Post XVII - Patents

Blood Gas Control - US4001142A
Publication Date - 1977-01-04
Inventor - James E. Turner, United States of America 

This patent is about a packaged and convenient trilevel control system for monitoring laboratory measurement of pH, Po2, and Pco2 with blood gas analyzing instruments. The object of this invention is to prepare a stable, aqueous solution possessing chemically significant values for pH, partial pressure of oxygen (Po2), partial pressure of carbon dioxide (Pco2) and bicarbonte concentration [HCO3 -] to be used as a control for monitoring instruments that measure these parameters. In simplest terms, what is disclosed is a satisfactory, color coded liquid control for pH, Po2, and Pco2 at three levels (alkalosis, acidosis, normal) free of all proteins. The three controls, in ready to use liquid form, are formulated to simulate physiological levels over the clinically significant range of acid base respiratory balance and function.

The liquid blood gas control of this invention is thus designed to react in like manner as blood. Whatever parameters may effect whole blood readings in the blood gas instrument, will also effect similar changes in the control. If a human error or mechanical error exists which effects the pH, Po2, or Pco2 of the blood, that error will also effect the blood gas control since both systems are the same. Another problem that was encountered in the development of the liquid blood gas control of this invention was the instability of certain dyes on exposure to direct sunlight. This was particularly true of several blue and red dyes tested for use in the alkalosis and acidosis controls. The instability of the dye was also accompanied by a decrease in the Po2 value. Apparently a light catalyzed oxidation was occurring which did not take place at a detectable rate in the dark. This problem was solved by the careful selection of suitable dyes for all three control levels.

One purpose for which the dyes were added to the control was to afford a visual discrimination between the various control ampuls. To agree with conventional acid base litmus color standards, a preferred color of the normal control would be yellow, for the acidosis the color control would be red, and for the alkalosis, the color control would be blue.

The dyes selected as showing the greatest amount of stability within this liquid gas control system were F, D and C yellow, amaranth al lake, and alphazurine FG dyes. The yellow dye which is the trisodium salt of 5-oxo-1-(p-sulfophenyl)-4-[(p-sulfophenyl)azo]-2-pyrazoline-3-carboxylic acid, was found to be chemically stable in all levels of the standard. The amaranth dye was used to give the red color to the acidosis control. The alphazurine dye was used to yield the blue color in the alkalosis control.