inclusion criteria: * diagnosis of covid-19 confirmed by positive polymerase chain reaction (pcr) for severe acute respiratory syndrome (sars-cov-2) in respiratory tract sample, plus pneumonia confirmed by imaging tests and arterial oxygen saturation (spo2) \<94% with ambient air or a partial pressure of oxygen to fraction of inspired oxygen (po2/fio2) ratio \<300 mmhg or spo2/fio2 ≤ 315. * acceptance to participate in the study and signing of the informed consent.

inclusion criteria: * diagnosis of covid-19 confirmed by positive polymerase chain reaction (pcr) for severe acute respiratory syndrome (sars-cov-2) in respiratory tract sample, plus pneumonia confirmed by imaging tests and arterial oxygen saturation (spo2) \<94% with ambient air or a partial pressure of oxygen to fraction of inspired oxygen (po2/fio2) ratio \<300 mmhg or spo2/fio2 ≤ 315. * acceptance to participate in the study and signing of the informed consent.

inclusion criteria: - diagnosis of covid-19 confirmed by positive polymerase chain reaction (pcr) for severe acute respiratory syndrome (sars-cov-2) in respiratory tract sample, plus pneumonia confirmed by imaging tests and arterial oxygen saturation (spo2) <94% with ambient air or a partial pressure of oxygen to fraction of inspired oxygen (po2/fio2) ratio <300 mmhg or spo2/fio2 ≤ 315. - acceptance to participate in the study and signing of the informed consent.

inclusion criteria: - diagnosis of covid-19 confirmed by positive polymerase chain reaction (pcr) for severe acute respiratory syndrome (sars-cov-2) in respiratory tract sample, plus pneumonia confirmed by imaging tests and arterial oxygen saturation (spo2) <94% with ambient air or a partial pressure of oxygen to fraction of inspired oxygen (po2/fio2) ratio <300 mmhg or spo2/fio2 ≤ 315. - acceptance to participate in the study and signing of the informed consent.