1. patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) \> 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. 2. participating in any other clinical trial for covid-19 3. pregnancy, or positive pregnancy test in a pre-dose examination. 4. open tracheostomy. 5. clinical contra-indication, as deemed by the pi or their designee. 6. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. 7. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef \< 45%). 8. significant hemoptysis 9. unable to provide informed consent (proxy consent is acceptable if available) 10. any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke

1. patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) \> 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. 2. participating in any other clinical trial for covid-19 3. pregnancy, or positive pregnancy test in a pre-dose examination. 4. open tracheostomy. 5. clinical contra-indication, as deemed by the pi or their designee. 6. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. 7. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef \< 45%). 8. significant hemoptysis 9. unable to provide informed consent (proxy consent is acceptable if available) 10. any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke

patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) > 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. participating in any other clinical trial for covid-19 pregnancy, or positive pregnancy test in a pre-dose examination. open tracheostomy. clinical contra-indication, as deemed by the pi or their designee. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef < 45%). significant hemoptysis unable to provide informed consent (proxy consent is acceptable if available) any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke

patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) > 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. participating in any other clinical trial for covid-19 pregnancy, or positive pregnancy test in a pre-dose examination. open tracheostomy. clinical contra-indication, as deemed by the pi or their designee. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef < 45%). significant hemoptysis unable to provide informed consent (proxy consent is acceptable if available) any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke

1. patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) > 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. 2. participating in any other clinical trial for covid-19 3. pregnancy, or positive pregnancy test in a pre-dose examination. 4. open tracheostomy. 5. clinical contra-indication, as deemed by the pi or their designee. 6. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. 7. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef < 45%). 8. significant hemoptysis 9. unable to provide informed consent (proxy consent is acceptable if available) 10. any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke

1. patient with severe hypoxemia who are unable to maintain an oxygen saturation (spo2) > 88% on a maximum supplemental oxygen of 6 l/m by nasal cannula and a non-rebreather facemask. 2. participating in any other clinical trial for covid-19 3. pregnancy, or positive pregnancy test in a pre-dose examination. 4. open tracheostomy. 5. clinical contra-indication, as deemed by the pi or their designee. 6. use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as intravenous lidocaine, or topical benzocaine or dapsone at screening. 7. known history or clinical evidence of heart failure or left ventricular dysfunction (lvef < 45%). 8. significant hemoptysis 9. unable to provide informed consent (proxy consent is acceptable if available) 10. any of the following conditions at time of possible enrollment: fulminant liver failure, acute coronary syndrome , renal failure requiring dialysis, bacteremia, shock, cardiac arrest, cardiac arrhythmia requiring acute treatment, delirium / encephalopathy, severe disseminated intravascular coagulation, gastrointestinal hemorrhage, hypoglycemia, pneumothorax, rhabdomyolysis / myositis, seizures, or acute stroke