Classical experiments in whole-body metabolism: open-circuit respirometry—diluted flow chamber, hood, or facemask systems

Abstract

For over two centuries, scientists have measured gas exchange in animals and humans and linked this to energy expenditure of the body. The aim of this review is to provide a comprehensive overview of open-circuit diluted flow indirect calorimetry and to help researchers to make the optimal choice for a certain system and its application. A historical perspective shows that ‘open circuit diluted flow’ is a technique first used in the 19th century and applicable today for room calorimeters, ventilated hood systems, and facemasks. Room calorimeters are a classic example of an open-circuit diluted flow system. The broadly applied ventilated hood calorimeters follow the same principle and can be classified as a derivative of these room calorimeters. The basic principle is that the subject breathes freely in a passing airflow that is fully captured and analyzed. Oxygen and CO2 concentrations are measured in inlet ambient air and captured outlet air. The airflow, which is adapted depending on the application (e.g., rest versus exercise), is measured. For a room indirect calorimeter, the dilution in the large room volume is also taken into account, and this is the most complex application of this type of calorimeter. Validity of the systems can be tested by alcohol burns, gas infusions and by performing repeated measurements on subjects. Using the latter, the smallest CV (%) was found for repeated VO2max tests (1.2%) with an SD of approximately 1 kJ min−1. The smallest SD was found for sleeping metabolic rate (0.11 kJ min−1) with a CV (%) of 2.4%.

Changes in sleeping energy metabolism and thermoregulation during menstrual cycle

“…On the other hand, this study could detect an increase in carbohydrate oxidation during sleep in the luteal phase. It is of note that reproducibility of energy expenditure during sleep is higher than that of the resting metabolic rate (Schoffelen & Plasqui, ).…”

Test‐retest variability of VO2max using total‐capture indirect calorimetry reveals linear relationship of VO2 and Power

“…As has been previously demonstrated, the successful validation of an individual calorimeter should prove suitability for the full range of technical and biological variability expected …”

“…As has been previously demonstrated, 15 the successful validation of an individual calorimeter should prove suitability for the full range of technical and biological variability expected. 16 In brief, technical validation must be able to mimick the biological aspects as found in real life, for instance, breathing frequencies or energy expenditure at applicable physiological ranges. In contrast, a calorimeter that cannot be directly validated at the applicable physiological ranges and/or measurement mode may yet be validated by comparison of stable subject group results obtained with a validated second calorimeter.…”

“…In contrast, a calorimeter that cannot be directly validated at the applicable physiological ranges and/or measurement mode may yet be validated by comparison of stable subject group results obtained with a validated second calorimeter. 16 To assess the validity of our hypothesis, both a total-capture indirect calorimeter and a calorimeter using breathby-breath mode were tested. The total-capture indirect calorimeter was validated for both technical accuracy and biological reproducibility.…”

Respiration chamber calorimetry and doubly labeled water: two complementary aspects of energy expenditure?

“…Respiration chambers are considered as classic method, ingeniously implemented more than one century ago by Max von Pettenkofer in Germany and Atwater in USA [5]. Today, there are many functional chambers dispersed around the world, either built by engineers (home-made built) or inspired from other existing metabolic chambers that showed good accuracy and precision [6].…”