The severely ill Covid-19 patients are placed in a prone, or face down, position on ventilators and it can cause permanent nerve damage in these patients, said the study, reports Xinhua.

The researchers have seen 20 patients from seven different hospitals with these injuries.

People who have been critically ill are expected to wake up with some generalized, symmetric weakness.

But the pattern of weakness in the COVID-19 patients caught the researchers' attention during rehabilitation since quite often an important joint such as the wrist, ankle or shoulder would be completely paralyzed on one side of the body.

The most common injuries are wrist drops, foot drops, loss of hand function and frozen shoulder.

Some patients had as many as four distinct nerve injury sites.

The researchers believe the nerve damage is the result of reduced blood flow (due to coagulated blood) and inflammation. Other non-COVID-19 patients on ventilators in this position rarely experience any nerve damage.

"It's shocking how big a problem it is," said lead investigator Colin Franz, a physician-scientist at Shirley Ryan AbilityLab and an assistant professor of physical medicine and rehabilitation and neurology at NU's Feinberg School of Medicine. "Ordinarily, very sick people can tolerate the position that helps their breathing. But COVID patients' nerves can't tolerate the forces other people can generally bear."

Based on this study and another, 12 percent to 15 percent of the most severely ill COVID-19 patients have permanent nerve damage. Based on the number of COVID patients worldwide, Franz estimated thousands of patients have been impacted.

Based on the findings, physicians are modifying the prone position protocol for COVID-19 patients at Northwestern Memorial Hospital in order to prevent nerve damage.

The researchers at NU and Shirley Ryan AbilityLab are working on a pressure map of hot spots for nerve sensitivity, radiology imaging to document the injury and skin sensors to help identify better "prone" position strategies.

The study has been accepted by the British Journal of Anaesthesia.

Also read: Some doctors moving away from ventilators for virus patients