(page number not for citation purposes) degree of dynamic hyperinflation in order to truly assess the effect of MV with heliox. However, our findings require re-evaluation in spontaneously breathing mechanically ventilated infants. Supportive therapy maintaining spontaneous breathing could very well be a key element while awaiting therapeutic modalities for mechanically ventilated infants with RSV LRTD [38] . Third, the measurements of our study were not blinded because connection of the heliox and the measurements were conducted by one investigator (MK). However, this might have introduced measurement bias. Fourth, ventilation with heliox may have influenced the tidal volume measurements of the AVEA ventilator. The AVEA is equipped with the Bicore CP100™ pulmonary mechanics monitor that has been validated previously [36, 39] . Finally, the AVEA performs in a similar way with respect to tidal volume measurement when heliox is used [40, 41] .