Datex-Ohmeda Aestiva 7900 SmartVent, Service Manual

Page: 75 / 181

4/Tests and Troubleshooting
1503-0151-000 5/26/0 4-29
Pressure Sensitivity Fail
1. Select "Display A/D Channels" from the main service menu.
Set Fresh gas flow to 2 Lpm.
Open the APL valve (0 cm H
2
O).
Place Bag to Vent switch in the Bag/APL position.
Connect a short tube between the inspiratory and expiratory flow
sensors.
The airway pressure, inspiratory flow and expiratory flow on the ventilator display
should read near zero (b.5 and -.5 Lpm flows).
2. Occlude the GMS (or MAS) bag port. Adjust the APL to read 10
cmH
2
O on the gauge. The flow may jump briefly, but should stabilize
to read b.5 and -.5 Lpm. Very gently push the tubes coming
from the flow sensors slightly in all directions. Observe to see if the
flow measurements jump.
Caution
w
If either sensor reads more than 2 Lpm, STOP. This indicates a possible
leak in the flow sensor pneumatic circuit. Skip steps 3 and 4, go directly
to step 5. If the pressure is increased further, the SIB may be damaged.
3. Adjust the APL to read 20 cmH
2
O on the gauge. The flows may jump
briefly, but should stabilize to read b.5 and -.5 Lpm.
4. Adjust the APL to read 40 cmH
2
O on the gauge. The flows may jump
briefly, but should stabilize to read b.5 and -.5 Lpm.
5. If the flow measurements on the ADC page stay near zero, the flow
sensors are good. If either sensor indicates a flow where there is
none, there may be a leak. To troubleshoot, reduce the circuit pres-
sure back to zero. Reverse the flow sensor connections at the SIB
interface panel and repeat the above tests.
6. If the problem follows the sensor, discard the sensor. It has a leak.
7. If the problem stays with the same side of the circuit, it is likely the
leak is in the tubing under the SE table top, not with the sensor.