Chen Xiaoxiao, Mukkamala Ramakrishna
Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA.
Am J Physiol Heart Circ Physiol. 2008 Jan;294(1):H362-71. doi: 10.1152/ajpheart.01061.2007. Epub 2007 Nov 9.
Heart rate (HR) power spectral indexes are limited as measures of the cardiac autonomic nervous systems (CANS) in that they neither offer an effective marker of the beta-sympathetic nervous system (SNS) due to its overlap with the parasympathetic nervous system (PNS) in the low-frequency (LF) band nor afford specific measures of the CANS due to input contributions to HR [e.g., arterial blood pressure (ABP) and instantaneous lung volume (ILV)]. We derived new PNS and SNS indexes by multisignal analysis of cardiorespiratory variability. The basic idea was to identify the autonomically mediated transfer functions relating fluctuations in ILV to HR (ILV-->HR) and fluctuations in ABP to HR (ABP-->HR) so as to eliminate the input contributions to HR and then separate each estimated transfer function in the time domain into PNS and SNS indexes using physiological knowledge. We evaluated these indexes with respect to selective pharmacological autonomic nervous blockade in 14 humans. Our results showed that the PNS index derived from the ABP-->HR transfer function was correctly decreased after vagal and double (vagal + beta-sympathetic) blockade (P < 0.01) and did not change after beta-sympathetic blockade, whereas the SNS index derived from the same transfer function was correctly reduced after beta-sympathetic blockade in the standing posture and double blockade (P < 0.05) and remained the same after vagal blockade. However, this SNS index did not significantly decrease after beta-sympathetic blockade in the supine posture. Overall, these predictions were better than those provided by the traditional high-frequency (HF) power, LF-to-HF ratio, and normalized LF power of HR variability.
心率（HR）功率谱指数作为心脏自主神经系统（CANS）的测量指标存在局限性，因为它们既不能有效标记β-交感神经系统（SNS），这是由于其在低频（LF）波段与副交感神经系统（PNS）重叠，也不能提供CANS的具体测量指标，因为心率还受到其他因素的影响[例如动脉血压（ABP）和瞬时肺容积（ILV）]。我们通过对心肺变异性进行多信号分析得出了新的PNS和SNS指数。基本思路是确定与ILV波动与HR（ILV→HR）以及ABP波动与HR（ABP→HR）相关的自主调节传递函数，以消除对HR的输入贡献，然后利用生理学知识在时域中将每个估计的传递函数分离为PNS和SNS指数。我们在14名受试者中针对选择性药理学自主神经阻滞对这些指数进行了评估。我们的结果表明，源自ABP→HR传递函数的PNS指数在迷走神经阻滞和双重（迷走神经+β-交感神经）阻滞后正确降低（P<0.01），在β-交感神经阻滞后没有变化，而源自相同传递函数的SNS指数在站立姿势下进行β-交感神经阻滞后和双重阻滞后正确降低（P<0.05），在迷走神经阻滞后保持不变。然而，在仰卧姿势下进行β-交感神经阻滞后，该SNS指数没有显著降低。总体而言，这些预测比传统的高频（HF）功率、LF与HF比值以及HR变异性的归一化LF功率所提供的预测更好。
