摘要
全身麻醉中伤害感受的监测具有重要的临床意义,近来研究者基于光电容积脉搏波(PPG)的幅度建立了伤害感受的监测指标,比如外科应激指数SSI和伤害感受响应指标RN。然而,PPG的幅度易受测量条件的影响,且所采用的标准化方法理论适用性不高。
因此,本论文的研究目的是从PPG的形态方面提出参数,并建立了一个基于其形态的伤害感受的监测指数SPMI。本论文的主要内容和创新成果如下：
(1)PPG特征点的检测算法
采用局部查找方法,结合一阶、二阶导数和逻辑判断条件建立了PPG的特征点检测算法。算法评估结果表明,在含有干扰信号的情况下,此算法的灵敏度和阳性预测率可达95%以上,该检测算法可靠。
(2)PPG幅度和形态的特异度和灵敏度研究
根据弹性腔理论,解析推导出了PPG的5个形态参数,QRC、ARD、ARA、ART和PBI。另外也研究了PPG的幅度参数PPGA。
以PPGA和ART为例对比了血流灌注、测量位置和测量体位变化时PPG幅度和形态的相对变化率,统计分析表明ART的相对变化率小于PPGA,表明PPG形态的特异度更高。
采用气管插管为伤害性刺激,并用不同的抗伤害感受药物浓度产生不同程度的伤害感受,以预测概率为指标评估了所有参数的灵敏度。结果表明表征气管插管时,灵敏度次序为PBI>ART>PPGA>ARD>ARA>QRC,形态参数和幅度参数不相上下。表征不同程度的伤害感受时,灵敏度次序PBI> ART>ARA>ARD>QR>PPGA,形态参数均高于幅度参数。
(3)基于PPG形态的外科指数SPMI的建立
采用多参数结合方法,经多元线性回归得到SPMI=30-43×PBI+45×ART。性能评估表明,插管前SPMI和瑞芬太尼药物浓度的Spearman相关系数为-0.30,插管时为-0.52,均高于SSI的-0.21。SPMI预测CSSA的预测概率为0.819,高于文献所报道的RN的0.78。
本论文基于PPG的形态特征,建立了一个抗伤害感受的指数SPMI,其性能优于基于PPG幅度的其它指数,有利于获得更好的麻醉效果。
The monitoring nociception is important in general anaesthesia, Photoplethysmographic pulse wave (PPG) has been explored for monitoring nociception since several years ago. Several parameters has been extracted from PPG and normalized to develop monitoring indices for nociception, like Surgical Stress Index (SSI) and Response Index of Nociception (RN). However, these indices are mainly composed of parameters of PPG magnitude, which can be easily influenced by measuring conditions. The normalization method also has intrinsic drawbacks. On the other hand, modality of PPG is without these drawbacks.
Therefore, the aim of this thesis was to extract parameters from the modality of PPG and develop an index named Surgical Pleth Modal Index (SPMI) for monitoring nociception. The following are innovation and main parts of the thesis.
(1) Detection algorithm for critical points in PPG.
A detection algorithm was proposed, which used a searching window and combined the first-order, second-order derivatives and rule-based logic. The estimation of the algorithm show that when detecting signal containing artifacts, both sensitivity and positive predictivity of the algorithm were above 95%. The result proved the validation of the algorithm.
(2) The study on specificity and sensitivity of the PPG magnitude and modality.
According to the theory of Windkessel model, Decay time constant of descending limb (QRC), area ratio of descending limb (ARD), area ratio of ascending limb (ARA), area ratio of a total period (ART) and pulse beat interval (PBI) were proposed as modal parameters. PPG magnitude (PPGA), a magnitude parameter, was also studied.
In specificity study, relative variations of PPGA and ART were compared when blood perfusion, measuring position and body posture changed. Taking the two parameters as examples, the less variation of ART indicated that the modality of PPG was less influenced by measuring condition and more specific to nociception.
In sensitivity study, nociception was induced by tracheal intubation, and its different levels were achieved by different anti-nociception concentrations of remifentanil. The prediction probability was adopted to compare the sensitivity of all the parameters. When predicting intubation, the order of sensitivity according to prediction probability was PBI>ART>PPGA>ARD>ARA>QRC. The differences of performance between magnitude parameter and modal parameters were not obvious. When predicting nociception of different levels, the order of sensitivity was PBI> ART>ARA>ARD>QRC>PPGA. The performances of all the modal parameters were better than the magnitude parameter.
(3) The development of Surgical Pleth Modal Index
With multi-parametric approaches and multiple linear regression, SPMI was developed as SPMI=30-43×PBI+45×ART. The Spearman coefficients between SPMI and the remifentanil concentration before and during intubation was-0.30 and-0.52, respectively. Both were higher than SSI (-0.21). The prediction probability of SPMI predicting CSSA was 0.819, higher than 0.78 of RN.
In conclusion, this thesis dedicated to meet the utmost challenge of nociception monitoring. SPMI was proposed and based on the modality of PPG. The performance of SPMI was better than SSI and RN. SPMI would monitor nociception and guide anesthesia in a better way.
引文
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