Evaluation of reflection of fluid volume state such as intrathoracic blood volume index and central venous pressure

Objectives To compare the changing trends[GS W1] of intrathoracic blood volume index(ITBVI) and central venous pressure(CVP) and their correlations with cardiac index(CI) according to changes of tidal volume(VT) during mechanical ventilation.Methods 24 patients who performed invasive mechanical ventilation and pulse index continuous cardiac output(PiCCO)monitoring were divided into normal cardiac function group[CI ≥ 2.2 L/(min·m)] and heart failure group[CI 2.2 L/(min·m)] according to CI.Under the synchronized intermittent mandatory ventilation(SIMV) mode,the VT was adjusted at 6,10,15 mL/kg levels.Respiratory parameters and hemodynamic data were collected 20 minutes after all above conditions.All the ventilation conditions were continued randomly.Results(1)In all the patients,CI and ITBVI decreased as VT increased,the mean airway pressure(Pmean) increased as VT increased;CVP had no significant changes during the three groups.(2)CVP had no correlations with CI during all the groups.ITBVI had correlations with CI in the heart failure group(R = 0.679,P 0.05).Conclusions ITBVI can reflect preload of the heart more accurately,it had better correlations with CI.