Objective: To observe the damage depth on normal canine trachea by using argon plasma coagulation (APC) at different power settings or cryoablation with different freezing duration , and to discuss the efficacy and safety of these different treatments.
Methods: APC (the power settings were 30 W and 60 W) and cryoablation (the freezing durations were 30 s and 60 s) were performed on the trachea of 8 dogs. The animals were killed 48 h after the treatment. The tracheal specimens were processed and divided into 5 groups: Cryoablation 30 s (Group A) , Cryoablation 60 s (Group B), APC 30 W (Group C), APC 60 W (Group D) and the control group. Gross observation, histopathological study and electron microscopic examination were performed.
Results: The tracheal injury in Group A and Group B reached the shallow part of airway cartilage layer, and 2 in Group B reached the deep part of airway cartilage layer. In Group A, cartilage cell degeneration could be seen, but in Group B, cartilage cell degeneration was worse and even necrosis was found. In Group C, the damage depth also reached the shallow part of the cartilage layer and necrosis of cartilage cells could be seen. In Group D, the damage depth reached the deep part of airway cartilage layer and even outer membrane of the trachea. More necrosis of cartilage cells was found.
Conclusion: When using cryoablation or APC with normal parameters, the injury in normal canine trachea could reach the shallow part of cartilage layer and cartilage cell degeneration could occur. When using APC 60 W, damage depth could reach the deep part of cartilage layer and even outer membrane of the trachea, leading to cartilage cell necrosis and even irreversible damage on airways. Therefore, it is highly recommended that, when managing lesions adjacent to or in the airway wall, APC ablation should be avoided and cryoablation time should be controlled within 30 s.