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Study Validates Improved Accuracy of New Sable Indirect Room Calorimetry System for Metabolic Measurement in Humans

May 11th, 2010

A study presented at the FASEB 2010 Experimental Biology Meeting in Anaheim, CA, demonstrates the improved accuracy of a new flow-through respirometry system. The system utilizes a patent-pending background baselining protocol to reduce errors associated with water vapor dilution, analyzer drift and variability in gas concentrations of incurrent air to provide more reliable results in room calorimetry. It allows researchers to monitor human metabolic rate and respiratory exchange ratio during rest or exercise bouts without any breaks or discontinuities, and without the loss of data due to baselining interrupts. The method uses multiple gas-analysis chains which interleave baseline and chamber readings in a complex fashion resulting in contiguous, unbroken metabolic records with one-second resolution. The technology will be incorporated into Sable Systems’ next generation of metabolic measurement systems.

 

“This new development represents a major advance in indirect room calorimetry, providing for more accurate measurement of metabolic activity,” said Edward L. Melanson, Ph.D., FACSM, University of Colorado, School of Medicine, Division of Endocrinology, Metabolism and Diabetes.  Dr. Melanson conducted the study, which will be published in an upcoming issue of the American Journal of Physiology-Regulatory, Integrative, and Comparative Physiology. “While most systems incorrectly assume that CO2 concentrations in incurrent air are constant and that analyzers do not drift,” said Dr. John Lighton, president of Sable Systems International and a co-author of the study, “this new approach by Sable Systems accurately corrects for analyzer drift and variations in incurrent CO2 concentrations.”

 

Indirect calorimeters are used to determine the metabolic rate of an organism by measuring respiratory gas exchange and oxygen consumption. Most systems in the United States are classified as “pull” systems, because they pull the air through the respirometry chamber. A major problem with pull systems has been the inefficiency of their gas-drying systems. The new Sable system uniquely addresses this problem by measuring the water vapor pressure in the incurrent and excurrent airstreams and adjusting the measured gas concentrations for the dilution effect of water vapor pressure, thus eliminating the need to dry the gasses. The novel “switching” method constantly measures the excurrent airstream while frequently checking the incurrent airstream, allowing for dynamic adjustment to the incurrent gas concentrations due to changes in gas concentrations in the incurrent air, and analyzer drift.

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