Abbott i-STAT 1 System Manual page 440

Clinical Significance
PO
(partial pressure of oxygen) is a measurement of the tension or pressure of oxygen dissolved in blood.
2
Some causes for decreased values of PO
or trauma to the brain), impaired gas exchange between alveolar air and pulmonary capillary blood (e.g.,
bronchitis, emphysema, or pulmonary edema), and alteration in the flow of blood within the heart or
lungs (e.g., congenital defects in the heart or shunting of venous blood into the arterial system without
oxygenation in the lungs).
sO (oxygen saturation) is the amount of oxyhemoglobin expressed as a fraction of the total amount of
2
hemoglobin able to bind oxygen (oxyhemoglobin plus deoxyhemoglobin).
sO is calculated from measured PO
2
However, this calculation assumes normal affinity of oxygen for hemoglobin. It does not take into account
erythrocyte diphosphoglycerate (2,3-DPG) concentrations which affect the oxygen dissociation curve. The
calculation also does not take into account the effects of fetal hemoglobin or dysfunctional hemoglobins
(carboxy-, met-, and sulfhemoglobin). Clinically significant errors can result from incorporation of such an
estimated sO value for oxygen saturation in further calculations, such as shunt fraction, or by assuming the
2
value obtained is equivalent to fractional oxyhemoglobin.
Oxygen saturation is a useful predictor of the amount of oxygen that is available for tissue perfusion. Some
causes for decreased values of sO
Temperature "Correction" Algorithm
PO is a temperature-dependent quantity and is measured at 37°C. The PO
2
other than 37°C can be 'corrected' by entering the patient's temperature on the chart page of the analyzer.
See section 12 'Procedure for Cartridge Testing' in the i-STAT 1 System Manual or section 11 'Patient and
Control Sample Testing' in the i-STAT System Manual for details. In this case, blood gas results will be
displayed at both 37°C and the patient's temperature. The PO
as follows :
3
Note: Patient temperature corrected results are only available on cartridges containing pH, PCO
PO
sensors.
2
Performance Characteristics
The performance characteristics of the sensors are equivalent in all cartridge configurations.
The typical performance data summarized below was collected in a health care facility by health care
professionals trained in the use of the i-STAT System and comparative method.
Precision data were collected in multiple sites as follows: Duplicates of each control fluid were tested in the
morning and in the afternoon on five days for a total of 20 replicates. The averaged statistics are presented
below.
PO2 - 2
include decreased pulmonary ventilation (e.g., airway obstruction
2
(X + 150X)
3
=100 __________________
sO
2
X + 150X + 23400
3
(0.48(pH-7.4)-0.0013(HCO
where X = PO • 10
2
and pH and from HCO
2
include low PO
or impaired ability of hemoglobin to carry oxygen.
2 2
Art: 714180-01L
-25))
3
calculated from measured PCO
3
reading at a body temperature
2
at the patient's temperature (T
2
and pH.
2
) is calculated
p
, and
2
Rev. Date: 01-Jul-13