Validity and reliability of a new portable telemetric calorimeter designed to measure oxygen consumption and carbon dioxide production

Objective: The purpose of the present study was to evaluate the precision and the accuracy of a new portable telemetric calorimeter developed for the measurement of oxygen consumption, carbon dioxide production and pulmonary ventilation. Design: An in vitro validation study. Methods: An experimental protocol was designed to generate a series of tidal volumes (from 100 ml to 6000 ml at 200 ml steps) at different respiratory rates (5, 8, 14, 20, 40, 60, 75 breaths-min(-1)). For this purpose, a standardized pulmonary waveform generator system was utilized. Moreover, in order to evaluate the measure of O-2 and CO2 concentrations at different temperatures (-10 degrees, 0 degrees, 15 degrees, 25 degrees, 40 degreesC), the instrument was placed inside an adjustable temperature and humidity chamber. Results: The accuracy of flow measurements was within +/-3% in respect to the real values throughout the entire range of physiological values, whereas the measurements of gas concentrations were within +/-1 % between 0 and 25 degreesC. Conclusions: The new portable telemetric calorimeter represents an easy to use instrument for the measure of energy expenditure during the activities of daily living. (C) 2001, Editrice Kurtis.