VALIDITY OF A LOW-FLOW PNEUMOTACH AND PORTABLE METABOLIC SYSTEM FOR MEASUREMENT OF BASAL METABOLIC RATE

Abstract

The accurate measurement of physiologic variables at rest is essential for determination of basal metabolic rate (BMR). Advances in technology have led to development of portable metabolic measurement systems which allow researchers to take systems into homes for the determination of BMR. The low flow volume produced during BMR assessment has proved difficult for portable units to accurately measure. Recently a pneumotach was developed for a portable metabolic measuring system for measuring oxygen consumption (VO2), carbon dioxide production (VCO2) and minute ventilation (VE) at rest. PURPOSE The purpose of this study was to investigate the validity of the MedGraphics VO2000 portable metabolic measurement system with a Low Flow Pneumotach (Medical Graphics Corp., St. Paul, MN) for the determination of VO2, VCO2 and VE at rest. METHODS A MedGraphics VO2000 equipped with a Low Flow Pneumotach was arranged in series to a MedGraphics CPX/D metabolic system. This back to front series allowed for identical samples to be obtained by both systems thus limiting biological and environmental variability from multiple testing sessions. Twenty-two(10 M, 12 F) young(24±6 yrs) healthy participants volunteered for this study. Mean height and weight were 173.2 cm(±10.2) and 73.5 kg(±10.9), respectively. Protocol consisted of subjects arriving to the laboratory after a 12 hr fast and lying quietly in a comfortable supine position for 10 minutes before data collection began. Inspired and expired gases were collected for 60 min. RESULTS Student's T-test demonstrated no significant difference (p < .05) between VO2, VCO2, or VE. These findings coincide with significant (P < 0.05) correlation coefficients of 0.78, 0.78 and 0.71 for VO2, VCO2, and VE, respectively. Bland-Altman plots indicated good agreement between the systems for VO2, VCO2 and VE. CONCLUSION Results of this study indicate that the MedGraphics VO2000 fitted with a Low Flow Pneumotach produces comparable results for VO2, VCO2 and VE to that of the MedGraphics CPX/D unit for measures of BMR.