Growth and Development in a Heliox Incubator Environment: A Long-Term Safety Study

Background: Neonates exposed to mechanical ventilation may develop bronchopulmonary dysplasia (BPD). BPD neonates exhibit a 25–30% increase in energy expenditure which may decrease the rate of growth and development. Heliox has been shown to improve pulmonary function and may decrease energy expenditure. We hypothesized that heliox would provide a safe environment for sustained growth and development. Objective: To assess the safety of the heliox environment we observed developmental milestones; recorded changes in weight, total length, limb length and head circumference; measured blood chemistries; compared primary organ and muscle weights, and analyzed muscle enzymatic activity. Design/Methods: Four-day-old rabbit pups (n = 27) were randomized into control (21% O2; 79% N2) or heliox (21% O2; 79% He) groups, then raised for 14 days at 26.7°C and 50% relative humidity. Pups were euthanized on day 14, blood drawn and primary organs, diaphragm and gastrocnemius weighed and snap-frozen. Results: All pups thrived in both environments, achieving expected developmental milestones. There were no physiologically significant group differences in weight, growth factors, tissue weight, blood chemistry or muscle enzyme activity. Conclusions: No observed long-term differences in growth or development. Results demonstrated that long-term heliox exposure is safe in this rabbit model. These data suggest that heliox administration may provide time for pulmonary improvement in the BPD population, warranting appropriate clinical trials.