1290 



HANDBOOK OK PHYSIOLOGY 



CIRCULATION II 



Blutgefass bei der Thermostromuhr-Messung. Pflugers 

 Arch. ges. Physiol. 262: 1, 1955. 



84. Wever, R., and J. Aschoff. Durchfluflmessung mit der 

 Diathermie-Thermostromuhr bei pulsierender Stromung. 

 Pflugers Arch. ges. Physiol. 262: 152, 1956. 



85. Wever, R., and J. Aschoff. Die Warmcdurchgangszahl 

 als DurchblutungsmalS am Menschen. Pflugers Arch. ges. 

 Physiol. 264: 272, 1957. 



86. Whitney, R. J. The measurement of volume changes in 

 human limbs. ./. Physiol., London 121 : I, 1953. 



87. Winder, C. V., J. Wax, and R. W. Thomas. Stable 

 precision in a readily assembled, continuously recording 

 bubble-flowmeter. J. Lab. Clin. Med. 42: 766, 1953. 



88. Wretlind, A. Recorder for blood flow determination. 

 Acta Physiol. Scand. 40: 196, 1957. 



89. Zijlstra, W. G., J. R. Brunsting, and L. B. Slikke, 

 Intravascular and intracardiac blood velocity patterns 

 recorded by means of NTC resistors. Xature 184: Suppl 

 13. 99>. '959- 



II. Admixing methods for measurement of regional blood flow 



WILHELM LOCHNER 



CONTENTS 



Blood Tissue Exchange Methods 

 Nitrous Oxide Method 



Measurement of cerebral blood flow 



Measurement of coronary blood flow 

 Other Test Substances 

 Test Substance Dilution Methods 



Measurement of Coronary Blood Flow 



Measurement of Cerebral Blood Flow 



Measurement of Flow in Other Organs 



Measurement of Flow in a Blood Vessel Without Interposing 



an Organ 



BLOOD TISSUE EXCHANGE METHODS 



X 1I1 mis Oxide Method 



MEASUREMENT OF CEREBRAL BLOOD FLOW. The nitrOUS 



oxide method for determination of cerebral blood 

 flow was developed by Kety & Schmidt (20, 22) in 

 1945. Since then it has become a standard method 

 for determinations in man of both cerebral and cor- 

 onary blood flow, especially because extensive opera- 

 tive procedures can be avoided. The nitrous oxide 

 method makes use of Fick's principle of blood flow 

 estimation. The test substance, nitrous oxide, is an 

 easily diffusible, inert gas which diffuses into the tis- 

 sues fast enough to allow equilibrium between gas 

 tensions in tissue and venous capillaries. With a known 

 partition coefficient of the gas, and under the assump- 

 tion that equilibrium between tissue and blood is 



reached, the amount of test substance taken up by 

 100 g of tissue can be calculated (21). Simultaneous 

 measurement of arteriovenous nitrous oxide difference 

 then permits calculation of the blood flow per minute 

 per 100 g of tissue. Applying Fick's principle, the 

 formula (22) is: 



CBF- 



IOOV u -S 



wherein 



.1 = arterial N-iO — concentration 

 I" = venous N;0 — concentration 

 S = partition coefficient for NoO between blood and 



tissue 

 ['„ = venous N 2 concentration after equilibrium reached 



in tissue during time u 

 CBF = cerebral blood flow per 100 g brain tissue per min 



The procedure of measurement is as follows: The 

 patient breathes a gas mixture of oxygen, nitrogen 

 and 1 5 per cent nitrous oxide over a period of 10 min 

 (time u). During this time, five consecutive blood 

 samples are taken simultaneously from the internal 

 jugular vein and from a peripheral artery. The sam- 

 ples must be collected under anaerobic conditions. 

 They are analyzed for NoO according to the method 

 of Orcut & Waters (33). [See also Kety (23).] Figure 1 

 shows arterial and venous time-concentration curves 

 of nitrous oxide in a typical determination. As can 

 be seen from the figure, ten blood samples have to be 

 analyzed, an undesirable feature of the method. A 

 modification of this method has been proposed by 

 Scheinberg & Stead (38) and by Bernsmeier & 

 Siemons (3). Intermittent sampling is replaced by 

 continuous sampling of only two probes, one arterial 



