Abstract
The novel coronavirus (SARS-CoV-2), which causes COVID-19, has been a challenging global threat since it emerged in December 2019. COVID-19 causes significant complications to the pulmonary system. Even though most patients have mild to asymptomatic infections, some still require intensive care and mechanical ventilation. Elderly patients and patients with other comorbidities such as cardiovascular diseases, obesity, diabetes mellitus, chronic obstructive pulmonary disease, and patients with immune disorders are at higher risk of developing acute respiratory distress syndrome (ARDS) and further life-threatening conditions, such as septic shock. 1 As the pulmonary system is the primary organ targeted by COVID-19, with the initial pulmonary tissue damage, COVID-19 infection results in mild, moderate, or severe pneumonia. These changes are described as ground-glass opacities that originate from the subpleural areas and then progressively extend to form consolidations. 2 Thoracic imaging is required to confirm the diagnosis as well as to monitor the progress of the disease. Chest radiography is the most common diagnostic imaging modality used because of its wide availability in most medical centers, despite low sensitivity in confirming the condition. The gold standard diagnostic imaging tool to evaluate patients is a computed tomogram (CT). 3 Moreover, chest CT uses ionizing radiation and requires patients’ transportation, consequently posing more contamination risk. During the pandemic, lung ultrasonography (LUS) has been established as a useful diagnostic tool for confirming and surveillance COVID-19 patients. This can be attributed to the diagnostic LUS features, which include portability, nonionizing radiation, dynamic imaging, and broad availability. Lung ultrasonography allows a semiquantitative assessment and monitoring of lung aeration in patients with hypoxemic lung injuries, caused by COVID-19. Several diagnostic scoring systems have been proposed to assess the changes in pulmonary tissue.4,5 These diagnostic scoring systems have different technical approaches, clinical environment settings, and clinical indications. An important focus is using an LUS scoring system employed in the intensive care unit, since it was the most frequently used during the pandemic to assess and monitor critically ill patients. To maximize the diagnostic benefit of LUS, it is highly advocated to follow the bedside lung ultrasound emergency (BLUE) protocol and use all the scanning points to assess the underlying lung tissue. I recommend that the sonographer starts with the anterior fields of the hemithorax using a linear transducer, then moves to the mid-auxiliary areas, and completes the examination with the posterior lung fields. The LUS scoring system is used to quantify the degree of loss of aeration during a scan, by using a scoring system with four levels when evaluating each image: a score of 0, for normal aeration, 1 for moderate loss, 2 for severe loss, and 3 for complete loss. These levels are based on the appearance of certain artifacts in the examination, such as A-lines and B-lines. The overall lung score obtained using sonography is calculated by adding up the scores assigned to each region. As a result, the total score can range from 0 to 36. Focusing on the posterior and anterior fields is really helpful in recommending the prone position for patients with COVID-19. The prone position is one of the therapeutic positions for patients with ARDS that demonstrates a significant improvement in oxygenation, for oriented nonintubated patients with COVID. A specific score has been suggested for use in the posterior regions of the lung to identify patients who will have a long-term positive response to the treatment of pronation. 6 An LUS score can be used to detect the change in lung aeration across all lung fields and it is recommended to place the patient in a prone position, to predict the response to it.
An LUS score system is a diagnostic tool used to monitor the level of lung aeration in patients with ARDS, who are receiving extracorporeal membrane oxygenation.4 A decrease in the score over time indicates that the injured lung is gradually recovering. The use of this score is particularly useful in these patients because it can be done at the bedside, which eliminates the high risk of transporting them to a radiology department. A semiquantitative approach can also be used to monitor the effectiveness of fluid resuscitation in critically ill patients, specifically in those with ARDS and shock. These changes in lung aeration are detected sooner than changes in the gas exchange. This is impacted by the fluid resuscitation treatment, which can temporarily improve oxygenation and consequently improve the patient’s hemodynamics. A reaeration semiquantitative LUS score, computed using the same four patterns before and after treatments that affect aeration, can accurately detect changes in lung aeration caused by 7 days of antibiotics treatment in patients with ventilator-associated pneumonia. 7 This score has a significant correlation with results from quantitative computed tomography.
Even before the pandemic, LUS proved its usefulness in monitoring mechanically ventilated patients, who are sensitive to movement and transportation. LUS can be used to determine the appropriate level of positive-end expiratory pressure (PEEP), evaluate the effectiveness of treatments, track the progression of respiratory disorders, and assist in the process of liberation from mechanical ventilation. 8
Lung ultrasonography is an effective method for evaluating the lung in various areas. Different scoring systems have been established and proven to expand the use of LUS as both a diagnostic tool and a way to monitor lung aeration. These scoring systems are tailored to specific clinical indications and should be used in the appropriate clinical environments. The ideal lung scoring system should consider all lung fields to carefully assess the changes post-infection and monitor the progress of the diseases.
Huriah Al Sultan, MS, RRT, RRT-NPS, RRT-ACCS