Prone positioning and inhaled nitric oxide: Synergistic therapies for acute respiratory distress syndrome

Background: Inhaled nitric oxide (INO) and prone positioning have both been advocated as methods to improve oxygenation in patients with acute respira tory distress syndrome (ARDS), This study was designed to evaluate the rela tive contributions of INO and prone positioning alone and in combination on gas exchange in trauma patients with ARDS, Methods: sixteen patients meeting the consensus definition of ARDs were stu died. Patients received mechanical ventilation in the supine position, mech anical ventilation plus INO at 1 part per million in the supine position, m echanical ventilation in the PP, and mechanical ventilation in the prone po sitioning plus INO at 1 part per million. A stabilization period of 1 hour was allowed at each condition. After stabilization, hemodynamic and gas exc hange variables were measured. Results: INO and prone positioning both increased Pao(2)/FIO2, compared wit h ventilation in the supine position. Pao(2)/FIO2 increased by 14% during u se of INO, and 10 of 16 patients (62%) responded to INO in the supine posit ion, Pao(2)/FIO2 increased by 33%, and 14 of 16 patients (87.5%) responded to the prone position. The combination of INO and prone positioning resulte d in an improvement in Pao(2)/FIO2 in 15 of 16 patients (94%), with a mean increase in Pao(2)/FIO2 of 59%, Pulmonary vascular resistance was reduced d uring use of INO, with a greater reduction in pulmonary vascular resistance seen with INO plus prone positioning (175 +/- 36 dynes.s/cm(5) vs. 134 +/- 28 dynes.s/cm(5)) compared with INO in the supine position (164 +/- 48 dyn es.s/cm(5) vs. 138 +/- 44 dynes.s/cm(5)). There were no significant hemodyn amic effects of INO or prone positioning and no complications were seen dur ing this relative short duration of study. Conclusions: INO and prone positioning can contribute to improved oxygenati on in patients with ARDs, The two therapies in combination are synergistic and may be important adjuncts to mechanical ventilation in the ARDS patient with refractory hypoxemia.