Only one criterion needs to apply for exclusion: 1. Patients who after 3 mins of ventilation with 10 cm H2O PEEP + 100% O2 i.e. at time of allocation (t0), have a SpO2 <50%, or a reliable SpO2 is impossible to obtain 2. Patients in severe kidney failure or dialysis, 3. Known or suspected pregnancy based on information on the time of inclusion. 4. Hypersensitivity to the active substance (NO) or to the excipient (N2) 5. Cardiac arrest 6. Patient in prison or custody by police 7. Staff present in treatment situation known to be pregnant 8. Any reason why, in the opinion of the treating physician, it is probably in the best interest of the patient not to participate in the trial. Female participants under the age of 50 years will be asked explicitly about possible pregnancy. If this cannot be obtained from the patient, next of kin will be asked if present. Information regarding exclusion criteria 2, 3 and 4 will be obtained from bystanders, often relatives or friends present at time of inclusion. If no clear information is available, the physicians shall include or exclude based on his/her best judgment at the time of inclusion.

Only one criterion needs to apply for exclusion: 1. Patients who after 3 mins of ventilation with 10 cm H2O PEEP + 100% O2 i.e. at time of allocation (t0), have a SpO2 <50%, or a reliable SpO2 is impossible to obtain 2. Patients in severe kidney failure or dialysis, 3. Known or suspected pregnancy based on information on the time of inclusion. 4. Hypersensitivity to the active substance (NO) or to the excipient (N2) 5. Cardiac arrest 6. Patient in prison or custody by police 7. Staff present in treatment situation known to be pregnant 8. Any reason why, in the opinion of the treating physician, it is probably in the best interest of the patient not to participate in the trial. Female participants under the age of 50 years will be asked explicitly about possible pregnancy. If this cannot be obtained from the patient, next of kin will be asked if present. Information regarding exclusion criteria 2, 3 and 4 will be obtained from bystanders, often relatives or friends present at time of inclusion. If no clear information is available, the physicians shall include or exclude based on his/her best judgment at the time of inclusion.