Improvement in oxygenation by prone position and nitric oxide in patients with acute respiratory distress syndrome

Objective: Inhaled nitric oxide (NO) and prone position improve arterial ox ygenation in patients with the acute respiratory distress syndrome. This st udy was undertaken to assess the combined effects of NO and prone position in these patients. Design: Prospective clinical study. Setting: General intensive care service in a community teaching hospital. Patients: 14 mechanically ventilated adult patients with the acute respirat ory distress syndrome (mean lung injury score 3.23 +/- 0.27). Measurements and results: We measured hemodynamic and oxygenation parameter s in the supine position and 2 h later in the prone position, before and du ring inhalation of 10 ppm NO. A positive response in oxygenation was define d as a greater than or equal to 20 % increment in the arterial oxygen tensi on/fractional inspired oxygen ratio (PaO2/FIO2). In the prone position PaO2 /FIO2 increased significantly (from 110 +/- 55 to 161 +/- 89 mmHg, p < 0.01 ) and venous admixture decreased (from 38 +/- 12 to 30 +/- 7 %, p < 0.01) c ompared to the supine position. Ten of the 14 patients were responders in t he prone position. In the supine position, inhalation of NO improved oxygen ation to a lesser extent, increasing PaO2/FIO2 to 134 +/- 63 mmHg (p < 0.01 ) and decreasing venous admixture to 35 +/- 12 %, (p < 0.01). Five of the 1 4 patients responded to NO inhalation supine and 8 of 14 responded prone (p = 0.22). The combination of NO therapy and prone positioning was additive in increasing PaO2/FIO2 (197 +/- 92 mmHg) and decreasing venous admixture ( 27 +/- 8% ) (p < 0.01). This combination also showed a positive oxygenation response on compared to the supine value without NO in 13 of the 14 patien ts (93 %), NO-induced changes in PaO2/FIO2 were correlated to changes in pu lmonary vascular resistance only in the prone position. Conclusions: In patients with the acute respiratory distress syndrome, the combination of NO and prone position is a valuable adjunct to mechanical ve ntilation.