1. patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy 2. diagnosis of acute respiratory distress syndrome 3. breastfeeding or pregnancy as evidenced by a positive pregnancy test. 4. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef \<40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension 5. history of frequent epistaxis (\>1 episode/month). 6. significant hemoptysis during the last 30 days prior to enrollment 7. methemoglobin level \>3% at screening 8. patients on systemic steroids (any formulation) within 30 days prior to enrollment. 9. history of daily, continuous oxygen supplementation 10. patients with bmi greater than or equal to 36 11. patient receiving drugs that have a contraindication with no, 12. patients with clinically significant anemia, e.g., hb \<100 g/l and thrombocytopenia, e.g., platelets \<75 thousand cells/mcl. 13. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. 14. the subject is identified by the investigator as being unable or unwilling to perform study procedures.

1. patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy 2. diagnosis of acute respiratory distress syndrome 3. breastfeeding or pregnancy as evidenced by a positive pregnancy test. 4. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef \<40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension 5. history of frequent epistaxis (\>1 episode/month). 6. significant hemoptysis during the last 30 days prior to enrollment 7. methemoglobin level \>3% at screening 8. patients on systemic steroids (any formulation) within 30 days prior to enrollment. 9. history of daily, continuous oxygen supplementation 10. patients with bmi greater than or equal to 36 11. patient receiving drugs that have a contraindication with no, 12. patients with clinically significant anemia, e.g., hb \<100 g/l and thrombocytopenia, e.g., platelets \<75 thousand cells/mcl. 13. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. 14. the subject is identified by the investigator as being unable or unwilling to perform study procedures.

patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy diagnosis of acute respiratory distress syndrome breastfeeding or pregnancy as evidenced by a positive pregnancy test. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef <40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension history of frequent epistaxis (>1 episode/month). significant hemoptysis during the last 30 days prior to enrollment methemoglobin level >3% at screening patients on systemic steroids (any formulation) within 30 days prior to enrollment. history of daily, continuous oxygen supplementation patients with bmi greater than or equal to 36 patient receiving drugs that have a contraindication with no, patients with clinically significant anemia, e.g., hb <100 g/l and thrombocytopenia, e.g., platelets <75 thousand cells/mcl. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. the subject is identified by the investigator as being unable or unwilling to perform study procedures.

patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy diagnosis of acute respiratory distress syndrome breastfeeding or pregnancy as evidenced by a positive pregnancy test. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef <40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension history of frequent epistaxis (>1 episode/month). significant hemoptysis during the last 30 days prior to enrollment methemoglobin level >3% at screening patients on systemic steroids (any formulation) within 30 days prior to enrollment. history of daily, continuous oxygen supplementation patients with bmi greater than or equal to 36 patient receiving drugs that have a contraindication with no, patients with clinically significant anemia, e.g., hb <100 g/l and thrombocytopenia, e.g., platelets <75 thousand cells/mcl. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. the subject is identified by the investigator as being unable or unwilling to perform study procedures.

1. patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy 2. diagnosis of acute respiratory distress syndrome 3. breastfeeding or pregnancy as evidenced by a positive pregnancy test. 4. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef <40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension 5. history of frequent epistaxis (>1 episode/month). 6. significant hemoptysis during the last 30 days prior to enrollment 7. methemoglobin level >3% at screening 8. patients on systemic steroids (any formulation) within 30 days prior to enrollment. 9. history of daily, continuous oxygen supplementation 10. patients with bmi greater than or equal to 36 11. patient receiving drugs that have a contraindication with no, 12. patients with clinically significant anemia, e.g., hb <100 g/l and thrombocytopenia, e.g., platelets <75 thousand cells/mcl. 13. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. 14. the subject is identified by the investigator as being unable or unwilling to perform study procedures.

1. patients who are treated with or require high flow nasal cannula, cpap, intubation, mechanical ventilation, or tracheostomy 2. diagnosis of acute respiratory distress syndrome 3. breastfeeding or pregnancy as evidenced by a positive pregnancy test. 4. subjects diagnosed with immunodeficiency, with history of congestive or unstable heart disease, left ventricular dysfunction (lvef <40%) or myocardial damage, severe pulmonary hypertension and/or unstable hypertension 5. history of frequent epistaxis (>1 episode/month). 6. significant hemoptysis during the last 30 days prior to enrollment 7. methemoglobin level >3% at screening 8. patients on systemic steroids (any formulation) within 30 days prior to enrollment. 9. history of daily, continuous oxygen supplementation 10. patients with bmi greater than or equal to 36 11. patient receiving drugs that have a contraindication with no, 12. patients with clinically significant anemia, e.g., hb <100 g/l and thrombocytopenia, e.g., platelets <75 thousand cells/mcl. 13. presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data, e.g., known or suspected thalassemia, sickle cell disease or other diseases associated with poor oxygen carrying capacity. 14. the subject is identified by the investigator as being unable or unwilling to perform study procedures.