Marchi Andrea, Bari Vlasta, De Maria Beatrice, Esler Murray, Lambert Elisabeth, Baumert Mathias, Porta Alberto
Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy; Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy;
Department of Biomedical Sciences for Health, University of Milan, Italy;
Am J Physiol Regul Integr Comp Physiol. 2016 Jun 1;310(11):R1134-43. doi: 10.1152/ajpregu.00541.2015. Epub 2016 Mar 23.
Muscle sympathetic nerve activity (MSNA) variability is traditionally computed through a low-pass filtering procedure that requires normalization. We proposed a new beat-to-beat MSNA variability computation that preserves dimensionality typical of an integrated neural discharge (i.e., bursts per unit of time). The calibrated MSNA (cMSNA) variability technique is contrasted with the traditional uncalibrated MSNA (ucMSNA) version. The powers of cMSNA and ucMSNA variabilities in the low-frequency (LF, from 0.04 to 0.15 Hz) band were computed with those of the heart period (HP) of systolic and diastolic arterial pressure (SAP and DAP, respectively) in seven healthy subjects (age, 20-28 years; median, 22 years; 5 women) during a graded head-up tilt. Subjects were sequentially tilted at 0°, 20°, 30°, 40°, and 60° table inclinations. The LF powers of ucMSNA and HP variabilities were expressed in normalized units (LFnu), whereas all remaining spectral markers were expressed in absolute units. We found that 1) the LF power of cMSNA variability was positively correlated with tilt angle, whereas the LFnu power of the ucMSNA series was uncorrelated; 2) the LF power of cMSNA variability was correlated with LF powers of SAP and DAP, LFnu power of HP and noradrenaline concentration, whereas the relationship of the LFnu power of ucMSNA variability to LF powers of SAP and DAP was weaker and that to LFnu power of HP was absent; and 3) the stronger relationship of cMSNA variability to SAP and DAP spectral markers compared with the ucMSNA series was confirmed individually. The cMSNA variability appears to be more suitable in describing sympathetic control in humans than traditional ucMSNA variability.
肌肉交感神经活动（MSNA）变异性传统上是通过需要归一化的低通滤波程序来计算的。我们提出了一种新的逐搏MSNA变异性计算方法，该方法保留了综合神经放电的典型维度（即单位时间内的爆发次数）。将校准后的MSNA（cMSNA）变异性技术与传统的未校准MSNA（ucMSNA）版本进行对比。在7名健康受试者（年龄20 - 28岁；中位数22岁；5名女性）进行分级头高位倾斜期间，计算了cMSNA和ucMSNA变异性在低频（LF，0.04至0.15 Hz）频段的功率，以及收缩期和舒张期动脉压（分别为SAP和DAP）的心动周期（HP）的功率。受试者依次在0°、20°、30°、40°和60°的台面倾斜角度下倾斜。ucMSNA和HP变异性的LF功率以归一化单位（LFnu）表示，而所有其余频谱标记均以绝对单位表示。我们发现：1）cMSNA变异性的LF功率与倾斜角度呈正相关，而ucMSNA系列的LFnu功率无相关性；2）cMSNA变异性的LF功率与SAP和DAP的LF功率、HP的LFnu功率以及去甲肾上腺素浓度相关，而ucMSNA变异性的LFnu功率与SAP和DAP的LF功率之间的关系较弱，与HP的LFnu功率无关系；3）与ucMSNA系列相比，cMSNA变异性与SAP和DAP频谱标记之间更强的关系在个体中得到了证实。与传统的ucMSNA变异性相比，cMSNA变异性似乎更适合描述人体的交感神经控制。
