Impact of open lung ventilation on right ventricular outflow impedance assessed by transoesophageal echocardiography

Introduction

Open lung concept ventilation is a method of ventilation intended to maintain end-expiratory lung volume by increased airway pressure [1]. Since this could increase right ventricular (RV) afterload, we investigated the effect of this method on RV outflow impedance during inspiration and expiration using transoesophageal echo-Doppler in a trial to differentiate the RV consequence of increasing lung volume from those secondary to increasing airway pressure during mechanical ventilation.

Methods

Thirty stable patients on MV because of different causes were enrolled prospectively in this single-center, cross-sectional clinical study. Each patient was firstly subjected to conventional ventilation (CV) with volume-controlled ventilation, followed by OLC ventilation by switching to a pressure-controlled mode, then a recruitment maneuver applied until PaO₂/FiO₂ > 375 torr. Hemodynamic (MAP, CVP and HR) and respiratory (peak, plateau and mean airway pressure and total and dynamic lung compliance) measurements were recorded before, 20 minutes after a steady state of both CV and 20 OLC ventilation. Also, transoesophageal ECHO Doppler was performed at the end of inspiration and end of expiration to calculate the mean acceleration (AC_mean), as a marker of the RV outflow impedance, 20 minutes after a steady state of both CV and OLC ventilation.

Results

During inspiration, AC_mean was significantly lower during CV compared with OLC ventilation (P < 0.001). Inspiration did not cause a significant decrease in AC_mean compared with expiration during OLV (P < 0.001) but did do so during CV. In comparison with baseline and CV, OLC ventilation was associated with a statistically significant higher CVP (P < 0.001 for both), higher total quasi-static lung compliance (P < 0.001 for both) and dynamic lung compliance (P = 0.001 for both). Moreover, the PaO₂/FiO₂ ratio of OLV was significantly higher than in baseline and CV (P < 0.001 for both).

Conclusions

OLC ventilation does not change RV afterload during inspiration and expiration as RV afterload appears primarily mediated through the tidal volume. Moreover, OLC ventilation provides a more stable hemodynamic condition and better oxygenation and lung dynamics.