RADIOMETER ABL800 FLEX - Page 182

ABL800 FLEX Reference Manual 6. Parameters
Oxyhemoglobin dissociation curve (ODC), Continued
The actual ODC
position
The actual position of the ODC at 37 °C for a given sample is, in principle,
determined in two steps:
1. The calculation of the combined effect on the ODC position at 37 °C of all
known causes for displacement (= ac in equation 46.13), and based on this
position:
2. The computation by a numerical method of the actual position of the ODC curve
by shifting it to pass through the known set of coordinates (P
0
, S
0
).
Eq. Description
46.13
a = ac + a6
46.14
ac = a1 + a2 + a3 + a4 + a5
46.15
a1 = −0.88 × (pH − 7.40)
46.16
a2 ln
CO
5.33
2
=×0048.
p
46.17
a3 MetHb=−
×
07.
F
46.18
( )
(
)
a4 HbF DPG=− × −006 002 5..Fc
46.19
a5 HbF=−
×
025.
F
Determining the
actual
displacement
Step Description
(I):
pO
2
, sO
2
can be used.
If sO
2
> 0.97, the calculation is based on (II) or (III) - see
below.
Coordinates (P
0
, S
0
) are calculated from equations (46.9)
and (46.11).
If FCOHb and FMetHb are not known, the default values
are used.
The ODC is shifted from the reference position to a
position which corresponds to the effect of all measured
parameters according to step (I).
The magnitude of the shift is “ac”.
The ODC is then further shifted to pass through the point
(P
0
, S
0
).
The magnitude of the shift is “a6”.
Continued on next page
6-45