Setting up a small animal respirometry system

In this introduction to respirometry video, we will configure the basic respirometry system shown here. The air source flows through a scrubber, into an air flow control device, to a baseliner, through an animal chamber, and also a bypass. Then the air gets measured for water vapor, then scrubbed of water vapor, measured for CO2, scrubbed of CO2, and finally measured for O2. And these measurements are logged in the data interface.

In this demonstration, we will simplify the system by removing the oxygen analyzer and the CO2 scrubber. It will give us these generic components. And for some of these components, we will use instrumentation available from Sable Systems, an Alicat mass flow control valve, a compact base liner, an RH-300 water vapor analyzer, a CA-10 CO2 analyzer, and a UI-3 device as a data collection and control interface. These all make up the components in our system schematic.

We will start by transferring our system schematic to the workbench surface. We will do this in order that air flows through this system. All the components in this system are mapped out in the direction of air flow and their physical position on the bench. This will be the general layout of the small animal system. The individual components can now be placed in order. The Drierite-Ascarite-Drierite scrubber removes CO2 and water vapor. The mass flow control valve regulates air flow rate. The CBL2 channels the air through the animal chamber or the baseline. This animal chamber is for small ectothermic vertebrates or larger invertebrates. The RH-300 measures water vapor from the animal. The small magnesium perchlorate scrubber removes water vapor prior to CO2 measurement. The CA-10 measures CO2. And the UI-3 interfaces with the instrument’s data acquisition and allows for digital control.

With all the units in place, the air flow path can now be mapped. The air source, compressed zero air, goes into the Drierite-Ascarite-Drierite column. And from the scrubber to the MFC device for flow control. Air flows at a controlled rate into the CBL2’s common inlet port. And the animal chamber connects to channel 1 ports. Channel 2 is for baseline. Take note, during baselining, the baseliner loops air flow back onto itself, bypassing the animal chamber. The baseliner’s common output connects to the input of the RH-300. And the RH-300 output connects to the mini scrubber. Last, the dried air flow is connected to the CA-10 inlet and then vents out.

Now all the components can be connected using Bev-A-Line tubing. Make sure to secure the lure connectors with a firm twist. Use the CBL2’s bottom connectors for air inlet. Connect the animal chamber to the CBL2’s channel 1 ports. Then connect the CBL2’s common outlet to the RH-300 inlet. The existing tube connectors can be used to stabilize small components. Now connect the water vapor scrubber to the CA-10 inlet. This completes all the air flow connections.

The electronic data acquisition and digital control connections can now be mapped. The CA-10 analog data output connects to the UI-3’s voltage input at input number 1. Water vapor data connects to voltage input number 2. Air flow rate connects to voltage input number 3. And the baseliner’s chamber and baseline status output connect to voltage input number 4. The UI-3 accessory board connects to the CBL2 to enable digital control.

Now all components can be electrically connected. Co-axial BNC cables are used for these data connections. Press in and twist them to lock. This ensures the proper electrical connection. For digital control, the UI-3’s accessory board uses a TRS cable. The final connection is a USB cable to the UI-3 for power and computer communication. Now connect a 12- or 15-volt power supply to all the instruments and power ON. Take note, the CA-10 requires a special Hypertronics power plug that we supply.

Now you can turn all the instruments on and check them for normal function. The analyzers can be left on for 24 hours to fully equilibrate to lab conditions. Equilibration can be done while air is flowing through the system. The system should now be ready to be connected to a computer and generate a setup file.