VIDEO: Tracking long-COVID lung damage using MRI and CT

Fain spoke in a session on assessment of ventilation and gas exchange in long-COVID to track long-COVID patients who had relatively mild cases of the virus (none were hospitalized) but are still experiencing respiratory and cognitive issues. His center used hyper-polarized Xe gas that is highly soluble in tissues and blood to calculate the amount of gas exchange in lung tissue into the blood. The hypothesis is there might be residual inflammation of damage to the lung tissue that prevents proper gas exchange. This is despite normal spirometry. Fain said this lower amount of oxygen exchange in the lung membranes might be the cause of cognitive issues. 

"There are abnormalities of gas exchange that create heterogeneity in the lungs that make it difficult for long-COVID patients to exchange oxygen into their blood stream," Fain explained. "We are finding that gas exchange is very regionally variable in long-COVID as compared to health subjects, and also there is an increased amount of uptake in what we are calling the tissue-plasma membrane component."

He said this seems to be related to neuro-cognitive issues, with symptoms persisting out to five months after the acute phase of the infection. 

The use of Xe gas is a pretty novel technique and is not widely used. It has been used in a couple COVID-19 studies show show gas flow in the lungs. This study goes a step beyond to also assess the gas exchange in lung tissue in these patients.
 
All of the patients in the study are experiencing shortness of breath (dyspnea), but only a portion of them have neuro-cognitive issues, Fain said. But, the patients with cognitive impairments are the patients found to have the poorest levels of gas exchange.  

"This is baseline data that can help us understand how to approach the therapy for theses prolonged symptoms people are experiencing," Fain said. 

Is long-COVID a disease state that happens in other repertory diseases?

One interesting takeaway is that these long-term impacts from COVID might be translatable to other respiratory diseases. According to Fain, COVID has been under the microscope with thousands of studies in a very short period of time, unlike other respiratory diseases like RVS, pneumonia or the flu. That might be the case because so many people have contracted the virus that we are just seeing a related high number of long-term impacts that very well might be involved in other ailments, but no one ever really studied it. 

"We're studying a respiratory infection disease at a very, very detailed level, and it is something we have never done before, or if we have, it has been in much smaller populations," Fain explained. "With so many people who have experienced COVID, we are seeing an impact due to this infectious disease process that we may not have seen before, but it may be common to respiratory infections generally. But now, we have millions of people with COVID, and millions of people experiencing long-COVID symptoms."

He said it is possible a faction of the population with the flu or pneumonia experience long-flu or long-pneumonia symptoms similar to long-COVID, but the numbers were small and dispersed enough where it has just gone unnoticed prior to the attention focused on COVID.

Find more COVID content related to medical imaging