[The effect of CPAP on the structure and function of upper airway of mini pig with OSAS]

This study sought to assess the effect of CPAP on the structure and function of upper airway of mini pig with OSAS induced by altitude hypoxia. 12 adult male mini pigs were randomly assigned to 2 groups, named A and B. The mini pigs in group A were treated with altitude hypoxia 6 h per day for 22 days, and then with CPAP 6 h per day for 30 days. The mini pigs in group B were treated with altitude hypoxia only. Pharyngeal CT scanning and respiratory pressure testing were performed after the treatments . At last all mini pigs were sacrificed and their pharyngeal tissue was acquired for pathological examination. Result of pharyngeal CT scanning showed that, in group A, both of transverse diameters of pharyngeal cave in anterior and posterior areas of hyoid bone increased significantly after CPAP treatment (P < 0.05), while the pharyngeal longitudinal diameters exhibited no significant change (P > 0.05). The thickness of pharyngeal posterior wall of the anterior areas of hyoid bone increased significantly (P < 0.05) after CPAP, while the thickness of the lateral wall displayed no significant change. The pharyngeal longitudinal diameters of group A after CPAP were shorter than those of group B, and the transverse diameters were longer than those of group B, but these differences were not statistically significant (P > 0.05). The pharyngeal posterior walls in soft palate area and anterior area of hyoid bone after CPAP were significantly thicker than those of group B (P < 0.05), but there were no significant differences between the two groups as far as lateral wall thickness was concerned (P > 0.05). After CPAP treatment, the pharyngeal inspiration pressure in group A decreased significantly (P < 0.05), and the pressure was significantly lower than that of group B. Microscopic findings showed that the epithelium was proliferated partly after CPAP treatment. The muscle fibers of group A became fatter and were arranged disorderly with unclear transverse striation. The dropsied and congestive subcutaneous tissues were also infiltrated with inflammatory cells. These pathological changes were more obvious in group B. The results suggested that CPAP treatment could normalize the structure and function of pharyngeal tissue in OSAS mini pigs.