Nitric oxide contamination of hospital compressed air improves gas exchange in patients with acute lung injury

Abstract

Objective: We tested the hypothesis that NO contamination of hospital compressed air also improves PaO2 in patients with acute lung injury (ALI) and following lung transplant (LTx). Design: Prospective clinical study. Setting: Cardiothoracic intensive care unit. Patients: Subjects following cardiac surgery (CABG, n=7); With ALI (n=7), and following LTx (n=5). Interventions: Four sequential 15-min steps at a constant FiO2 were used: hospital compressed air-O2 (H1), N2-O2 (A1), repeat compressed air-O2 (H2), and repeat N2-O2 (A2). Measurements and results: NO levels were measured from the endotracheal tube. Cardiorespiratory values included PaO2 were measured at the end of each step. FiO2 was 0.46±0.05, 0.53±0.15, and 0.47±0.06 (mean±SD) for three groups, respectively. Inhaled NO levels during H1 varied among subjects (30-550 ppb, 27-300 ppb, and 5-220 ppb, respectively). Exhaled NO levels were not detected in 4/7 of CABG (0-300 ppb), 3/6 of ALI (0-140 ppb), and 3/5 of LTx (0-59 ppb) patients during H1, whereas during A1 all but one patient in ALI and three CABG patients had measurable exhaled NO levels (P<0.05). Small but significant decreases in PaO2 occurred for all groups from H1 to A1 and H2 to A2 (132-99 Torr and 128-120 Torr, P <0.01, respectively). There was no correlation between inhaled NO during H1 and exhaled NO during A1 or the change in PaO2 from H1 to A1. Conclusions: Low-level NO contamination improves PaO2 in patients with ALI and following LTx.