床旁实时浓度监测氦气稀释法检测功能残气量的实验观察

Monitoring of functional residual capacity by bedside real-time concentration via helium dilution technique

目的探讨床旁实时浓度监测氦气稀释法（RHe法）检测功能残气量的准确性、精度及重复性。方法选择18例健康比格犬，利用静脉注射油酸制作急性呼吸窘迫综合征（ARDS）动物模型，在制作动物模型前后采用床旁RHe法及胸部CT扫描法检测功能残气量，实验过程中，实时监测实验动物呼吸、心率、血压等生命体征，选用Bland-Altman分析法及配对t检验进行统计学分析。结果对于造模前健康肺，CT扫描法检测功能残气量（FRCCT）与床旁RHe法检测功能残气量（FRCRHe）呈线性相关，回归方程为FRCRHe=0．959×FRCCT＋23．3（R^2=0．89，P〈0．0001）。RHe法与CT法的偏倚为（6．3±27．6）ml（1．5％±7．1％），95％可信区间为-47．7-60．3ml；对于造模后ARDS肺，直线回归方程为FRCRHe=0．693×FRCCT＋66．4（R^2=0．507，P〈0．001）。RHe法与CT法的偏倚为（7．9±27．1）ml（4．5％±13．6％），95％可信区间为-45．3～61．1ml。两次FRCRHe之间的差别在健康肺和ARDS肺分别为（-0．1％±5．8％）和（0．2％±9％）。结论床旁RHe法用于检测健康及ARDS模型肺功能残气量均具有良好的准确性、精度及重复性。

Objective To explore the accuracy, precision and repeatability of bedside real-time concentration monitoring via helium dilution （ RHe ） in ventilated dogs with and without acute respiratory distress syndrome （ARDS）. Methods Functional residual capacity （FRC） measurements were performed with computer tomography （FRCcT） and RHe （FRCRHe ） in 18 adult male beagle dogs. Blood gas analysis was conducted for baseline, post-lung injury and end-of-experiment. Vital signs were monitored continuously. And the differences were compared between two techniques and repeated FRCRHe s. Results For healthy lungs, FRCCT and FRCRHe were linearly correlated （ R^2 = 0. 89, P 〈 0.0001 ）. Bias between FRCRHe and FRCCT was 6. 3 ±27. 6 ml （1.5% ±7. 1% ） with 95% confidence interval limits of -47. 7 and 60. 3 ml respectively. For ARDS lung, FRCRHe = 0. 693 × FRCCT ± 66.4 （R^2 = 0. 507, P 〈 0. 00 1 ）. Bias between FRCRHe and FRCcT was 7, 9 ± 271 ml （4. 5% ± 13.6% ） with 95% confidence interval limits of -45.3 and 61.1 ml respectively. And the differences of repeated FRCRnes were -0. 1% ± 5.8% and 0.2% ± 9% in normal and ARDS lungs respectively. Conclusion The technique of bedside RHe may be used for measuring FRC with excellent accuracy, precision and repeatability.