SUMMARY
Objective
To evaluate effects of age (immature vs adult) and location along the trachea on the biomechanical properties (via a tensile stress relaxation test) and biochemical properties (water content and total proteoglycan content) of canine tracheal ring cartilage.
Sample population
Entire trachea from 8 immature and 8 adult dogs.
Procedure
A section of each tracheal ring from 8 immature dogs (6 months old) and 8 adult dogs (2 to 3 years old) was tested biomechanically (maximal stress, equilibrium stress, equilibrium modulus, and percentage of relaxation) and processed for biochemical analysis (water content and total proteoglycan content). Two rings from each trachea were prepared for histologic analysis (H&E or safranin-O staining).
Results
Biomechanical and biochemical parameters were not different between cervical and thoracic rings of either age group. Mean maximal stress, equilibrium stress, and equilibrium modulus were significantly higher for adult, compared with immature, dogs. However, percentage of relaxation for adult dogs was significantly lower. Tracheal rings of adult dogs had a significantly higher proteoglycan content and a significantly lower water content than did those of immature dogs. Water content and biomechanical parameters were significantly correlated, and proteoglycan content and biomechanical properties were significantly but weakly correlated. On histologic sectioning, a qualitative decrease in safranin-O staining in the rings of immature dogs also was observed.
Conclusions and Clinical Relevance
Biomechanical and biochemical properties of the canine tracheal ring cartilage are altered with age. However, location of the ring along the trachea did not affect these properties for either age group. Results lend support to the theory that proteoglycan content has some effect on tensile properties of tracheal rings and may explain increased compliance observed in rings from dogs with collapsed trachea. (Am J Vet Res 1998;59:18–22)
