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Updated: May 6, 2026
Evaluation of Respiratory System Mechanics in Mice using the Forced Oscillation Technique
Published on: May 15, 2013
Determination of respiratory system mechanics during inspiration and expiration by FLow-controlled EXpiration (FLEX):
S Schumann1, U Goebel, J Haberstroh
1Department of Anesthesiology and Critical Care Medicine, University Medical Centre Freiburg, Freiburg, Germany - stefan.schumann@uniklinik-freiburg.de.
Background:
Differences between inspiratory and expiratory lung mechanics result in the hysteresis of the pressure volume-loop. While hysteresis area is a global parameter describing the difference between inspiration and expiration in mechanics under quasi-static conditions, a detailed analysis of this difference under the dynamic conditions of mechanical ventilation is feasible once inspiratory and expiratory compliance (Cin/Cex) are determined separately. This requires uncoupling of expiratory flow rate and volume (V).
Methods:
Five piglets were mechanically ventilated at positive end-expiratory pressure (PEEP) levels ranging from 0 to 15 cmH2O. Expiratory flow rate was linearized by a computer-controlled resistor (flow-controlled expiration). The volume-dependent Cin(V) and Cex(V) profiles were calculated from the tracheal pressure volume-loops.
Results:
The intratidal curve-progression of Cex(V) was altogether higher with a steeper slope compared to Cin(V). With increasing positive end-expiratory pressure (PEEP) dynamic hysteresis area decreased and Cex(V) tended to run more parallel to Cin(V).
Conclusion:
The relation between inspiratory and expiratory compliance profiles is associated with the hysteresis area and behaves PEEP dependent. Analysing the Cin-Cex-relation might therefore potentially offer a new approach to titrate PEEP and tidal volume.
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