Inclusion Criteria:  Ability to understand and willing to sign an ICF. Male and female patients, age at least 18 years. Diagnosed with COVID-19 at admission to the ICU. Diagnosed with echocardiographic signs of pulmonary artery systolic pressure (PASP) >40 mmHg.  Exclusion Criteria:  History of chronic PH, as judged by the Investigator at screening Known New York Heart Association (NYHA) Functional Class III or IV symptoms Left heart failure with ejection fraction (EF) < 35 % Acute coronary syndrome Body Mass Index (BMI) > 40 kg/m2 Estimated glomerular filtration rate (eGFR) < 30 mL/min MetHb >3% PCO2 > 7 Indication of liver disease, defined by serum levels of either alanine aminotransferase (ALT), aspartate aminotransferase (AST) or alkaline phosphatase (ALP) above 3 x upper limit of normal (ULN) at screening Haemoglobin <80 g/dL Thrombocytopenia (platelet count <80000/mm3) Prothrombin time International ratio (INR) > 1.4 Pregnancy, or a positive pregnancy test Ongoing daily treatment the last 3 days with non-steroidal anti-inflammatory drugs Known active malignancy within the past 3 years History of allergy/hypersensitivity to PD or ongoing allergy/hypersensitivity or history of hypersensitivity to drugs with a similar chemical structure or class to PDNO. History of any other clinically significant disease or disorder Participation in any interventional clinical study