Helium-oxygen mixture does not improve gas exchange in mechanically ventilated children with bronchiolitis

INTRODUCTION: Heliox has been found to reduce both the arterial carbon dioxide tension (PaCO(2)) and work of breathing in children and adults with status asthmaticus. We hypothesized that, in mechanically ventilated children with bronchiolitis, increasing the ratio of helium:oxygen concentrations would improve both ventilation and oxygenation. OBJECTIVE: To examine the effect of varying concentrations of heliox mixtures on ventilation and oxygenation in mechanically ventilated children with bronchiolitis. PATIENTS AND METHODS: This was a case series, with a nonrandomized, unblinded, repeated-measures design, which was conducted in a pediatric intensive care unit in a children's hospital. Ten patients, aged 1-9 months, were mechanically ventilated in SIMV mode with the following gas mixtures delivered at 15-min intervals: 50%/50% nitrogen/oxygen, 50%/50% heliox, 60%/40% heliox, 70%/30% heliox, and return to 50%/50% nitrogen/oxygen. Two-factor, repeated-measures analysis of variance was used to determine whether the different gas mixtures affected the mean PaCO(2), the ratio of arterial oxygen tension (PaO(2)) to fractional inspired oxygen (FiO(2)), or the ratio of PaO(2) to alveolar oxygen tension (P(A)O(2)). RESULTS: No statistical or noticeable difference was found between the mean PaCO(2), PaO(2)/FiO(2), or PaO(2)/PAO(2) values while the patients were receiving the four different gas mixtures (P = 0.93, 0.98, and 0.96, respectively). CONCLUSION: The use of different heliox mixtures compared with 50%/50% nitrogen/oxygen in mechanically ventilated children with bronchiolitis did not result in a significant or noticeable decrease in ventilation or oxygenation.