User's Manual

Telemetry Transmitters User Manual Page 5 of 10
checked to assure that it is properly turned off before storage. If the original transmitter package was saved, place
the transmitter into the plastic packaging. This will help to identify the transmitter and the calibration values
associated with it. There is no effective way to maintain unit sterility during storage, therefore each unit will require
sterilization again at the time of use. Sterilization prior to storage is necessary to prevent spread of bacteria during
handling.
Considerations With Pressure Transmitters
When measuring blood pressure telemetrically, it is essential to verify that the measurements are accurate, since a
small percentage of these devices exhibit long-term drift. Verification can be done in a variety of ways, including
pressure chambers, arterial cannulation, comparison to a mercury manometer, etc. Arterial cannulation is normally
used only if it is necessary to check the accuracy of the device at a time other than at implantation or explantation.
For most protocols this is not necessary. Since those devices that exhibit long-term drift while implanted almost
always drift toward lower pressure, validation of accuracy at implantation and explantation can provide a simple and
reliable method for assuring that the measurements obtained during the course of the study are accurate. The
following procedure will determine if the pressure transmitter is reading zero prior to implantation or if there is a
deviation (zero offset).
Checking Accuracy Prior to Implantation
All DSI transmitters are carefully calibrated and tested prior to being shipped. However, we strongly recommend
that all pressure devices be checked immediately prior to surgery. The following protocol will allow you to verify
that the pressure transmitter is functioning normally prior to surgical placement in an animal.
To check offset, turn the transmitter on approximately 24 hours prior to surgery. This will allow the electronics time
to stabilize. The calibration information from each transmitter should be entered into the Configuration Program of
Dataquest and each transmitter should be assigned to a receiver. It is important that the Dataquest Acquisition
Program be running and that at least one ambient pressure sample is recorded prior to checking zero offsets.
Just prior to surgery the transmitter should be placed on its assigned receiver in the sterile pack. It is very important
that the catheter tip be level with the body of the transmitter. If the catheter is above or below the level of the
transmitter body, the measured values will be affected by this "head pressure" and will not be accurate. Usually, if
the transmitter is checked while it is still in the sterile pack, the unit is held in the proper position for zero offset.
The value being measured by the transmitter can now be visualized using Waveform Trace in the Acquisition
Program. By right-clicking the mouse you can select tracking. This will bring up a dialogue box that shows x values
and y values. By moving the mouse on the waveform, you will be able to see where the offset lies. For units
manufactured within the previous three months, this value should be within 3 mmHg of zero to comply with
manufacturer specifications. Units older than three months may experience a larger offset. If desired, right clicking
the mouse and selecting Print can make a hard copy of a trace. This should be kept with study data as verification of
initial accuracy. Another accuracy verification option is to collect the pressure "waveform" or offset in the same way
you would sample from the animal, using the Save and Trace option in the Acquisition Program. This procedure
would save the pressure offset data in the same file with the animal's data, permanently associating the offset value
to the animal.
If the value of offset is outside ±3mmHg, contact your DSI Service Representative for further instructions. If your
transmitters have been on the shelf for an extended period of time and they have an unacceptable zero offset, it may
be possible to adjust calibration values to compensate for the offset. If you are routinely experiencing offsets prior
to implantation greater than ±3 mmHg, your ambient pressure monitor (APR-1) may require recalibration.
If your experimental protocol or quality standards (such as FDA GLP) require that transmitter accuracy be checked
more thoroughly, we recommend placing the transmitter in a chamber that can be pressurized using a mercury
manometer and verifying the accuracy of the device at several pressures (e.g., 0, 100, and 200 mmHg). Such a
chamber can be fabricated by your mechanical shop or purchased from DSI.