Impairment of nasal airway under intermittent hypoxia during growth period in rats

Objective To clarify the influences of intermittent hypoxia (IH) on the growth and development of the midfacial area, including the nasal cavity, in growing rats. Design Seven-week-old male Sprague-Dawley rats were divided into two groups: the experimental group (n = 5), which was exposed to IH for 8 h during light periods at a rate of 20 cycles/h (nadir, 4% O₂ to peak, 21% O₂ with 0% CO₂), and the control group (n = 5), which was exposed to room air. After 3 weeks, the maxillofacial structures in both groups were evaluated with respect to the height, width, length, surface area, cross-sectional area, and volume of the nasal cavity using soft X-ray and micro-CT. Results The experimental group showed a significantly smaller cross-sectional area and volume than did the control group. The surface area exhibited no significant differences between the two groups, although it tended to be smaller in the experimental group than in the control group. The nasal volume divided by the length of the tibia (for comparison with whole-body growth) was significantly smaller in the experimental group than in the control group. Conclusions These data suggest that IH exposure suppresses growth and development of the nasal cavity and may result in nasal breathing disturbance.