Which of the following inhaled gas is used to decrease pulmonary aery pressure in adults and infants?
Nitrous oxide
Nitrogen dioxide
Nitric oxide
Nitrogen
C i.e. Nitric oxide Nitric oxide (NO) or endothelium derived relaxing factor (EDRF) is synthesized from L-arginine by nitric oxide synthase (NOS) enzyme in endothelium of blood vesselsQ. Physiologically it causes vasodilation & decreases vascular resistance throughout the bodyQ. It activates guanylyl cyclase producing C-GMP and binds rapidly to Hb & gets inactivatedQ. Whereas inhaled NO is a selective pulmonary-vasodilator decreases pulmonary aery pressure in infants & adults and improves V/P ratioQ. So it is used in treatment of pulmonary aery hypeensionQ. It has no systemic vasodilatory effectQ. Systemic effects of breathing NO includes platetlet & leukocyte inhibition and oxidation of extraerythrocytic hemoglobin. Inhaled NO decreases vascular smooth muscle cell hyperplasia & increases alveolarization in the injured developing limb. This pulmonary vascular & alveolar developmental effect of NO is used to prevent or ameliorate pulmonary hypeension in infants with congenital hea disease and chronic lung disease in premature infants.