Standing up to the challenge of standing:: a siphon does not support cerebral blood flow in humans

被引:60
作者
Dawson, EA
Secher, NH
Dalsgaard, MK
Ogoh, S
Yoshiga, CC
González-Alonso, J
Steensberg, A
Raven, PB
机构
[1] Univ Copenhagen, Rigshosp, Dept Anesthesia, Copenhagen Muscle Res Ctr, DK-2100 Copenhagen O, Denmark
[2] Univ N Texas, Hlth Sci Ctr, Dept Integrat Physiol, Ft Worth, TX 76107 USA
关键词
internal jugular vein; external jugular vein;
D O I
10.1152/ajpregu.00196.2004
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Model studies have been advanced to suggest both that a siphon does and does not support cerebral blood flow in an upright position. If a siphon is established with the head raised, it would mean that internal jugular pressure reflects right atrium pressure minus the hydrostatic difference from the brain. This study measured spinal fluid pressure in the upright position, the pressure and the ultrasound-determined size of the internal jugular vein in the supine and sitting positions, and the internal jugular venous pressure during seated exercise. When the head was elevated similar to25 cm above the level of the heart, internal jugular venous pressure decreased from 9.5 (SD 2.8) to 0.2 (SD 1.0) mmHg [n = 15; values are means (SD); P < 0.01]. Similarly, central venous pressure decreased from 6.2 (SD 1.8) to 0.6 (SD 2.6) mmHg (P < 0.05). No apparent lumen was detected in any of the 31 left or right internal veins imaged at 40degrees head-up tilt, and submaximal ( n = 7) and maximal exercise ( n = 4) did not significantly affect internal jugular venous pressure. While seven subjects were sitting up, spinal fluid pressure at the lumbar level was 26 ( SD 4) mmHg corresponding to 0.1 ( SD 4.1) mmHg at the base of the brain. These results demonstrate that both for venous outflow from the brain and for spinal fluid, the prevailing pressure approaches zero at the base of the brain when humans are upright, which negates that a siphon supports cerebral blood flow.
引用
收藏
页码:R911 / R914
页数:4
相关论文
共 18 条
[1]   DOES GRAVITATIONAL PRESSURE OF BLOOD HINDER FLOW TO THE BRAIN OF THE GIRAFFE [J].
BADEER, HS .
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-PHYSIOLOGY, 1986, 83 (02) :207-211
[2]  
Diem K, 1970, DOCUMENTA GEIGY SCI
[3]   VERTEBRAL VENOUS PLEXUS AS A MAJOR CEREBRAL VENOUS OUTFLOW TRACT [J].
EPSTEIN, HM ;
LINDE, HW ;
CRAMPTON, AR ;
CIRIC, IS ;
ECKENHOFF, JE .
ANESTHESIOLOGY, 1970, 32 (04) :332-+
[4]   CARDIOVASCULAR, VENTILATORY AND CATECHOLAMINE RESPONSES TO MAXIMAL DYNAMIC EXERCISE IN PARTIALLY CURARIZED MAN [J].
GALBO, H ;
KJAER, M ;
SECHER, NH .
JOURNAL OF PHYSIOLOGY-LONDON, 1987, 389 :557-568
[5]   GRAVITATIONAL HEMODYNAMICS AND EDEMA PREVENTION IN THE GIRAFFE [J].
HARGENS, AR ;
MILLARD, RW ;
PETTERSSON, K ;
JOHANSEN, K .
NATURE, 1987, 329 (6134) :59-60
[6]   GRAVITY AND THE CIRCULATION - OPEN VS CLOSED SYSTEMS [J].
HICKS, JW ;
BADEER, HS .
AMERICAN JOURNAL OF PHYSIOLOGY, 1992, 262 (05) :R725-R732
[7]   SIPHON MECHANISM IN COLLAPSIBLE TUBES - APPLICATION TO CIRCULATION OF THE GIRAFFE HEAD [J].
HICKS, JW ;
BADEER, HS .
AMERICAN JOURNAL OF PHYSIOLOGY, 1989, 256 (02) :R567-R571
[8]  
HIL L, 1897, J PHYSL, V21, P328
[9]   The collapse factor in the measurement of venous pressure - The flow of fluid through collapsible tubes [J].
Holt, JP .
AMERICAN JOURNAL OF PHYSIOLOGY, 1941, 134 (02) :0292-0299
[10]   CEREBRAL BLOOD FLOW AND OXYGEN CONSUMPTION IN MAN [J].
LASSEN, NA .
PHYSIOLOGICAL REVIEWS, 1959, 39 (02) :183-238