Treatment of pulmonary disorders associated with hypoxemia and / or smooth muscle constriction and / or inflammation comprises administering into the lungs as a gas a compound with an NO group which does not form NO2 / NOx in the presence of oxygen or reactive oxygen species at body temperature. Treatment of cardiac and blood disorders, e.g., angina, myocardial infarction, heart failure, hypertension, sickle cell disease and clotting disorders, comprises administering into the lungs as a gas, a compound which reacts with cysteine in hemoglobin and / or dissolves in blood and has an NO group which is bound in said compound so that it does not form NO2 / NOx in the presence of oxygen or reactive oxygen species at body temperature. Exemplary of the compound administered in each case is ethyl nitrite. Treatment of patient in need of improved oxygenation, blood flow of and / or thinning of blood comprises providing in the patient a therapeutic amount of red blood cells loaded with nitrosylated hemoglobin. A method is directed to screening drugs that increase level of nitrosoglutathione in airway lining fluid.