Norwegian School of Veterinary Science, Department of Production Animal Clinical Sciences, P.O. Box 8146 Dep., NO-0033 Oslo, Norway.
Physiol Behav. 2010 Aug 4;101(1):74-80. doi: 10.1016/j.physbeh.2010.04.018. Epub 2010 May 5.
The objective assessment of pain is difficult in animals and humans alike. Detrended fluctuation analysis (DFA) is a method which extracts "hidden" information from heart rate time series, and may offer a novel way of assessing the subjective experience associated with pain. The aim of this study was to investigate whether any fractal differences could be detected in heart rate time series of sheep due to the infliction of ischaemic pain. Heart rate variability (HRV) was recorded continuously in five ewes during treatment sequences of baseline, intervention and post-intervention for up to 60 min. Heart rate time series were subjected to a DFA, and the median of the scaling coefficients (alpha) was found to be alpha=1.10 for the baseline sequences, 1.01 for the intervention sequences and 1.00 for the post-intervention sequences. The complexity in the regulation of heartbeats decreased between baseline and intervention (p approximately 0.03) and baseline and post-intervention (p approximately 0.01), indicating reperfusion pain and nociceptive sensitization in the post-intervention sequence. Random time series based on Gaussian white noise were generated, with similar mean and variance to the HRV sequences. No difference was found between these series (p approximately 0.28), pointing to a true difference in complexity in the original data. We found no difference in the scaling coefficient alpha between the different treatments, possibly due to the small sample size or a fear induced sympathetic arousal during test day 1 confounding the results. The decrease in the scaling coefficient alpha may be due to sympathetic activation and vagal withdrawal. DFA of heart rate time series may be a useful method to evaluate the progressive shift of cardiac regulation toward sympathetic activation and vagal withdrawal produced by pain or negative emotional responses such as fear.
疼痛的客观评估在动物和人类中都很困难。去趋势波动分析（DFA）是一种从心率时间序列中提取“隐藏”信息的方法，可能为评估与疼痛相关的主观体验提供一种新方法。本研究旨在探讨是否可以检测到由于缺血性疼痛引起的绵羊心率时间序列中的任何分形差异。在长达 60 分钟的基础期、干预期和干预后期间，连续记录了五只母羊的心率变异性（HRV）。对心率时间序列进行了 DFA，发现基线序列的中位数标度系数（alpha）为 1.10，干预序列为 1.01，干预后序列为 1.00。心跳调节的复杂性在基线和干预之间（p 约为 0.03）以及基线和干预后（p 约为 0.01）之间降低，表明干预后序列中存在再灌注疼痛和伤害感受敏化。基于高斯白噪声生成了随机时间序列，其均值和方差与 HRV 序列相似。这些序列之间没有差异（p 约为 0.28），表明原始数据的复杂性存在真实差异。我们发现在不同处理之间的标度系数 alpha 没有差异，这可能是由于样本量小，或者在测试日 1 期间由于恐惧引起的交感神经兴奋混淆了结果。标度系数 alpha 的降低可能是由于交感神经激活和迷走神经撤退。心率时间序列的 DFA 可能是一种有用的方法，可以评估疼痛或负面情绪反应（如恐惧）引起的心脏调节向交感神经激活和迷走神经撤退的渐进转变。
