ORIGINAL ARTICLES   Free access

Minerva Anestesiologica 2014 January;80(1):19-28

Copyright © 2014 EDIZIONI MINERVA MEDICA

lingua: Inglese

Determination of respiratory system mechanics during inspiration and expiration by FLow-controlled EXpiration (FLEX): a pilot study in anesthetized pigs

Schumann S. ¹, Goebel U. ¹, Haberstroh J. ², Vimlati L. ³, Schneider M. ¹, Lichtwarck-Aschoff M. ³, Guttmann J. ¹ ✉

¹ Department of Anesthesiology and Critical Care Medicine, University Medical Centre Freiburg, Freiburg, Germany; ² Experimental Surgery, CEMT, University Medical Centre Freiburg, Freiburg, Germany; ³ Department of Surgical Sciences/Section of Anaesthesiology and Critical Care Medicine, Uppsala University, Uppsala, Sweden

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.