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.
- The advantages and principles
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.
- The advantages and principles
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 advantages and principles
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.
- The advantages and principles
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.
- The advantages and principles
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.
- The advantages and principles
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.
- The advantages and principles
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.
- The advantages and principles
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.
- The advantages and principles
page 9