Martino Paul F, Miller Daniel P, Miller Justin R, Allen Michael T, Cook-Snyder Denise R, Handy Justin D, Servatius Richard J
Biology Department, Carthage College, Kenosha, WI, United States.
Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States.
Front Neurosci. 2020 Nov 13;14:588813. doi: 10.3389/fnins.2020.588813. eCollection 2020.
Behaviorally inhibited (BI) temperament is marked by heightened behavioral sensitivity to environmental threats. The degree to which threat sensitivity is reflected in cardiorespiratory responses has been relatively unexplored. Female college students were exposed to modest hypercapnia (7.0% CO) or ambient air (AA) while engaging in a computerized task with cued reinforcement features. All physiological variables except for blood pressure were processed in 4 min epochs corresponding to pre-exposure, exposure, and post-exposure. Primary respiratory measures were respiratory frequency (f), tidal volume (V), and minute ventilation (V). Electrocardiograms (ECGs) were processed using ARTiiFACT software with resultant heart rate variability (HRV) measures in the frequency domain and time domain. Consistent with the literature, modest hypercapnia increased V, F, and V. No differences in respiratory parameters were detected between BI and non-behaviorally inhibited individuals (NI). For HRV in the time domain, RMSSD and NN50 values increased during CO inhalation which then returned to pre-exposure levels after CO cessation. Hypercapnia increased high frequency (HF) power which then recovered. BI exhibited reduced low frequency (LF) power during the pre-exposure period. For NI, LF power reduced over the subsequent phases ameliorating differences between BI and NI. Hypercapnia improved the task performance of BI. This is the largest study of female reactivity to hypercapnia and associated HRV to date. In general, hypercapnia increased time domain HRV and HF power, suggesting a strong vagal influence. Those expressing BI exhibited similar respiratory and HRV reactivity to NI despite inherently reduced LF power. Although 7% CO represents a mild challenge to the respiratory and cardiovascular systems, it is nonetheless sufficient to explore inherent difference in stress reactivity in those vulnerable to develop anxiety disorders.
行为抑制（BI）气质的特点是对环境威胁的行为敏感性增强。威胁敏感性在心肺反应中的体现程度相对尚未得到充分研究。女大学生在进行具有提示强化特征的计算机任务时，暴露于适度的高碳酸血症（7.0%二氧化碳）或环境空气（AA）中。除血压外，所有生理变量均在对应于暴露前、暴露和暴露后的4分钟时间段内进行处理。主要呼吸指标为呼吸频率（f）、潮气量（V）和分钟通气量（V）。心电图（ECG）使用ARTiiFACT软件进行处理，得出频域和时域中的心率变异性（HRV）指标。与文献一致，适度的高碳酸血症增加了V、f和V。在BI个体和非行为抑制个体（NI）之间未检测到呼吸参数的差异。对于时域中的HRV，在吸入二氧化碳期间，RMSSD和NN50值增加，然后在停止吸入二氧化碳后恢复到暴露前水平。高碳酸血症增加了高频（HF）功率，随后恢复。BI在暴露前期表现出低频（LF）功率降低。对于NI，LF功率在随后阶段降低，缩小了BI和NI之间的差异。高碳酸血症改善了BI的任务表现。这是迄今为止关于女性对高碳酸血症和相关HRV反应性的最大规模研究。总体而言，高碳酸血症增加了时域HRV和HF功率，表明有强烈的迷走神经影响。尽管LF功率固有降低，但表现出BI的个体与NI表现出相似的呼吸和HRV反应性。虽然7%的二氧化碳对呼吸和心血管系统构成轻度挑战，但它仍足以探索那些易患焦虑症的个体在应激反应性方面的内在差异。
