Siemens RAPIDLAB 248 Operator's Manual page 133

Operating Principles
Oxygen Saturation (Estimated)
Oxygen saturation (O
volume of oxygen carried to the maximum volume that can be carried.
Knowledge of oxygen saturation is useful for predicting the amount of
oxygen actually available for the tissues and can be used to determine the
effectiveness of oxygen therapy.
NOTE:
estimated O
Qt), or by assuming that the value obtained is equivalent to fractional
oxyhaemoglobin
where N = pO
Because oxygen saturation also depends on the level of carbon monoxide
and 2,3 diphosphoglycerate (2, 3 DPG) in the blood, the calculated value for
oxygen saturation may not be equal to that actually measured for patients
showing abnormal levels of 2, 3 DPG or carbon monoxide. The equation
does not account for these variations, therefore the oxygen saturation that
is reported should only be used as an estimate of the actual value.
Total Carbon Dioxide (ctCO
Total carbon dioxide (ctCO
distinguishing between metabolic and respiratory acid-base disorders.
Carbon dioxide exists in several forms in blood plasma, but only two forms,
dissolved CO
recommendations
Patient Temperature Correction
All measurements and calculations are based on a standard temperature of
37°C. Actual patient temperature values can be entered during sample
analysis which allows the 248 to provide temperature corrected results.
The following equations, based on NCCLS recommendations
and where T = 37°C if not entered.
SAT) is a ratio, expressed as a percentage of the
2
Clinically significant errors can result from incorporating an
SAT value in further calculations, such as shunt fraction (Qsp/
2
18 .
4
N – 15N
O SAT =
2
4 3
N – 15N
x 10 [0.48(pH–7.4) – 0.0013 BE(B)]
2
and HCO –
2 3
16 , the following equation is used:
–
ctCO = cHCO + (0.0307 x pCO
2 3 act
pH(T) = pH – (0.0147 – 0.0065 x (7.4 – pH)) x (T – 37)
pCO (T) = pCO x 10
2 2
pO (T) = pO x 10 (A x (T – 37))
2 2
where A = 5.49 x 10 –11
9.72 x 10
3 2
+ 2045N + 2000N
2
+ 2400N – 31,100N + (2.4 x 10
)
2
), in combination with pH and pCO
2
are quantitatively significant. Based on NCCLS
)
2
(0.019 x (T – 37))
x pO 3.88 + 0.071
2
–9 x pO 3.88 + 2.3
2
Page G-9
x 100
6
)
, is useful in
2
16 , are used: