Siemens RAPIDLAB 248 Operator's Manual page 131

Operating Principles
pO
Complete laboratory evaluation of oxygenation requires much more than
simple blood gas measurements. Assessment of ventilatory system and
acid-base status is essential to properly interpret clinical significance of
arterial oxygenation status. However, many patients can be evaluated and
treated successfully using blood gases alone if clinical observations and
patient history are taken into account
The measurement of pO
hypoxemia (a deficiency of O
Calculated Parameters
The 248 calculates other parameters of interest to clinicians, and uses
several different equations to provide these parameters. Unless otherwise
noted, all measured values used in equations are at 37°C.
Bicarbonate Ion (HCO
Bicarbonate (HCO
plays a major role in maintaining the pH level in blood. It is present in
large amounts in the blood as a result of the dynamic state of CO
blood. The majority of CO
The kidneys are the major controller of bicarbonate ion. Bicarbonate levels
are clinically significant in helping to determine the non-respiratory, renal
(metabolic) component in acid-base disorders.
Changes in HCO
acidosis or alkalosis disorders are of metabolic origin. In metabolic acidosis,
HCO
in pH. Conversely, in metabolic alkalosis, HCO
decrease in H
There are two versions of bicarbonate, the actual value and the standard
value, available in the System Set Up menu.
Actual Bicarbonate (HCO
Based on the National Committee for Clinical Laboratory Standards
(NCCLS) recommendations
Standard Bicarbonate (HCO
The equation described by VanSlyke and Cullin
standard bicarbonate
If no ctHb value has been entered, a value of 15g/dL is assumed.
2
–
) is the major buffer substance present in the body, and
3
–
levels along with pH values can help determine if
3
– levels decrease causing an increase in H
3
+
which leads to an increase in pH.
cHCO – = 0.0307 x pCO
3 act
–
cHCO = 24.5 + 0.9A + (A–2.9)
3 std
where A = BE(B) – (0.2ctHb(100–O
14 .
is significant in evaluating the degree of
2
in arterial blood) present in a patient.
2
–
)
3
is transported as HCO
2
–
act)
3
16
x 10 (pH – 6.105)
2
–
std)
3
2
(2.65 + 0.31ctHb)/1000
SAT)/100)
2
in the
2
– .
3
+ which leads to a decrease
– levels increase, causing a
3
17 is used for calculating
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