1. pao2/fio2 ≥ 300 at the time of enrollment 2. a previous msc infusion not related to this trial 3. history of pulmonary hypertension (who class iii/iv) 4. history of left atrial hypertension or decompensated left heart failure. 5. pregnant or lactating patient 6. unstable arrhythmia 7. patients with previous lung transplant 8. patients currently receiving chronic dialysis 9. patients currently receiving extracorporeal membrane oxygenation (ecmo) 10. presence of any active malignancy (except non-melanoma skin cancer) 11. any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% 12. moderate to severe liver disease (ast and alt \>5 x uln) 13. severe chronic respiratory disease with a paco2 \> 50 mm hg or the use of home oxygen 14. baseline qt prolongation 15. moribund patient not expected to survive \> 24 hours

1. pao2/fio2 ≥ 300 at the time of enrollment 2. a previous msc infusion not related to this trial 3. history of pulmonary hypertension (who class iii/iv) 4. history of left atrial hypertension or decompensated left heart failure. 5. pregnant or lactating patient 6. unstable arrhythmia 7. patients with previous lung transplant 8. patients currently receiving chronic dialysis 9. patients currently receiving extracorporeal membrane oxygenation (ecmo) 10. presence of any active malignancy (except non-melanoma skin cancer) 11. any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% 12. moderate to severe liver disease (ast and alt \>5 x uln) 13. severe chronic respiratory disease with a paco2 \> 50 mm hg or the use of home oxygen 14. baseline qt prolongation 15. moribund patient not expected to survive \> 24 hours

pao2/fio2 ≥ 300 at the time of enrollment a previous msc infusion not related to this trial history of pulmonary hypertension (who class iii/iv) history of left atrial hypertension or decompensated left heart failure. pregnant or lactating patient unstable arrhythmia patients with previous lung transplant patients currently receiving chronic dialysis patients currently receiving extracorporeal membrane oxygenation (ecmo) presence of any active malignancy (except non-melanoma skin cancer) any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% moderate to severe liver disease (ast and alt >5 x uln) severe chronic respiratory disease with a paco2 > 50 mm hg or the use of home oxygen baseline qt prolongation moribund patient not expected to survive > 24 hours

pao2/fio2 ≥ 300 at the time of enrollment a previous msc infusion not related to this trial history of pulmonary hypertension (who class iii/iv) history of left atrial hypertension or decompensated left heart failure. pregnant or lactating patient unstable arrhythmia patients with previous lung transplant patients currently receiving chronic dialysis patients currently receiving extracorporeal membrane oxygenation (ecmo) presence of any active malignancy (except non-melanoma skin cancer) any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% moderate to severe liver disease (ast and alt >5 x uln) severe chronic respiratory disease with a paco2 > 50 mm hg or the use of home oxygen baseline qt prolongation moribund patient not expected to survive > 24 hours

1. pao2/fio2 ≥ 300 at the time of enrollment 2. a previous msc infusion not related to this trial 3. history of pulmonary hypertension (who class iii/iv) 4. history of left atrial hypertension or decompensated left heart failure. 5. pregnant or lactating patient 6. unstable arrhythmia 7. patients with previous lung transplant 8. patients currently receiving chronic dialysis 9. patients currently receiving extracorporeal membrane oxygenation (ecmo) 10. presence of any active malignancy (except non-melanoma skin cancer) 11. any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% 12. moderate to severe liver disease (ast and alt >5 x uln) 13. severe chronic respiratory disease with a paco2 > 50 mm hg or the use of home oxygen 14. baseline qt prolongation 15. moribund patient not expected to survive > 24 hours

1. pao2/fio2 ≥ 300 at the time of enrollment 2. a previous msc infusion not related to this trial 3. history of pulmonary hypertension (who class iii/iv) 4. history of left atrial hypertension or decompensated left heart failure. 5. pregnant or lactating patient 6. unstable arrhythmia 7. patients with previous lung transplant 8. patients currently receiving chronic dialysis 9. patients currently receiving extracorporeal membrane oxygenation (ecmo) 10. presence of any active malignancy (except non-melanoma skin cancer) 11. any other irreversible disease or condition for which 6-month mortality is estimated to be greater than 50% 12. moderate to severe liver disease (ast and alt >5 x uln) 13. severe chronic respiratory disease with a paco2 > 50 mm hg or the use of home oxygen 14. baseline qt prolongation 15. moribund patient not expected to survive > 24 hours