Structure of the rat nasal mucosa after acute and chronic hyperbaric oxygen therapy

Objective: We aimed at the identification of putative morphologic changes induced in the rat nasal mucosa by acute or chronic hyperbaric oxygen (HBO ₂) treatment. Study design: Nasal samples were obtained from three groups of eight adult Wistar rats. The first group was submitted to 30 daily sessions of 100-minute-long HBO₂ treatments at 2.5 ATA, the second group to a single 485-minute-long HBO₂ session following the U.S. Navy Table 6 extended twice at 2.8 and 1.9 ATA, and the third group was composed of rats not submitted to any HBO₂ therapy. Methods: Samples of anterior portion of the lower nasal turbinates (concha nasalis ventralis) were collected after sacrifice and head dissection of the animals. The samples were processed for light and electron microscopy and for morphometric analysis. Inflammatory leukocyte infiltration was evaluated by a semiquantitative method. Non-parametric ANOVA was applied to evaluate statistical differences between leukocyte infiltration, and ANOVA one-way was used to evaluate the thickness of epithelium and basement membrane from samples of HBO₂-treated rats and untreated rats. Results: Samples of the turbinate mucosa of the rats submitted to chronic HBO₂ treatment showed a significant increase in the thickness of the epithelium and a mild enhancement in the number of infiltrating leukocytes when compared with data from samples from untreated rats or from rats submitted to a single HBO₂ treatment. Conclusions: Chronic HBO₂ treatment causes only minor changes in the architecture of the nasal mucosa of the rat; they reflect a mild inflammatory response of the respiratory tract to the increase in pressure and in oxygen content induced by HBO₂ No significant morphological changes were observed after a single HBO₂ treatment