CEREBRAL BLOOD FLOW IN MAN AT HIGH ALTITUDE - ROLE OF CEREBROSPINAL FLUID PH IN NORMALIZATION OF FLOW IN CHRONIC HYPOCAPNIA
CEREBRAL BLOOD FLOW IN MAN AT HIGH ALTITUDE - ROLE OF CEREBROSPINAL FLUID PH IN NORMALIZATION OF FLOW IN CHRONIC HYPOCAPNIA
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DOI：
10.1161/01.res.19.2.274
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发表时间：
1966-01-01
影响因子：
20.1
通讯作者：
HORNBEIN, TF
中科院分区：
文献类型：
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作者：
SEVERINGHAUS, JW;CHIODI, H;HORNBEIN, TF
本文用N_2O法测定了7名正常人在海拔3810米高原6 ~ 12小时和3 ~ 5天的脑血流量。用红外N_2O分析仪测定呼气末P_2O [N_2O张力]，使其保持恒定15分钟，并测定血N_2O，为此设计了一种简单的气体提取方法。此外，脑血流量的急性变化估计从脑A-V O2的差异。对照脑血流量为43 ml/100 g/min。在海拔6 ~ 12小时增加24%，3 ~ 5天增加13%。3 - 5天后，4例受试者的脑脊液pH值正常（7.31），而动脉血pH值呈碱性（7.47）;动脉血PCO 2 [CO2张力]从41 mmHg降至30 mmHg。急性纠正缺氧恢复脑血流量控制，而平均PCO 2仍然是31毫米汞柱。当PaO 2 =170，PaCO 2 =35 mm Hg时，吸入空气中加入O2和CO2使脑血流量增加34%。通过外推获得的值表明，如果动脉PCO 2升高至对照（41 mm Hg），脑血流量将比对照高60%。因此，脑血流量似乎在主要的PaCO 2下恢复正常，这可能是因为脑脊液和脑血管平滑肌细胞外液的pH值通过穿过血脑屏障的主动转运而保持正常。据推测，一种离子不可渗透的屏障将血流与脑小动脉平滑肌的细胞外液分开。
Cerebral blood flow was determined by an N2O method in 7 normal men at sea level and after 6 to 12 hr. and 3 to 5 days at 3810 m altitude. An infrared N2O analyzer was used both to measure end-tidal Pn2o [N2O tension] so that it could be kept constant for 15 min. and to determine blood N2O,for which a simple gas extraction method was devised. In addition, acute changes in cerebral blood flow were estimated from cerebral A-V O2 differences. Control cerebral blood flow was 43 ml/100 g/ min..it increased 24% at 6 to 12 hr. and 13% at 3 to 5 days at altitude. After 3 to 5 days, pH of cerebrospinal fluid was normal (7.31) in 4 subjects while arterial blood pH was alkaline (7.47); arterial blood PCO2 [CO2 tension] has fallen from 41 to 30 mm Hg. Acute correction of hypoxia restored cerebral blood flow to control while mean PCO2 was still 31 mm Hg. Addition of O2 and CO2 to inspired air raised cerebral blood flow 34% above control at PaO2=170, PaCO2=35 mm Hg. Values obtained by extrapolation suggest that if arterial PCO2 was raised to control (41 mm Hg), cerbral blood flow would have been 60% above control. Cerebral blood flow thus appears to return to normal at the prevailing PaCO2, probably because the pH of cerebrospinal fluid and of the extracellular fluid of cerebral vascular smooth muscle is kept normal by active transport across the blood-brain barrier. It is postulated that an ion-impermeable barrier separates the blood stream from extracellular fluid of the smooth muscle of cerebral arterioles.