Setting up a Small Animal Respirometry System: Adding Oxygen Measures

This video demonstrates how to properly configure the respirometry system setup file to accurately acquire data, record data, and control key components of the system.

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In a previous video, we set up a respirometry system for small animals. It was a simple push system designed for animals with lower metabolic signals. Scrubbed air flows through the animal chamber at a controlled rate and then water vapor and CO2 are measured.

To recap the system, air from the cylinder is scrubbed of CO2 and water vapor with Drierite and Ascarite.  Flow is controlled by a mass flow control valve, goes to the compact baselining unit, out to the animal chamber, flows into the humidity meter and measures water vapor from the animal, then goes through a small scrubber column, and finally CO2 is measured by a carbon dioxide analyzer.

For slightly larger animals or animals with an elevated metabolic rate, we can expect larger gas changes as well. Those larger changes will allow us to add the measurement of oxygen consumption to this respirometry system. Adding an oxygen analyzer will require some small modifications to the system.

We will add an oxygen analyzer downstream from the CO2 analyzer. We will add a CO2 and water vapor scrubber between the CO2 analyzer and the oxygen analyzer. And we will add a data acquisition connection to record the oxygen data.

  • First place the FC-10 oxygen analyzer on the CA-10 CO2 analyzer.
  • To eliminate CO2 from the animal, we’ll use an Ascarite Drierite scrubber. So, place a small scrubber column between the outlet of the CA-10 and the inlet of the FC-10.
  • Take note the Drierite is needed to remove trace water vapor from the Ascarite.
  • Now connect the power cable for the FC-10.
  • And connect the BNC cable to the kilopascal’s percent connector on the FC-10, and connect the other end of the BNC cable to channel 5 on the UI-3 for data acquisition.
  • Turn the FC-10 on and allow it to equilibrate and warm up.

To recap:

  • Compressed air is scrubbed, and flow is regulated.
  • Air is directed by the baseliner through the animal chamber.
  • Water vapor is measured and then scrubbed from the air.
  • CO2 is measured and then CO2 and water vapor are removed before oxygen is measured.
  • In this configuration, the system can measure animal metabolic rates at flow rates up to about 200 ml/minute. This is good for large insects, groups of insects or small ectotherms.

Larger animals or those with greater metabolic rates will require higher flow rates. This will require a larger animal chamber and specific modifications to the airflow and regeneration and regulation in the system. Do take note the current system uses compressed air and a mass flow control valve. For higher flow rates over 200 ml/minute, a different system is more practical.

  • Start the reconfiguration by removing the compressed air cylinder and the mass flow control valve.
  • Don’t forget to disconnect the mass flow control valve from both the air lines and the data line.
  • But we do want to keep our large scrubber column.
  • Now add a larger animal chamber at the baseliner.
  • And then add a mass flow system and a buffer vessel to sample the ambient air.
  • We’ll start with our scrubber column.
  • And we’ll place the MFS next to the compact baseliner.
  • We’ll connect the scrubber outlet to the MFS flow meter inlet.
  • And we’ll place a buffer vessel nearby and connect the sample tube from the buffer vessel to the scrubber inlet.
  • The buffer vessel acts as a low-pass filter to dampen air fluctuations in CO2 and water vapor.
  • We’ll connect the CBL common to the MFS pump outlet.
  • And finally, we will switch out our animal chamber: disconnect the small animal chamber and replace it with a larger volume animal chamber that uses similar push-to-connect fittings.
  • And finally, we’ll connect the analog flow rate output of the MFS to channel three on the UI-3. We will keep the same data connection.

Our final recap:

  • Ambient air from a buffer vessel is scrubbed and flow is regulated by the MFS.
  • Air is directed by the baseliner through the animal chamber and goes out to the humidity meter for the measurement of water vapor.
  • Water vapor is scrubbed from the air.
  • The CO2 is measured, and then CO2 and water vapor are scrubbed before finally oxygen is measured.

In our final configuration, the system can measure animal metabolic rates at flow rates up to 750 mls/minute. This will be good for amphibians, reptiles and the smaller ectothermic vertebrates – small birds and small mammals.