inclusion criteria: * 1） male or female, aged between 18 and 75 (including boundary values) at screening. 2) severe or critically ill patients who have been diagnosed with a novel coronavirus during hospitalization (covid-19). 3) after treatment, the patients have met the discharge criteria of "covid-19 diagnosis and treatment guideline", and the time from hospital discharge is at least 1 month at the time of enrollment. the clinical symptoms of the subjects did not worsen significantly as compared with that at the time of discharge, and the covid-19 nucleic acid test results are negative for at least 2 consecutive times (one of which could be the nucleic acid test before discharge). 4) forced vital capacity/per predicted (fvc% pred) ≥ 50%. 5) 50% ≤ fev1 %pred ≤80%。 6) subject (or legally authorized representative) provides written informed consent prior to initiation of any study procedures. understands and agrees to comply with planned study procedures. 7) agrees not to participate in other drug/device studies until the study is completed.

inclusion criteria: * 1） male or female, aged between 18 and 75 (including boundary values) at screening. 2) severe or critically ill patients who have been diagnosed with a novel coronavirus during hospitalization (covid-19). 3) after treatment, the patients have met the discharge criteria of "covid-19 diagnosis and treatment guideline", and the time from hospital discharge is at least 1 month at the time of enrollment. the clinical symptoms of the subjects did not worsen significantly as compared with that at the time of discharge, and the covid-19 nucleic acid test results are negative for at least 2 consecutive times (one of which could be the nucleic acid test before discharge). 4) forced vital capacity/per predicted (fvc% pred) ≥ 50%. 5) 50% ≤ fev1 %pred ≤80%。 6) subject (or legally authorized representative) provides written informed consent prior to initiation of any study procedures. understands and agrees to comply with planned study procedures. 7) agrees not to participate in other drug/device studies until the study is completed.

inclusion criteria: - 1） male or female, aged between 18 and 75 (including boundary values) at screening. 2) severe or critically ill patients who have been diagnosed with a novel coronavirus during hospitalization (covid-19). 3) after treatment, the patients have met the discharge criteria of "covid-19 diagnosis and treatment guideline", and the time from hospital discharge is at least 1 month at the time of enrollment. the clinical symptoms of the subjects did not worsen significantly as compared with that at the time of discharge, and the covid-19 nucleic acid test results are negative for at least 2 consecutive times (one of which could be the nucleic acid test before discharge). 4) forced vital capacity/per predicted (fvc% pred) ≥ 50%. 5) 50% ≤ fev1 %pred ≤80%。 6) subject (or legally authorized representative) provides written informed consent prior to initiation of any study procedures. understands and agrees to comply with planned study procedures. 7) agrees not to participate in other drug/device studies until the study is completed.

inclusion criteria: - 1） male or female, aged between 18 and 75 (including boundary values) at screening. 2) severe or critically ill patients who have been diagnosed with a novel coronavirus during hospitalization (covid-19). 3) after treatment, the patients have met the discharge criteria of "covid-19 diagnosis and treatment guideline", and the time from hospital discharge is at least 1 month at the time of enrollment. the clinical symptoms of the subjects did not worsen significantly as compared with that at the time of discharge, and the covid-19 nucleic acid test results are negative for at least 2 consecutive times (one of which could be the nucleic acid test before discharge). 4) forced vital capacity/per predicted (fvc% pred) ≥ 50%. 5) 50% ≤ fev1 %pred ≤80%。 6) subject (or legally authorized representative) provides written informed consent prior to initiation of any study procedures. understands and agrees to comply with planned study procedures. 7) agrees not to participate in other drug/device studies until the study is completed.