Improved gasometric methods for estimating oxygen content and percentage saturation in haemoglobin dissociation curve determinations.

B y using carbon m onoxide as a reagent for releasing oxygen from blood solutions (instead o f the custom ary potassium ferricyanide) and by com bining the techniques o f the Van Slyke constant-volum e gasom etric apparatus and the Scholander gas analysis apparatus, a precise m ethod has been devised o f estim ating oxygen content and carbon m onoxide capacity sim ul­ taneously on one and the same sample o f blood solution. The procedure elim inates various errors inherent in the determ ination o f oxygen percentage saturation, when oxygen content and capacity are successively m easured on separate samples. The m ethod has been extensively tested on sheep blood solutions containing 3 to 4 g haem oglob in/100 ml. and is considered to give an accuracy o f +0*5 in the oxygen percentage saturation o f such solutions. In its present form the m ethod is only applicable to solutions containing a negligible am ount o f dissolved nitrogen, but it is probable th at this restriction could be rem oved by the simple addition to the technique suggested in the text. M odifications are also described in the usual tonom eter technique for equilibrating blood solutions w ith various pressures o f oxygen, and for transferring the equilibrated blood solution to the V an Slyke apparatus for analysis. The techniques o f the present paper have been specially used for obtaining oxyhaem oglobin dissociation curve data o f higher accuracy than hitherto available. From these im proved data it has for the first tim e been possible to calculate directly, and in m any cases w ith fair precision, the values o f the equilibrium constants o f the four successive reactions o f haem o­ globin w ith oxygen.