Houssière Anne, Najem Boutaina, Cuylits Nicolas, Cuypers Sophie, Naeije Robert, van de Borne Philippe
Department of Physiology, Erasme Hospital, Brussels, Belgium.
Am J Physiol Heart Circ Physiol. 2006 Jul;291(1):H210-5. doi: 10.1152/ajpheart.01168.2005.
Peripheral chemoreflex inhibition with hyperoxia decreases sympathetic nerve traffic to muscle circulation [muscle sympathetic nerve activity (MSNA)]. Hyperoxia also decreases lactate production during exercise. However, hyperoxia markedly increases the activation of sensory endings in skeletal muscle in animal studies. We tested the hypothesis that hyperoxia increases the MSNA and mean blood pressure (MBP) responses to isometric exercise. The effects of breathing 21% and 100% oxygen at rest and during isometric handgrip at 30% of maximal voluntary contraction on MSNA, heart rate (HR), MBP, blood lactate (BL), and arterial O2 saturation (SaO2) were determined in 12 healthy men. The isometric handgrips were followed by 3 min of postexercise circulatory arrest (PE-CA) to allow metaboreflex activation in the absence of other reflex mechanisms. Hyperoxia lowered resting MSNA, HR, MBP, and BL but increased Sa(O2) compared with normoxia (all P < 0.05). MSNA and MBP increased more when exercise was performed in hyperoxia than in normoxia (MSNA: hyperoxic exercise, 255 +/- 100% vs. normoxic exercise, 211 +/- 80%, P = 0.04; and MBP: hyperoxic exercise, 33 +/- 9 mmHg vs. normoxic exercise, 26 +/- 10 mmHg, P = 0.03). During PE-CA, MSNA and MBP remained elevated (both P < 0.05) and to a larger extent during hyperoxia than normoxia (P < 0.05). Hyperoxia enhances the sympathetic and blood pressure (BP) reactivity to metaboreflex activation. This is due to an increase in metaboreflex sensitivity by hyperoxia that overrules the sympathoinhibitory and BP lowering effects of chemoreflex inhibition. This occurs despite a reduced lactic acid production.
高氧对外周化学反射的抑制作用可减少交感神经向肌肉循环的传出活动[肌肉交感神经活动（MSNA）]。高氧还可减少运动期间的乳酸生成。然而，在动物研究中，高氧会显著增加骨骼肌感觉末梢的激活。我们检验了这样一个假设：高氧会增强MSNA以及平均血压（MBP）对等长运动的反应。我们测定了12名健康男性在静息状态下以及在最大自主收缩量30%的等长握力运动期间呼吸21%和100%氧气时对MSNA、心率（HR）、MBP、血乳酸（BL）和动脉血氧饱和度（SaO2）的影响。等长握力运动后进行3分钟的运动后循环停滞（PE-CA），以在无其他反射机制的情况下激活代谢反射。与常氧相比，高氧降低了静息状态下的MSNA、HR、MBP和BL，但提高了SaO2（所有P<0.05）。与常氧运动相比，高氧运动时MSNA和MBP的增加幅度更大（MSNA：高氧运动时为255±100%，常氧运动时为211±80%，P=0.04；MBP：高氧运动时为33±9 mmHg，常氧运动时为26±10 mmHg，P=0.03）。在PE-CA期间，MSNA和MBP仍保持升高（均P<0.05），且高氧时升高幅度大于常氧（P<0.05）。高氧增强了对代谢反射激活的交感神经和血压（BP）反应性。这是由于高氧增加了代谢反射敏感性，从而抵消了化学反射抑制的交感抑制和血压降低作用。尽管乳酸生成减少，但这种情况仍会发生。
