Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland.
Department of Anaesthesiology, Clinical Pharmacology, Intensive Care and Emergency Medicine, University of Geneva, Geneva, Switzerland.
Eur J Appl Physiol. 2021 Nov;121(11):3173-3187. doi: 10.1007/s00421-021-04769-3. Epub 2021 Aug 14.
We tested the vagal withdrawal concept for heart rate (HR) and cardiac output (CO) kinetics upon moderate exercise onset, by analysing the effects of vagal blockade on cardiovascular kinetics in humans. We hypothesized that, under atropine, the φ amplitude (A) for HR would reduce to nil, whereas the A for CO would still be positive, due to the sudden increase in stroke volume (SV) at exercise onset.
On nine young non-smoking men, during 0-80 W exercise transients of 5-min duration on the cycle ergometer, preceded by 5-min rest, we continuously recorded HR, CO, SV and oxygen uptake ([Formula: see text]O) upright and supine, in control condition and after full vagal blockade with atropine. Kinetics were analysed with the double exponential model, wherein we computed the amplitudes (A) and time constants (τ) of phase 1 (φ) and phase 2 (φ).
In atropine versus control, A for HR was strongly reduced and fell to 0 bpm in seven out of nine subjects for HR was practically suppressed by atropine in them. The A for CO was lower in atropine, but not reduced to nil. Thus, SV only determined A for CO in atropine. A did not differ between control and atropine. No effect on τ and τ was found. These patterns were independent of posture.
The results are fully compatible with the tested hypothesis. They provide the first direct demonstration that vagal blockade, while suppressing HR φ, did not affect φ of CO.
通过分析迷走神经阻断对人体心血管动力学的影响，我们测试了心率（HR）和心输出量（CO）动力学在中等运动起始时的迷走神经撤退概念。我们假设，在阿托品作用下，HR 的φ振幅（A）将降至零，而 CO 的 A 仍为正值，这是由于运动起始时心搏量（SV）的突然增加。
在 9 名年轻非吸烟男性中，在周期测功机上进行 5 分钟的 0-80 W 运动瞬变，之前有 5 分钟的休息，我们连续记录 HR、CO、SV 和耗氧量（[Formula: see text]O）直立和仰卧位，在对照条件下和完全迷走神经阻断后用阿托品。动力学用双指数模型进行分析，其中我们计算了相位 1（φ）和相位 2（φ）的振幅（A）和时间常数（τ）。
与对照相比，在阿托品中 HR 的 A 明显降低，在七名受试者中的 HR 降至 0 bpm，在他们中 HR 几乎被阿托品抑制。CO 的 A 在阿托品中较低，但未降至零。因此，SV 仅决定了阿托品中的 CO 的 A。A 在对照和阿托品之间没有差异。未发现 τ 和 τ 的影响。这些模式与姿势无关。
结果完全符合测试假设。它们首次直接证明，迷走神经阻断虽然抑制了 HR φ，但对 CO 的 φ 没有影响。
