Rev. Date: 02-Aug-11 Art: 714182-00R
PCO
2
AND CALCULATED VALUES
FOR HCO
3
, BASE EXCESS AND
ANION GAP
PCO
2
is measured by direct potentiometry. In the calculation of results for PCO
2
, concen tration is related
to potential through the Nernst equation. Results are measured at 37°C when using cartridges that require
thermal control and corrected to 37°C when using cartridges that do not require thermal control.
Calculated Values
When a cartridge includes sensors for both pH and PCO
2
, bicarbonate (HCO
3
), total carbon dioxide (TCO
2
)
and base excess (BE) are calculated.
1
log HCO
3
= pH + log PCO
2
– 7.608
BE
ecf
= HCO
3
– 24.8 + 16.2 (pH – 7.4)
BE
b
= (1 - 0.014*Hb) * [ HCO
3
- 24.8 + (1.43 * Hb + 7.7) * (pH - 7.4) ]
Anion Gap is calculated in the EC8+ and CHEM8+ catridges as follows:
Anion Gap (EC8+) = (Na + K) – (Cl + HCO
3
)
Anion Gap (CHEM8+) = (Na + K) – (Cl + (TCO
2
- 1))
See below for information on factors affecting results. Certain substances, such as drugs, may affect
analyte levels in vivo.
2
If results appear inconsistent with the clinical assessment, the patient sample should
be retested using another cartridge.
Intended Use
The test for PCO
2
, as part of the i-STAT System, is intended for use in the in vitro quantification of carbon
dioxide partial pressure in arterial, venous, or capillary whole blood.
PCO
2
measurements are used in the diagnosis, monitoring, and treatment of respiratory disturbances and
metabolic and respiratory-based acid-base disturbances.
Bicarbonate is used in the diagnosis and treatment of numerous potentially serious disorders associated
with changes in body acid-base balance.
Contents
Each i-STAT cartridge contains one reference electrode (when potentiometric sensors are included in
the cartridge configuration), sensors for the measurement of specific analytes, and a buffered aqueous
calibrant solution
that contains known concentrations of analytes and preservatives
. For cartridges that
contain a sensor for the measurement of
P
CO
2
, a list of reactive ingredients is indicated below:
Reactive Ingredient
Carbon Dioxide (CO
2
)
Metrological Traceability
The i-STAT System test for carbon dioxide partial pressure measures carbon dioxide partial pressure
in arterial, venous, or capillary whole blood (dimension kPa) for in vitro diagnostic use. P
CO
2
values
assigned to i-STAT’s controls and calibration verification materials are traceable to U.S. National Institute of
Standards and Technology (NIST) standard reference materials via commercially available certified specialty
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