inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting state(room air) 3. arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression \> 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; 3. requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). 4. the informed consent form signed.

inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting state(room air) 3. arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression \> 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; 3. requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). 4. the informed consent form signed.

inclusion criteria: 18 years old ≤ age ≤ 80 years old, both men or women. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: respiratory distress, rr ≥ 30 times/min finger oxygen saturation (spo2) ≤93% in resting state(room air) arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position pulmonary imaging shows lesion progression > 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). the informed consent form signed.

inclusion criteria: 18 years old ≤ age ≤ 80 years old, both men or women. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: respiratory distress, rr ≥ 30 times/min finger oxygen saturation (spo2) ≤93% in resting state(room air) arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position pulmonary imaging shows lesion progression > 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). the informed consent form signed.

inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting state(room air) 3. arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression > 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; 3. requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). 4. the informed consent form signed.

inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed sars-cov-2 infection, and meet at least one of the following criteria: confirmed severe covid-19 in no more than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting state(room air) 3. arterial partial pressure of oxygen to fraction of inspired oxygen (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression > 50% within 24-48 hours. symptoms,signs or chest imaging indicates ali/ards; 3. requiring a mask oxygen therapy,high-flow nasal cannula oxygen therapy(hfnc). 4. the informed consent form signed.

inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed severe covid-19 in less than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting 3. oxygenation index (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression > 50% within 24-48 hours. 3. symptoms, signs or chest imaging indicates severe pneumonia or ali/ards, requiring a mask oxygen therapy, nasal high-flow therapy (hfnc) or non-invasive positive pressure ventilation. 4. the informed consent form signed.

inclusion criteria: 1. 18 years old ≤ age ≤ 80 years old, both men or women. 2. confirmed severe covid-19 in less than 5 days who meets any of the following criteria: 1. respiratory distress, rr ≥ 30 times/min 2. finger oxygen saturation (spo2) ≤93% in resting 3. oxygenation index (pao2/fio2) ≤ 300 mmhg (1 mmhg = 0.133kpa) in supine position 4. pulmonary imaging shows lesion progression > 50% within 24-48 hours. 3. symptoms, signs or chest imaging indicates severe pneumonia or ali/ards, requiring a mask oxygen therapy, nasal high-flow therapy (hfnc) or non-invasive positive pressure ventilation. 4. the informed consent form signed.