The Berlin-Buch respiration chamber for energy expenditure measurements

Abstract

Purpose: We present a methodological overview of a respiration chamber at the Experimental and Clinical Research Center in Berlin, Germany. Since 2010, we investigated 750 healthy subjects and patients with various diseases. We routinely measure resting energy expenditure (REE), dietary-induced thermogenesis, and activity energy expenditure.

Methods: The chamber is a pull calorimeter with a total volume of 11,000 L. The majority of measurements is done with a flow rate of 120 L/min, yielding a favorable time constant of 1.53 h. The gas analysis system consists of two paramagnetic O₂ sensors and two infrared CO₂ sensors, one for incoming and one for outgoing air samples. O₂ and CO₂ sensors are calibrated simultaneously before each measurement with a 6 min calibration routine. To verify the accuracy of the whole the calorimetric system, it is validated every 2 weeks by 2 h acetone burning tests.

Results: Validation factors (calculated/measured) of 20 representative 2 h acetone burning tests were 1.03 ± 0.03 for [Formula: see text], 1.02 ± 0.02 for [Formula: see text], 0.99 ± 0.02 for RER, and 1.03 ± 0.03 for EE. Four repeated 60 min REE measurements of a healthy woman showed variabilities of 231.9 ± 4.8 ml/min for [Formula: see text] (CV 2.1%), 166.0 ± 6.3 ml/min for [Formula: see text] (CV 3.8%), 0.73 ± 0.03 for RER (CV 4.6%), and 4.55 ± 0.07 kJ/min for EE (CV 1.6%).

Conclusions: The data presented show that our respiration chamber produces precise and valid EE measurements with an exceptionally fast responsiveness.

Keywords: Diet-induced thermogenesis; Energy expenditure; Respiration chamber; Whole-room calorimeter.

Fig. 1

Photograph (A) and layout (B) of the pull-type, open-circuit respiration chamber in Berlin, Germany. 1, table; 2, television set; 3, cameras; 4, Passive Infrared Sensors; 5, chair with footrest; 6, bicycle ergometer; 7, toilet; 8, air lock; 9, air conditioning

Fig. 2

Representative time course of A oxygen (O₂) and B carbon dioxide (CO₂) concentration during an automatic calibration routine; incoming sensors (dotted lines), outgoing sensors (solid lines), valves switch at 0, 120, 240, and 360 s (dashed vertical lines). Results of calibrations (n = 60) over 2 years for C, E oxygen sensors and D, F carbon dioxide sensors; incoming sensors (closed circles), outgoing sensors (open circles), reference gas concentration (dashed lines), and linear regression results (dotted lines). R² values by simple linear regression

Fig. 3

Validation factors (calculated/measured) for $\dot{V}{\text{O}}_2$, $\dot{V}{\text{CO}}_2$, respiratory exchange ratio (RER), and energy expenditure (EE) of 20 2 h acetone burning tests

Fig. 4

Time course of one representative 20 h validation to determine chamber volume. Oxygen (O₂) incoming–outgoing (solid line), carbon dioxide (CO₂) outgoing–incoming (dotted line)

Fig. 5

Mean response time (n = 6) of the chamber after opening the door four times (240, 480, 720, and 960 s; n = 24) for 10 s (dashed vertical lines). Oxygen (O₂) incoming–outgoing (solid line), carbon dioxide (CO₂) outgoing–incoming (dotted line)

Fig. 6

Energy expenditure (EE; A) and respiratory exchange ratio (RER; B) of 13 healthy subjects at rest (REE) and during 40 min of moderate bicycle exercise (0.5 W/kg bodyweight) followed by 30 min recovery in an armchair. Before starting to exercise, subjects drank a 75 g glucose load. Data analysis is presented in 10 min (open circles) and 5 min (closed circles) intervals to demonstrate chamber resolution