Structure of the rat tracheal mucosa after chronic intermittent hypoxia or chronic hyperbaric oxygen therapy.

Objective: This paper is aimed at identifying putative morphological changes induced in the rat's tracheal mucosa by chronic hyperbaric oxygen (HBO) treatment or chronic intermittent hypoxia (CIH). Study Design: Tracheal samples were obtained from three groups of 11, 12 and 13 adult Wistar rats. The first group was submitted to 20 sessions of 100 min-long HBO treatment; the second group was submited to eucapnic CIH for 35 days; and the third group was not submitted to any CIH or HBO therapy. Methods: Four proximal tracheal rings were collected after sacrifice and neck dissection of the animals. The samples were processed for both light microscopy and morphometric analysis. Inflammatory leukocyte infiltration was evaluated by a semi-quantitative method. Unpaired t test and Bernoulli distribution were applied to evaluate statistical differences in the data collected from the three groups. Results: Both CIH and HBO promote an increase in the thickness of the epithelium and of the basement membrane of the rat tracheal mucosa, as well as an increment in the number of infiltrating leukocytes, when compared with results seen in the untreated group. In the HBO group there was a significant lack of seromucous glands, as opposed to the results obtained in the CIH group. Conclusions: Chronic HBO and CIH exposure causes only minor changes in the architecture of the tracheal mucosa of the rat. The respiratory tract of the rat showed a mild inflammatory response when subject to variations of pressure and oxygen content. Apparently these effects do not constitute a critical issue on prescribing HBO treatments and in the management of sleep apnea patients.