inclusion criteria: - 49 critically-ill covid-19 patients are included. - all of the patients were with pneumonia and residing in rcu - age ≥ 18 y - with dyspnea and oxygen saturation less than 90% in resting state. - at their first 3 days in rcu either receiving o2 therapy, c-pap, or on ventilators. - all of the patients were residing in infectious diseases wards before being transferred to rcu.

inclusion criteria: - 49 critically-ill covid-19 patients are included. - all of the patients were with pneumonia and residing in rcu - age ≥ 18 y - with dyspnea and oxygen saturation less than 90% in resting state. - at their first 3 days in rcu either receiving o2 therapy, c-pap, or on ventilators. - all of the patients were residing in infectious diseases wards before being transferred to rcu.