Lung parenchyma stress response to step strains

Lung tissue mechanics have been measured by the response of lung tissue strips to uniaxial step strains. We investigated the behaviour of tissue in response to steps of both increasing and decreasing strains for different amplitudes at a single operating point and at different operating points for different amplitudes. The behaviour at three different stress operating points for one amplitude was also measured. A single response was similar to that found in experiments by Hildebrandt of whole lungs subjected to a step in volume. The response was desirable by either log(t) or a t^-k relationship. We have found that for strain steps performed at different amplitudes and operating stresses the time dependent behaviour is to a great extent separable from the dependence on amplitude and operating point.