How It Works

Why you need a Mini-Thermacage

The maintenance of small animal body temperature during and especially post surgical procedure has always been a significant matter for concern. Whilst under anaesthetic, the animal’s body temperature can drop significantly and this can of course lead to loss of life. Animals then need to be replaced and work has to be repeated. Heat pads were introduced to combat this and became widely used. It was seen however that direct heat is difficult to regulate and can lead to animals becoming either too warm, not warm enough or achieving the right temperature but only in certain parts of their bodies.

The Thermacage was developed to solve this problem and to provide a warming mechanism to assist in blood sampling. The principle of the Thermacage is that warm air is circulated evenly, at a defined temperature throughout an animal holding chamber.

The Mini-Thermacage has been designed to be used where space is at a premium, for example in ventilated change stations and on smaller work surfaces. The animal compartments have tension sprung closing lids allowing technicians to carry out single handed animal manipulation, in and out of the holding spaces. The springs have been designed to provide enough tension to keep the animal safely in its compartment but at the same time allow the user easy access and avoid animal discomfort on entry and exit. The compartment lids have a bevelled leading edge again to ensure animal and user comfort during exit and entry. A soft recessed pad in the lid cushions closure to avoid animals being shocked when the lid closes. See Figure 1.

Flexibility

The Mini-Thermacage gives you the option to have 2, 3 or 4 individual animal enclosure. By taking out the easily removable dividers, the user can double the size of the enclosure to accommodate rats.

To allow the user to switch between two, three or four secure compartments, compartment doors can be linked using the special catches to allow just two doors, three or four depending on requirements. See Figure 2

 

Door Damper

Door-Dampners

Dampener can reduce noise
levels by up to 15db

Figure 1

Locking Door Catch

Door-Catch

The door catch offers 2, 3 or 4
door flexibility

Figure 2

Heat Diffuser

diffuser

The diffuser provides a balanced
heat flow between all compartments

Figure 3

 

Even Heat Distribution

Table 1.        Optimal Rodent Body Temperatures.

Species

Core body temp (rectal)

Optical surgical recovery

Optimal tempfor tail bleed (N3CR data)

Mouse

38-39°C

25-30°C

39-40°C

Rat

36-40°C

25-30°C

39-40°C

 

Graph A. shows the in use temperature distribution results for the original and improved mini-thermacages. The results show considerable improvement in even heat distribution and temperature control.  This improvement can be attributed to the development of the air diffuser which is shown in Figure 3.   The diffuser provides a balanced heat flow between all the compartments and maintains 0.175% heat tolerance between the compartments.  9 out of 10 cages tested have equal 35 degree temperature across all compartments with the occasional 0.5 degree of difference.  The comparative airflows can be seen in Figure 4.

 

Graph A.

graph

 

Bespoke heater elements are used in the mini-thermacage, as standard heater assemblies are too hot for this application. A standard element is rewired to add resistance and therefore reduce the temperature outputted from the heater. This in turn allows a smoother flow of lower heat which is more comfortable for the animals.

 

Simple Heat Control

The WEST controller (figure 5.) works in conjunction with the heater and incorporates an easy tune feature; this P.I.D. controller has a simplified user interface and automatic tuning. The controller calculates the fluctuation in temperature extremely accurately and soothes out any deviation in temperature.

 

Heat-transfer                    display

Figure 4                                                                                    Figure 5