Increased effort during partial ventilatory support is not associated with lung damage in experimental acute lung injury

Dietrich Henzler,Paolo Pelosi,Zhaolin Xu,Nada Ismaiel,Alf Schmidt,Haibo Zhang,Arthur S Slutsky

doi:10.1186/s40635-019-0272-z

Abstract

BackgroundAn on-going debate exists as to whether partial ventilatory support is lung protective in an acute phase of ARDS. So far, the effects of different respiratory efforts on the development of ventilator-associated lung injury (VALI) have been poorly understood.To test the hypothesis whether respiratory effort itself promotes VALI, acute lung injury (ALI) was induced in 48 Sprague Dawley rats by hydrochloric acid aspiration model. Hemodynamics, gas-exchange, and respiratory mechanics were measured after 4 h of ventilation in pressure control (PC), assist-control (AC), or pressure support with 100% (PS100), 60% (PS60), or 20% (PS20) of the driving pressure during PC. VALI was assessed by histological analysis and biological markers.ResultsALI was characterized by a decrease in PaO2/FiO2 from 447 ± 75 to 235 ± 90 mmHg (p < 0.001) and dynamic respiratory compliance from 0.53 ± 0.2 to 0.28 ± 0.1 ml/cmH2O (p < 0.001). There were no differences in hemodynamics or respiratory function among groups at baseline or after 4 h of ventilation. The reduction of mechanical pressure support was associated with a compensatory increase in an inspiratory effort such that peak inspiratory transpulmonary pressures were equal in all groups. The diffuse alveolar damage score showed significant lung injury but was similar among groups. Pro- and anti-inflammatory proteins in the bronchial fluid were comparable among groups.ConclusionsIn experimental ALI in rodents, the respiratory effort was increased by reducing the pressure support during partial ventilatory support. In the presence of a constant peak inspiratory transpulmonary pressure, an increased respiratory effort was not associated with worsening ventilator-associated lung injury measured by histologic score and biologic markers.

Highlights

An on-going debate exists as to whether partial ventilatory support is lung protective in an acute phase of acute respiratory distress syndrome (ARDS)
Traditionally reserved for use in weaning, is often used in all phases of mechanical ventilation [6, 7], the potential of increased respiratory effort to the dependent lung to contribute to VILI is a matter of debate [8]
Averaging data for all groups, the mean arterial pressure decreased from 144 ± 23 at BL to 119 ± 27 mmHg at acute lung injury (ALI)-BL (p < 0.001), cardiac output remained stable at 122 ± 30 and 121 ± 34 ml/min (p = 0.34), respectively

Summary

Introduction

An on-going debate exists as to whether partial ventilatory support is lung protective in an acute phase of ARDS. Henzler et al Intensive Care Medicine Experimental (2019) 7:60 with reduced tidal volume [1], limited inspiratory plateau and driving pressure [2], and positive end-expiratory pressure (PEEP) [3] has been shown to improve outcomes in patients with acute respiratory distress syndrome (ARDS). Partial ventilatory support allows spontaneous breathing efforts during mechanical ventilation and preserves respiratory muscle function [5]. Traditionally reserved for use in weaning, is often used in all phases of mechanical ventilation [6, 7], the potential of increased respiratory effort to the dependent lung to contribute to VILI is a matter of debate [8]

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