[Nitric oxide inhalation test in patients with ARDS: preliminary assessment of the effect on arterial oxygenation]

OBJECTIVE: Inhaled NO can improve arterial oxygenation in ARDS. We evaluated the incidence and the magnitude of this effect during a short test of NO inhalation. This was performed in 24 consecutive mechanically ventilated patients with ARDS in order to assess the interest of NO for the therapy of hypoxemia in each case. DESIGN: Retro-spective study. SETTING: ICU in a University Hospital. PATIENTS: 24 hypoxemic patients with ARDS (lung injury score, LIS, 2.9 +/- 0.52), treated with conventional mechanical ventilation. INTERVENTIONS: Tests were performed using a mean inhalatory NO dose of 14 +/- 6 ppm. A pair of PaO2 data was obtained for each patient from two blood gas analysis, performed one just before and one 15 min after the start of NO inhalation. RESULTS: The mean baseline PaO2 was 76 +/- 21 mmHg and significantly increased with NO inhalation to 97 +/- 34 mmHg (p = 0.0001). Considering the individual response to NO, patients were arbitrarily classified as responders when the increase of PaO2 from baseline was > or = 10%. Sixteen patients were identified as responders, showing a mean increase of PaO2 from baseline by 40 +/- 26%, while the remaining 8 patients resulted non responders (mean change 1 +/- 5.7%). In no case a clinically significant decrease of PaO2 was observed during NO inhalation. The response to NO did not correlate with the LIS (r = 0.019) and with baseline PaO2 (r = 0.31). CONCLUSIONS: Inhaled NO doses of 14 +/- 6 ppm increased on the average the PaO2 in a group of ARDS patients, the individual response being however variable. A deterioration of arterial oxygenation was never observed. Even if the criteria for predicting the response to NO still remain to be defined, a short test seems to reliably provide a first estimate of the magnitude of the response.