Noh Yeonsik, Posada-Quintero Hugo F, Bai Yan, White Joseph, Florian John P, Brink Peter R, Chon Ki H
Department of Electrical and Computer Engineering, College of Nursing, University of Massachusetts, Amherst, MA, United States.
Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States.
Front Physiol. 2018 Feb 27;9:110. doi: 10.3389/fphys.2018.00110. eCollection 2018.
Prolonged and high pressure diving may lead to various physiological changes including significant alterations of autonomic nervous system (ANS) activity that may be associated with altered physical performance, decompression sickness, or central nervous system oxygen toxicity. Ideally, researchers could elucidate ANS function before, during, and after dives that are most associated with altered function and adverse outcomes. However, we have a limited understanding of the activities of the ANS especially during deeper prolonged SCUBA diving because there has never been a convenient way to collect physiological data during deep dives. This work is one of the first studies which was able to collect electrocardiogram (ECG) data from SCUBA divers at various depths (33, 66, 99, 150, and 200 ftsw; equivalent to 10.05, 20.10, 30.17, 45.72, and 60.96 m of salt water, respectively) breathing different gas mixtures (air, nitrox and trimix). The aim of this study was to shed light on cardiac ANS behavior during dives, including deep dives. With the aid of dry suits, a Holter monitor that could handle the pressure of a 200 ft. dive, and a novel algorithm that can provide a useful assessment of the ANS from the ECG signal, we investigated the effects of SCUBA dives with different time durations, depths and gas mixtures on the ANS. Principal dynamic mode (PDM) analysis of the ECG, which has been shown to provide accurate separation of the sympathetic and parasympathetic dynamics, was employed to assess the difference of ANS behavior between baseline and diving conditions of varying depths and gas mixtures consisting of air, nitrox and trimix. For all depths and gas mixtures, we found consistent dominance in the parasympathetic activity and a concomitant increase of the parasympathetic dynamics with increasing diving duration and depth. For 33 and 66 ft. dives, we consistently found significant decreases in heart rates (HR) and concomitant increases in parasympathetic activities as estimated via the PDM and root mean square of successive differences (RMSSD) for all time intervals (from the first 5 min to the last 30 min) at the bottom depth when compared to the baseline depth at sea level. The sympathetic dynamics did not change with dive duration or gas mixtures, but at the 150 and 200 ft. dives, we found a significant increase in the sympathetic dynamics in addition to the elevated parasympathetic dynamics when compared to baseline The power spectral density (PSD) measures such as the low frequency (LF), high frequency (HF) and its ratio, and approximate entropy (ApEn) indices were not as consistent when compared to PDM-derived parasympathetic dynamics and RMSSD index.
长时间高压潜水可能导致各种生理变化，包括自主神经系统（ANS）活动的显著改变，这可能与身体机能改变、减压病或中枢神经系统氧中毒有关。理想情况下，研究人员可以在与功能改变和不良后果最相关的潜水之前、期间和之后阐明ANS功能。然而，我们对ANS的活动了解有限，尤其是在更深的长时间水肺潜水中，因为在深潜过程中从未有过方便的方法来收集生理数据。这项工作是首批能够从水肺潜水员在不同深度（33、66、99、150和200英尺海水深度；分别相当于10.05、20.10、30.17、45.72和60.96米的盐水深度）呼吸不同气体混合物（空气、氮氧混合气和 Trimix 混合气）时收集心电图（ECG）数据的研究之一。本研究的目的是阐明潜水期间，包括深潜期间心脏ANS的行为。借助干式潜水服、能够承受200英尺潜水压力的动态心电图监测仪以及一种可以从ECG信号中对ANS进行有效评估的新算法，我们研究了不同时长、深度和气体混合物的水肺潜水对ANS的影响。采用已被证明能准确分离交感和副交感神经动力学的ECG主动态模式（PDM）分析，来评估在不同深度以及由空气、氮氧混合气和Trimix混合气组成的气体混合物的潜水条件下，基线与潜水条件之间ANS行为的差异。对于所有深度和气体混合物，我们发现副交感神经活动始终占主导地位，并且随着潜水时长和深度的增加，副交感神经动力学随之增加。对于33英尺和66英尺的潜水，与海平面基线深度相比，我们始终发现，在所有时间间隔（从最初5分钟到最后30分钟）的海底深度，通过PDM和逐次差值均方根（RMSSD）估计的心率（HR）显著下降，同时副交感神经活动增加。交感神经动力学不会随潜水时长或气体混合物而变化，但在150英尺和200英尺的潜水时，与基线相比，除了副交感神经动力学升高外，我们还发现交感神经动力学显著增加。与基于PDM得出的副交感神经动力学和RMSSD指数相比，诸如低频（LF）、高频（HF）及其比值以及近似熵（ApEn）指数等功率谱密度（PSD）测量结果并不那么一致。
