Bayer HealthCare Rapidlab 800 - Manual (Page 650)

IĆ30 800 Series Operator's Manual
Oxygen Capacity of Hemoglobin
The oxygen capacity of hemoglobin (BO
2
or O
2
CAP ) is the maximum amount of
oxygen that the hemoglobin in a given quantity of blood can carry. This value
represents the potential of hemoglobin to bind to oxygen and includes all the
oxygen that can be bound to the available hemoglobin.
38 The oxygen capacity of
hemoglobin, with hemoglobin oxygen saturation and oxygen content, is a useful
parameter for determining the amount of oxygen in the blood that is actually
available to the tissues and for determining the effectiveness of oxygen therapy.
The oxygen capacity reference range for arterial blood for a normal population is
17.6 to 23.6 mL/dL.
The oxygen capacity of hemoglobin is determined using the following equation:
O
2
CAP
+ 1.xx
FO
2
Hb
) FHHb
100
x ctHb
where 1.xx represents the oxygen binding factor of hemoglobin and is a value in
the range of 1.30 to 1.40 specified in the CO-ox module setup
p50
Half saturation of hemoglobin by oxygen (p50) indicates the partial pressure of
oxygen when oxygen has saturated 50% of the available hemoglobin. The p50
value indicates the position of the oxygen-hemoglobin dissociation curve.
27 Unless
a CO-oximeter is connected to the 800 system, p50 is an entered value only.
S low p50 shifts the curve to the left and indicates increased oxygen-hemoglobin
affinity
S high p50 shifts the curve to the right and indicates decreased oxygen-hemoglobin
affinity
The p50 value is useful in indicating the presence of abnormal hemoglobin that
affects the oxygen transport mechanism, and as an indirect measure of the 2,3 DPG
concentration. It can also indicate changes in pH, pCO
2
, and temperature. 26,27
The p50 value is reported for sO
2
values between 20% and 90% and is determined
using the following equation:
p50
+ 26.6 (pO
2
10 ć0.48(7.4ćpHĂ)Ă0.0013BEvt) )ńpO
2
S
where pO
2
= measured pO
2
corrected to 37
°
C and pH 7.4, and pO
2
S = pO
2
corresponding to measured sO
2
calculated as follows: 31