Effects of respiratory rate on venous-to-arterial CO2 tension difference in septic shock patients undergoing volume mechanical ventilation

Zhixiang Guo,Yapeng Wang,Shenglin Ge,Chao Xie,Guofang Hua,Yuedong Li

doi:10.1186/s40001-020-00402-9

Abstract

BackgroundTo explore the effects of the respiratory rate (RR) on the venous-to-arterial CO2 tension difference (gapCO2) in septic shock patients undergoing volume mechanical ventilation.MethodsAdult patients with septic shock underwent volume mechanical ventilation between October 2015 and October 2016. RR was started at 10 breaths/min, and 2 breaths/min were added every 60 min until 16 breaths/min was reached. At every point, central venous and arterial blood gas measurements were obtained simultaneously.ResultsIn this study, gapCO2 induced by hyperventilation significantly increased, while the central venous carbon dioxide pressure (PvCO2) and the partial pressure of CO2 (PaCO2) in arteries decreased. The decreasing trend of the PaCO2 was more obvious than that of the PvCO2. HCO3− and ctCO2 were markedly decreased, when the RR was increased (P < 0.05). Central venous oxygen saturation (ScvO2) had a decreasing trend between 14 (77.1 ± 8.3%) and 16 (75.2 ± 8.7%) breaths/min; however, the difference was not significant.ConclusionsIn septic patients undergoing ventilation, respiratory alkalosis induced by hyperventilation caused an increase in the gapCO2. Clinicians should cautiously interpret the gapCO2 in hemodynamically stable ventilated septic shock patients and its relationship with low cardiac output and inadequate perfusion.

Highlights

To explore the effects of the respiratory rate (RR) on the venous-to-arterial C O2 tension difference (gapCO2) in septic shock patients undergoing volume mechanical ventilation
Hyperventilation induced a significant RR-dependent increase in the gapCO2, which was related to the combined trend of decreases in PaCO2 and PvCO2 (Figs. 1 and 2)
Changes in HCO3− were paralleled by a significant decrease in ctCO2 (Fig. 3). ScvO2 significantly increased with increasing RR from 10 to 14 breaths/min, but had a decreasing trend from 14 to 16 breaths/min

Summary

Introduction

To explore the effects of the respiratory rate (RR) on the venous-to-arterial C O2 tension difference (gapCO2) in septic shock patients undergoing volume mechanical ventilation. A few authors have reported that the central venousto-arterial CO2 difference (gapCO2) demonstrated prognostic value in different conditions [5,6,7,8] and have recommended that the g apCO2 combined with the S cvO2 and lactate values should be used to rule out patients with persistent global hypoperfusion [3]. Little is known about the gapCO2 and respiratory rate (RR) in septic shock patients undergoing volume mechanical ventilation. In this study, we investigated the underlying effect of the RR on the gapCO2 in septic shock patients undergoing volume mechanical ventilation

Methods

Results

Discussion

Conclusion