Effects of different tidal volume ventilation on the cardiac diastolic function in severe cases

Objective To compare the effects of different tidal volume ventilation on cardiac diastolic function in severe cases.Methods A total of 208cases,receiving mechanical ventilation from 2008to 2013in Intensive Care Unit of the First People′s Hospital of Northern New District of Chongqing,were enrolled.In the bi-level positive airway pressure(BIPAP)mode,inspiratory pressure was adjusted to makes the tidal volume(VT)was maintained at 6,8,10,15mL/kg.Central venous pressure(CVP)and hemodynamic indexes were detected,and left ventricular ejection fraction(LVEF)was monitored after the maintenance of condition,mentioned above,for 30min,when the other supportive conditions of respirator were kept as the same.According to the cardiac index(CI),patients were divided into normal heart function group(CI≥2.2L·min-1·m-2)and poor cardiac function group(CI2.2L·min-1· m-2).According to LEVF value,patients were divided into systolic heart failure(LEVF40%)and diastolic heart failure(≥40%).Mechanical ventilation parameters were immediately adjusted,when patient was with significant decreasing of heart rate(HR)or blood pressure,or malignant arrhythmia.To avoid the influence of positive end expiratory pressure(PEEP),PEEP value was set at 5cmH2O in each group.Results At the same breath mode condition, CI,intrathoracic blood volume index(ITBVI),early diastolic spectrum amplitude(peak E)/diastolic spectrum amplitude(peak A)ratio(E/A)decreased with the increasing of VT,but mean airway pressure(Pmean)and systemic vascular resistance index(SVRI)increased,all of which were with significant difference(P0.05).While HR and LEVF were without significant difference between different groups(P0.05).Under the same breath mode and supportive conditions of respirator,CI,ITBVI and Pmean in patients with normal heart function were without significant difference between different group(P0.05).Among patients with poor cardiac function,CI value was the highest in 8mL/kg of VT group,but was relatively low in 6,10and 15mL/kg of VT group,which were with statistical difference(P0.05).Conclusion The VT should be set to 6-8mL/kg during mechanical ventilation,which might be without obvious influence on hemodynamics indexes and be applicable for the treatment of patients with normal or poor cardiac function.