NEW YORK (REUTERS) - Some coronavirus patients who would have been admitted into the emergency department at a New York hospital are being sent home with an oxygen-monitoring device as the city's medical system struggles to reserve resources for only the sickest people.

The new programme at NewYork-Presbyterian Hospital is an example of how doctors are adapting and loosening normal protocols to ease the strain on emergency rooms and intensive care units in New York state, the epicentre of the coronavirus pandemic in the United States.

Since last week, more than 200 people with confirmed or suspected Covid-19, the respiratory illness caused by the virus, have been sent home with a pulse oximetre to track their oxygen levels. A doctor or nurse practitioner follows up with them via video conference.

"Some of these patients might have been on the borderline of admission," Dr Rahul Sharma, who is overseeing the programme as the chief of emergency medicine at Presbyterian's Weill Cornell Medical Centre, said in an interview.

An oximeter is a small electronic device that clips onto a fingertip to indirectly measure the oxygen saturation of a patient's blood. In severe Covid-19 cases, the virus can block up the lungs, hindering their ability to pass oxygen from the air into the bloodstream. While most who contract the virus recover, it has killed at least 4,900 people in the city, according to a Reuters tally.

Some of the NewYork-Presbyterian patients are also being sent home with a 14 kg portable oxygen concentrating machine which sends oxygen-rich air through a nasal cannula, a two-pronged tube inserted into the nostrils.

The patient is asked to log their oximetre readings to share with a doctor or nurse practitioner at 12-hour and 24-hour consultations. The patient may be re-admitted to the hospital if they take a turn for the worse.

No patient in the programme is known to have died at home as of Wednesday, but about 15 per cent were asked to return to hospital to be admitted for inpatient care, a hospital spokesman said.

At least two other hospital systems outside of New York unveiled similar new programmes using oximetres in late March.

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Doctors at other hospitals said Presbyterian's approach could have benefits for patients with a disease about which they still have much to learn.

"There's no guarantees in either direction, there are risks to hospitalisation and there are risks with sending people home," Dr Laura Burke, an assistant professor of emergency medicine at Harvard Medical School, said in an interview.

Doctors have noticed there can be a worrisome lag in symptoms among some Covid-19 patients, with oxygen saturation dropping for some time before a patient is aware of breathing problems.

For patients that turn up at an emergency department with other Covid-19 symptoms, giving a pulse oximetre to use at home could be one way to "err on the side of safety," Burke said.