Design of climate respiration chambers, adjustable to the metabolic mass of subjects

Open-circuit respiration chambers can be used to measure gas exchange and to calculate heat production (Q) of humans and animals. When studying short-term changes in Q, the size of the respiration chamber in relation to the subject of study is a point of concern. The washout time of a chamber, defined as the proportion of the chamber size to the rate of ventilation, needs to be minimised for accurate measurement of short term changes in Q. To date, most respiration chambers have a fixed size, limiting their use for different species, sizes and number of subjects, thus hampering studying the short term dynamics of Q. This chapter presents various approaches to the design, construction and testing of respiration chambers, adjustable to the metabolic mass inside. As investment costs for constructing respiration chambers are high, flexibility in the use of chambers can contribute substantially to an efficient use of resources. Furthermore, an outline is given to sensor criteria and calibration and finally, the validation of a whole indirect-calorimetric system is described. Air leak tolerance is defined and attention is paid to caretaking of animals, excreta collection and animal and personnel welfare and safety. Respiration facilities, recently constructed at Wageningen University are presented as an example. Briefly, four 45 m2 climate chambers can be used, e.g. for heat or cold stress experiments, to incubate eggs or as a hygiene barrier. Within each chamber, one or two smaller airtight, size adaptable respiration rooms, can be built in where ambient temperature, humidity and ventilation rate can be controlled independently. In each respiration room a wide range of ventilation flow rates can be accomplished and both hypobaric and hyperbaric air pressure control can be established, allowing energy metabolism experiments with specific pathogen free animals (hyperbaric) or trials with infectious agents (hypobaric).