1. intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. 2. receiving \> 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% 3. using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) 4. receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. 5. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. 6. history of group 1 pulmonary hypertension. 7. pregnancy 8. active breast feeding 9. severe chronic kidney disease, either receiving renal replacement therapy or egfr \< 15 ml/min/m2 10. acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. 11. clinically relevant spontaneous alteration of mental state 12. inability to provide written informed consent.

1. intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. 2. receiving \> 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% 3. using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) 4. receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. 5. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. 6. history of group 1 pulmonary hypertension. 7. pregnancy 8. active breast feeding 9. severe chronic kidney disease, either receiving renal replacement therapy or egfr \< 15 ml/min/m2 10. acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. 11. clinically relevant spontaneous alteration of mental state 12. inability to provide written informed consent.

intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. receiving > 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. history of group 1 pulmonary hypertension. pregnancy active breast feeding severe chronic kidney disease, either receiving renal replacement therapy or egfr < 15 ml/min/m2 acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. clinically relevant spontaneous alteration of mental state inability to provide written informed consent.

intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. receiving > 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. history of group 1 pulmonary hypertension. pregnancy active breast feeding severe chronic kidney disease, either receiving renal replacement therapy or egfr < 15 ml/min/m2 acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. clinically relevant spontaneous alteration of mental state inability to provide written informed consent.

1. intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. 2. receiving > 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% 3. using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) 4. receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. 5. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. 6. history of group 1 pulmonary hypertension. 7. pregnancy 8. active breast feeding 9. severe chronic kidney disease, either receiving renal replacement therapy or egfr < 15 ml/min/m2 10. acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. 11. clinically relevant spontaneous alteration of mental state 12. inability to provide written informed consent.

1. intubated or prior intubation (during present hospitalization) or anticipated intubation within the subsequent 2 hours. 2. receiving > 5l/min flow nasal o2 to maintain o2sat greater than or equal to 92% 3. using high-flow nasal cannula (hfnc) or non-invasive ventilation (niv) 4. receiving ino, a pde5 inhibitor, oral or intravenous nitrates, nitroprusside, prilocaine, sulfonamides, or riociguat. 5. other major pulmonary, cardiac, such as chronic obstructive lung disease or heart failure, or systemic illness or disease involvement with potential to represent the primary driver for clinical deterioration within the next 3 days. 6. history of group 1 pulmonary hypertension. 7. pregnancy 8. active breast feeding 9. severe chronic kidney disease, either receiving renal replacement therapy or egfr < 15 ml/min/m2 10. acute kidney injury (aki), evidenced by acute doubling of serum creatinine within previous 48 hours. 11. clinically relevant spontaneous alteration of mental state 12. inability to provide written informed consent.