As COVID-19 case numbers continue to increase in most countries, regrettably more people are needing care at their local intensive care unit. Some even require ventilation, a form of breathing support often only considered when a patient is having extreme difficulty breathing on their own and keeping their body saturated with oxygen.

Most people may have some idea of what ventilation is, not least from watching medical programs like ER or Grey’s Anatomy, but less familiar may be the technique of “proning.” With proning, patients are placed on their fronts, often to increase the effect of ventilation, but increasingly it is also being used without ventilation to assist with breathing.

So how does it work? This video (below) from Dr Ron Daniels, a consultant in Critical Care in the National Health Service in the U.K. is a great explainer of the theory behind why proning is working for many COVID-19 patients.

We approached Dr Daniels with some further questions about proning, based on his excellent Twitter explainer.

After proning, would turning people onto their backs again before turning them prone again maximize their lung function?

“Yes, absolutely, this [proning] is about rotational ventilation. We tend to nurse the patient prone for 16-18 hours, before turning them back onto their backs for 6-8 hours. Whilst a patient is prone for prolonged periods, gradually the front parts of their lungs become compressed and less able to exchange oxygen, so if we left the patient in that position they’d gradually deteriorate,” said Daniels.

At what stage of infection with COVID-19 is proning suitable?

“This is usually a decision made for patients who are already intubated and on a ventilator, and for whom we’re struggling to achieve adequate oxygen levels in the blood. So, if a patient is receiving high concentrations of oxygen through the ventilator (close to 100%), and their blood oxygen levels are too low, we prone,” said Daniels.

Are there any issues with proning, for example for people who are obese/overweight, or might have other health conditions?

“Proning a patient is demanding on staff. To turn a patient prone safely we ideally need 6 members of staff. The only really absolute ‘no’ is in someone with an unstable spine. However, if a patient is very overweight not only does it reduce the likelihood of a positive outcome, but also it places additional strain on staff, so we may elect not to offer proning,” said Daniels.

Does proning only work in combination with ventilating a COVID-19 patient, or can it help on its own?

“There isn’t good evidence for a prone position in people who aren’t ventilated, but some patients with chronic lung conditions report that it helps, and some physicians outside Critical Care are trying it. Theoretically, the effect should be less beneficial – it works in a ventilated patient because those patients are not moving for prolonged periods,” said Daniels.

Is proning frequently used for people hospitalized with other respiratory infections or diseases for the purpose of increasing their blood oxygen levels?

“Yes, but it seems particularly effective in patients with COVID-19, in part because there’s a significant inflammatory component to their respiratory disease which responds well to this kind of therapy,” said Daniels.

Does proning have any notable negative side-effects at all?

“There’s a risk of pressure sores, and it does make it more difficult to deliver mouth care and suction the patient’s secretions, but these can be minimized by good nursing care. There’s also a small risk that the ‘lines’ we used to deliver drugs might become kinked and therefore blocked, but again care and attention mitigate against this,” said Daniels.

Increasingly, proning is being recommended for COVID-19 patients in ICU, with the U.K. intensive care society recently releasing new guidelines for its use. Several clinical trials are also underway to specifically assess the benefits of the practice in patients with COVID-19, although it will take a while for the data to come through in order to really see whether proning is helping COVID-19 patients on a large-scale.