When should you use lung point-of-care ultrasound (POCUS) to help diagnose COVID-19?

The COVID-19 pandemic has created major disruptions in society and health care around the world. Clinicians have had to adapt to the diagnosis and management of this new disease. 

Lung ultrasound is a powerful diagnostic tool for COVID-19. It gives clinicians the ability to rapidly assess and evaluate patients for the likelihood of having COVID-19.

 

Advantages of lung ultrasound for COVID-19 diagnostics

There are four main advantages to using point-of-care ultrasound (POCUS) for diagnosing COVID-19:

1. Allows for rapid and bedside COVID-19 testing 
2. Reduces exposure to ionizing radiation 
3. Reduces viral exposure to other healthcare workers
4. Spares the need for other diagnostic testing 

^{Figure 1. Point-of-care ultrasound (POCUS) for COVID-19 diagnostics allows for rapid bedside testing, reduces exposure to ionizing radiation, reduces viral exposure to other healthcare workers, and spares the need for other diagnostic tests.} 

 

Absolute indications for lung POCUS

There are seven important indications for a diagnostic lung ultrasound: 

1. Undifferentiated dyspnea
2. Respiratory failure
3. Shock
4. Unstable for transfer 
5. COVID-positive and decompensated 
6. COVID-positive and hypotensive 
7. COVID-positive and hypoxic 

The most important indication for a diagnostic lung ultrasound in a patient with suspected COVID-19 is shock! 

^{Figure 2. Definite indications for lung ultrasound include undifferentiated dyspnea, respiratory failure, shock, unstable for transfer, COVID-positive and decompensated, COVID-positive and hypotensive, and COVID-positive and hypoxic.} 

 

Relative indications for lung POCUS

Not all patients will benefit from a lung ultrasound. But there are three main groups of patients who would potentially benefit from a lung ultrasound: 

1. Patients with COVID-19 with uncertain dispositions
2. Patients with COVID-19 unable to get RT-PCR testing 
3. Patients in overcrowded hospitals with a high prevalence of COVID-19 

COVID-positive patients with uncertain dispositions

Potential indications include patients who clinically have COVID-19, but you are uncertain about disposition. For example, should we admit the patient or instruct them to quarantine themselves at home? If we admit the patient, do we admit them to a general floor or do they need a bed in the intensive care unit? 

 

 

COVID-positive patients unable to get RT-PCR testing

Other patients who may be candidates for lung ultrasound are those who clinically have COVID-19, but for whom you do not want to obtain RT-PCR testing or who are anxious about RT-PCR, and you want to be able to offer data to support your clinical impression.

Patients in overcrowded hospitals with a high prevalence of COVID-19

As well, consider lung ultrasound when you are overwhelmed with patients, there is a high prevalence of COVID-19, and you want to move rapidly to reduce testing for patients who are well enough to go home.

^{Figure 3. Potential indications for a lung ultrasound include COVID-positive patients with uncertain dispositions, patients that are unable to do RT-PCR testing, and patients in overcrowded hospitals with a high prevalence of COVID-19.} 

Contraindications for lung POCUS

It is important to note that not everyone should get a scan. There are costs in terms of your time and exposure to the SARS-CoV-2 virus. In general, if an ultrasound is not going to change what you do—don’t do the scan! 

You don’t need to do an ultrasound if a patient is clinically well with typical symptoms, likely has COVID-19 with moderate to high prevalence or risk factors, and there is no concern for an alternative diagnosis. 

COVID-19 pre-test probability and prevalence in the community 

The reason why pre-test probability and prevalence are important is that lung ultrasounds for COVID-19 are nonspecific. This means that the findings can overlap with other conditions. 

So, when you decide to perform a scan, you have to consider the results in terms of the prevalence of COVID-19 in your community and the patient’s overall risk.

If prevalence is high, your lung ultrasound findings will be more helpful to include the likelihood of COVID-19. If prevalence is low, and the lung ultrasound is suggestive of COVID-19, you have to consider alternative pathologies that look similar to COVID-19 on the lung ultrasound.

^{Figure 4. Lung ultrasound results have to be considered in terms of community prevalence of COVID-19. If prevalence is high, your lung ultrasound findings will be more helpful to include the likelihood of COVID-19. If prevalence is low, and the lung ultrasound is suggestive of COVID-19, you have to consider alternative pathologies that look similar to COVID-19 on the lung ultrasound.}

 

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