A trial to evaluate the mechanical anisotropy in human lung ; Aim for elucidating why centrilobular type emphysema occurs predominantly at upper lung

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It has not been elucidated why centrilobular emphysema, associated with cigarette smoke, occurs predominantly at upper lung. Respiratory movement in the upper lobe is smaller than that in the lower lung. We hypothesize that reconstruction of extra cellular matrix varies according to range of mechanical load by respiratory movement. Based on this hypothesis the threshold against mechanical stress in the upper lung may be lower than that in the lower lung. In this context we tried to evaluate mechanical anisotropy in human lung to make clear the role of mechanical property in development of centrilobular emphysema.We prepared sheet samples from coronal plate of human lung. Slit samples for mechanical measurements were prepared by cutting the sheet samples. The threshold against mechanical stress was evaluated by stretching the samples until their breakdown.As a result, the mechanical stretching strength in the upper lung was lower than in the lower lung. This result suggests that the distribution of mechanical property may contribute to the development of centrilobular emphysema.