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Background

The Clermont-Ferrand-based Laboratory of Human Nutrition runs two Calorimetrics Chambers for human research. Built in late 1993 and commissioned for service in early 1994, they were designed and engineered along the lines of the INRA's Theix-based Calorimetrics facilities originally used for large herbivores (Vermorel et al., 1973).
The original analytics bay was kept operational up to September 2008. It did not undergo any major change, and the on-line analyzers networked in were Maihak Oxygor 610 (O2) and Unor 610 (CO2) systems.
The new analytics bay, which has been operational since October 2008, ushered in an upgrade to the internal fixtures and facilities, together with a full refit of the gas supply lines. It is currently outfitted with brand new Siemens analyzers.
The data acquisition system that has been running since the outset is based on a centralized data acquisition station. Up to late 2008, this system barely changed, but it was earmarked for a full-blown retrofit in 2009 to integrate an in-PC data capture board. In parallel, new software will be written and developed.
Data processing is one of the processes that is readjusted to fit individual protocol in order to deliver the results best geared to the study needs.

Descriptive outline of the Calorimetrics Chambers

Each of the two Calorimetrics Chambers occupies 10 m² of floorspace for a total volume of over 32 m3.

The chambers are designed to host indirect calorimetric measurement of energy expenditure based on the respiratory exchange ratios of the in-room volunteers.
Each room is comfortably air-conditioned via a constant open-circuit air recycling system, and is temperature and humidity-controlled.

Inside the chambers, the space and furnishings have been designed to offer volunteers the most comfortable experience possible. Commodities include a table, a chair, a bed, a bedside table with reading light, a sink, and toilets. During protocol rest periods, volunteers can relax with the HiFi and video system comprising tuner, cassette-player, CD, plus combination DVD/VHS player, and options for connecting a games console). During the physical activity phases, each room can be switched around and readapted, with a treadmill, an exercise bike, or a stepper. Each room is also equipped with a telephone and an intercom. A microwave oven is provided for heating up meals.

Moving on, each room is linked up to an electrocardiograph so that each volunteer's heart rate can be monitored and logged. Although this parameter does not enter directly into the energy expenditure calculations, it does help tie heart rate to the kinetics of energy expenditure.
Since the Calorimetrics Chambers host volunteers over periods stretching from 24 hrs up to several days, supervisory surveillance staff are on constant standby. Surveillance continuity is assured overnight by a duty watchman lodging in a simple bedroom.
The Calorimetrics Chambers are equipped with a series of alarms networked into the duty watchman's lodgings:

• buzzer bells hand-triggered by the volunteers
• cardiac alert system
• fire alarm
• technical alarm

The analytics bay features four Siemens analyzers (one pair per chamber), Oxymat 6 analyzers for continuous O2 metrics and Ultramat 6 analyzers for continuous CO2 metrics.
Each chamber has a mass flowmeter that permanently measures air extraction rate (air exchange) in the 1 to 10 m3/h rate bracket.
The battery of sensors in each chamber is rounded off with a temperature probe, humidity sensor, and an atmospheric pressure sensor.
Data readings are captured via a link-up between the central measurement station, which acts as a hub connecting all the sensors, and the computer acquisition system. One data acquisition sequence and one data backup sequence are run every 60 seconds.

The research environment

A research structure harnessing complementary equipment facilities with multidisciplinary competencies can design and deliver fully-developed protocols.
The human nutrition research centre ('CNRH') housing the chambers assigns qualified staff (doctors, clinical research assistants, nurses, dieticians and a cook) to provide full protocol management logistics backup:

• recruitment of volunteers, scheduling management
• medical screening for the inclusion of volunteers
• sampling
• producing calibrated meals in order to stringently control the volunteers' dietary intake and energy balance

Complementary skillsets and equipment facilities:

• Datex monitor plus canopy system for measuring at-rest metabolism on-site
• Actiheart and ArmBand for running home-based estimates of energy expenditure based on a series of metrics (heart rate, actigraphy, temperature)
• Dual X-ray absorptiometry (DXA) for measuring body composition and bone mineral density
• Multi-frequency bioelectric impedance analysis and skinfold testing to measure body composition
• Doubly-labelled water method for measuring metabolic rate over a one-week period, and for gauging body composition