Effect of spray cryotherapy on respiratory function in canine models of chronic bronchitis

Abstract

Objective: Our aim was to explore whether SCT is effective in improving respiratory function in a canine model of chronic bronchitis and to further elucidate the associated biological mechanisms. Methods: A total of ten experimental dogs were recruited for this study, eight of which were exposed to sulfur dioxide (SO2) for 6 months as a model group and the other two as healthy controls. We analyzed and compared the differences of respiratory function, airway morphology and inflammatory cell infiltration at 1-, 3- and 6-month intervals after SCT treatment and further explored the intrinsic correlations. Results: Respiratory function was significantly reduced after six months of SO2 exposure compared to healthy controls. PIF and PEF significantly decreased by 30.64% and 18.35%, respectively. Other respiratory function indicators such as TV, tI, tE, MV, EIP, EF25%, EF50%, EF75%, IF25%, IF50%, IF75%, FIaV, FEaV and CI also showed a significant downward trend (P<0.05). Respiratory function and airway morphometry were significantly improved at 1-, 3-, and 6- month intervals after SCT compared to chronic bronchitis group. The number of infiltrated neutrophils and macrophages per unit area of airway epithelium was negatively correlated with respiratory function, implying that decreased respiratory function was accompanied by more infiltration of neutrophils and macrophages. Conclusions: SCT significantly improved respiratory function, airway morphometry and infiltrated inflammatory cell count in a canine model of chronic bronchitis for at least six months. Our study identifies the relevant biological mechanisms by which infiltrating neutrophil and macrophage counts can have a critical impact on respiratory function.