Physiological Studies in the Prone Position in Patients With ARDS

PP has been shown to effectively improve the prognosis of patients with severe ARDS, but not all patients with ARDS can benefit from PP, and the implementation of the PP has a certain clinical risks and side effects, we lack a convenient predictors to guide doctors to determine whether patients should implement the PP. Clinical usually observe the P/F improved as whether PP treatment effective reference, but there are literature points out that the rising P/F after PP can not predict the better prognosis. one of the mechanisms for ARDS patients benefit from PP is proved to be improve V/Q, the change of the V/Q may determine whether the PP treatment effectively is an important indicator. PaO2:FiO2 ratio was usually used to evaluate the effect of PP, but some studies did not support this conclusion. PP has been shown to change ventilation-perfusion ratio, dead space may be better physiological indicators, simplify dead space ratio and Ventilatory ratio can be easily accessed at bedside and is associated with mortality of patients with ARDS. The purpose of this study is to observe the predictive value of P/F, VD-etCO2/VT, and VR on the treatment effect of ARDS undergoing PP.

Inclusion criteria

• Intubated patients
• Undergoing mechanical ventilation
• Moderate to severe ARDS
• Undergoing prone positioning
• Age≥18 years old

Exclusion criteria

• Pregnant
• Cardiac structural shunt
• Extracorporeal membrane oxygenation performed
• Undergo extracorporeal CO2 removal
• Pulmonary embolism
• Other situation that may affect the accuracy of PetCO2 monitoring
• Prone positioning session less than 10 hours