Introduction This study presents the results of the influence of inhaled nitric oxide (iNO) on the immune system of infants with respiratory diseases on mechanically ventilation (MV).

Purpose Decrease neonatal mortality.

Materials and methods In a controlled, randomised, blinded clinical trial 37 newborns with respiratory diseases on MV were included. In group I 20 patients received iNO (10 ppm, 24 h; "Pulmonox mini", "Messer II NO Therapeutics", Austria). Newborns in group II (n = 17) did not receive iNO. On admission and at 3–5 days, subpopulations of lymphocytes were studied by the one-parameter immunophenotyping using reagents company Immunotech Beckman Coulter (USA): CD3, CD4, CD8, CD14, CD19, CD34, CD56, CD69, CD71, CD95 monoclonal antibody, the relative content of lymphocytes in apoptosis using AnneksinV + labelled FITK and propidium iodide (PL+), labelled with PE (Saltag, USA). The statistical power of the study was 80% (α ≤ 0.05).

Results In group I an increase of mature monocytes (CD14⁺) to 23.1 ± 0.8% (p < 0.05) was observed on 3–5 days. The relative content of CD69 was reduced to 3.8 ± 0.21%, and in lymphocytes in apoptosis to 7.12 ± 0.46% (AnnexinV-FITC⁺PI), and to 0.79 ± 0.07% (AnnexinV-FITC⁺PI⁺, p < 0.001). Duration of MV was 4.1 ± 1.4 days in group I and 18 ± 3.4 in group II. All newborns in group I survived and had no septic complications. None of the patients showed clinical or laboratory evidence of adverse effects of iNO. In group II 7 newborns died, 5 developed neonatal sepsis.

Conclusion Inhaled NO in mechanically ventilated newborns increased the relative content of mature macrophages and decreased the number of lymphocytes in apoptosis. Most importantly, the incidence of sepsis and fatal outcome was reduced in iNO-treated newborns.