Human Gradient‐Layer Calorimeter: Development of an Accurate and Practical Instrument for Clinical Studies

Abstract

A whole body gradient-layer calorimeter was designed for thermophysiologic studies in hospitalized patients. The instrument was assembled in a room adjoining a metabolic ward. The patient lies recumbent on a stretcher which is wheeled into the calorimeter on tracks. Once inside, the patient's head extends through one wall into a clear plastic canopy. The canopy is partially open on one side and is the entry point for fresh air into this open-circuit system. Heat flux transducers in the calorimeter walls, a thermopile in the exit air stream, and a platemeter in conjunction with wet and dry bulb thermometers allow measurement of total, wet, and dry heat losses from the subject. All calorimeter output signals are routed to a microcomputer system which processes the data and provides real-time output of results. A mannequin heat source is used to calibrate the gradient layer. Testing with a variety of wet/dry heat sources indicate total, wet, and dry heat measurements are accurate to within 2-3%. A typical study of resting energy expenditure requires 1 hr, and protocols of up to 6 hr are well tolerated. The calorimeter has proven to be reliable, accurate, and easy to operate. These qualities, combined with good patient tolerance, make it ideal for metabolic studies.

The Determination of Changes in Body Heat Content during Exercise Using Calorimetry and Thermometry

“…As with floẇ calorimetry, effluent air must be analysed for changes in water vapour content in order to account for evaporative heat loss which is particularly important for studies involving exercise and the accurate determination of DH b . Gradient layer calorimetry has been used by several prominent researchers for various clinical and thermophysiologic applications (Jequier, 1975;McManus et al, 1984;Meis et al, 1994;Seale and Rumpler, 1997;Seale et al, 1991;Spinnler et al, 1973).…”

Η Επίδραση Των Παραγόντων Του Περιβάλλοντος Στην Άσκηση

“…Δεδομένου ότι η διαφορά στην αντίσταση εξαρτάται από τη διαφορά θερμοκρασίας και την απώλεια θερμότητας. Το θερμιδόμετρο «gradient layer» χρησιμοποιήθηκε ευρέως τις τελευταίες τρεις δεκαετίες του 20ου αιώνα σε διάφορες κλινικές και θερμορυθμιστικές μελέτες (Chappuis, Pittet, & Jequier, 1976;Jequier, 1975;McManus et al, 1984;Meis et al, 1994).…”