Airway and parenchymal tissue resistance and elastance in ex vivo sheep lungs: Effects of bronchochallenge and deep inspiration

Am J Physiol Lung Cell Mol Physiol. 2022 May 10. doi: 10.1152/ajplung.00033.2022. Online ahead of print.ABSTRACTLung resistance (RL) is determined by airway and parenchymal tissue resistance, as well as the degree of heterogeneity in airway constriction. Deep inspirations (DIs) are known to reverse experimentally induced increase in RL, but the mechanism is not entirely clear. The first step towards understanding the effect of DI is to determine how each of the resistance components is affected by DI. In the present study, we measured RL and apparent airway resistance (RAW, which combines the effects of airway resistance and airway heterogeneity) simultaneously before and after a DI in acetylcholine (ACh)-challenged ex vivo sheep lungs. We found that at normal breathing frequency (0.25 Hz) ACh-challenge led to doubling of RL, 80.3% of that increase was caused by an increase in RAW; the increase in apparent tissue resistance (RT) was insignificant. 57.7% of the increase in RAW was abolished by a single DI. After subtracting RAW from RL, the remaining RT was mostly independent of ACh-challenge and its reduction after a DI came mostly from the change in the mechanical properties of lung parenchyma. We conclude that at normal breathing frequency, RL in an unchallenged lung is mostly composed of RT, and the increase in RL due to ACh-challenge stems mostly from the increase in RAW and that both RAW and RT can be greatly reduced by a DI, likely due to a reduction in true airway resi...

Source: American Journal of Physiology. Lung Cellular and Molecular Physiology - May 10, 2022 Category: Cytology Authors: Shou-Jin Dong Lu Wang Pasquale Chitano Dragos Mihai Vasilescu Peter D Par é Chun Y Seow Source Type: research