无创心排血量监测系统对急性呼吸窘迫综合征猪模型呼吸循环功能的评价意义

The significance of non invasive cardiac output monitoring system on evaluating circulatory and respiratory function in pig with acute respiratory distress syndrome

目的：探讨无创心排血量监测（NICO）系统在急性呼吸窘迫综合征（ARDS）中的应用价值，为临床应用提供基础实验依据。方法选择11只健康雄性家猪，经中心静脉缓慢注入0.2 mL/kg的油酸复制ARDS动物模型。应用压力控制通气对ARDS模型进行肺复张；采用NICO系统监测肺死腔率（VD/VT），以确定最佳呼气末正压（PEEP）；同时测定心排血量（CO）及呼吸功能，记录基础值、ARDS时以及最佳PEEP时ARDS模型猪的VD/VT、肺动态顺应性（Cdyn）、氧合指数（PaO2/FiO2）、肺泡通气量（Valv）及动脉血氧饱和度（SaO2）等参数，计算肺内分流率（Qs/Qt）。同时应用脉搏指示连续心排血量监测技术（PiCCO）测量CO，并与NICO测量的CO进行线性回归分析。结果有7只猪成功制备ARDS模型；通过最低VD/VT方法测定的最佳PEEP值为（15.71±1.80）cmH2O（1 cmH2O＝0.098 kPa）。与基础值比较，ARDS时VD/VT、Qs/Qt明显增加〔VD/VT：（72.29±8.58）%比（56.00±11.06）%，Qs/Qt：（21.04±15.05）%比（2.00±1.32）%，均P＜0.05〕，SaO2、Valv则明显降低〔SaO2：0.888±0.108比0.999±0.053，Valv（mL）：92.06±35.22比146.11±45.43，均P＜0.05〕；而在用最佳PEEP通气后VD/VT、Qs/Qt、SaO2、Valv均恢复到基础值水平〔分别为：（61.07±9.30）%、（3.21±6.10）%、0.989±0.025、（117.14±41.14）mL〕。ARDS时Cdyn、PaO2/FiO2均较基础值明显降低〔Cdyn（mL/cmH2O）：14.43±5.50比38.14±6.72，PaO2/FiO2（mmHg，1 mmHg＝0.133 kPa）：78.71±23.22比564.37±158.85，均P＜0.05〕；应用最佳PEEP通气后二者均较ARDS时明显升高〔分别为：（19.71±4.86）%、（375.49±141.30）mmHg，均P＜0.05〕，但仍明显低于基础值（均P＜0.05）。在给予最佳PEEP通气后，NICO测量的CO较ARDS时有所下降，由（4.18±2.46）L/min 降至（3.95±2.69）L/min，但差异无统计学意义（P＞0.05）。应用NICO监测系统测量的CO与PiCCO测量的CO有较好的相关性（r2＝0.925，P＜0.001）。结论应用NICO监测系统可以很好地监测ARDS时的呼吸功能及CO，并且通过NICO监测最低VD/VT可以作为滴定最佳PEEP的方法。

Objective To investigate the effect of non invasive cardiac output monitoring（NICO）system in pig model with acute respiratory distress syndrome（ARDS）,and to provide experimental basis for clinical application. Methods Eleven anaesthetized and ventilated ARDS male pig models were induced by intravenously infusing 0.2 mL/kg oleic acid. Lung recruitment was condocted by pressure control ventilation on pigs with ARDS. The optimal positive end-expiratory pressure（PEEP）was determined by optimal dead space fraction〔the ratio of dead space to tidal volume（VD/VT）〕. Cardiac output（CO）was determined by NICO,the respiratory function was monitored, and the VD/VT,dynamic compliance（Cdyn）,oxygenation index（PaO2/FiO2）,the volume of alveolar ventilation（Valv） and arterial blood oxygen saturation（SaO2）were recorded before infusing oleic acid,after stabilization of ARDS model and at optimal PEEP level,and the intrapulmonary shunt fraction（Qs/Qt）was calculated. CO was also determined by application of pulse indicated continuous cardiac output（PiCCO）,and the linear regression analysis between CO determined by NICO and CO determined by PiCCO was conducted. Results Seven experimental ARDS pigs model were successfully established. The optimal PEEP identified by the lowest VD/VT method was（15.71±1.80）cmH2O （1 cmH2O=0.098 kPa）. Compared with before infusing oleic acid,VD/VT and Qs/Qt after stabilization of ARDS model were significantly increased〔VD/VT：（72.29±8.58）% vs.（56.00±11.06）%,Qs/Qt：（21.04±15.05）%vs.（2.00±1.32）%,both P〈0.05〕,and SaO2 and Valv were significantly decreased〔SaO2：0.888±0.108 vs. 0.999±0.053,Valv（mL）：92.06±35.22 vs. 146.11±45.43,both P〈0.05〕. VD/VT,Qs/Qt,SaO2 and Cdyn at optimal PEEP level were improved to the levels before infusing oleic acid〔（61.07±9.30）%,（3.21±6.10）%, 0.989±0.025,（117.14±41.14）mL〕. Cdyn and PaO2/FiO2 after stabilization of ARDS model were significantly lowered compared with those before infusing oleic acid〔Cdyn （mL/cmH2O）：14.43±5.50 vs. 38.14±6.72, PaO2/FiO2 （mmHg, 1 mmHg=0.133 kPa）：78.71±23.22 vs. 564.37±158.85, both P〈0.05〕. Cdyn and PaO2/FiO2 at optimal PEEP level〔（19.71±4.86）%,（375.49±141.30）mmHg〕were elevated compared with the levels after stabilization of ARDS model（both P〈0.05）,but still lower than those before infusing oleic acid（both P〈0.05）. Compared with the levels after stabilization of ARDS model,CO at optimal PEEP level showed obvious decrease from（4.18±2.46）L/min to（3.95±2.69）L/min without significant difference（P〉0.05）. There was linear correlation between CO determined by NICO and CO determined by PiCCO（r2=0.925,P〈0.001）. Conclusions NICO technique provides a useful and accurate non invasive estimation of CO and respiratory function.VD/VT provided by NICO can titrate the optimal PEEP in patients with ARDS.