Bari Vlasta, Vaini Emanuele, De Maria Beatrice, Cairo Beatrice, Pistuddi Valeria, Ranucci Marco, Porta Alberto
Annu Int Conf IEEE Eng Med Biol Soc. 2018 Jul;2018:2780-2783. doi: 10.1109/EMBC.2018.8512782.
Baroreflex sensitivity (BRS) can be noninvasively assessed from heart period (HP) and arterial pressure (AP) variability series via the estimation of the gain of the transfer function (TF) in the low frequency (LF, 0.04-0.15 Hz) band. However, different strategies can be adopted to pick the value of the TF gain and different fiducial AP values can be considered. In this study we compared different strategies to reduce the TF gain into a unique maker: i) sampling the TF gain in correspondence of the maximum of the HP-AP squared coherence; ii) sampling the TF gain at the weighted average of the central frequencies of AP spectral components; iii) calculating the average of the TF gain in the LF band. Indexes were computed using alternatively systolic AP (SAP) or diastolic AP (DAP) series in combination with HP. Results were obtained in 129 patients undergoing coronary artery bypass graft surgery before (PRE) and after (POST) the induction of general anesthesia with propofol and remifentanil. The reduction of BRS during general anesthesia is expected as a result of overall depression of the cardiovascular control even in this group of pathological subjects already featuring a low BRS before general anesthesia induction. We found that the expected decrease of BRS was observed regardless of the strategy using DAP. Moreover, regardless of series (i.e., SAP or DAP), the sampling of TF gain at the weighted average of the central frequencies of the AP spectral components has the greatest statistical power in distinguishing the two experimental conditions. We recommend the use of this strategy in assessing BRS via TF analysis and a more frequent exploitation of the DAP series.
压力反射敏感性（BRS）可通过估计低频（LF，0.04 - 0.15Hz）频段传递函数（TF）的增益，从心动周期（HP）和动脉压（AP）变异性序列中进行无创评估。然而，可以采用不同的策略来选取TF增益值，并且可以考虑不同的基准AP值。在本研究中，我们比较了将TF增益简化为单一指标的不同策略：i）在HP - AP平方相干性最大值处采样TF增益；ii）在AP频谱成分中心频率的加权平均值处采样TF增益；iii）计算LF频段内TF增益的平均值。使用收缩压AP（SAP）或舒张压AP（DAP）序列与HP交替组合来计算指标。结果在129例接受冠状动脉搭桥手术的患者中获得，这些患者在使用丙泊酚和瑞芬太尼诱导全身麻醉前（PRE）和后（POST）进行了测量。即使在这组全身麻醉诱导前BRS就已经较低的病理受试者中，由于心血管控制的整体抑制，全身麻醉期间BRS降低也是预期的。我们发现，无论使用DAP的何种策略，均观察到了BRS的预期下降。此外，无论使用何种序列（即SAP或DAP），在AP频谱成分中心频率的加权平均值处采样TF增益在区分两种实验条件时具有最大的统计效力。我们建议在通过TF分析评估BRS时使用该策略，并更频繁地使用DAP序列。
