压力与容量控制通气模式对危重症患者心排血指数和胸腔内血容量指数影响的比较研究

摘要

目的 比较在机械通气过程中双水平气道正压(BIPAP)与同步间歇指令通气(SIMV)两种模式对患者心排血指数(CI)、胸腔内血容量指数(ITBVI)的影响.方法 选择24例因各种原因需行有创机械通气和脉搏指示连续心排血量(PiCCO)技术监测血流动力学的患者,根据CI分为心功能正常组(9例)和心功能低下组(15例).在BIPAP模式下,调整吸气压使潮气量(VT)分别维持于6、10、15ml/kg,其他参数不变,呼吸机模式改为SIMV后,VT调节同前.以上各种条件维持20 min后测量呼吸力学及中心静脉压(CVP)、CI、ITBVI指标,试验过程中上述参数随机选择进行.结果 在心功能正常组,两种呼吸模式间CI、ITBVI、心率(HR)、平均动脉压(MAP)、平均气道压(Pmean)、内源性呼气末正压(PEEPi)的变化均无明显差异(P值分别为0.067、0.124、0.348、0.328、0.110、0.187);而外周循环阻力指数(SVRI)在10 ml/kg VT时,BIPAP模式下高于SIMV模式(P=0.030).在心功能低下组,CI、ITBVI在SIMV模式下降明显,仅在10ml/kgVT时CI差异有统计学意义(P<0.05);在6、10、15 ml/kg VT时BIPAP模式下Pmean均较SIMV模式低(P值分别为0.003、0.000、0.004);而SVRI、HR、MAP及PEEPi在不同VT水平两种呼吸模式间差异均无统计学意义.结论 两种通气模式随VT增加均可使CI、ITBVI降低.在相同VT时,压力控制模式(BIPAP)较容量控制模式(SIMV)Pmean相对低,对CI、ITBVI影响相对较小,因此,应用PiCCO监测容量变化时通气模式可影响CI、ITBVI.%Objective To compare the effect of control mode of pressure and volume of mechanical ventilation on cardiac index(CI),intrathoracic blood volume index(ITBVI)in patients.Methods Twentyfour patients in whom mechanical ventilation and pulse indicator continuous cardiac output(PiCCO)monitoring were necessary were involved,and they were divided into normal heart function group(9 cases)and heart dysfunction group(15 cases)on the base of CI.Mechanical ventilation was used with the mode of bi-level positive airway passage(BIPAP),and the inspiratory pressure was maintained at the tidal volume (VT)of 6,10,15 ml/kg.After the mechanical ventilation mode was changed to synchronized intermittent mandatory ventilation(SIMV)and maintained for 20 minutes,breathing mechanics and central venous pressure(CVP),CI,ITBVI were measured.Results In the normal heart function group,there were decrease in mean arterial pressure(MAP),CI and ITBVI,increase in heart rate(HR),mean airway pressure(Pmean)and intrinsic positive end expiratory pressure(PEEPi)in both modes of mechanical ventilation without significant difference(P values were 0.067,0.124,0.348,0.328,0.110,0.187,respectively).Systemic vascular resistance index(SVRI)was higher in the BIPAP group compared with SIMV group(P=0.030).In the heart dysfunction group,the CI and ITBVI were decreased in the SIMV mode,and CI was decreased significantly in the 10 ml/kg group(P<0.05).Pmean in BIPAP group was increased than that in SIMV group in all Vt levels(P values were 0.003,0.000,0.004,respectively).There was no significant difference in SVRI,HR,MAP and PEEPi in all groups.Conclusion In the two mechanical ventilation modes,with an increase in Vt,CI and ITBVI may decrease.The Pmean is lower when BIPAP mode in used compared with SIMV,when VT is same.So mechanical ventilation and VT can influence the readings of CI and ITBVI when PiCCO monitoring is employed.