Nitric oxide is produced by various forms of nitric oxide synthases (NOS). Nitric oxide exerts various physiologic functions; NO produces vasodilation, inhibits thrombocytes aggregation, effects immune response and serves as a signal messenger. Nitric oxide with superoxide generates peroxynitrite which destructs proteins by nitration. Nitric oxide can be applied in ARDS, septic shock, ischemic conditions, diabetes, inflammatory conditions, rheumatoid arthritis and other clinical settings. It is used also in inhalational therapy.

        Key words: nitric oxide – nitric oxide synthase – ARDS – nitric oxide inhalation