Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing
Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing
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DOI：
10.1152/japplphysiol.00906.2006
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发表时间：
2007-03-01
影响因子：
3.3
通讯作者：
Levine, Benjamin D.
中科院分区：
文献类型：
--
作者：
Claassen, Jurgen A. H. R.;Zhang, Rong;Levine, Benjamin D.
临床经颅多普勒评估脑血管反应性（CVMR）使用稳态条件下脑血流速度（CBFV）与潮气末CO2（PETCO 2）的线性回归。然而，脑血流量（CBF）-PETCO 2的关系是非线性的，即使在CO2的中度变化。此外，CBF在高碳酸血症期间通过动脉血压（ABP）的增加而增加。我们使用了一种改良的再呼吸方案来估计CBFV和PETCO 2在短暂的逐呼吸变化期间的CVMR。10名健康受试者（6名男性）进行了15秒的过度通气，然后进行5分钟的再呼吸，补充O-2以维持动脉血氧饱和度恒定。为了尽量减少ABP变化对CVMR估计的影响，计算脑血管传导指数（CVCi）。通过线性和非线性逻辑回归来量化CBFV-PETCO 2和CVCi-PETCO 2关系。在三名受试者中，记录了肌肉交感神经活动。从过度通气到再呼吸，PETCO 2（20-61 Torr）、CBFV（基线的-44至+104%）、CVCi（-39至+64%）和ABP（-19至+23%）发生了显著变化（均P < 0.01）。高碳酸血症时，肌肉交感神经活动增加446%。CVCi与PETCO 2的线性回归斜率不如CBFV（3与5%/Torr; P = 0.01）。CBF-PETCO 2（r（2）= 0.97）和CVC 1-PETCO 2（r（2）= 0.93）的Logistic回归上级线性回归（r（2）= 0.91，r（2）= 0.85; P = 0.01）。PETCO 2为40-50 Torr时，CVMR最大（6-8%/Torr）。总之，CBFV和CVCi对PETCO 2瞬时变化的响应可以通过非线性逻辑函数来描述，表明CVMR估计在从低碳酸血症到高碳酸血症的范围内变化。此外，CVC 1-PETCO 2关系的定量可以最大限度地减少ABP变化对CVMR估计的影响。所开发的方法提供了在二氧化碳瞬时逐次呼吸变化下对CVMR的深入了解。
Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO2 ( PETCO2) under steady-state conditions. However, the cerebral blood flow (CBF)-PETCO2 relationship is nonlinear, even for moderate changes in CO2. Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and PETCO2. Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O-2 to maintain arterial oxygen saturation constant. To minimize effects of changes in ABP on CVMR estimation, cerebrovascular conductance index (CVCi) was calculated. CBFV-PETCO2 and CVCi-PETCO2 relationships were quantified by both linear and nonlinear logistic regression. In three subjects, muscle sympathetic nerve activity was recorded. From hyperventilation to rebreathing, robust changes occurred in PETCO2 (20-61 Torr), CBFV (-44 to +104% of baseline), CVCi (-39 to +64%), and ABP (-19 to +23%) (all P < 0.01). Muscle sympathetic nerve activity increased by 446% during hypercapnia. The linear regression slope of CVCi vs. PETCO2 was less steep than that of CBFV (3 vs. 5%/Torr; P = 0.01). Logistic regression of CBF-PETCO2 (r(2) = 0.97) and CVCi-PETCO2 (r(2) = 0.93) was superior to linear regression (r(2) = 0.91, r(2) = 0.85; P = 0.01). CVMR was maximal (6-8%/Torr) for PETCO2 of 40-50 Torr. In conclusion, CBFV and CVCi responses to transient changes in PETCO2 can be described by a nonlinear logistic function, indicating that CVMR estimation varies within the range from hypocapnia to hypercapnia. Furthermore, quantification of the CVCi-PETCO2 relationship may minimize the effects of changes in ABP on the estimation of CVMR. The method developed provides insight into CVMR under transient breath-by-breath changes in CO2.