不同机械通气模式对人机同步性以及膈肌功能影响的实验研究

Effect of different mechanical ventilation modes on patient-ventilator synchrony and diaphragm function in rabbit model of acute respiratory distress syndrome

目的探讨不同机械通气模式对急性呼吸窘迫综合征(ARDS)人机同步性以及膈肌功能的影响。方法以18只新西兰大白兔,盐酸吸入法复制ARDS模型,氧合指数(PaO2/FiO2)<200 mmHg认为造模成功。随机数字表法分为3组:容量辅助控制通气组(A/C组)、压力支持通气组(PSV组)和神经电活动辅助通气组(NAVA组)。目标潮气量(VT)初设设置为6 ml/kg,最佳氧合法选择呼气末正压(PEEP)。分组机械通气4 h,通气过程中监测呼吸力学、气体交换、人机同步性指标。4 h后处理动物取膈肌标本,测定膈肌中丙二醛(MDA)、超氧化物歧化酶(SOD)及还原型谷胱甘肽(GSH)含量。样本均数间的两两比较采用q检验。结果造模后分组机械通气1~4 h,3组PaO2/FiO2比较差异无统计学意义(F=1.029,P>0.05);NAVA组VT较PSV组显著降低,RR、EAdi较A/C组显著增加(均P<0.05)。NAVA组吸气触发延迟时间、吸呼气转换延迟时间显著低于A/C组和PSV组(F=14.312、9.342,均P<0.05)。NAVA组人机不同步指数(3.1%±1.0%)显著低于A/C组(22.3%±5.2%)和PSV组(8.4%±2.3%)(F=7.192,P<0.05)。NAVA组气道峰压(Ppeak)与膈肌电活动峰值(EAdipeak)呈显著正相关(r=0.97±0.16,P<0.05);A/C组和PSV组Ppeak与EAdipeak间无相关性(r=0.38±0.13、0.46±0.15,均P>0.05)。NAVA组的膈肌匀浆中MDA水平显著低于A/C组(P<0.05);NAVA组的膈肌匀浆中SOD、GSH水平均显著高于A/C组(均P<0.05)。结论在轻中度ARDS机械通气时,NAVA通气模式保留自主呼吸,维持人机同步,有利于避膈肌偏心性收缩、减轻膈肌氧化应激,有望减轻呼吸机相关膈肌功能障碍。

Objective To observe the effect of different modes of mechanical ventilation on patient-ventilator synchrony and diaphragm function in rabbits with acute respiratory distress syndrome(ARDS).Methods Eighteen New Zealand rabbit models of ARDS were induced by intratracheal infusion hydrochloric acid until the oxygenation index(PaO2/FiO2)was less than 200 mmHg,and then divided into three groups with random number:assisted-controlled mechanical ventilation(A/C)group,pressure support ventilation(PSV)group and neurally adjusted ventilatory assist(NAVA)group.All of them were ventilated for four hours with the targeted tidal volume(VT)(6 ml/kg)and the positive end-expiratory pressure(PEEP)titrated with the maximum oxygenation method.Gas exchange,pulmonary mechanics and patient-ventilator synchrony were determined during 4 h of ventilation and the concentrations of malondialdehyde(MDA),superoxide dismutase(SOD)and glutathione(GSH)in diaphragm were measured after 4 h of ventilation.The q test was used for the multiple comparison of the sample mean.Results There were no significant differences in PaO2/FiO2 between three groups during ventilation 1-4 h(F=1.029,P>0.05).The VT in NAVA group was obviously lower than that in PSV group and the respiratory rate(RR)and the electrical activity of diaphragm(EAdi)were higher than those in A/C group(all P<0.05).The trigger delay and off cycle delay the in NAVA group were markedly lower than those in A/C and PSV group during ventilation 1-4 h(F=14.312,9.342,both P<0.05).Asynchrony index in NAVA group(3.1%±1.0%)was obviously lower than those in A/C group(22.3%±5.2%)and PSV group(8.4%±2.3%)(F=7.192,P<0.05).In NAVA group,peak EAdi(EAdipeak)and peak airway pressure(Ppeak)were markedly correlated(r=0.97±0.16,P<0.05),while Ppeak delivery in A/C and PSV group was not correlated to EAdipeak(r=0.38±0.13,0.46±0.15,both P>0.05).Compared with A/C group,the concentration of MDA in the diaphragm in NAVA group was obviously lower(P<0.05).SOD and GSH level inthe diaphragm in NAVA group were both obviously higher than those in A/C group(both P<0.05).Conclusions It is helpful to avoid eccentric contraction of diaphragm,lessen oxidative stress and alleviate ventilator-related diaphragm dysfunction by keeping spontaneous breathing as far as possible and subject-ventilator synchrony when ventilation in ARDS with NAVA.