Heart rate variability (HRV) is a well-established surrogate of cardiac and emotional health that reflects the balance between sympathetic and parasympathetic activity of the autonomic nervous system. We examined the impact of manipulating exhalation to inhalation ratio (E:I) on HRV, without altering the intrinsic breathing rate of healthy individuals. We hypothesized that a longer exhalation relative to inhalation (E:I > 1) would shift HRV metrics in a direction consistent with increased parasympathetic activity. Twenty-eight individuals (16 young [6M, age = 21–28];12 older adults [6M, age = 66–80]) completed a task during which they paced breathing according to their intrinsic respiratory rate, but altered onset of exhalation and inhalation according to 1:1 sound cue (equal exhalation and inhalation duration) or 2:1 cue (exhalation twice as long as inhalation). Paced 1:1 breathing followed these task conditions to examine residual effects. Estimates of actual E:I ratio based on thoracic movement were 1.08(0.16) for 1:1 task and 1.33(0.20) for 2:1 task, which were significantly different from one another. HRV metrics derived from electrocardiogram included root mean square of the successive differences between normal heartbeats (RMSSD) and high-frequency (HF) HRV. Analyses of HRV metrics by block showed that RMSSD and HF-HRV were higher in the 2:1 task condition compared to 1:1. Time series analysis showed that HF-HRV increased after the end of the 2:1 task block and remained elevated for four minutes. These findings suggest that longer duration of exhalation relative to inhalation, without altering breathing rate, acutely increased RMSSD and HF-HRV, consistent with enhancement of cardiac vagal tone.

中文翻译：

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呼吸过程中呼气与吸气比的增加会增强健康成年人的高频心率变异性

心率变异性 (HRV) 是心脏和情绪健康的公认替代指标，它反映了自主神经系统的交感神经和副交感神经活动之间的平衡。我们检查了操纵呼气与吸气比 (E:I) 对 HRV 的影响，而不改变健康个体的内在呼吸频率。我们假设相对于吸气（E:I > 1）更长的呼气会使 HRV 指标向与副交感神经活动增加一致的方向移动。28 人（16 名年轻人 [6M，年龄 = 21-28]；12 名老年人 [6M，年龄 = 66-80]）完成了一项任务，在此期间他们根据自身的呼吸频率调整呼吸，但改变了呼气的开始根据 1:1 声音提示（呼气和吸气持续时间相等）或 2 吸气：1 个提示（呼气时间是吸气时间的两倍）。以 1:1 的节奏呼吸遵循这些任务条件来检查残余影响。基于胸椎运动的实际 E:I 比估计为 1:1 任务的 1.08(0.16) 和 2:1 任务的 1.33(0.20)，两者之间存在显着差异。源自心电图的 HRV 指标包括正常心跳 (RMSSD) 和高频 (HF) HRV 之间连续差异的均方根。按块对 HRV 指标的分析表明，与 1:1 相比，2:1 任务条件下的 RMSSD 和 HF-HRV 更高。时间序列分析显示 HF-HRV 在 2:1 任务组结束后升高，并持续升高 4 分钟。这些发现表明，在不改变呼吸频率的情况下，相对于吸气而言，更长的呼气持续时间会急剧增加 RMSSD 和 HF-HRV，