Effect of mechanical ventilation guided by esophageal pressure on hemodynamics and oxygen metabolism of SAP porcine model with IAH / 中华急诊医学杂志

ABSTRACT

Objective To study the effect of mechanical ventilation guided by esophageal pressure on hemodynamics and oxygen metabolism of severe acute pancreatitis (SAP) swine model with intra-abdominal hypertension (IAH) Methods By self-controlled study,SAP model was made by infusing sodium taurocholate (5％) into the pancreatic duct in 6 domestic swine.Mechanical ventilator mode was volumeassist control with tidal volume 10 ml/kg ; FiO2 40％ and PEEP 5 cm H2O (routine ventilation) given to SAP model swine.After 3 h ventilation,pneumo-peritoneum was made with N2 gas to increase the intraabdominal pressure (IAP) to 25 mm Hg in SAP swine.Three more hours later,PEEP was adjusted as the measurement of esophageal pressure (Pes guided ventilation) to such a level that trans-pulmonary pressure stayed above 0 cm H2O during end-expiratory occlusion.During the investigation period,heart rate (HR),cardiac output index (CI),central venous pressure (CVP),mean arterial pressure (MAP) and pulmonary arterial wedge pressure (PAWP) were continuously recorded with the aid of Swan-Ganz catheter and ECG monitor,and oxygen partial pressure of artery (PaO2) and carbon dioxide partial pressure of artery (PaCO2) were measured by blood-gas analysis.In addition,systemic oxygen delivery (DO2) and systemic oxygen consumption (VO2) were calculated by using the data of blood-gas analysis of arterial and central venous blood.Results No swine model was subjected to barotrauma.After routine mechanical ventilation,there were significant differences in HR,CI,MAP,CVP,PAWP,Ppeak,Pplat,Pes,pulmonary compliance (Cstat),PaO2,and DO2 between SAP and IAH in swine (all P ＜ 0.05).Compared with routine ventilation,however,PaO2 and Cstat improved significantly with lower CI and increased Pplat after PEEP adjusted according to measurements of esophageal pressure (all P ＜ 0.05).The lactate decreased significantly after esophageal pressure guided ventilation (all P ＜ 0.05).There were no significant changes in PaCO2,HR,MAP,CVP and PAWP in IAH swine after mechanical ventilation with routine parameters (all P ＞ 0.05).Conclusions There were remarkable effects on oxygen metabolism in response to mechanical ventilation guided by esophageal pressure.In case of clinical application of mechanical ventilation,the results of this study are in favor of setting transpulmonary pressure according to measurements of esophageal pressure in SAP patients with IAH in an early stage.