One week is generally adequate time for tissue growth that will stabilize a flow probe in a chronic implant and produce adequate signal quality for flow measurements. If signal quality after one week is insufficient, consider the following:
- What flowmeter is being used (400-series or T106 or T206)?
- The discontinued flowmeter models T106 and T206 will generally register lower signal levels with higher frequency probes such as the 1.5SL flow probe.
- The signal quality is much better with a 400-series flowmeter.
- Does the probe have a 4-pin connector?
- Probes with a 4-pin connector require a calibration “key”. The calibration key must match the probe’s serial number.
- Check that the probe size is displayed on the digital display of a 400-Series meter in test mode. It will display the probe size and then NO SIG. If it displays “NO.PR.” then this may be a key from a different probe or the key is possibly bad.
Is an extension cable being used?
- The maximum extension cable length of a probe will depend on the connector type.
- With a 4-pin connector, the extension cable should be no more than 1.85 meters long.
- Longer cables may degrade the signal.
- If it is a 10-pin connector, the cable should be no more than 1.25 meters long.
- Check that the extension cable is working properly with another probe.
- Also, check that the pins are lined up correctly with the indentation in the extension cable.
Is a swivel being used for conscious measurements in animals with implanted flow probes?
- Check that the solder connections are wired correctly and there are no loose connections.
- Remove the swivel and check the probe with an extension cable.
ACUTE SIGNAL QUALITY
- What was the signal quality with saline before closing the animal?
- How many signal bars were lit (400-series flowmeter LED display), or what was the signal strength voltage in test mode?
- NOTE: Signal strength will always decrease in a chronic implant over time.
- A marginal probe signal (~.35 millivolts) may be too low for a reading.
- Signal should be > 0.7 volts prior to implanting.
MEDIUM ON PROBE DURING IMPLANT
- Was any medium used on the probe when implanting?
- QuickSil is recommended to stabilize nanoprobe positioning.
- NOTE: Any type of medium in the probe lumen will impede signal quality.
- Is “No acoustic signal” being reported on the Flow Meter?
- If “No flow signal” is being displayed, the probe may not be on the vessel properly or might be occluded.