Centro Universitario de Defensa (CUD), Academia General Militar (AGM), Zaragoza, Spain; BSICoS Group, Aragón Institute of Engineering Research (I3A), IIS Aragón, University of Zaragoza, Zaragoza, Spain.
Department of Biomedical Engineering, University of Connecticut, Storrs CT, USA.
Comput Methods Programs Biomed. 2022 Feb;214:106527. doi: 10.1016/j.cmpb.2021.106527. Epub 2021 Nov 19.
an evaluation of Principal Dynamic Mode (PDM) and Orthogonal Subspace Projection (OSP) methods to characterize the Autonomic Nervous System (ANS) response in three different hyperbaric environments was performed.
ECG signals were recorded in two different stages (baseline and immersion) in three different hyperbaric environments: (a) inside a hyperbaric chamber, (b) in a controlled sea immersion, (c) in a real reservoir immersion. Time-domain parameters were extracted from the RR series of the ECG. From the Heart Rate Variability signal (HRV), classic Power Spectral Density (PSD), PDM (a non-linear analysis of HRV which is able to separate sympathetic and parasympathetic activities) and OSP (an analysis of HRV which is able to extract the respiratory component) methods were used to assess the ANS response.
PDM and OSP parameters follows the same trend when compared to the PSD ones for the hyperbaric chamber dataset. Comparing the three hyperbaric scenarios, significant differences were found: i) heart rate decreased and RMSSD increased in the hyperbaric chamber and the controlled dive, but they had the opposite behavior during the uncontrolled dive; ii) power in the OSP respiratory component was lower than power in the OSP residual component in cases a and c; iii) PDM and OSP methods showed a significant increase in sympathetic activity during both dives, but parasympathetic activity increased only during the uncontrolled dive.
PDM and OSP methods could be used as an alternative measurement of ANS response instead of the PSD method. OSP results indicate that most of the variation in the heart rate variability cannot be described by changes in the respiration, so changes in ANS response can be assigned to other factors. Time-domain parameters reflect vagal activation in the hyperbaric chamber and in the controlled dive because of the effect of pressure. In the uncontrolled dive, sympathetic activity seems to be dominant, due to the effects of other factors such as physical activity, the challenging environment, and the influence of breathing through the scuba mask during immersion. In sum, a careful description of the changes in all the possible factors that could affect the ANS response between baseline and immersion stages in hyperbaric environments is needed for better interpretation of the results.
评估主要动态模式（PDM）和正交子空间投影（OSP）方法，以描述在三种不同高压环境下自主神经系统（ANS）的反应。
在三种不同的高压环境中（a）高压室内部，（b）受控海水浸泡，（c）实际水库浸泡，在两个不同阶段（基线和浸泡）记录心电图（ECG）信号。从心电图的 RR 系列中提取时域参数。从心率变异性信号（HRV）中，使用经典的功率谱密度（PSD）、PDM（HRV 的非线性分析，能够分离交感和副交感活动）和 OSP（HRV 的分析，能够提取呼吸分量）方法来评估 ANS 的反应。
与 PSD 方法相比，PDM 和 OSP 参数在高压室数据集上呈现出相同的趋势。比较三种高压环境，发现有显著差异：i）在高压室和受控潜水时心率降低，RMSSD 增加，但在非受控潜水时则相反；ii）在情况 a 和 c 中，OSP 呼吸分量的功率低于 OSP 剩余分量的功率；iii）PDM 和 OSP 方法在两次潜水时均显示交感活动显著增加，但副交感活动仅在非受控潜水时增加。
PDM 和 OSP 方法可以作为替代 PSD 方法来测量 ANS 反应。OSP 结果表明，心率变异性的大部分变化不能用呼吸变化来描述，因此 ANS 反应的变化可以归因于其他因素。在高压室和受控潜水时，时域参数反映了迷走神经的激活，这是由于压力的影响。在非受控潜水时，由于物理活动、挑战性环境以及潜水时通过水肺面具呼吸的影响等其他因素的影响，交感活动似乎占主导地位。总之，需要仔细描述高压环境中基线和浸泡阶段之间可能影响 ANS 反应的所有因素的变化，以便更好地解释结果。
