How and why Eurotrol s CueSee Hypoxic works Thank you for taking the time to learn some of the advantages and principles behind Eurotrol s CueSee Hypoxic for the validation of low po2 blood gas measurements. page 1
First, we need to go back to the basics of oxygen transport in blood. As you know, hemoglobin in red blood cells is the primary vehicle for transporting oxygen in the body. Oxygen is also carried dissolved in the plasma, but to a much lesser degree. So, about 98.5% of the oxygen in arterial blood is bound by hemoglobin in the red cells and about 1.5% is physically dissolved in the plasma. On average, hemoglobin increases the total blood oxygen capacity seventyfold! page 2
The oxygen solubility in blood plasma is described by Henry s Law (one of the gas laws) which states: The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. The oxygen binding capacity of Hemoglobin does not follow Henry s Law and can be best explained with the oxygen-hemoglobin dissociation curve. In its most simple form, the oxygen-hemoglobin dissociation curve describes the relationship between the partial pressure of oxygen on the x-axis and the oxygen saturation on the y-axis. page 3
Each hemoglobin molecule contains 4 heme groups with iron cores to which oxygen binds. Therefore, 1 molecule of hemoglobin can bind 4 molecules of oxygen. The shape of the curve results from the fact that when oxygen binds to hemoglobin, it changes the structure of the hemoglobin molecule, making it easier for more oxygen to bind. The binding of the first molecule is difficult. However, this facilitates the binding of the second, third and fourth. As a result of this cooperative binding, almost all of the hemoglobin is saturated with oxygen. As this limit is approached at pressures above 60 mmhg, very little additional binding occurs and the curve levels out, resulting in the S-shape. Now that you have a clear picture on how blood carries oxygen, you can understand that it is impossible to make a Quality Control material for validating a low po2 without Hemoglobin. page 4
An ampule with an aqueous liquid that is in equilibrium with a po2 of 15 mmhg will have a very small amount of oxygen dissolved, according to Henry s law. As soon as this ampule is opened for sampling, the liquid is contaminated with room air which has a po2 of 160 mmhg. An ampule with a real hemoglobin matrix that is in equilibrium with a po2 of 15 mmhg will contain much more oxygen, most of which is bound by Hemoglobin as explained with the oxygen-hemoglobin dissociation curve. The reading of such a product would be easily 50-60 mmhg po2 on a blood gas instrument. page 5
As soon as this ampule is opened, the contamination of room air with a po2 of 160 mmhg that will dissolve in the water is negligible compared with the oxygen carried by the hemoglobin. On top of that, changes in po2 of these liquids, when exposed to a higher po2, will not happen as fast because the Hemoglobin will first bind more oxygen to get a higher level of oxygen saturation with hardly any changes in po2 as explained by the S-shape in the oxygen-hemoglobin dissociation curve. page 6
Back in 2008, Eurotrol developed CueSee Hypoxic, the only low po2 control in the world with a hemoglobin matrix that behaves like real blood. In that same year, a study was carried out in more than 1400 laboratories that measured both CueSee Hypoxic and an aqueous control with a low po2. The results plotted in the graph clearly show CueSee Hypoxic: - Reports much lower results - Shows very small imprecision, and - Shows identical results on all different instruments. page 7
For CueSee Hypoxic with a value of 16 mmhg, all instruments reported a target value between 16 +/- 4 mmhg. For blood gas quality control materials in the low po2 range, this is quite an accomplishment. In summary, CueSee Hypoxic is a unique and superior product to validate low po2 on blood gas instruments. It offers the following benefits: - You can assess the accuracy and precision of low po2 measurements - It s ideal for method comparisons and AMR validation - It s comparable to whole blood tonometry, without the use of a tonometer - It is compatible with all common blood gas instruments - True hemoglobin buffering provides a 10-minute open ampule stability page 8
As with all our quality control products, Eurotrol provides CueSee Online, a free online service for comparing your quality control data with peers. Eurotrol s helpful staff is always available to assist you in placing an order, evaluating a sample or for any questions or feedback you might have. With a simple import tool, enter your results and then generate statistics, reports, and graphs that will satisfy any regulatory inspector. CueSee Online is a true enhancement to any quality control program. page 9