The Initial Response to Inhaled Nitric Oxide Treatment for Intensive Care Unit Patients with Acute Respiratory Distress Syndrome

Abstract

Background: Inhaled nitric oxide (INO) can improve hypoxemia and reduce pulmonary hypertension, but there is a wide range of response to INO. Objectives: The aim of this study was to evaluate the effect of different INO concentrations in acute respiratory distress syndrome (ARDS) patients. Methods: Thirty-two adult ARDS patients who were supported by mechanical ventilator were included. INO was given at a concentration of 1, 5, 10, 20 and 40 ppm, sequentially. Arterial blood gas and mean pulmonary artery pressure (MPAP) were measured 30 min after INO concentrations changed. Results: There was a significant increase in PaO₂/FiO₂ (p < 0.0001) and a decrease in pulmonary vascular resistance index and MPAP (p < 0.0001) after INO use. INO concentrations required for improving oxygenation were in the range of 1–20 ppm, whereas concentrations required for decreasing MPAP were in the range of 1–40 ppm. PaO₂/FiO₂ worsened when the INO dose was adjusted above 20 ppm. Sixty-nine percent of ARDS patients were responders; 31% of them were nonresponders. Among responders, 64% of patients responded at 1 ppm, 36% at 5 ppm. Conclusions: The optimal doses for improving oxygenation and reducing PAP differ. The maximum PaO₂/FiO₂ was observed at a lower INO concentration than that required for the minimal MPAP. There was no further improvement in PaO₂/FiO₂ when the INO dose was adjusted above 20 ppm. Higher doses of INO treatment worsened oxygenation.