusion; a Meta-Analysis Test characteristics of ultrasonography for the detection of pneumothorax: a systematic review and meta-analysis imaging showing normal lung visualized with fixed subcutaneous tissue and parietal pleural, but movement from the visceral pleura (vertical arrows), termed the seashore sign. The lung pulse is a normal subtle lung movement with the cardiac pulse (vertical arrows). An A-line is seen at the bottom of the image.