Direct Calorimetry by Means of the Gradient Principle

Abstract

A rapidly responding calorimeter for continuous recording of biological heat exchange has been described. The method is based on the enclosure of the subject in a shell completely lined with a uniform heat flow metering layer (``gradient layer'') while ventilatory and respiratory heat losses are determined in heat exchange meters based on the same technic. The measurement comprises in one thermoelectric potential the sum of all components of heat loss (radiant, convective, conductive, and evaporative fractions). Partitioning measurements of respiratory and evaporative heat losses are readily obtained. Environmental conditions can be closely controlled, and widely varied. The gradient calorimeter with its rapid response (time lag 42 seconds) is specifically designed for studies of reflex mechanisms involved in temperature control. It is, however, suggested that the characteristics described will, in general, encourage wider application of direct calorimetry in experimental and clinical studies.

Foetal heat production in the fowl

“…The calorimeter is based on the gradient principle. Gradient calorimeters for investigation of metabolic activity in man have been developed by Benzinger & Kitzinger (1949), and a more simple apparatus adapted for measurements on small domestic animals by Prouty, Barrett & Hardy (1949). Our subject, the developing chicken embryo, needs special precautions with the equipment, as there must be a carefully maintained incubation temperature of the calorimeter vessel and ventilation adequately adapted to the oxygen need on each day of incubation.…”

Effect of Body Position on Energy Expenditure of Preterm Infants as Determined by Simultaneous Direct and Indirect Calorimetry

“…The calorimeter operated based on the gradient-layer principle originally described by Benzinger and Kitzinger. 12 The calorimeter had a heated water jacket to allow thermal support of the infant during calorimetric measurements. The outer dimensions of the calorimeter chamber were 37.5 x 38.5 x 68.5 cm.…”

Direct animal calorimetry, the underused gold standard for quantifying the fire of life

“…An important and enduring advance in direct calorimetry occurred with the advent of Benzinger and Kitzinger’s thermoelectric gradient layer calorimeter (Benzinger et al 1949). A commercial version of the thermoelectric gradient layer calorimeter became available (Thermonetics, La Jolla, CA) based on efforts by Heinz F. Poppendiek (Poppendiek et al 1972) and has been utilized in a number of studies (e.g., (Seale et al 1991; Meis et al 1994; Gordon et al 1995; Seale et al 1997; Gordon et al 1998; Gordon et al 2003; Gordon 2004)) including our own (Kaiyala et al 2005; Kaiyala et al 2007b; Kaiyala et al 2007a).…”