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Effect of tidal volume and positive end-expiratory pressure on lung hysteresis of healthy piglets
Critical Care volume 18, Article number: P286 (2014)
Introduction
Growing evidence suggests that, as long as the total lung capacity is not overcome, dynamic (that is, tidal volume, VT) is more injurious than static (that is, positive end-expiratory pressure, PEEP) lung deformation [1]. Because the lung behaves like a viscoelastic body [2], hysteresis may play a role in the development of ventilator- induced lung injury. The aim of the study was to investigate the effects of increasing VT or PEEP on lung hysteresis.
Methods
In eight healthy piglets we measured total hysteresis and the peak inspiratory pressure (Ppeak) while randomly increasing VT (with no PEEP) or PEEP (with fixed VT). P1 was extrapolated from the drop in airway pressure during an end-inspiratory pause [3]. Hysteresis attributable to lung parenchyma was computed as: total hysteresis - ((Ppeak - P1) x VT).
Results
The main findings are shown in Figure 1. P values refer to oneway repeated-measures analysis of variance.
Conclusion
Lung hysteresis increases with VT, but not with PEEP Further studies are needed to prospectively evaluate the role of lung hysteresis in the pathogenesis of ventilator-induced lung injury.
References
Protti A, et al.: Which is the most important strain in the pathogenesis of ventilator-induced lung injury: dynamic or static? Curr Opin Crit Care 2014, 20: 33-38. 10.1097/MCC.0000000000000047
Bayliss LE, et al.: The visco-elastic properties of the lung. Q J Exp Physiol 1939, 29: 27-47.
Bates JHT, et al.: General method for describing and extrapolating monotonic transients and its application to respiratory mechanics. Med Biol Eng Comput 1987, 25: 131-135. 10.1007/BF02442840
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Andreis, D., Milesi, M., Pugni, P. et al. Effect of tidal volume and positive end-expiratory pressure on lung hysteresis of healthy piglets. Crit Care 18 (Suppl 1), P286 (2014). https://doi.org/10.1186/cc13476
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DOI: https://doi.org/10.1186/cc13476