A Spectrophotometric Method of Estimating Blood Oxygen Using the Unicam SP 600

Accurate estimations of percentage oxygen saturation and oxygen capacity are frequently needed in research and routine investigation of patients suffering from diseases of the heart and lungs. Blood gas analysis for this purpose is time consuming and requires the services of a highly skilled technician. Further, the methods need to be in constant use if reliable results are to be obtained. Accurate results require duplicate or triplicate estimations. The increasing use of cardiac catheterization in diagnosing congenital heart disease has created a need for a simple and reliable method for rapid estimations. A number of authors have described spectrophotometric methods designed to suit different types of instrument (Nahas, 1951; Wade, Bishop, Cumming, and Donald, 1953; Stainsby, Fales, and Lilienthal, 1955). In the present paper we describe a modification of the method of Holling, MacDonald, O'Halloran, and Venner (1955) suitable for the " unicam" SP 600. Individual determinations can be made in less than two minutes and the method is suitable for use in the dark at catheterization. It thus provides a simple and reliable technique for estimations of oxygen saturation on blood samples during the course of catheterization.