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Synchronous direct gradient layer and indirect room calorimetry
1Diet and Human Performance Laboratory, Beltsville Human Nutrition Research Center, Maryland 20705, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 7, 1998
Summary
This study developed a method to accurately compare human heat emission and energy expenditure using dual calorimeters. Corrected measurements show equivalence, except during sleep, revealing insights into the body's heat regulation.
Area of Science:
- Human Physiology
- Metabolic Research
- Biomedical Engineering
Background:
- Accurate measurement of human energy expenditure and heat emission is crucial for understanding metabolic processes and thermoregulation.
- Existing direct and indirect calorimetry systems have different response times, hindering direct comparison of their measurements.
- A dual room-sized calorimeter was employed to simultaneously assess heat emission and energy expenditure in human subjects.
Purpose of the Study:
- To develop and validate a system of equations to correct for response time delays in dual direct/indirect calorimetry.
- To accurately compare simultaneous measurements of heat emission and energy expenditure in humans.
- To investigate discrepancies between heat emission and energy expenditure during different physiological states, such as sleep and wakefulness.
Main Methods:
- Utilized a dual direct/indirect room-sized calorimeter at the Beltsville Human Nutrition Research Center.
- Developed and tested a system of equations to correct for calorimeter response time differences.
- Validated the system using alcohol combustion as a simulated human subject.
- Conducted 24-hour measurements on 10 human subjects.
Main Results:
- Calorimetry systems, both raw and corrected for response time, demonstrated high accuracy (99.9%) in performance tests with alcohol combustion.
- Corrected heat emission measurements were found to be equivalent to corrected energy expenditure measurements (99.8%) over 24 hours in human subjects.
- Heat emission significantly exceeded energy expenditure by 14% during sleep, with this difference reversing during the day.
Conclusions:
- The developed correction system enables accurate comparison of direct and indirect calorimetry outputs.
- Simultaneous measurement of heat emission and energy expenditure provides valuable insights into human heat regulation.
- Observed differences between heat emission and energy expenditure during sleep suggest a dynamic change in the body's stored heat, impacting energy balance studies.
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