‘Honeycomb change’All of that can cause the deposition of yellow fibrotic scar tissue, creating a “honeycomb change" that makes the lungs completely solid, said David Kleiner, who heads autopsy pathology in the National Institutes of Health Clinical Center in Bethesda, Maryland.The process irreversibly destroys the tiny grape-like air sacs through which gas is exchanged in the lungs, Kleiner said in a lecture on Covid autopsies in July. “Patients really only survive to that fibrotic stage if they are intubated," he said, adding that the harmful scarring can occur within a couple of weeks of lung injury.Such cases have led to lung transplants around the world, according to a study in The Lancet Respiratory Medicine journal last month,.