COVID-19 may very well be the ultimate trickster when it comes to sonography. On lung ultrasound, many lung pathologies will show similar features to COVID-19 and it takes a well-trained eye to spot the differences. So how do you differentiate between COVID-19 and other pathologies when you're scanning your patient's lungs? In this video, you'll learn about the point-of-care ultrasound (POCUS) findings typical of diseases other than COVID-19, what to scan when you suspect that the dyspnea may not be COVID-19-related, and why sonographic B-lines may be the key to finding out what's really going on.
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By the end of this course, you will master the use of point-of-care ultrasound (POCUS) in the evaluation of patients suspected of having COVID-19. You’ll know when to consider alternative diagnoses, based on the POCUS scan, as well as understand the evidence for using ultrasound in this population.
One of the great things about lung ultrasound is they can help us make a range of diagnoses, not just COVID-19. You might suspect COVID-19 in a patient, but that doesn't mean you'll find it. You have to keep an open mind to diagnose other diseases because ultrasound findings are not specific for COVID-19.
This is especially important in patients who have other comorbidities. Sonographic B lines are produced by diseases that affect the interstitium of the lung, so we can see them in a range of diseases. Pulmonary edema from congestive heart failure is a classic example, both congestive heart failure and COVID-19 can produce diffuse bilateral B lines.
Here's an example of a patient with congestive heart failure. Clinical history, physical examination, and lab testing must be integrated with the lung ultrasound findings to help distinguish the difference between the B line seen in this patient versus ones we might see in COVID-19. Looking closely at the pleura may help tip you off that the B lines you're seeing are cardiogenic and not arising from COVID-19 or another primary pulmonary etiology.
B lines in congestive heart failure tend to arise off the pleura directly, and small consolidations or an irregular pleura are uncommon. You could consider using M mode to help you appreciate the features of the pleura more clearly. Pneumonia is another common cause for dyspnea or hypoxia as well, especially when the patient presents with fever.
Most pneumonias start at the lung periphery, and so they will touch the pleura. This makes them amenable to visualization with ultrasound, and lung ultrasound is an excellent diagnostic test for pneumonia. When you're looking for a pneumonia with lung ultrasound, seek out a larger dominant consolidation, such as we see here.
You might also see adjacent B lines or parapneumonic effusion. This is different from COVID-19 in that bacterial pneumonias are typically a unilateral process, not bilateral. Large pleural effusions are not typical of COVID-19. If you find one, which would appear on ultrasound as an anechoic space above the diaphragm with a spine sign, as we see here, consider another diagnosis.
Pneumothorax is a classic diagnosis to make with lung ultrasound. It's an important alternative explanation for someone who's short of breath. It could be an older person with chronic obstructive pulmonary disease, or a young person presenting with dyspnea. This is the lung ultrasound of the patient with a pneumothorax. Consider that on this scan, there's no movement or lung sliding seen on the right part of the pleura.
This is sensitive, but not totally specific for diagnosing a pneumothorax. But on the left side of the pleura, there's movement as the lung slides in. This is a lung point sign and specific for pneumothorax. Other viral illnesses with lung involvement may have a very similar appearance to COVID-19.
Again, we have to think about prevalence and pretest probability to interpret our lung ultrasound correctly. Here's a child with bronchiolitis. We notice a similar signature to the ones we've seen in COVID-19, with B lines, and an irregular pleura, and small consolidations. Interstitial lung disease, such as pulmonary fibrosis also produces a very similar appearance to COVID-19.
This is a patient who presented with decompensated interstitial lung disease. Respect the clinical context and history when interpreting your lung ultrasound scan. This person has interstitial lung disease, and not COVID-19. COVID-19 can cause acute respiratory distress syndrome or ARDS, and the appearance of severe COVID-19 and ARDS or lung ultrasound will converge.
We'll find B lines, small consolidations, irregular pleura, in areas of spared long. If you see this pattern, but weren't suspecting COVID-19, keep an open mind for an alternative cause for ARDS or add COVID-19 to the differential diagnosis. And then of course, there are cardiac causes for dyspnea such as tamponade. This patient with a pericardial effusion has tamponade.
Point-of-care limited echocardiography is a valuable adjunct to your lung scans. The big takeaway here is that there are other diseases that can cause shortness of breath and respiratory failure. Lung ultrasound can help you make these diagnoses too. You must remember to consider the history and clinical context, especially as the ultrasound findings in COVID-19 are not specific.