The majority of methods for measuring metabolic rate in human subjects require that the person under investigation wear a face mask, or use a breathing tube, for breath collection. While these methods are extremely effective, they do not allow for completely natural movement or activity, since the subject is tethered to a breath collection device. The device may also affect natural breathing patterns.
Measuring the energy costs of normal human activity requires that the subject be confined in a metabolic room. This is a large sealed chamber though which air of a known gas composition is flushed at a measured flow rate. The effluent air is sub-sampled for gas analysis, and the differential gas concentrations of O2, CO2 and water vapor are used to calculate VO2 and VCO2. Gas flow rates through the room must be high, so the differential gas concentrations (e.g. pO2in minus pO2out) are small as a consequence.
In the past, measurement of low differential concentrations of O2 in a background of ambient air presented researchers with insurmountable difficulties. However, Qubit Systems was the first company to design a differential O2 analyzer with sufficient resolution to make such measurements easily. Qubit’s S104 DOX Differential O2 Analyzer has a resolution of 1 ppm O2 against air, which is more than sufficient for measurements of VO2 and RER in metabolic rooms, pods and in hood systems.
The S104 DOX Differential O2 Analyzer
• ±1 ppm oxygen resolution against air (that’s 0.0001%!)
• Widest dynamic range of any oxygen analyzer
• Easy calibration without special calibration gases
• Separate analog signals for reference sample and differential pO2
Both the reference and sample oxygen sensors are monitored independently at the same time. The integrated calibration system uses ambient air so there is no need for costly calibration gases. Calibration is quick, accurate and perfectly linear over the entire dynamic range of the analyzer. Just flush the analyzer with dry air and impose a differential pressure between the sample and reference cells with the valve system supplied. The software calculates the differential O2 at the measured system pressure and inputs the data. All sensors required for calibration are integral components of the DOX. The calibration is extremely accurate and measurements have excellent repeatability.
Customized Room, Pod and Hood Respirometers
We can provide all the components for metabolic measurements with human subjects:
- O2 and CO2 Analyzers
- Water Vapor Analysis and Control
- Gas Mixing and Control Systems
- Pumps, Flow Controllers, Gas Pressure Regulators
- Controlled Environment Chambers
- Tubing, Fittings, Valves
- Data Acquisition and Control Software
If you already possess some hardware and software components that you prefer to use, we can work with you to integrate the Qubit components you require into your existing system.
Our gas analyzers have the resolution and accuracy required to measure VO2 and VCO2 in any size of subject under resting or active conditions in small to large metabolic rooms, pod systems, and also with hoods for measuring RMR.