Bourdillon Nicolas, Yazdani Sasan, Subudhi Andrew W, Lovering Andrew T, Roach Robert C, Vesin Jean-Marc, Kayser Bengt
Institute of Sports Sciences of the University of Lausanne, Lausanne, Switzerland.
Applied Signal Processing Group, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Front Physiol. 2018 Jun 21;9:767. doi: 10.3389/fphys.2018.00767. eCollection 2018.
Baroreflex sensitivity (BRS) is essential to ensure rapid adjustment to variations in blood pressure (BP). Little is known concerning the adaptive responses of BRS during acclimatization to high altitude at rest and during exercise. Twenty-one healthy sea-level residents were tested near sea level (SL, 130 m), the 1st (ALT1) and 16th day (ALT16) at 5,260 m using radial artery catheterization. BRS was calculated using the sequence method (direct interpretation of causal link between BP and heartrate). At rest, subjects breathed a hyperoxic mixture (250 mmHg O, end tidal) to isolate the preponderance of CO chemoreceptors. End-tidal CO varied from 20 to 50 mmHg to assess peripheral chemoreflex. Rebreathing provoked incremental increase in CO, increasing BP to assess baroreflex. During incremental cycling exercise to exhaustion, subjects breathed room air. Resting BRS decreased in ALT1 which was exacerbated in ALT16. This decrease in ALT1 was reversible upon additional inspired CO, but not in ALT16. BRS decrease during exercise was greater and occurred at lower workloads in ALT1 compared to SL. At ALT16, this decrease returned toward SL values. This study is the first to report attenuated BRS in acute hypoxia, exacerbated in chronic hypoxia. In ALT1, hypocapnia triggered BRS reduction whilst in ALT16 resetting of chemoreceptor triggered BRS reduction. The exercise BRS resetting was impaired in ALT1 but normalized in ALT16. These BRS decreases indicate decreased control of BP and may explain deteriorations of cardiovascular status during exposure to high altitude.
压力反射敏感性（BRS）对于确保快速适应血压（BP）变化至关重要。关于在静息和运动状态下适应高海拔过程中BRS的适应性反应，人们知之甚少。21名健康的海平面居民在海平面附近（SL，130米）、海拔5260米的第1天（ALT1）和第16天（ALT16）接受了桡动脉插管测试。使用序列法（直接解读血压与心率之间的因果关系）计算BRS。静息时，受试者呼吸高氧混合气（呼气末氧分压250mmHg）以分离CO化学感受器的优势作用。呼气末CO分压从20至50mmHg变化以评估外周化学反射。再呼吸使CO逐渐增加，使血压升高以评估压力反射。在递增式自行车运动至疲劳过程中，受试者呼吸室内空气。静息BRS在ALT1时降低，在ALT16时加剧。ALT1时的这种降低在额外吸入CO后可逆，但在ALT16时不可逆。与SL相比，运动期间BRS的降低在ALT1时更大且发生在较低工作量时。在ALT16时，这种降低恢复至SL值。本研究首次报告急性缺氧时BRS减弱，慢性缺氧时加剧。在ALT1时，低碳酸血症引发BRS降低，而在ALT16时化学感受器重置引发BRS降低。运动时BRS重置在ALT1时受损，但在ALT16时恢复正常。这些BRS降低表明对血压的控制减弱，可能解释了暴露于高海拔期间心血管状态的恶化。
