Experimental Airway Smooth Muscle Response to Transverse Oscillations

This paper presents an in vitro investigation of the stiffness variation of contracted airway smooth muscle subjected to external transverse oscillations. Two stiffness definitions are used to quantify the results, the dynamic stiffness to reflect variations during oscillation and the static stiffness to represent the net effect of oscillation. Under isometric contraction, these two stiffnesses are determined before, during and after oscillations. The results show that the dynamic stiffness has the tendency of decreasing with increasing frequency below 40 Hz; afterwards, the stiffness slightly increases. The static stiffness, however, remains almost unchanged for all frequencies except at 5 Hz where a small reduction is observed. Also it is observed that an increase in the length change ratio leads to a decrease in both stiffnesses. The difference in the behaviour of dynamic and static stiffness changes may be attributed to the effect of elasticity and mass inertia.