Meeting Abstract

41.1  Tuesday, Jan. 5  Background baselining: A new approach to metabolic measurement LIGHTON, JRB; Sable Systems International lighton@sablesys.com

Because traditional respirometry measures metabolic rates as a function of the difference between incurrent and excurrent gas concentrations (usually air entering and leaving a sealed chamber or a mask), the accuracy with which small changes in gas concentrations are measured can limit the overall accuracy of the technique. Usually flow-through respirometry requires frequent measurement of incurrent gas concentrations in order to accurately characterize the effect of the organism under study on (incurrent – excurrent) gas concentrations. The repeated measurement of incurrent gas concentrations is usually referred to as “baselining.” Baselining, though necessary, interrupts measurements and disrupts the continuity of metabolic recordings. As a result, researchers have had to trade off between temporal continuity and accuracy. Differential gas analyzers, although an improvement on single-channel analyzers, do not eliminate the baselining requirement. I have developed a technique (patent pending; free license to academic researchers) that allows baselining to occur in the background. Signal processing of the resultant raw data reassembles a complete, unbroken metabolic recording. I present some details of the technique, and data from three case studies: A 24-hour metabolic recording of a mouse with running wheel, gas concentrations in a scientific meeting room, and data from a 28,000 liter room calorimeter for humans showing a 24-hour response-corrected metabolic record (VO₂, VCO₂, EE and RQ) including episodes of activity and sleep, and demonstrating excellent temporal resolution.