Investigation of the Mechanical Properties of the Human Tracheal Cartilage

BACKGROUND: The tracheal cartilage plays an important role in maintaining the mechanical stability of the trachea, as it keeps the trachea open and prevents its collapse under the negative pressures of the respiratory cycle. This study aimed to evaluate and compare the mechanical properties of cartilage specimens from the cranial and caudal regions of the human trachea and compare the results with respect to age and sex of the subjects. MATERIALS AND METHODS: After obtaining human trachea samples from brain-dead, organ-donating patients and storing them in appropriate conditions, the prepared cartilage samples from the cranial and caudal regions of the trachea were subjected to uniaxial tension and stress relaxation experiments to obtain the corresponding Young’s modulus and relaxation percentage values, respectively. The results were compared in terms of the position (cranial or caudal) in the trachea, and age and sex of the patients. RESULTS: Based on the results, no statistically significant effect of the position in the trachea on the Young’s modulus of the human tracheal cartilage samples was observed, despite the generally stiffer behavior of cartilage samples from the cranial region compared to those from the caudal region of the trachea. For both the cranial and caudal regions, no significant effect of sex on the stiffness of the tracheal cartilage was observed; further, the cartilage samples of the human trachea (from both cranial and caudal regions) of the old subjects were significantly stiffer than those of the young subjects. Based on the stress relaxation data, no significant effect of age, sex, or position on the relaxation percentage was observed. CONCLUSION: The tracheal cartilage samples of the old patients are significantly stiffer than those of the young patients. Sex and position in the trachea (cranial vs caudal) do not significantly influence the mechanical properties of the human tracheal cartilage samples. The results of this study can be useful in designing tracheal tissue-engineered scaffolds, which should be mechanically compatible with the native trachea.