Pfoh Jamie R, Tymko Michael M, Abrosimova Maria, Boulet Lindsey M, Foster Glen E, Bain Anthony R, Ainslie Philip N, Steinback Craig D, Bruce Christina D, Day Trevor A
Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada.
School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
Exp Physiol. 2016 Mar;101(3):432-47. doi: 10.1113/EP085498.
What is the central question of this study? We aimed to characterize the cardiorespiratory and cerebrovascular responses to transient and steady-state tests of the peripheral chemoreflex and to compare the hypoxic ventilatory responses (HVRs) between these tests. What is the main finding and its importance? The cardiovascular and cerebrovascular responses to transient tests were small in magnitude and short in duration. The steady-state isocapnic hypoxia test elicited a larger HVR than the transient 100% N(2) test, but the response magnitudes were correlated within individuals. The transient test of the HVR elicits fewer systemic effects than steady-state techniques and may have greater experimental utility than previously appreciated. Carotid chemoreceptors detect changes in arterial PO(2) and PCO(2), eliciting a peripheral chemoreflex (PCR). Steady-state (SS) hypoxia tests using dynamic end-tidal forcing (DEF) have been used to assess the hypoxic ventilatory response (HVR) but may be confounded by concomitant systemic effects. Transient tests of the PCR have also been developed but are not widely used, nor have the cardiovascular and cerebrovascular responses been characterized. We characterized the cardiorespiratory and cerebrovascular responses to transient tests of the PCR and compared the HVR between transient and SS-DEF tests. We hypothesized that the cardiovascular and cerebrovascular responses to the transient tests would be minimal and that the respiratory responses elicited from the transient and SS-DEF tests would be different in magnitude and not well correlated within individuals. Participants underwent five consecutive trials of two transient tests [three-breath 100% N(2) (TT-N(2)) and a single-breath 13% CO(2), in air] and two 10 min SS-DEF tests [isocapnic (SS-ISO) and poikilocapnic (SS-POI) hypoxia]. In response to the transient tests, heart rate, mean arterial pressure and the middle and posterior cerebral artery blood velocity increased (all P < 0.01), but responses were small (all <10%) and transient. Although the TT-N(2) and SS-POI tests elicited similar HVR magnitudes, they were not well correlated within individuals (r = 0.064, P = 0.79). The TT-N(2) test elicited a smaller HVR than the SS-ISO test, but they were correlated within individuals (r = 0.57, P = 0.008). Given that the transient tests exploit the temporal domain of the peripheral chemoreceptors and have minimal cardiovascular and cerebrovascular confounders, we suggest that they may have broader utility than previously appreciated.
本研究的核心问题是什么？我们旨在描述对周围化学反射的瞬态和稳态测试的心肺和脑血管反应，并比较这些测试之间的低氧通气反应（HVR）。主要发现及其重要性是什么？对瞬态测试的心血管和脑血管反应幅度小且持续时间短。稳态等碳酸血症低氧测试比瞬态100%氮气测试引发更大的HVR，但个体内反应幅度具有相关性。HVR的瞬态测试比稳态技术引发的全身效应更少，可能具有比以前认识到的更大的实验效用。颈动脉化学感受器检测动脉血氧分压和二氧化碳分压的变化，引发周围化学反射（PCR）。使用动态呼气末强制（DEF）的稳态（SS）低氧测试已用于评估低氧通气反应（HVR），但可能会受到伴随的全身效应的混淆。PCR的瞬态测试也已开发出来，但未被广泛使用，心血管和脑血管反应也未得到描述。我们描述了对PCR瞬态测试的心肺和脑血管反应，并比较了瞬态和SS-DEF测试之间的HVR。我们假设对瞬态测试的心血管和脑血管反应将最小，并且瞬态和SS-DEF测试引发的呼吸反应在幅度上会有所不同，且个体内相关性不佳。参与者连续进行了两项瞬态测试[三次呼吸100%氮气（TT-N₂）和一次呼吸13%二氧化碳，在空气中]和两项10分钟的SS-DEF测试[等碳酸血症（SS-ISO）和异碳酸血症（SS-POI）低氧]的五次连续试验。对瞬态测试的反应中，心率、平均动脉压以及大脑中动脉和后动脉血流速度增加（均P<0.01），但反应较小（均<10%）且是瞬态的。尽管TT-N₂和SS-POI测试引发的HVR幅度相似，但个体内相关性不佳（r = 0.064，P = 0.79）。TT-N₂测试引发的HVR比SS-ISO测试小，但个体内具有相关性（r = 0.57，P = 0.008）。鉴于瞬态测试利用了周围化学感受器的时间域，且心血管和脑血管混淆因素最小，我们认为它们可能具有比以前认识到的更广泛的效用。
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