Mindray SV300 - Page 217

B-17
Effect of interfering gas
Gas under test
Error (％O
2
)
50% He/50% O
2
<1 %
80% N
2
O/20% O
2
1 % to 1.5 %
4% Halothane/28.8% O
2
/67.2% N
2
O 1.5 % to 2 %
5% Sevoflurane/28.5% O
2
/ 66.5%
N
2
O
1 % to 1.5 %
5% Enflurane/28.5% O
2
/66.5% N
2
O 1.2 % to 1.8 %
5% Isoflurane/28.5% O
2
/66.5% N
2
O 1.2 % to 1.8 %
5% CO
2
/ 28.5% O
2
/66.5% N
2
O <1 %
Theory of Operation
O
2
sensor can monitor the patient’s FiO
2
. O
2
sensor is of the self-powered, diffusion limited,
metal-air battery type comprising an anode, electrolyte, diffusion barrier and air cathode as shown
below:
At the cathode oxygen is reduced to hydroxyl ions according to the equation:

 OHeOHO 442
22
The hydroxyl ions in turn oxidise the metal anode as follows:

 eOHPbOOHPb 42242
2
Overall the cell reaction may be represented as:
Air supply
Cathode
Electrolyte
Anode
Load resistor
Solid membrane
Diffusion barrier