The determination of dissolved nitrogen in blood by gas phase chromatography

A method for measuring dissolved nitrogen in blood is described. Gas-phase chromatography is used. The apparatus is provided with a column of 5 A molecular sieve material and with an extraction chamber. CO2 and O2 are absorbed. As in Lenfant's method, extraction by equilibration is completed by elution. The main features are: the design of the extraction chamber, faciliting gas flow; an auxiliary circuit for freeing the chamber and the reagents from nitrogen, in which the pressure can be equilibrated against the inlet pressure of the column; the care taken to avoid any kind of contamination; the use of a special guide mounted on the blood-transfer syringe, which makes it possible to get reproducible samples at last the checking and measurement of the residual nitrogen which makes it possible to extract and measure the whole of the dissolved nitrogen. At the present stage, the accuracy of the method is better than 1.5% and the coefficient of variation of the reproducibility is 0.57%. These results make the method suitable for measuring (PaN2-PAN2) in cases of chronic respiratory insufficiency.