When a person goes on a ventilator, the muscles that typically handle their breathing start to atrophy within hours. Many patients are put on sedatives to make it easier for the machine to take over. But this immobilizes other parts of their body and leads to widespread weakness.

The risk of dying remains higher than average for at least a year after getting off a ventilator, a risk tied to both the number of days spent on the machine and other health conditions the patient had before falling sick.

Diana didn’t have the best health track record going in. She is a two-time colon-cancer survivor with high blood pressure, iron deficiency and a few extra pounds. She has only vague memories of her days on a ventilator, waking up in pain unable to talk or move, before drifting back into a troubled sleep full of dreams of her deceased relatives. Her husband, Carlos, with no previous medical condition, had a totally different experience. He spent three days on a ventilator, mildly sedated, spending his days napping or sitting in an armchair watching television.

Yet both now face the ordeal of recovering from their treatments. Fortunately, they were able to avoid the worst-case scenario, a condition known as Post-ICU syndrome that can afflict as many as half of Covid-19 patients who survive on a ventilator, says the Cleveland Clinic’s Khouli.

“These patients become deconditioned,’’ he says. “Some behave like they are really paralyzed, as if they are quadriplegics. They can barely move their muscles.’’

Hospitals are gearing up to treat these survivors, who already number in the hundreds. Some, like SUNY Downstate Medical Center in New York, are setting up entire rehabilitation floors to help people coming off ventilators learn how to live again. Others are trying to cut back use of the device, avoiding a rush to ventilators when oxygen may be all that’s needed.

There are also devices in development to help with recovery, such as Liberate Medical’s VentFree Muscle Stimulator. It uses electrical stimulation to trigger contractions in the abdominal wall muscles, allowing patients to “exercise,” even while they are unconscious, to keep them in some semblance of shape. The goal is to help wean them off the devices faster and ultimately boost survival rates, says Chief Executive Officer Angus McLachlan.

In patients who develop acute respiratory distress — a common condition with Covid-19 marked by dramatic drops in oxygen levels — there is a second stage where scarring in the lungs develops, the University of California Irvine’s Lee says. As inflammatory and other cells invade the space, the architecture of the lungs is permanently changed.

The machines also can cause cognitive impairment, Rodricks says. A patient who worked as an accountant may have a tough time going back to work. An elderly person who was previously independent might struggle to perform daily tasks such as driving or grocery shopping. And a runner might never be able to hit the same pace again.

“Your overall condition may take some time to get back to its pre-Covid, pre-ICU state — if it ever gets back to that pre-ICU state,” he says.