Direct comparison of inhaled nitric oxide and aerosolized prostacyclin in acute respiratory distress syndrome

Abstract

Inhalation of NO and aerosolization of PGI2 have been suggested to achieve selective pulmonary vasodilation and improvement of arterial oxygenation in patients with ARDS. We directly compared these two modes of transbronchial vasodilator therapy in 16 ARDS patients mechanically ventilated (mean lung injury score [1] 2.75 +/- 0.05). Patients were randomized to receive either first NO and then PGI2, or vice versa. Each drug was individually titrated to find the maximum improvement of arterial oxygenation. Gas exchange variables, including data from the multiple inert gas elimination technique (MIGET), and hemodynamics under application of NO/PGI2 were compared with pre- and post-challenge values. NO (17.8 +/- 2.7 ppm) increased Pa O2/FI O2 from 115 +/- 12 to 144 +/- 15 mm Hg (p<0.01) and reduced the shunt-flow from 33.1 +/- 3.6 to 26.6 +/- 4.5% (p<0.05). Aerosolized PGI2 (7.5 +/- 2.5 ng/kg min) augmented Pa O2/FI O2 from 114 +/- 12 to 135 +/- 12 mm Hg (p<0.01), and decreased shunt from 33.5 +/- 3.8 to 26.0 +/- 3.9% (p<0.05). In 10 patients, both NO and PGI2 caused an increase in Pa O2/FI O2 by at least 10 mm Hg. Two further patients displayed an improvement of arterial oxygenation in response to either NO or PGI2. NO decreased mean pulmonary artery pressure from 34.8 +/- 2.2 to 33.0 +/- 1.8 mm Hg, and PGI2 from 35.0 +/- 2.2 to 31.9 +/- 1.7 mm Hg (p<0.05). We conclude that individually titrated doses of inhaled NO and aerosolized PGI2 effect selective pulmonary vasodilation and redistribute blood-flow from shunt-areas to well-ventilated regions with nearly identical efficacy profiles.