Inhaled nitric oxide in acute respiratory failure in adults

We have assessed the acute effects of inhaled nitric oxide 8, 32 and 128 volumes per million (vpm) on pulmonary haemodynamics and arterial oxygenation in patients with severe acute respiratory failure. Fourteen patients requiring artificial ventilation with mean pulmonary artery pressures greater than 30 mm Hg were given inhaled nitric oxide; haemodynamic values and blood-gas tensions were measured before and after 10 min of inhalation of nitric oxide. Nitric oxide inhaled at 8, 32 and 128 vpm decreased mean pulmonary artery pressure by 1.7 (SD 2.2), 3.2 (2.6) and 3.3 (3.3) mm Hg, pulmonary vascular resistance by 20 (64), 53 (57) and 66 (54) dyn s cm−5 and increased arterial oxygen tension by 2.5 (3.6), 3.0 (5.1) and 2.9 (3.9) kPa, respectively. All changes were significant (P < 0.05 or less) except for changes in pulmonary vascular resistance at 8 vpm. The improvement in arterial oxygenation with 128 vpm was related to pulmonary vascular resistance before commencing nitric oxide. The major beneficial effect of nitric oxide in acute respiratory failure would appear to be improvement in oxygenation rather than reduction in pulmonary artery pressure. The degree of improvement in arterial oxygenation with nitric oxide was related directly to pulmonary vascular resistance before treatment.