The respiratory function of the blood.

  • Barcroft, Joseph, 1872-1947.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The respiratory function of the blood. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    Measurement (\f' C. Take the apparatus out of the bath, open the taps. Take the bottle L. Put potassium foiTicyauide into the reservoir, replace the bottle, put the apparatus in the bath, and proceed as in the determination of the oxygen capacity. Let the measurement of C give a pressure of 60 mm. The percentage saturation = 100 ^^^g^—^ i.e. 68 7o • This determination gains considerably in accuracy owing to the fact that neither the quantity of blood used nor the constant of the apparatus enters into the calcula- tion. There is therefore no need to calibrate the pipette used or even to exercise extreme caution in measuring the amount of blood used for the experiment. It is of course unnecessary to correct for temperature and pressure, the correction affecting B and G alike. On the other hand one must reckon with the fact that the unsaturated blood will take up nitrogen and oxygen from the air of the apparatus in which the blood is shaken in quantities which depend upon the composition and temperature of the gas with which the blood has previously been in equilibrium. The general principles upon which the calculation for this correction is made are set out under the measurement of oxygen in unsaturated blood. For blood taken from a tonometer at 13 7„ or from the body it is generally sufficiently accurate to add 4 °/ to the observed saturation. Determination of the difference hetiveen the qucmtities of oxygen contained in 1 c.c. of arterial and 1 c.c. of venous blood with the differential manometer. If, as is usually the case, the arterial blood is nearly saturated with oxygen, relatively to the venous blood, this determination is one of the easiest in blood gas analysis. . Place 2 c.c. of ammonia in each of the bottles, in L place 1 c.c. of venous blood, m R 1 C.C. of arterial blood. See that the stoppers are gi-eased and that they are free from all traces of ferri- cyanide and that the taps are open. Place the bottles on the apparatus, and the apparatus wdth its bottles in the water bath. After five minutes read. Suppose the readings to be Left Right Zero error 120 > 119-5 0-5 Close the taps ; see that the meniscus does not move for two minutes. Shake for one minute and place in the bath for one minute alternately till a constant reading is obtained. Let this be Left Right Diff. Zero error p 127 112-5 14-5 -6 14 If k be the constant of the apparatus, pxk is the difference between the oxygen in the arterial and venous blood. A few words may be said about the limitations of this method.