Facial cooling and peripheral chemoreflex mechanisms in humans
Facial cooling and peripheral chemoreflex mechanisms in humans
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DOI：
10.1111/j.1748-1716.2008.01876.x
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发表时间：
2008-10-01
影响因子：
6.3
通讯作者：
van de Borne, P.
中科院分区：
文献类型：
--
作者：
Argacha, J. F.;Xhaet, O.;van de Borne, P.
目的：动脉氧分压的降低激活外周化学感受器，其增加通气，并且在呼吸停止后降低心率。我们测试的假设，面部冷却促进这些外周chemoreflex mechanism.Methods：Chemoreflex控制评估的呼吸困难反应缺氧（10%O-2的N-2）和心动过缓的反应，自愿呼气末呼吸暂停的最大持续时间在12个年轻的，健康的受试者。我们记录了每分钟通气量、血红蛋白O-2饱和度、RR间期（QRS波群两个R波之间的时间）和RR间期的标准差（SDNN），这是整个研究中心脏迷走神经活动的标志。结果：冷空气使面部温度降低了11摄氏度（P < 0.0001），但在常氧期间不影响每分钟通气量。而面部降温可增加缺氧时的反应性（P < 0.05）。在有冷空气的缺氧性呼吸暂停期间，RR间期增加了呼吸暂停前平均RR的31 ± 8%，而在没有面部冷却的情况下，呼吸暂停前平均RR增加了17 ± 5%（P < 0.05）。尽管呼吸暂停持续时间相同且氧饱和度降低，但仍发生了这种增加。结论：面部降温可促进正常人外周化学感受器反射机制，并能增加低氧时的SDNN（P < 0.05）。此外，同时潜水反射和外周化学反射激活增强心脏迷走神经激活，并有利于呼吸停止后进一步心动过缓。
Aim: Reductions in arterial oxygen partial pressure activate the peripheral chemoreceptors which increase ventilation, and, after cessation of breathing, reduce heart rate. We tested the hypothesis that facial cooling facilitates these peripheral chemoreflex mechanisms.Methods: Chemoreflex control was assessed by the ventilatory response to hypoxia (10% O-2 in N-2) and the bradycardic response to voluntary end-expiratory apnoeas of maximal duration in 12 young, healthy subjects. We recorded minute ventilation, haemoglobin O-2 saturation, RR interval (the time between two R waves of the QRS complex) and the standard deviation of the RR interval (SDNN), a marker of cardiac vagal activity throughout the study. Measurements were performed with the subject's face exposed to air flow at 23 and 4 degrees C.Results: Cold air decreased facial temperature by 11 degrees C (P < 0.0001) but did not affect minute ventilation during normoxia. However, facial cooling increased the ventilatory response to hypoxia (P < 0.05). The RR interval increased by 31 +/- 8% of the mean RR preceding the apnoea during the hypoxic apnoeas in the presence of cold air, compared to 17 +/- 5% of the mean RR preceding the apnoea in the absence of facial cooling (P < 0.05). This increase occurred despite identical apnoea durations and reductions in oxygen saturation. Finally, facial cooling increased SDNN during normoxia and hypoxia, as well as during the apnoeas performed in hypoxic conditions (all P < 0.05).Conclusion: The larger ventilatory response to hypoxia suggests that facial cooling facilitates peripheral chemoreflex mechanisms in normal humans. Moreover, simultaneous diving reflex and peripheral chemoreflex activation enhances cardiac vagal activation, and favours further bradycardia upon cessation of breathing.