User's Manual

Telemetry Transmitters User Manual Page 6 of 10
Checking Accuracy at Explantation
It is also valuable to check the zero offset of the transmitter at the end of the experiment. If the device was accurate
prior to implantation and at explantation, it is safe to assume that the measurements were also accurate in between.
To do a post implantation offset, the transmitter should be carefully removed from the animal. If it is necessary to
cut the catheter, this should only be done using a new scalpel blade at a 45° angle to the catheter. Using scissors to
cut the catheter will ruin the sensor.
Gently clean the catheter to remove any blood or tissue debris from the tip. It is essential that the temperature of the
transmitter be stable while the offset is checked. This can be done by placing it in a beaker of water at 37° Celsius
immediately upon removal from the animal. The water in the beaker should be just barely deep enough to cover the
body of the implant to avoid any affect of head pressure on the offset measurement. Alternately, the transmitter may
be left at room temperature for 1 to 2 hours, but maintaining the temperature close to 37° Celsius is preferable.
Once the temperature of the transmitter has stabilized, the unit should be placed on its receiver and the value
recorded as described above. Refer to product literature or contact DSI for drift specifications. If you are
experiencing excessive drift, please contact your DSI Service Representative for assistance.
By checking the zero offset before and after implantation, you can be confident that the data being collected are
accurate. If accuracy needs to be verified during the experiment, there are various methods for achieving this.
Contact DSI for more information on these techniques.
Regelling Pressure Transmitters
Because of the small diameter of the catheter tip, transmitters can be difficult to reuse in the event that the first
implantation is not successful. Try to insert as much of the catheter into the vessel as possible. This will allow it to
be reused by leaving the residual glue outside of the vessel with each successive use. Cleaning the tip of the catheter
and replacing lost gel can be difficult with pressure transmitters. However, the following guidelines will greatly
increase your success with this procedure.
The tip of the catheter will probably need to be re-gelled in the event that the animal dies while the transmitter is still
implanted. When the transmitter cools from body temperature to ambient temperature, the fluid in the catheter
typically recedes due to thermal expansion and blood products are drawn into catheter tip. The most important factor
in removing this material is to flush it out before it solidifies. A stream of warm saline from a syringe can be used to
gently flush debris out of the catheter tip prior to regelling.
Make sure the transmitter is turned on and you have your AM radio close by. This allows you to audibly monitor the
amount of pressure you are exerting during the procedure. Expel a small amount of gel before entering the catheter
tip to prevent introduction of air bubbles into the catheter tip. With the radio turned on to monitor applied pressure,
carefully insert the tip of the gel syringe into the lumen of the catheter tip past the foreign material. Be sure not to
insert the gel syringe tip beyond the interface of the distal gel plug and the catheter fluid. This interface is sometimes
difficult to see, but the gel plug never extends beyond 1.5 mm from the distal tip of the catheter.
With the gel syringe in place, firmly apply pressure to the plunger of the syringe, which will back-fill the catheter tip
and slowly force the foreign material out the distal tip. Don't rush this procedure; it is a slow process due to the
viscosity of the gel and the small ID of the syringe needle.
In the event that you are unable to remove all foreign material from the catheter tip using the above method, there is
a more risky maneuver. If performed incorrectly, excessive pressure can be applied to the pressure sensor and
destroy the transmitter! Do not attempt this procedure without monitoring applied pressure with an AM
radio!
As a last resort, you can gently squeeze the catheter tip with clean, gloved, fingers to expel contaminants from the
distal end. Start by grasping the stem material at the proximal aspect of the thin walled section. Pressure can then be
progressively applied in a proximal to distal direction. This motion will expel tip contents without applying
excessive pressure to the transmitter. The pitch emitted by the transmitter will change is you squeeze the catheter; if
the pitch changes rapidly, relax your grip on the catheter and proceed more slowly. The expelled material can be
wiped away with wet gauze. Before releasing the pressure, apply a drop of gel to the distal tip and allow the gel to