Health authorities around the world are trying to find ways to fill their hospitals with more ventilators to cope with increasing numbers of coronavirus patients.

Car manufacturers are offering to help build more of the machines. In New York, city mayor Bill de Blasio says he needs 15,000.

While the vast majority of people who catch the Covid-19 disease experience only mild symptoms, about 6% need hospital care, with older patients at higher risk.

Australian authorities say they are confident they can avoid any shortage of ventilators.

Experts have told Guardian Australia that these efforts will be crucial, because a shortage of ventilators would put lives at risk.

“The reason this is a crisis is because without the ventilators, patients will die,” says Prof David Story, deputy director of the University of Melbourne’s Centre for Integrated Critical Care, and a staff anaesthetist at Austin Hospital.

Prof Sarath Ranganathan, a board member of Lung Foundation Australia and director of respiratory and sleep medicine at Melbourne’s The Royal Children’s Hospital, said: “The experience in Italy and Spain, and the modelling used by mathematicians around the world, indicates the number of people who will become critically ill with Covid-19 will greatly exceed the capacity to care for them using respiratory support.

“Without access to ventilators many patients who might survive the infection will die.”

What is a ventilator and how does it work?

A mechanical ventilator is a machine that’s used to support patients with severe respiratory conditions that impact the lungs, including pneumonia.

Before a patient is placed on a ventilator, Day says medical staff – often anaesthetists – will perform a procedure called intubation.

After a patient is sedated and given a muscle relaxant, a tube is placed through the mouth and into the windpipe.

Day says the procedure is routine but, with Covid-19 patients, medical staff need to take extreme precautions to make sure they do not become infected with the virus.

“We have people almost in full hazmat suits,” he says.

The breathing tube is then attached to the ventilator and medical staff can adjust the rate that it pushes the air and oxygen into the lungs, and adjust the oxygen mix.

When would a patient go onto a ventilator?

Before deciding to put a patient onto a ventilator, Story says doctors are looking for signs of “respiratory failure”.

“The breathing rate will increase, they’ll look distressed, the CO2 in the blood goes up and they can become sedated and confused,” he says.

He says while a normal breathing rate is about 15 breaths a minute, if the rate gets to about 28 times a minute, then this is a signal that ventilation may be needed.

Before going on a mechanical ventilator, Prof John Wilson, president-elect of the Royal Australasian College of Physicians and a respiratory physician, says there may be other attempts to increase a patient’s oxygen levels.

These “non-invasive” methods of ventilation can include masks and oxygen tanks.

Story says that with Covid-19, medical staff were looking to avoid non-invasive methods because patients would still cough and splutter, increasing the risk of the virus being transferred to medical staff.

How soon might a patient need a ventilator and for how long?

Ranganathan says once a doctor sees that a patient needs a ventilator, “it is required quickly”.

He says: “The patient can be sustained for short periods of time using manual forms of ventilation such as using a bag and mask system with oxygen, but usually being attached to a ventilator needs to happen within 30 minutes if critical.”

Story says that in severe Covid-19 patients, a life-threatening condition can develop called acute respiratory distress syndrome (Ards) that requires ventilators to deliver smaller volumes of oxygen and air, but at higher rates.

This could mean a patient may need to be on a ventilator “for weeks”.

To avoid complications from the breathing tube going down the throat, Story says a tracheostomy is carried out so the tube can go straight into the windpipe through the neck.

“Patients can be more awake with tracheostomy and the hole just heals itself,” says Story.

“If patients develop Ards they will be in an intensive care unit for weeks and they’ll die without ventilators.”

Why a shortage of ventilators matters, and what’s being done to avoid it.

One of the most obvious ways to avoid a shortage of ventilators, is to reduce the numbers of people catching the disease in the first place. That means following all the health advice, including social distancing and hygiene rules.

In Australia, the Australian Healthcare and Hospitals Association, the Australia and New Zealand Intensive Care Society and the industry minister, Karen Andrews, have all expressed confidence that a shortage can be avoided.

The Australian government is also investigating whether ventilators used on animals in veterinary clinics could be converted. Sleep apnoea machines and anaesthetic machines are also options.

Story says ventilators used in ambulances could be used as back up.

All of that work will be crucial in saving lives if the social distancing measures and community lockdowns don’t stem the flow of patients into critical care.

Wilson said: “Health care workers responsible for managing severe life-threatening cases like Covid-19 are extremely concerned regarding their ability to use appropriate support for large numbers of patients expected to suffer respiratory failure.

“In essence, this means that many will not be able to be treated with mechanical ventilation and difficult decisions will have to be made by staff, families and patients about the limits of support. There are many ethical dilemmas in this, and none can be easily resolved.”