A FAST RESPONDING COMBINED DIRECT AND INDIRECT CALORIMETER FOR HUMAN-SUBJECTS

The construction and performance of a 5.4 m(3) combined direct and ind irect calorimeter for human subjects is described. The calorimeter was constructed for studies on human subjects primarily undergoing fast a lterations in heat production and heat losses. e.g. after a meal or du ring physical excercise. A heat sink and a heat substitution principle is used to measure sensible heat losses directly. Evaporative heat lo sses are determined by measuring water vapour input and output. Indire ct calorimetry is performed by measuring output air flow and changes i n gas composition of the air entering and leaving the calorimeter. The response times (90%) for sensible heat and evaporative heat were foun d to be 4 min and 34 min, respectively. Three alcohol combustion tests gave a recovery of CO2 and O-2 in the range 92-97%. The recovery of w ater was found to be in the range 56-89%. (C) 1998 IPEM. Published by Elsevier Science Ltd. All rights reserved.