ITC IRMA TruPoint Blood Analysis System - Manual (Page 149)

C.5
Oxygen Saturation 6
Oxygen saturation (O
2
Sat) is the amount of oxyhemoglobin in a solution
expressed as a fraction of the total amount of hemoglobin able to bind oxygen
(oxyhemoglobin plus deoxyhemoglobin). The IRMA TruPoint analyzer
calculates oxygen saturation from a measured pO
2
and an assumed
oxyhemoglobin dissociation curve. These results differ significantly from
direct measurement. Clinically significant errors can result from incorporation
of this calculated value in further calculations, such as shunt fraction, or by
assuming that the value obtained is equivalent to the oxyhemoglobin fraction.
O
2
Sat = 100 [(pO
2
')
4
- 67.07(pO
2
')
3
+ 2121(pO
2
')
2
- 8532 x pO
2
']
[(pO
2
') 4 - 67.07(pO
2
') 3 +2396(pO
2
') 2 -31350 x pO
2
'+936000]
› pO
2
' = pO
2
x 10 [0.48(pH-7.4)]
Total Hemoglobin
Total Hemoglobin (tHb) is estimated from % hematocrit using the following
equation:
tHb (g/dL) = % Hct x MCHC /100
› MCHC, Mean Corpuscular Hemoglobin Concentration, is assumed to be
34 g/dL.
› tHb(mM) = tHb(g/dL)
1.6114
pH Normalized Ionized Calcium
pH Normalized iCa results can be reported for pH values between 7.2 and 7.6.
pH Normalized iCa results represent the iCa result normalized to a pH value
of 7.400 using the following equation:
iCa(N) = iCa(1 - [0.53 x (7.4 - pH)])