WASHINGTON - Amid the rush to supply hospitals with ventilators, there's a sad truth: At least half of covid-19 patients who require ventilators don't survive.

As many as two-thirds of these critically ill patients - who struggle to breathe as their lungs fill up with fluid - end up succumbing to the illness caused by the novel coronavirus, according to early reporting on deaths out of China, Italy and the United States. While helpful, ventilators are far from a miracle cure for the virus sweeping through the United States.

"They're called life support for a reason - they just keep people alive while typically buying time for something else to heal the lungs," Scott Halpern, a bioethicist at the University of Pennsylvania, told The Washington Post's Carolyn Y. Johnson and Ariana Eunjung Cha.

Ventilators are used, typically in intensive care units, to assist patients with breathing by helping the lungs inhale and exhale air. The process involves inserting a tube into a patient's mouth or nose and down their windpipe. Mechanical ventilators are often used on patients with brain injury, stroke or when they have pneumonia (a condition often resulting from influenza).

Hospitals short on ventilators amid a surge of covid-19 patients are one of the most pressing worries of public health leaders as the country tries to mobilize against the virus. Chief among the problem areas is New York City, where Democratic Gov. Andrew Cuomo has said the state received 1,000 ventilators from the Chinese government and another 140 from Oregon. Last Thursday, Trump announced he was using the Defense Production Act to ensure several companies including General Electric and Medtronic get the materials they need to build ventilators.

Trump struck a typically boastful tone at Monday night's press briefing, promising the government is "ready to roll" with "almost 10,000" ventilators from the national stockpile and more being built by private industry. But the president has been in an ongoing argument with governors who say they're not getting what they need from the federal government in terms of ventilators, masks and gowns - called personal protective equipment - with Trump claiming those needs might be exaggerated.

"Wherever that monster goes, we're able to move with it," the president said. "We have people ready and waiting to bring them."

Here's what studies suggest about covid-19 patients who are sick enough to be put on a ventilator:

- According toLondon's Intensive Care National Audit and Research Centre study on 165 critically ill patients in England, Wales and Northern Ireland, 66% of patients who received respiratory support died.

That's significantly more than patients who typically die after being put on ventilators. Just 36% of these patients died from 2017 to 2019, according to the study.

- Nine out of 18 covid patients on ventilators in Seattle-area hospitals died and just six had recovered enough to breathe on their own, according to a study published Monday in the New England Journal of Medicine.

The researchers noted these patients needed especially high oxygen requirements soon after being intubated - and that patients typically required the ventilator for longer than a week.

"The earliest extubation occurred 8 days after initiation of invasive mechanical ventilation, which suggests that acute respiratory failure due to Covid-19 may require prolonged mechanical ventilation lasting days to weeks," they wrote.

- In another study of critically ill patients in Wuhan, China, where the virus originated, 30 out of 37 patients who received ventilation died.

So even if the Trump administration follows through on bold promises to deliver more ventilators to undersupplied hospitals, that can only go so far in stemming a death toll research models say could reach 100,000 or more in the United States.

Monday, a widely cited model from the University of Washington's Institute for Health Metrics and Evaluation (IHME) slightly downgraded its national fatality prediction from 82,141 deaths to 81,766 deaths, although that model conflicts with several others projecting deaths, equipment shortages and projected peaks. Some state leaders are growing increasingly concerned about how the White House is using the University of Washington model to deny state requests for equipment and help in preparations, Carolyn and William Wan report.

"The stark differences between the IHME model and dozens of others being created by states exposes the glaring lack of national models provided publicly by the White House or agencies such as the Centers for Disease Control and Prevention for local leaders to use in planning or preparation," they write.

And for patients who survive being put on a ventilator, a host of other challenges await.

"Many will suffer long-term physical, mental and emotional issues, according to a staggering body of medical and scientific studies," Johnson and Cha write. "Even a year after leaving the intensive care unit, many people experience post-traumatic stress disorder, Alzheimer's-like cognitive deficits, depression, lost jobs and problems with daily activities such as bathing and eating."

"Patients with covid-19 typically stay on ventilators for prolonged periods which increases the likelihood of long-term complications," they add. "The risk of infection also means they are cut off from human contact, which also increases the risk of psychological issues."

"We normally kneel at their bedside and hold their hand and ask them, 'How are you' and tell them, 'It is my privilege to help you.' Instead what they are getting is someone in spacesuit garb with very little time to spend with them," E. Wesley Ely, a professor at Vanderbilt University in Nashville, told our colleagues.