- participating in another clinical trial of an investigational treatment for covid-19 - methemoglobin > 3% - evidence of severe multi organ failure - use of assisted ventilation prior to initiation of ino - pregnancy or positive pregnancy test pre-dose - open tracheostomy - chronic use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as lidocaine, prilocaine, benzocaine, nitroprusside, isosorbide, or dapsone at screening - history or clinical evidence of systolic heart failure, left ventricular dysfunction (lvef <40%) - subjects reporting massive hemoptysis associated with the current illness or with radiologically proven pulmonary embolus

- participating in another clinical trial of an investigational treatment for covid-19 - methemoglobin > 3% - evidence of severe multi organ failure - use of assisted ventilation prior to initiation of ino - pregnancy or positive pregnancy test pre-dose - open tracheostomy - chronic use of a nitric oxide donor agent such as nitroglycerin or drugs known to increase methemoglobin such as lidocaine, prilocaine, benzocaine, nitroprusside, isosorbide, or dapsone at screening - history or clinical evidence of systolic heart failure, left ventricular dysfunction (lvef <40%) - subjects reporting massive hemoptysis associated with the current illness or with radiologically proven pulmonary embolus