New Imaging Technique Starkly Reveals The Source of Long COVID in The Lungs

While COVID vaccinations have saved millions of lives by lowering the overall severity of the disease, over one-tenth of individuals who have recovered are still experiencing symptoms after the original sickness has gone.

These individuals have a stunning assortment of over 200 symptoms, including dizziness, diarrhea, shortness of breath, exhaustion, and terrible brain fog, which can last months or even years.

According to St. Joseph's Health Care London respirologist Michael Nicholson, even long COVID patients who have breathing difficulty get normal findings on traditional clinical breathing tests.

However, a new imaging tool has finally identified the root of the breathing difficulty.

"The findings allowed us to show that there was a physiological impact on [patient] lungs that correlated with their symptoms," Nicholson explains.

(Alexander Matheson)

The images show how COVID-19 may cause substantial harm to our sensitive respiratory organs. Whether it's the virus or the body's response to it, some mechanism has successfully pruned the function of patients' lung arteries, snipping off many of the tiniest ones where vital gas exchange occurs.

The researchers, lead by Western University physicist Alexander Matheson, asked 40 participants to breath a polarized xenon gas isotope - 34 with post-acute COVID-19 syndrome and 6 without. Under MRI, the gas echoes at a distinctive frequency, allowing researchers to see the activity of small airways and blood vessels in real time.

"For those who are symptomatic post-COVID, even if they hadn't had a severe enough infection to be hospitalized, we are seeing this abnormality in the exchange of oxygen across the alveolar membrane into the red blood cells," explains Grace Parraga, a medical biophysicist at Western University.

"What we saw on the MRI was that the transition of the oxygen into the red blood cells was depressed in these symptomatic patients who had had COVID-19, compared to healthy volunteers." 

Because flu symptoms are the most visible and prevalent indicators of COVID-19, it is sometimes ignored as just another respiratory disease. However, COVID-19 is also a vascular disease, which means it can interfere with the circulatory system. Endothelial cells, which line the walls of our blood arteries and hearts, are directly targeted by viral particles.

MRI scans reveal vascular damage; CT scans demonstrate abnormalities in the finest blood arteries in our lungs.

Furthermore, a prior study found a change in blood distribution inside the lungs of hospitalized COVID patients from smaller to bigger blood vessels.

The team offers many probable causes for the observed shift in gas exchange, which is depicted in the diagram below.

Possible mechanisms for disrupted gas exchange. (Matherson et al., Radiology, 2022)

The vessels may be losing flexibility, reducing the amount of blood available for xenon to bind to (B), new blood flow patterns caused by changes in vessels elsewhere may be shunting the blood away from the gas exchange regions (C), or there is a physical blockage preventing the blood from getting there (D) (D).

Matheson and colleagues warn that the limited sample size restricts their capacity to generalize, but they call for more research. And, whatever the process is, it is abundantly obvious that getting the virus may seriously disrupt the circulatory system.

Despite loosening restrictions in many areas of the world, the worldwide pandemic continues, and each SARS-CoV-2 infection increases the risk of vascular damage, ranging from clotting issues to heart disease.

"I was on oxygen for almost two months after COVID, and it took me almost three months to get to a place where I could go for a walk without gasping for air," bobsled Olympic gold medalist Alex Kopacz, one of the research participants, noted.

"The take-home message for me is that we have to remember that this virus can have very serious long-term consequences, which are not trivial. In my case, prior to getting sick, I didn't think it would really affect me."

This research was published in Radiology.