The effectiveness of heliox in acute respiratory distress syndrome

INTRODUCTION: The management of acute respiratory distress syndrome (ARDS) was investigated with the use of heliox in an experimental model. OBJECTIVES: To investigate whether heliox can be considered a new therapeutic approach in ARDS. METHODS: ARDS was designed in Wistar albino male rats, 250-300 g in weight, by intratracheal instillation of physiological saline solution. Anesthezied and tracheotomized rats with ARDS were pressure-controlled ventilated. At the end of 210 min, helium gas was tried. All rats were assigned to two groups: Group 1 (n = 10) was the control group, and was given no treatment; group 2 (n = 7) was given heliox (He: O-2 = 50: 50). The heliox group received heliox for 1 h continously. Rats were continued to be kept on a ventilator through the experiment. Two hours after the last inhalation, both lungs of the rats were excised for both histopathological examination and immunohistochemical evaluation. STATISTICAL ANALYSIS USED: Histopathological grading were expressed as median interquartile range. Mann-Whitney U-test was used to assess the relationships between the variables. RESULTS: The infiltation of neutrophils were decreased in rats treated with heliox. Edema in the interstitial and intraalveolar areas was less than that of the control rats. Also, the diminishing of perivascular and/or intraalveolar hemorrhage was apperant. Hyaline membrane (HM) formation decreased in the heliox group compared with the control group. Decreased inducible nitric oxide synthase expression was shown via immunohistochemical examination in the heliox group. CONCLUSION: The present study histopathologically indicated the effectiveness of heliox in the decreasing of neutrophil infiltation, interstitial/intraalveolar edema, perivascular and/or intraalveolar hemorrhage and HM formation in ARDS. Besides the known effect of heliox in obstructive lung disease, inhaled heliox therapy could be associated with the improvement of inflamation in ARDS.