Protocol A Participant in any other clinical trial of an experimental treatment for COVID-19, pregnancy, clinical contraindication of the attending physician, use of a nitric oxide donor agent, such as nitroglycerin or drugs known to increase methaemoglobin, such as lidocaine, prilocaine, benzocaine or dapsone, heart failure, left ventricular dysfunction, history of hemoptysis. Protocol B Participant in any other clinical trial of an experimental treatment for COVID-19, Pregnancy, clinical contraindication of the attending physician, indication for hospitalization at the time of evaluation, use of a nitric oxide donor agent, such as nitroglycerin or drugs prepared by increasing methemoglobin, such as lidocaine, prilocaine, benzocaine, or dapsone, heart failure, left ventricular dysfunction, hx of hemoptysis.

Protocol A Participant in any other clinical trial of an experimental treatment for COVID-19, pregnancy, clinical contraindication of the attending physician, use of a nitric oxide donor agent, such as nitroglycerin or drugs known to increase methaemoglobin, such as lidocaine, prilocaine, benzocaine or dapsone, heart failure, left ventricular dysfunction, history of hemoptysis. Protocol B Participant in any other clinical trial of an experimental treatment for COVID-19, Pregnancy, clinical contraindication of the attending physician, indication for hospitalization at the time of evaluation, use of a nitric oxide donor agent, such as nitroglycerin or drugs prepared by increasing methemoglobin, such as lidocaine, prilocaine, benzocaine, or dapsone, heart failure, left ventricular dysfunction, hx of hemoptysis.

Participant in any other clinical trial of an experimental treatment for COVID-19, pregnancy, clinical contraindication of the attending physician, use of a nitric oxide donor agent, such as nitroglycerin or drugs known to increase methaemoglobin, such as lidocaine, prilocaine, benzocaine or dapsone, heart failure, left ventricular dysfunction, history of hemoptysis.

Participant in any other clinical trial of an experimental treatment for COVID-19, pregnancy, clinical contraindication of the attending physician, use of a nitric oxide donor agent, such as nitroglycerin or drugs known to increase methaemoglobin, such as lidocaine, prilocaine, benzocaine or dapsone, heart failure, left ventricular dysfunction, history of hemoptysis.