What Constitutes Intermediate Disease?
Once the images have been taken, they are scored on a 0-3 scale for each of the 14 areas, with no weighting on any individual area.
A score of 0 is given when the pleural line is continuous and regular, with the presence of A-lines, denoting that the lungs are unaffected.
An area is given a score of 3 when the scan shows dense and largely extended white lung tissue, with or without consolidations, indicating severe disease.
At both ends of this spectrum, there is agreement between the Italian protocol and an algorithm developed by the Butterfly Network.
However, the two differ when it comes to scoring intermediate cases. On the Butterfly algorithm, the suggestion is to look for B-lines, caused by fluid and cellular infiltration into the interstitium, and to weigh that against the need for supplementary oxygen.
The Italian team, in contrast, says a score of 1 is given when the pleural line is indented, with vertical areas of white visible below.
A score of 2 is given when the pleural line is broken, with small to large areas of consolidation and associated areas of white below.
Demi told Medscape Medical News that they did not refer to B-lines in their protocol as their visibility depends entirely on the imaging frequency and the probe used.
“This means that scoring on B-lines, people with different machines would give completely different scores for the same patient.”
He continued: “We prefer to refer to horizontal and vertical artifacts, and provide an analysis of the patterns, which is related to the physics of the interactions between the ultrasound waves and lung surface.”
In response, Mike Stone, MD, Legacy Emanuel Medical Center, Portland, Oregon, and director of education at Butterfly, said there appears to be wide variation in lung findings that “may or may not correlate with the severity of symptoms.”
He told Medscape Medical News it is “hard to know exactly if someone with pure B-lines will progress to serious illness or if someone with some subpleural consolidations will do well.”
A Negative Ultrasound Is the Most Useful
Volpicelli believes that, in any case, any patient with an intermediate pattern will require further diagnosis, such as other imaging modalities and blood exams, and the real role of lung ultrasound is in assessing patients at either end of the spectrum.
“In other words, there are situations where lung ultrasound can be considered definitive,” he told Medscape Medical News. “For instance, if I see a patient with mild signs of the disease, just fever, and I perform lung ultrasound and see nothing, lung ultrasound rules out pneumonia.”
“This patient may have COVID-19 of course, but they do not have pneumonia, and they can be treated at home, awaiting the result of the swab test. And this is useful because you can reduce the burden in the emergency department.”
Volpicelli continued: “On the other hand, there are patients with acute respiratory failure in respiratory distress. If the lung ultrasound is normal, you can rule out COVID-19 and you need to use other diagnostic procedures to understand the problem.”
“This is also very important for us because it’s crucial to be able to remove the patient from the isolation area and perform CT scan, chest radiography, and all the other diagnostic tools that we need.”
Are Wireless Machines Needed? Not Necessarily
With regard to the use of wireless technology, the Italian team says that “in the setting of COVID-19, wireless probes and tablets represent the most appropriate ultrasound equipment” because they can “easily be wrapped in single-use plastic covers, reducing the risk of contamination,” and making sterilization easy.
Stone suggests that integrated portable devices, however, are no more likely to cause cross-contamination than separate probes and tablets, as they can fit within a sterile sheath as a single unit.
Volpicelli, for his part, doesn’t like what he sees as undue focus on wireless devices for lung ultrasound in the COVID-19 protocols.
He is concerned that recommending them as the best approach may be sending out the wrong message, which could be very “dangerous” as people may then think they cannot perform this screening with standard ultrasound machines.
For him, the issue of cross contamination with standard lung ultrasound machines is “nonexistent. Cleaning the machine is quite easy and I do it hundreds of times per week.”
He does acknowledge, however, that if the lung ultrasound is performed under certain circumstances, for example when a patient is using a continuous positive airway pressure (CPAP) machine, “the risk of having the machine contaminated is a little bit higher.”
“In these situations...we have a more intensive cleaning procedure to avoid cross-contamination.”
He stressed: “Not all centers have wireless machines, whereas a normal machine is usually in all hospitals.”
“The advantages of using lung ultrasound [in COVID-19] are too great to be limited by something that is not important in my opinion,” he concluded.
Stone is director of education at the Butterfly Network. No other conflicts of interest were declared.
This article first appeared on Medscape.com.