Q&A Report: Experimental Design Considerations to Optimize Chronic Cardiovascular Telemetry Studies

Phil Griffiths, PhD, answers top questions from a recent webinar on chronic cardiovascular telemetry studies and considerations for experimental design.

The answers to these questions have been provided by:

Phil Griffiths, PhD
Research Sales Manager – Europe

What are the current physiological metrics that can be captured with telemetry? Are there any future metrics that will become available?

Rat telemetry: Pressure (TRM54P), Pressure and Biopotential (TRM54PB), Dual Pressure (TRM54PP), Pressure and Sympathetic Nerve Activity (TRM56SP), Biopotential (TR50B), Dual Biopotential (TR50BB), Tissue Oxygen (TR57Y), Optogenetics Stimulation and Biopotential Recording (TR58AB). All rat telemeters also support temperature recording.

Mouse telemetry: Biopotential and Activity (MT10B). Our Product Team is investigating the feasibility of producing a mouse pressure telemeter which incorporates the solid-state sensing technology.

Find more information on our telemetry options here: https://www.adinstruments.com/research/animal/telemetry.

A 2F catheter for pressure telemetry is suitable for a rat, but likely is quite large for a mouse. Is there another option for chronic mouse studies?

The 2F catheter is designed specifically for use in rats. At the moment we do not have a pressure telemeter suitable for use in mice but the feasibility for this is being investigated by our Product Team.

Previous studies suggested major surgery artifacts up to 1 week post-surgery. With telemetry, have you seen similar times suggesting not achieving baseline data "until AFTER one week"?

Yes, I absolutely recommend applying a standard 1 week surgical recovery period before collecting baseline data. This helps to allow physiological parameters to stabilize and the effects of analgesia/antibiotics to wear off. The nice thing with the Kaha Sciences telemetry system is that you can still record data during this time and track surgical recovery, without the concern of using up valuable battery life, thanks to the wireless power technology.

Can you recover the telemetry device from a mouse and reuse in another animal?

The mouse biopotential telemeters are currently designed for single use. This is because the biopotential lead wires are hollow and difficult to clean effectively between mice. Therefore there is an inherent risk of infection on reimplantation and as such we don’t recommend this.

How long will charge last before you need to boost the power on the special platform?

The rat telemeters have a built in battery to provide back-up power and support data recording up to 5 metres from the SmartPad, for between 4-6 hours depending on the telemeter model. At the end of this behavioral study the rat can be returned to the home-cage on the SmartPad and the telemeter battery will recharge.

The mouse telemeters do not have a battery, to minimize the implant size, and are only powered when inside the wireless power field. This means they are only suitable for use during home-cage recording.

Considering mice prefer socialization, would it be better to keep animals in the same cage and separate only during data recording, or directly after surgery and keeping them alone to avoid stress?

It’s certainly better to single-house animals immediately after surgery to prevent their cage mates from interfering with any surgical wounds. Regarding long-term housing of mice for telemetry, it is only possible to record from one mouse per cage. As such you could either house them together and simply separate them for recording sessions, or include an unimplanted cage mate during continuous recording.

Cohousing of 2 implanted rats is possible with Kaha Telemetry, however I would still recommend separating animals for a few days post-surgery.

Since there are no battery limitations in the Kaha telemetry, what are the causes of failures of this telemetry unit?

The solid-state pressure sensors on the rat telemeters are delicate and need to be handled with care during implantation, explantation and cleaning. Often failures of the unit and pressure recording are associated with damage to the pressure sensor introduced during these times. The surgical videos on the ADInstruments website provide recommendations for minimizing this risk.

Is there real time viewing of data or do you have to download after acquiring the data?

Kaha Telemetry does not work by data-logging. The data is transmitted from telemeters, via the SmartPads or tBases to a PowerLab and is acquired in real time by the LabChart 8 or LabChart Lightning software. This is great for observing differences between experimental groups in real time and performing some online data analysis.

Is it a better strategy to record continuously for 24 hours, and then determine what data to keep or analyze?

Certainly advances in data storage mean that continuous recording is a very good option now. This also increases the amount of data that you can extract from each animal and raises the possibility of carrying out more complex analysis. Having said that, the flexibility offered by Kaha Telemetry and ADInstruments Data Acquisition means that you can tailor your data collection to suit your experiment.

Can telemetry signals be correctly recorded while animals are running on a treadmill? Is there any interference from the treadmill motor?

The rat telemeters have a built in battery to support data recording up to 5 meters from the SmartPad, for between 4-6 hours depending on the telemeter model. Running a rat on a treadmill would certainly be supported and to the best of my knowledge there would be no interference from the treadmill motor. At the end of this behavioral study the rat can be returned to the home-cage on the SmartPad and the telemeter battery will recharge.

The mouse telemeters do not have a battery and are designed for home-cage recording where the telemeter remains in the wireless power field. Having said that, it might be possible to position a tBase close enough to the mouse running on the treadmill to ensure powering continues so I’d recommend you contact your local ADI Sales Specialist to discuss further.

Can your LabChart software capture video snapshots or continuous recording?

The Video Capture Module of LabChart 8 Pro can capture video which is sychronized with the waveform. For large telemetry installations this can be challenging though because there is a requirement to multiplex cameras for each cage into one video feed.

For short term experiments, e.g. days, do people ever put the catheter into the target and then just glue the transducer on the back to minimize surgery for the animal?

I’m not aware of anyone doing this with Kaha Telemetry. The telemeters are ideally placed in the abdominal cavity for optimal wireless power transfer so positioning on the back may lead to powering issues. I know that you can use jackets with other telemetry systems though to hold the telemeter body outside the animal, simply with the catheter/electrodes implanted.

Does the wireless power alter the animal's core temperature?

No, this does not happen and we can provide data to show that there is no effect of wireless powering on core temperature. There is a feedback mechanism between the telemeter and SmartPad or tBase which ensures the wireless power output is optimal for the telemeters requirements. Additionally if the telemeter temperature exceeds a set point, the wireless power field is disabled.