Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia
Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia
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DOI：
10.1152/japplphysiol.00285.2014
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发表时间：
2014-11-15
影响因子：
3.3
通讯作者：
Shoemaker, J. Kevin
中科院分区：
文献类型：
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作者：
Coverdale, Nicole S.;Gati, Joseph S.;Shoemaker, J. Kevin
为了确定高碳酸血症 (HC) 和低碳酸血症 (HO) 期间大脑中动脉 (MCA) 脑血流速度 (CBFV) 的经颅多普勒超声 (TCD) 测量作为脑血流量 (CBF) 的替代值的准确性，我们检查了在 HC 或 HO 期间 MCA 的横截面积 (CSA) 是否发生变化，以及基于 TCD 的 CBFV 估计值是否与相衬 (PC) 磁共振成像的估计值相同。 MCA CSA 通过基线、H2O（30 次呼吸/分钟的过度通气）和 HC（6% 二氧化碳）期间的 3T 磁共振图像进行测量。 CBFV 的 PC 和 TCD 测量值是在这些协议期间的不同日期测量的。 CSA 和 TCD CBFV 用于计算 CBF。 HC 期间，CSA 从 5.6 +/- 0.8 增加到 6.5 +/- 1.0 mm(2)（P < 0.001，n = 13），而呼气末二氧化碳分压 (PETCO2) 从 37 +/- 3 增加到 46 +/- 5 Torr (P < 0.001)。在 HO 期间，CSA 从 5.8 +/- 0.9 下降到 5.3 +/- 0.9 mm(2)（P < 0.001，n = 15），而 PETCO2 从 36 +/- 4 下降到 23 +/- 3 Torr（P < 0.001）。比较 PC 和 TCD 期间的基线、HO 和 HC 期间的 CBFV，组内相关系数为 0.83（P < 0.001）。 HC 期间 CBF 相对于基线的相对增加比 TCD CBFV 大 18 +/- 8% (P < 0.001)，HO 期间 CBF 的相对下降比 TCD CBFV 的变化大 7 +/- 4% (P < 0.001)。这些发现挑战了 MCA 的 CSA 不会因 PETCO2 的适度变化而变化的假设。
To establish the accuracy of transcranial Doppler ultrasound (TCD) measures of middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) as a surrogate of cerebral blood flow (CBF) during hypercapnia (HC) and hypocapnia (HO), we examined whether the cross-sectional area (CSA) of the MCA changed during HC or HO and whether TCD-based estimates of CBFV were equivalent to estimates from phase contrast (PC) magnetic resonance imaging. MCA CSA was measured from 3T magnetic resonance images during baseline, HO (hyperventilation at 30 breaths/min), and HC (6% carbon dioxide). PC and TCD measures of CBFV were measured during these protocols on separate days. CSA and TCD CBFV were used to calculate CBF. During HC, CSA increased from 5.6 +/- 0.8 to 6.5 +/- 1.0 mm(2) (P < 0.001, n = 13), while end-tidal carbon dioxide partial pressure (PETCO2) increased from 37 +/- 3 to 46 +/- 5 Torr (P < 0.001). During HO, CSA decreased from 5.8 +/- 0.9 to 5.3 +/- 0.9 mm(2) (P < 0.001, n = 15), while PETCO2 decreased from 36 +/- 4 to 23 +/- 3 Torr (P < 0.001). CBFVs during baseline, HO, and HC were compared between PC and TCD, and the intraclass correlation coefficient was 0.83 (P < 0.001). The relative increase from baseline was 18 +/- 8% greater (P < 0.001) for CBF than TCD CBFV during HC, and the relative decrease of CBF during HO was 7 +/- 4% greater than the change in TCD CBFV (P < 0.001). These findings challenge the assumption that the CSA of the MCA does not change over modest changes in PETCO2.