Horiuchi Masahiro, Endo Junko, Dobashi Shohei, Kiuchi Masataka, Koyama Katsuhiro, Subudhi Andrew W
Division of Human Environmental Science, Mount Fuji Research Institute, Japan.
Integrated Graduate School Department of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi, Japan.
Exp Physiol. 2016 Oct 1;101(10):1276-1284. doi: 10.1113/EP085789. Epub 2016 Sep 11.
What is the central question of this study? Acute hypoxia reduces dynamic cerebral autoregulation (dCA); however, it is unclear what level of hypoxia is necessary to exert this effect. We sought to investigate whether dCA would be reduced during progressive periods of normobaric hypoxia using a duplex Doppler ultrasound technique to evaluate the volumetric blood flow. What is the main finding and its importance? We showed that dCA decreased linearly as inspired O decreased from 21 to 12%. Additionally, symptoms of acute mountain sickness were related to changes in dCA. Our results may provide a sensitive and clinically relevant test to evaluate the risk of acute mountain sickness. Cerebral blood flow is maintained at relatively constant levels over a wide range of perfusion pressures via cerebral autoregulation (CA). Although acute hypoxia reduces dynamic CA, it is unclear what level of hypoxia is necessary to exert this effect. We evaluated dynamic CA during progressive normobaric hypoxia (∼1 h at each of 21, 18, 15 and 12% O ) using duplex ultrasonography to measure volumetric changes in common carotid artery blood flow of 11 healthy young men. Dynamic CA was evaluated by the thigh-cuff method and represented as the rate of regulation of vascular conductance. On a separate occasion, symptoms of acute mountain sickness were evaluated during 6 h of prolonged hypoxia (fractional inspired O of 14.1%) using the Lake Louise Questionnaire. Repeated-measures ANOVA with linear trend analysis indicated that dynamic CA decreased progressively as fractional inspired O was reduced (P < 0.001). Spearman rank order analysis revealed that symptoms of acute mountain sickness were related to changes in the rate of regulation of vascular conductance from 21 to 15% (r = -0.869, P = 0.006) and from 21 to 12% O (r = -0.648, P = 0.040), respectively. These results suggest that dynamic CA worsens with progressive hypoxia and that reductions in dynamic CA during moderate to severe hypoxia (<15% O ) may be related to the severity of acute mountain sickness.
本研究的核心问题是什么?急性低氧会降低动态脑自动调节功能(dCA);然而,尚不清楚需要何种程度的低氧才能产生这种效应。我们试图利用双功多普勒超声技术评估容积性血流,以研究在常压性低氧的进展期dCA是否会降低。主要发现及其重要性是什么?我们发现,随着吸入氧浓度从21%降至12%,dCA呈线性下降。此外,急性高原病的症状与dCA的变化有关。我们的结果可能为评估急性高原病风险提供一种敏感且与临床相关的检测方法。通过脑自动调节功能(CA),脑血流量在广泛的灌注压范围内维持在相对恒定的水平。虽然急性低氧会降低动态CA,但尚不清楚需要何种程度的低氧才能产生这种效应。我们使用双功超声检查测量11名健康年轻男性颈总动脉血流的容积变化,评估在常压性低氧进展期(分别在21%、18%、15%和12%氧浓度下各持续约1小时)的动态CA。通过大腿袖带法评估动态CA,并将其表示为血管传导率的调节速率。在另一个时间段,使用路易斯湖问卷评估在长时间低氧(吸入氧分数为14.1%)6小时期间的急性高原病症状。重复测量方差分析及线性趋势分析表明,随着吸入氧分数降低,动态CA逐渐下降(P<0.001)。Spearman等级分析显示,急性高原病症状分别与从21%至15%(r=-0.869,P=0.006)和从21%至12%氧浓度(r=-0.648,P=0.040)的血管传导率调节速率变化有关。这些结果表明,动态CA随着低氧进展而恶化,中度至重度低氧(<15%氧浓度)期间动态CA的降低可能与急性高原病的严重程度有关。