Problems with gas exchange and density of blood vessels in the lungs have both been reported in Long COVID studies, yet these findings have never been linked to one another, or to limited exercise capacity. Now the biggest MRI study of Long COVID patients, published in the journal Radiology, is the first to identify a potential reason for these ongoing symptoms.*

What the researchers did

For the LIVECOVIDFREE study, scientists used a unique imaging method to get a clearer picture of COVID-19’s impact on lung function. Forty participants aged 18-80 years were enrolled. Thirty-four of them had Long COVID, and six acted as healthy controls. 

• Despite normal breathing test results, participants had experienced breathlessness for more than 6 weeks after recovery from infection, with some still symptomatic after nearly 9 months.
• While lying inside a magnetic resonance imaging (MRI) machine, participants breathed in polarized xenon gas, enabling researchers to view the workings of micro-structures in the participants’ lungs.

Said Grace Parraga, Ph.D., lead study author and Western University’s Tier 1 Canada Research Chair in Lung Imaging to Transform Outcomes, “With our MRI technique, we can watch in real time the air moving through the alveolar membrane and through to the blood cells; and we can actually see the function of the tiny alveolar sacs in the lungs.”

What they found

The research team found that the transfer of oxygen between lung alveoli and red blood cells was impaired in participants with Long COVID. The impairment was not observed in the healthy volunteers.

Looking even more closely at the lungs using computed tomography (CT) imaging, the scientists also found abnormal blood vessel density, indicating COVID-19’s potential impact on small blood vessels in the lungs that are essential to transporting oxygen through the body.

This abnormality was consistent in both people with Long COVID who had been hospitalized with severe COVID-19, and those who had recovered from their initial infection without hospitalization. 

What it means

The MRI results ultimately linked:

• Lung changes in blood vessel density and oxygen exchange, 
• Lingering breathlessness with exertion, and 
• Decreased exercise capacity.

Alex Kopacz, a young, fit Canadian Olympic gold medalist bobsledder who participated in the study, said that the results help explain why it’s taken him nearly three months to be able to go for a simple walk without getting out of breath. 

“The take-home message for me,” he said, “is that we have to remember that this virus can have very serious long-term consequences, which are not trivial.”

Fortunately, the knowledge that, despite normal pulmonary function testing, complications can exist in the lungs after COVID-19, has already enabled more effective treatment for these Long COVID symptoms. 

A year-long follow-up study has been initiated to better understand these underlying processes.

*Mackay, C. (2022, June 28). Innovative lung-imaging technique shows cause of long-COVID symptoms. Medical Xpress. https://medicalxpress.com/news/2022-06-lung-imaging-technique-covid-symptoms.html

“MRI.” by liz west is licensed under CC BY 2.0