Trail of bubbles leads scientists to new detection of coronavirus

A doctor who checks comatose COVID-19 patients for signs of a stroke, instead stumbles upon a new indication of how the virus can damage the lungs – thanks to a test that used small air bubbles and a robot.

Dr. Alexandra Reynolds, a neurologist at New York’s Mount Sinai Health System, was initially stunned when she detected “the cacophony of sound” created by those harmless bubbles that flow through a patient’s bloodstream. passed to patient.

However, it is strange finding enthusiastic lung specialists now studying as it helps to explain why the sickest coronavirus patients do not get enough oxygen even though they are on ventilators.

The story tells how months in the pandemic scientists are still struggling to discover the very ways in which the coronavirus attacks – and to find hints in surprising places.

When patients were rushed to hospitals in New York last week, Mount Sinai’s intensive care unit that normally treats patients with brain disease was transformed into a COVID-19 ward, where patients were severely sedated as ventilators kept alive.

“When we wake them up, will we notice that they have some horrible brain damage?” worried Reynolds, who at first did not have much way to control self-functioning except to monitor patients’ students.

A bed test called a transcranial Doppler uses sound waves to detect blood flow in the brain, but it was too risky for health professionals to stand at patients’ heads for extended periods of time.

That Reynolds turned to a new robot version, a headset that once positioned over the patient can do the tracking automatically. She used it to perform what is called a bubble study, a commonly used, painless test for stroke risk that involves salt extraction with small air bubbles in a vein. As the microspheres circulate, the smallest blood vessels in healthy lungs – called capillaries – fall and filter them out of the bloodstream.

Over several nights in the ICU, Reynolds tested some of her sickest coronavirus patients – and repeatedly kept NovaSignal’s robotic Doppler measuring blocks that, instead of filtering away, somehow reached her brain.

“This was really bizarre,” Reynolds said. Bubbles often prevent lung filtration by slipping through a heart defect, which is a known stroke risk, but “there’s no way everyone suddenly has a hole in their heart.”

But at Mount Sinai lung expert Dr. Hooman Poor, the bubble mystery could be “essentially the missing link” why these patients were not getting enough oxygen: Maybe that abnormal dilated lung capillaries, not a heart problem, were seeping through the bubbles.

Poor and Reynolds did more tests. By the end of the pilot study, 15 of 18 tested patients had detected microbubbles in the brain. And supporting Pory’s theory, patients with the most bubbles also had the lowest oxygen levels, researchers reported earlier this month in the American Journal of Respiratory and Critical Care Medicine.

Why would capillaries matter?

Coronavirus patients on ventilators have what is called ARDS as acute respiratory distress syndrome, an inflammatory lung function that, when caused by other infections, blocks oxygen by stiffening lungs. But the coronavirus does not stifle the lungs, Poor explained.

His new theory: Doctors know that the coronavirus attacks the lining of blood vessels, causing dangerous clots. Bubble research may suggest that blood is being diverted from clogged vessels to unusually widespread – and therefore flowing too fast to absorb oxygen properly.

A rare disorder called hepatopulmonary syndrome causes the same abnormality, and it has been diagnosed with a bubble test.

The findings are preliminary, not evidence that dilated blood fats are a problem. Still, some autopsies have linked COVID-19 to deformed lung capillaries.

Next up is a larger study that aims to see if measuring bubbles can help doctors check if patients are improving or deteriorating.

The report “I really think it’s going to generate a lot of talk” among lung specialists because it “is more evidence that blood fat is really where the action is,” said Drs. Corey Kershaw of the University of Texas Southwestern Medical Center, who was not involved in the pilot study.

He warned that researchers should definitely prove that a heart defect does not play a role.

But, “it’s an example of, there are so many things we don’t know yet,” Kershaw added, praising the creativity used to find this last clue.


The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.