Simultaneous monitoring of intratidal compliance and resistance in mechanically ventilated piglets: A feasibility study in two different study groups.

Abstract Compliance measures the force counteracting parenchymal lung distension. In mechanical ventilation, intratidal compliance–volume ( C ( V ))-profiles therefore change depending on PEEP, tidal volume ( V T ), and underlying mechanical lung properties. Resistance counteracts gas flow through the airways. Due to anatomical linking between parenchyma and airways, intratidal resistance–volume ( R ( V ))-profiles are hypothesised to change in a non-linear way as well. We analysed respiratory system mechanics in fifteen piglets with lavage-induced lung injury and nine healthy piglets ventilated at different PEEP/ V T -settings. In healthy lungs, R ( V )-profiles remained mostly constant and linear at all PEEP-settings whereas the shape of the C ( V )-profiles showed an increase toward a maximum followed by a decrease (small PEEP) or volume-dependent decrease (large PEEP). In the lavage group, a large drop in resistance at small volumes and slow decrease toward larger volumes was found for small PEEP/ V T -settings where C ( V )-profiles revealed a volume-dependent increase (small PEEP) or a decrease (large PEEP and large V T ). R ( V )-profiles depend characteristically on PEEP, V T , and possibly whether lungs are healthy or not. Curved R ( V )-profiles might indicate pathological changes in the underlying mechanical lung properties and/or might be a sign of derecruitment.