The metabolic measurement system is mainly used to measure the oxygen consumption and carbon dioxide generation of small animals, obtain metabolic parameters of conscious animals (rats, mice), and analyze metabolic data without any invasive surgery.

The respiratory gas analyzer collects gas concentration signals from the outlet and inlet of the plethysmography chamber. The changes in O2 and CO2 concentrations are monitored in real-time and used to calculate parameters such as VO2 (oxygen consumption), VCO2 (carbon dioxide production), RQ, MR, etc.

Use indirect calorimetry to measure energy consumption, oxygen consumption (VO2), and carbon dioxide production (VCO2) in rats and mice. Large animals, including humans, can be conveniently monitored using a fitted mask with a respirator for flow measurement and a sample port for gas analyzers. However, for small animals such as rodents, this method is difficult or impossible to successfully implement, and metabolic chambers are used instead.

The metabolic chamber can be a sealed small compartment, through which fresh air (Vi) flows at a known and set flow rate. Animals breathe in the sealed compartment, consuming O2 and producing CO2 through metabolic activities. The outlet gas of the sealed compartment has a lower O2 concentration (FoO2) than the inlet gas, The concentration of CO2 (FoCO2) will be higher than the inlet. Adjust the flow rate (Vi) through the chamber to prevent the accumulation of CO2 in the chamber. During this process, a difference of 0.2-1.0% in FoCO2/FiCO2 is sufficient to be detected. Adjust the chamber flow rate (Vi) until FoCO2 enters the detection range. By measuring data such as Vi, FiO2, FiCO2, FoO2, and FoCO2, we can calculate oxygen consumption (VO2), CO2 production (VCO2), respiratory exchange rate (RER), and metabolic heat production or energy consumption (EE).

Experimental device
The controlled flow rate (Vi) is adjustable and controllable, and is monitored by a flow meter. The gas analyzer measures O2 and CO2 at the inlet or outlet of the chamber, depending on the setting of the plug valve. Due to the need for accurate metabolic equations and precise measurements of inlet and outlet gases, the analyzer will periodically switch between monitoring inlet, reference gases (FiO2, FiCO2), and outlet gases (FoO2, FoCO2), using a plug valve to select the gas sample source. This technology can correct any small drift or absolute inaccuracy in measurements; Obtain important differential data (FiO2-FoO2 and FoCO2 FiCO2).

Schematic diagram of GEMINI metabolic research system operation

Main features:

·Applied to drug metabolism research and sleep apnea research, and widely used in drug toxicity research;

·Single channel, dual channel, eight channel, and sixteen channel configurations can be configured according to experimental needs, and metabolic measurements can be performed on multiple animals simultaneously;

·The software can perform linear analysis and statistics, and can monitor up to 8 breathing chambers simultaneously;

·Suitable box sizes can be selected based on the weight of the animal;

·Using paramagnetic method for oxygen measurement and analysis;

·Measurement and analysis of carbon dioxide using infrared frequency emission method;

·Using solid-state thermal energy flow rate for gas flow detection;
·Can automatically sample sequentially in multiple volumetric recording boxes;
·The system can automatically calibrate and is easy to operate.

Accessories package

Other precautions
·In theory, any gas flow rate passing through a sealed chamber with live animals will result in a decrease in O2 and an increase in CO2. However, the greater the difference in inlet/outlet gas, the more accurate the results will be (within a reasonable range)
·This sealed chamber is used as a mixing chamber, where the inlet airflow mixes with the exhaled breath of animals (usually small), ultimately reaching equilibrium that can be measured at the chamber outlet. To achieve the best results, the inlet flow rate is set based on the outlet CO2 concentration to achieve an ideal CO2 difference of 0.2-1.0%. At the same time, the O2 difference will also increase, which will make the results more accurate;
·It is best to use a single set of gas sensors to measure the concentration of reference gas and chamber outlet gas. This allows for a direct comparison between the inlet/outlet sample values. In the schematic, a three-way valve is used to switch between monitoring reference gas or outlet gas. A three-way electric solenoid valve can be used instead to remotely control the selection of the sample source. This method involves multiplexing a set of sensors between the sampling reference gas and the outlet of one or more metabolic chambers;
·The units for metabolic measurement and results can be in ml/min, ml/min/g, L/h/kg, or any combination. Most numerical values can be easily converted through simple multiplication or division

For the calculation method of respiratory metabolism, please refer to:

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