Coronavirus: Why are Covid-19 patients lying face down?

WHO recommends that Covid-19 patients with respiratory failure be placed prone for 12-16 hours.

As Covid-19 cases continue to increase worldwide, we have become increasingly familiar with the images of intensive care in hospitals.

A detail about the patients connected to the ventilators in the intensive care units is remarkable:

Most patients lie face down.

This ancient technique seems to work for people who have trouble breathing due to respiratory diseases.