Abstract：
UNASSIGNED: What is the central question of this study? Do cardiorespiratory experience-dependent effects (EDEs) differ between two different stimulus durations of acute isocapnic intermittent hypoxia (IHx; 5-min vs. 90-s cycles between hypoxia and normoxia)? What is the main finding and its importance? There was long-term facilitation in ventilation and blood pressure in both IHx protocols, but there was no evidence of progressive augmentation or post-hypoxia frequency decline. Not all EDEs described in animal models translate to acute isocapnic IHx responses in humans, and cardiorespiratory responses to 5-min versus 90-s on/off IHx protocols are largely similar.
UNASSIGNED: Peripheral respiratory chemoreceptors monitor breath-by-breath changes in arterial CO2 and O2 , and mediate ventilatory changes to maintain homeostasis. Intermittent hypoxia (IHx) elicits hypoxic ventilatory responses, with well-described experience-dependent effects (EDEs), derived mostly from animal work involving intermittent 5-min cycles of hypoxia and normoxia. These EDEs include post-hypoxia frequency decline (PHxFD), progressive augmentation (PA) and long-term facilitation (LTF). Comparisons of these EDEs between animal models and humans using similar IHx protocols are lacking. In addition, it is unknown whether shorter bouts of hypoxia, which may be more relevant to clinical conditions, elicit EDEs of similar magnitudes in humans. Respiratory (frequency, tidal volume and minute ventilation ( V ̇ I ) and cardiovascular (heart rate and mean arterial pressure (MAP)) variables were measured during and following two patterns of acute isocapnic IHx in 14 healthy human participants (four female): (1) 5 × 5 min and (2) 5 × 90 s on/off hypoxia. Participants\' end-tidal P O 2 was clamped at 45 Torr during hypoxia and 100 Torr during normoxia. We found that (1) PHxFD and PA were not present in either IHx pattern (P > 0.14), (2) LTF was present in V ̇ I following both 5-min (P < 0.001) and 90-s isocapnic IHx trials (P < 0.001), and (3) LTF was present in MAP following 5-min isocapnic IHx (P < 0.001), and trended towards significance following 90-s IHx (P = 0.058). We demonstrate that acute isocapnic IHx alone may not elicit all of the EDEs that have been described in animal models. Additionally, ventilatory LTF occurred regardless of the length of hypoxia-normoxia cycles.
UNASSIGNED: Peripheral respiratory chemoreceptors monitor breath-by-breath changes in arterial CO2 and O2 , and mediate ventilatory changes to maintain homeostasis. Intermittent hypoxia (IHx) elicits hypoxic ventilatory responses, with well-described experience-dependent effects (EDEs), derived mostly from animal work involving intermittent 5-min cycles of hypoxia and normoxia. These EDEs include post-hypoxia frequency decline (PHxFD), progressive augmentation (PA) and long-term facilitation (LTF). Comparisons of these EDEs between animal models and humans using similar IHx protocols are lacking. In addition, it is unknown whether shorter bouts of hypoxia, which may be more relevant to clinical conditions, elicit EDEs of similar magnitudes in humans. Respiratory (frequency, tidal volume and minute ventilation ( V ̇ I ) and cardiovascular (heart rate and mean arterial pressure (MAP)) variables were measured during and following two patterns of acute isocapnic IHx in 14 healthy human participants (four female): (1) 5 × 5 min and (2) 5 × 90 s on/off hypoxia. Participants\' end-tidal P O 2 was clamped at 45 Torr during hypoxia and 100 Torr during normoxia. We found that (1) PHxFD and PA were not present in either IHx pattern (P > 0.14), (2) LTF was present in V ̇ I following both 5-min (P < 0.001) and 90-s isocapnic IHx trials (P < 0.001), and (3) LTF was present in MAP following 5-min isocapnic IHx (P < 0.001), and trended towards significance following 90-s IHx (P = 0.058). We demonstrate that acute isocapnic IHx alone may not elicit all of the EDEs that have been described in animal models. Additionally, ventilatory LTF occurred regardless of the length of hypoxia-normoxia cycles.
摘要：
■这项研究的中心问题是什么？急性等二氧化碳间歇性缺氧的两种不同刺激持续时间之间的心肺体验依赖性效应（EDEs）是否不同（IHx；5分钟vs.低氧和常氧之间的90-s周期）？主要发现及其重要性是什么？两种IHx方案中的通气和血压均长期促进，但没有证据表明进行性增加或缺氧后频率下降.并非所有动物模型中描述的EDEs都会转化为人类的急性等二氧化碳IHx反应，5分钟和90秒开/关IHx方案的心肺反应在很大程度上相似。
■外周呼吸化学感受器监测动脉CO2和O2的逐次呼吸变化，并介导通气变化以维持体内平衡。间歇性缺氧（IHx）引起低氧通气反应，具有良好描述的经验依赖效应(EDEs)，主要来自涉及间歇性5分钟缺氧和常氧循环的动物工作。这些EDE包括缺氧后频率下降(PHxFD)，渐进增强(PA)和长期促进(LTF)。缺乏使用类似IHx方案的动物模型和人类之间的这些EDE的比较。此外,尚不清楚是否有较短的缺氧发作，这可能与临床状况更相关，在人类中引起相似量级的EDEs。呼吸（频率，在14名健康人参与者（4名女性）的两种急性等二氧化碳IHx模式期间和之后，测量了潮气量和每分钟通气量（VäI）和心血管（心率和平均动脉压（MAP））变量：（1）5×5分钟和（2）5×90s开/关缺氧。参与者的潮气末PO2在缺氧时被夹在45托，在常氧时被夹在100托。我们发现(1)PHxFD和PA均不存在于IHx模式中(P>0.14)，（2）在5分钟（P<0.001）和90s等二氧化碳IHx试验（P<0.001）后，LTF存在于VäI中，和（3）LTF存在于MAP后5分钟等二氧化碳IHx（P<0.001），在90-sIHx后有显著性趋势(P=0.058)。我们证明，单独的急性等二氧化碳IHx可能不会引起动物模型中描述的所有EDEs。此外,通气性LTF的发生与缺氧-常氧周期的长短无关。
■外周呼吸化学感受器监测动脉CO2和O2的逐次呼吸变化，并介导通气变化以维持体内平衡。间歇性缺氧（IHx）引起低氧通气反应，具有良好描述的经验依赖效应(EDEs)，主要来自涉及间歇性5分钟缺氧和常氧循环的动物工作。这些EDE包括缺氧后频率下降(PHxFD)，渐进增强(PA)和长期促进(LTF)。缺乏使用类似IHx方案的动物模型和人类之间的这些EDE的比较。此外,尚不清楚是否有较短的缺氧发作，这可能与临床状况更相关，在人类中引起相似量级的EDEs。呼吸（频率，在14名健康人参与者（4名女性）的两种急性等二氧化碳IHx模式期间和之后，测量了潮气量和每分钟通气量（VäI）和心血管（心率和平均动脉压（MAP））变量：（1）5×5分钟和（2）5×90s开/关缺氧。参与者的潮气末PO2在缺氧时被夹在45托，在常氧时被夹在100托。我们发现(1)PHxFD和PA均不存在于IHx模式中(P>0.14)，（2）在5分钟（P<0.001）和90s等二氧化碳IHx试验（P<0.001）后，LTF存在于VäI中，和（3）LTF存在于MAP后5分钟等二氧化碳IHx（P<0.001），在90-sIHx后有显著性趋势(P=0.058)。我们证明，单独的急性等二氧化碳IHx可能不会引起动物模型中描述的所有EDEs。此外,通气性LTF的发生与缺氧-常氧周期的长短无关。
