Lung Ultrasound in a COVID Pandemic – Choosing Wisely
Source: AJUM August 2020 23(3):159-166
This is an opinion paper on the role of lung ultrasound and POCUS in the management of COVID-19 patients. It starts with the classical comparison of crisis management in medicine to aviation industry. The authors note that in contrast to aviation, the clinician’s life is not at imminent danger in a situation of failure. This has changed by the COVID-19 pandemic where clinicians now need to make urgent decision and exposed to some personal risk.
The paper reviews four important questions that should be answered by each provider, which will help the provider customize lung ultrasound provision: Why, what, who, and when?
WHY should lung ultrasound be performed – and why not
Lung ultrasound (LUS) has been used in disaster areas for triage, management and decision-making. LUS has the advantage of being more convenient that CT scan and better than chest x-ray (CXR) and can be used in all groups of patients, including children and pregnant women.
While LUS cannot image below aerated lung, however proponents claim that LUS is easy, rapid, reliable, repeatable and low risk in expert hands. LUS opponents argue that it does not add value if it does not replace other imaging (such as chest X-ray) or if management decisions are already being made on clinical signs, symptoms and other investigations. In addition, it should be recognized that LUS requires patient contact so is an infection risk for the provider, especially in in COVID-19 era.
WHAT is lung ultrasound – and what is it not?
Since ultrasound does not penetrate through an air interface, lung ultrasound studies the lung periphery at the chest wall-visceral pleura interface. Analysis is made to lung movement, the reﬂective properties of the peripheral lung and of the pleural space. The nature of the lung parenchyma creates a reflection pattern at the is characteristic of normal and diseased lung, the density of lung tissue, alveoli and interstitial ﬂuid, and the pulmonary air patterns. The distribution of abnormalities gives an indication of the disease process.
CT studies have demonstrated that the lung pathology of patients with COVID-19 appears to be a predominantly bilateral, subpleural condition, which is generally accessible to LUS. In a small patient cohort, LUS has been shown to correlate with CT ﬁndings.
In COVID patients, the disease seems to progress from asymmetric patches of B lines, to either widespread B-line pattern (interstitial syndrome), and/or areas of pleural line irregularity with or without subpleural consolidations. However, while LUS findings are characteristic of pathologies, they are not speciﬁc – LUS cannot differentiate early COVID-19 from other viral pneumonitis. In the setting of this pandemic, LUS assesses the pleural surface for changes that are characteristic of COVID-19. However, other potential causes of dyspnea or deterioration such as pneumothorax or pleural effusion should be evaluated, and the ultrasound examination can also be extended to include cardiac exam to assess for cardiac etiology of respiratory failure.
The authors conclude the paper by discussing who, when and how to perform LUS in patients with suspected infection of COVID-19