Coronavirus, COVID-19, Covid-19
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So much of the news around Covid-19 is scary, but there is a hopeful item to share: A steep rise in the learning curve of doctors treating critically ill coronavirus patients.

Doctors are learning more about just how weird this disease can be when people get sick enough to be hospitalized. Some say that unlike typical cases of severe pneumonia, in which the lungs stiffen and look cloudy on CT scans, about half of patients with severe Covid-19 have healthier, more elastic lungs, and report little trouble breathing "- even as their blood-oxygen levels drop to dangerous lows.

One New York critical care doctor, Cameron Kyle-Sidell of Maimonides Medical Center, writes in WebMD that it looked like oxygen starvation associated with high altitude, as if tens of thousands of New Yorkers "are stuck on a plane at 30,000 feet and the cabin pressure is slowly being let out."

High altitude symptoms

A handful of other doctors relate comparable cases to the New York Times. Todd Bull, a pulmonologist and critical care doctor at the University of Colorado, tells me they've been seeing similar cases. "I'm covering nights at the ICU and going to see patients and they say they feel okay," he says, "While their oxygen is plummeting."

Doctors are learning more about patients with these weird high-altitude-like symptoms and how to treat them and sharing that information across borders and time zones. For example, Bull says he found some interesting insights into the conundrum in a paper by Luciano Gattinoni, an intensive care doctor and guest professor at the University of Gottingen in Germany, in the journal Intensive Care Medicine.

It has to do with the pulmonary vascular bed, the system of blood vessels that carry oxygen from the lungs, which is one of Bull's specialties, along with critical care and altitude-related disease. "The lungs are really quite smart," he says.

When patients develop pneumonia, the lungs sense low levels of oxygen and can constrict blood vessels in damaged parts of the lungs to channel blood to the areas that still function. This process fails in a condition called high-altitude pulmonary edema (HAPE), in which the lungs essentially get confused.

It makes doctors wonder if the virus is somehow scrambling the signals and preventing the proper rechanneling of blood, Bull explains. The virus infects the epithelial cells, which line the nasal passages and lungs; but blood flow in the lungs is regulated by deeper, endothelial cells. "I'm not aware of a virus doing anything like that before "- it would be new and different."

Understanding more about how this works will help doctors figure out how to treat it.

Gattinoni's paper suggested that lungs with this HAPE-like condition might be particularly vulnerable to injury from ventilator use "- when pressure from the air being pumped in damages the delicate air sacs called alveoli, which exchange oxygen with the bloodstream. And while a few people have proclaimed that ventilators are "overused" for Covid-19 patients, Bull says more often the problem is that they might not be used optimally.

Anecdote is king

When doctors use a ventilator, they heavily sedate a patient, then thread a tube into the lungs to pump in air. The technique can save lives by allowing the lungs to heal from damage inflicted by the virus, says Michael Mohning, a pulmonary critical care doctor treating Covid-19 patients at National Jewish Health in Denver. The ventilator gives the doctors back information about a patient's lung function, and the pressure has to be adjusted just right to avoid causing injury while avoiding oxygen starvation.anecdote is king

Some doctors are reporting that patients with the altitude-like symptoms do better without a ventilator, instead getting extra oxygen through non-invasive means "- the two-pronged cannulas that deliver oxygen to the nose, or the CPAP masks used for sleep apnea. So far the reports are anecdotal, but eventually studies will sort out the best treatment for different symptoms and severity of disease.

Doctors are also trying medications, going with inhaled drugs that would make sense in similar pulmonary patients. In theory, these should go to the parts of the lungs that still work "- but these tests are not taking place in clinical trials, and doctors aren't always sure that the drugs they are offering are helping. This isn't the way we like to practice medicine, Bull says, but in the land of no data, anecdote is king. In a few weeks, when they are able to get results from clinical trials on drugs like the much-discussed malaria drug hydroxychloroquine and several antivirals such as Remdesevir, the standard of care will vastly improve.

Doctors will also be able to eventually study the HAPE-like symptoms using cell culture and animal models. But not now. They're just too busy.

Normally, Bull says they'd see two or three patients at any given time with severe respiratory failure but now it's 50 or 60. With such a big surge in patients, and so many health care workers out sick or quarantined, many critical care doctors are now supervising other doctors who've filled in from other specialties. Those other doctors might not be as skilled with a ventilator, and there's risk involved, "but of course that's the way we have to do things right now."

Bull uses the analogy that they are all in the fog of war, with different people seeing just part of the picture. "You've got to keep your eyes open, and if you see something that doesn't make sense, you want to study it," he says. That's the only way to lift the fog of war and put all the pieces together.

The learning curve is exponential, but doctors still have much to learn. Hospitals are likely to be surging with patients over the next several weeks and doctors are still figuring out how to treat them. The more effective social distancing is at flattening the infection curve, Mohning says, "the more time we have to learn about this disease and how to treat it."