Sluggish gas exchange in the lungs may be involved in long-COVID brain fog

COVID-19
Brain MRI

Nur Ceren Demir / iStock

Lower rates of gas exchange in the lungs may contribute to impaired cognitive function ("brain fog") tied to long COVID, according to a small study to be presented at next week's Radiological Society of North America's (RSNA's) annual meeting in Chicago.

Pulmonary gas exchange is the movement of oxygen from the lungs to the bloodstream and carbon dioxide from the bloodstream to the lungs.

Novel approach to assess multiorgan relationship

University of Iowa researchers in Iowa City evaluated the link between pulmonary gas exchange on magnetic resonance imaging (MRI), structural and functional brain MRI, lung-function tests, and performance on cognitive tests in long-COVID patients. 

For the study, 10 female and 2 male COVID-19 survivors with a median age of 59 years who had persistent shortness of breath, fatigue, or both, were recruited from a post-COVID clinic. 

Lung MRI
Author-provided map showing low gas exchange in the lungs.

"This is the first time that MRI has been used to jointly assess lung and brain function to investigate their relationship in long COVID," lead author Keegan Staab, graduate research assistant in the Department of Radiology at the University of Iowa in Iowa City, said in an RSNA news release. "This research is new in that it combines multiple unique imaging types to study a multiorgan relationship in a disease population."

Lower gray- and white-matter volumes in brain

The findings suggest that impaired pulmonary gas exchange may be related to cognitive dysfunction and diminished brain gray-matter and white-matter volumes in long-COVID patients. They also indicate that increased cerebral blood flow may be tied to decreased gas exchange in these patients, the authors said.

"If these findings can be generalized to the long COVID population, the study suggests that there may be a causative relationship between cognitive dysfunction and lung dysfunction, suggesting a potential treatment strategy using methods that target improved gas exchange," senior author Sean Fain, PhD, professor and vice-chair for research in the University of Iowa's Department of Radiology, said in the release.

It's also a possibility that the disease mechanism that impairs pulmonary gas exchange also leads to higher brain perfusion through downstream vascular injury in both lung and brain.

Keegan Staab

Staab called for larger studies of the link between gas exchange and blood flow in the brain in long-COVID patients. "This relationship could be a compensatory mechanism where lower lung function is compensated by higher cardiac output and higher brain perfusion," he said. 

"It's also a possibility that the disease mechanism that impairs pulmonary gas exchange also leads to higher brain perfusion through downstream vascular injury in both lung and brain."

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