Roche cobas b 123 User Manual

Roche Diagnostics
104 Instructions for Use · Version 13.0
4 Theoretical foundations cobas b 123 POC system
Parameters and calculations
Shunt (Qs/Qt)
The shunt parameter is a measure of the direct mixing of venous blood into the
oxygenated blood circulation. The shunt parameter gives the short circuit volume
relating to the total volume (% - value).
[6]
To determine it, 2 independent measurements are needed.
Both measurements have to be carried out with the same patient ID. Define the
patient ID as an input value. To do this, press the following buttons: Utilities
> Configuration > Measurement > Data input > Input values
1. Measurement with the “mixed venous” blood type:
Select the “mixed venous” blood type
2. Measurement with the “arterial” blood type:
Select the “arterial” blood type. The desired value for Q
s
/Q
t
is determined.
q
You cannot calculate the shunt value with a combination of arterial and venous blood.
You cannot change input values, such as patient ID, after a measurement in order to
calculate the shunt value.
You can measure samples from other patients while you wait for the 2 Qs/Qt partial
measurements.
The maximum time between 2 Qs/Qt partial measurements is 30 minutes.
Additional information Calculating shunt requires the following measurement and calculation values:
o tHb, SO
2
(arterial)
o PO
2
(arterial)
o PAO
2
o ctO
2
(arterial)
To obtain these measured and calculated values, select the “arterial” blood type.
Also, calculating shunt requires a ctO
2
(mixed venous) value. To calculate this, select
the “mixed venous” blood type.
To select the blood type for a measurement, define blood type as an input value. To
do this, press the following buttons: Utilities > Configuration > Measurement
> Data input > Input values
Unit: [%]
Equation 4-25
avDO
2
is used for the calculation instead of ctO
2
(a) and ctO
2
(v).
u avDO
2
(p. 103)
Q
s
shunt flow
Q
t
heart minute volume
Q
s
/Q
t
fraction of shunted cardiac output
SaO
2
arterial oxygen saturation fraction
0.00314])aOAO()
100
aO
(1tHb1.39(v))tO(a)tO[(
0.00314])aOAO()
100
aO
(1tHb[1.39100
Q
Q
22
2
22
22
2
t
s
⋅−+−⋅⋅+−
⋅−+−⋅⋅⋅
=
PP
S
cc
PP
S

Roche cobas b 123 Specifications

General

Brand	Roche
Model	cobas b 123
Category	Medical Equipment
Language	English