Most biological tissues exhibit visco-elastic behavior. In particular, the respiratory system tissues do not maintain a constant stress when volume is increased: the stress slowly relaxes, approaching a constant lower value (stress relaxation). In the same way, after a reduction in respiratory system volume, the achieved lower stress slowly increases and approaches a higher constant value (stress recovery).

It was shown that body temperature increments reduce stress relaxation (Rubini, Resp Physiol Neurobiol 2011, 175:255-260), and present experiments were performed to evaluate the effect of body temperature on rat respiratory system stress recovery.

Constant deflation flow arrests were applied after respiratory system inflation to study the successive airway pressure time course, which defines respiratory system stress recovery.

Measurements were performed at two body temperatures, 36.6±0.3 and 39.0±0.1 °C. Body warming was achieved using an infrared lamp.

We found that stress recovery also is reduced by increasing body temperature. Pressure-time curves after deflation arrest were fitted by equations derived by a specific mathematical model, and a good agreement was found with experimental data. Model parameters exhibited significant changes with body temperature variations, suggesting that temperature-dependent micro-structural rearrangement phenomena in the tissues of alveolar wall were involved in the stress recovery decrement.