LONDON • The United Kingdom's National Health Service (NHS) has warned its hospitals to limit the number of people using ventilators, after a London hospital was almost depleted of oxygen as it was treating too many coronavirus patients who needed help to breathe.

The Covid-19 virus at its most lethal attacks the lungs, making ventilators - which pump breathable air into a patient - critical for hospitals around the world as they are swamped with coronavirus cases.

Raising the alarm on Monday, NHS England told hospitals the risk of putting too many people on ventilators constituted a "critical safety concern" which could have major consequences for all patients relying on oxygen to stay alive, The Guardian reported yesterday.

NHS England said the sudden spike in the use of mechanical ventilators and continuous positive airway pressure (CPAP) machines - which use a mask to deliver constant and steady air pressure - could cut off the supply of oxygen altogether to all patients who need it.

CPAP machines involve non-invasive assisted ventilation, whereas a mechanical ventilator involves introducing a tube down the patient's trachea when the patient is unable to breathe on his own.

Figures published on Wednesday showed a total of 2,352 people with Covid-19 have died in the UK.

The NHS is expecting the arrival next week of the first ventilators which Britain has ordered, as the country seeks to boost capacity in the face of the virus outbreak.

Britain has ordered 10,000 of them from a consortium including Ford, Airbus and McLaren, with other companies also producing their own equivalents.

"This weekend, the first thousands of new ventilator devices will roll off the production line and be delivered to the NHS next week," Cabinet Office minister Michael Gove told reporters. "From there, they will be rapidly distributed to the front line."

Prime Minister Boris Johnson on Wednesday promised to ramp up testing for the virus after his government faced criticism for being slower than some European peers to roll out mass checks for front-line health workers and the population, Reuters reported.

Britain initially took a restrained approach to the outbreak but changed tack after modelling showed a quarter of a million people in the country could perish.