MORPHOLOGICAL REASONS FOR CHOOSING TRACHEOTRACHEAL ANASTOMOSIS AT VARYING RESECTION EXTENT

Aims. The work was aimed at morphological substantiation of choosing tracheotracheal anastomosis at varying extent of resection. Materials and methods. The work presents data of morphological changes in the tracheal wall tissues in the anastomosis region in resection of various extents. For this purpose, a chronic experiment was conducted in animals (54 dogs), which simulated clinical cases of treatment of patients with tracheal pathology. The morphology of cartilagenous tissue, perichondrium and surrounding loose connective tissue was assessed. The cellular composition of tissues in the region of anastomosis was studied. Results. The study showed direct relation between pathological changes in the region of tracheotracheal anastomosis and extent of resection. When more than four tracheal rings were resected, significant impairment of architectonics of cartilagenous tissue and perichondrium was revealed, up to necrosis, which leads to tracheomalacia and increased risk of stenotic process. Slowing of reparative processes and the presence of chronic, slow-current inflammatory process in the region of anastomosis were noted, which is due to the anatomical features of the organ blood supply. Conclusions. The analysis of the obtained morphological data suggests inadmissibility of continuous suture on the trachea when making tracheal anastomosis, and feasibility of Davydov’s suture and the proposed technique.

The study was performed according to all the regulations, protocols, and ethical norms on the studies with experimental animals (Strasburg, France, 1986 The histological and morphometrical study was performed at x200 and x400 magnification.
It included the evaluation of cartilaginous tissue, perichondrium, surrounding loose connective tissue, and the cellular composition count in the area of anastomosis.
For the objectivization of the processes observed in tissues, the authors used the cellular index, i.e. the ratio of resident cells (macrophages, fibroblasts, fibrocytes) to non-resident cells (neutrophils, lymphocytes, eosinophils).
It was suggested that the cellular index < 1 indicates the exudative phase of the inflammatory process and the cellular index > 1 indicates the proliferative phase. Repeated placing of anastomosis by the studied methods (sampled biological material labeled "without tension" Resection of the anastomosis area in the same animals on certain Days (biomaterial labeled "resection of 4 tracheal rings") For the statistical analysis of the obtained results, the mean arithmetic and mean square deviation were calculated. After that, the calculation of the confidential interval (CI) was performed at p ≤ 0.05.

RESULTS.
The experiment "without tension" showed that the method of tracheo-tracheal anastomosis with suturing of the organ without its resection was not significant because, in this study, the stenosing of the tracheal lumen was not observed.
In the experiment with the resection of 4 tracheal rings in the 3 rd series of tests on Day 7 and Day 30, the area of stenosis was 5 and 2.5 times smaller, respectively, in comparison with the 1 st and 2 nd series of tests.
In the experiment with the resection of 8 tracheal rings in the 3 rd series of tests, the area of stenosis was 2.5 and 2 times smaller in comparison with the 1 st and 2 nd series, respectively.
The histological study in the experiment "without tension" in the 1 st and 2 nd series of tests revealed inflammatory events observed during the experiment. At later stages, necrosis was observed ( Figure 1).     In the 3 rd series of tests, there were necrotic changes in the mucosal layer, focal thickening of the epithelium, crateriform dilatation of submucosal glands. Blood filling and stasis of blood vessels were observed. The formation of immature connective tissue cicatrix was registered, which led to a continuous transformation of the connective tissue capsule around the anastomosis ( Figure 5). On Day 14 and Day 30, in the 2 nd and 3 rd series of tests after the "resection of 8 tracheal rings", there was a tendency towards the transition from the phase of exudation to the phase of proliferation (the cellular index was approaching 1). At this stage, in the 1 st series of tests, there was a significant inflammatory reaction (the cellular index was significantly lower than 1).
Thus, after the "resection of 8 tracheal rings" in all the studied series at all the stages, there was an inflammatory process in the area of tracheo-tracheal anastomosis. However, only in the 2 nd and 3 rd series of tests, there was a tendency towards the reduction of inflammatory events.

CONCLUSIONS.
1 The formation of tracheo-tracheal anastomosis after the resection of more than 4 tracheal rings is associated with high post-operational risks.
2 It is not advisable to apply continuous suturing during the formation of tracheo-tracheal anastomosis with tension.