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Appendix F
51
Frequently Asked Questions
1. When I start ventilation, why is underpressure constantly displayed?
If no connection is made to the "To Animal" port, this is the proper indication. The
fault will clear when airway pressure is detected.
If proper connections have been made, there is most likely a leak in the system. Make
sure that the O-ring has been installed properly before installing the glass cylinder.
Verify that the cylinder has been tightened properly.
If barbed ports at the front of the machine have been replaced make sure that they
are fully tightened to be flush with the front bezel.
Finally, check for leaks in the tubing and at the animal's airway.
If you are using the Inspira ASVp in pressure-control mode and the average airway
pressure is greater than 3 cmH 2 O, the machine will attempt to adjust the flow rate to
increase the airway pressure. If an underpressure condition continues (Paw much less
than desired) and the tidal volume is larger than expected, check for system leaks.
2. When I change or install a cylinder, why is it not detected properly?
The Inspira uses two micro-switches to detect the two different cylinder sizes. The
rear-most switch actuates when the 10cc cylinder is installed. Both switches actuate
when the 100cc cylinder is installed. If the 10cc cylinder is not being detected, first
make sure that the rear-most actuator arm is resting against the side of the cylinder.
If it isn't, just reposition the actuator arm. Next, make sure that the switches are actu-
ating. Gently pull back on the actuator arm(s) contacting the installed cylinder and
listen for a click. If the switch clicks it had not been actuated. This indicates that the
actuator arm's bend angle has not been set properly. This may be easily corrected by
gently increasing the bend angle of the actuator arm(s).
3. Why does it seem like the volume delivered is too low?
It is possible that there is a system leak. Check for leaks as described in the answer
to question 1.
In volume-control mode, if the inspiration pressure limit is reached the machine will
cycle to expiration before total tidal volume is delivered. Make sure that restrictions
in the airway circuit are minimized and make sure that the pressure limit isn't set too
low.
If you are using side-stream gas monitoring, tidal volume will need to be adjusted
(increased) to account for the sample volume.
If system dead space is high, tidal volume will need to be adjusted to account for it.
Please note that the machine's calculations for tidal volume and respiration rate based
on the animal's weight are for healthy mammals in a resting state and do not account
for additional dead space which may be introduced by the user's system set-up. Dead-
space volume should be calculated and the tidal volume should be increased accord-
ingly. The animal's respiratory health must also be considered when adjusting respi-
Publication 5404-001-REV-C
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