Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States.
Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada.
Am J Physiol Regul Integr Comp Physiol. 2023 May 1;324(5):R625-R634. doi: 10.1152/ajpregu.00113.2022. Epub 2023 Mar 6.
During hypoxic exposure, humans with high-affinity hemoglobin (and compensatory polycythemia) have blunted increases in heart rate compared with healthy humans with typical oxyhemoglobin dissociation curves. This response may be associated with altered autonomic control of heart rate. Our hypothesis-generating study aimed to investigate cardiac baroreflex sensitivity and heart rate variability among nine humans with high-affinity hemoglobin [6 females, O partial pressure at 50% [Formula: see text] (P) = 16 ± 1 mmHg] compared with 12 humans with typical affinity hemoglobin (6 F, P = 26 ± 1 mmHg). Participants breathed normal room air for a 10-min baseline, followed by 20 min of isocapnic hypoxic exposure, designed to lower the arterial partial pressure O ([Formula: see text]) to ∼50 mmHg. Beat-by-beat heart rate and arterial blood pressure were recorded. Data were averaged in 5-min periods throughout the hypoxia exposure, beginning with the last 5 min of baseline in normoxia. Spontaneous cardiac baroreflex sensitivity and heart rate variability were determined using the sequence method and the time and frequency domain analyses, respectively. Cardiac baroreflex sensitivity was lower in humans with high-affinity hemoglobin than controls at baseline and during isocapnic hypoxic exposure (normoxia: 7 ± 4 vs. 16 ± 10 ms/mmHg, hypoxia minutes 15-20: 4 ± 3 vs. 14 ± 11 ms/mmHg; group effect: = 0.02, high-affinity hemoglobin vs. control, respectively). Heart rate variability calculated in both the time (standard deviation of the N-N interval) and frequency (low frequency) domains was lower in humans with high-affinity hemoglobin than in controls (all < 0.05). Our data suggest that humans with high-affinity hemoglobin may have attenuated cardiac autonomic function.
在低氧暴露期间，与具有典型氧合血红蛋白解离曲线的健康人类相比，具有高亲和力血红蛋白（和代偿性红细胞增多症）的人类的心率增加幅度较小。这种反应可能与心率自主控制的改变有关。我们的假设生成研究旨在调查 9 名具有高亲和力血红蛋白的人类（6 名女性，[Formula: see text]的氧分压为 16 ± 1 mmHg）和 12 名具有典型亲和力血红蛋白的人类（6 名女性，P = 26 ± 1 mmHg）之间的心脏压力感受器反射敏感性和心率变异性。参与者在基线时正常呼吸空气 10 分钟，然后进行 20 分钟的等碳酸低氧暴露，目的是将动脉血氧分压 ([Formula: see text]) 降低到约 50 mmHg。记录心率和动脉血压的逐拍变化。在低氧暴露期间，数据在 5 分钟的时间段内进行平均，从正常氧合的最后 5 分钟基线开始。使用序列法和时频域分析分别确定自发性心脏压力感受器反射敏感性和心率变异性。在基线和等碳酸低氧暴露期间（正常氧合：7 ± 4 对 16 ± 10 ms/mmHg，低氧分钟 15-20：4 ± 3 对 14 ± 11 ms/mmHg；组间效应： = 0.02，高亲和力血红蛋白与对照组相比），具有高亲和力血红蛋白的人类的心脏压力感受器反射敏感性低于对照组。在具有高亲和力血红蛋白的人类中，心率变异性在时间（NN 间期标准差）和频率（低频）两个域中均低于对照组（所有 < 0.05）。我们的数据表明，具有高亲和力血红蛋白的人类可能具有减弱的心脏自主功能。
