VALIDITY OF A LOW-FLOW PNEUMOTACH AND PORTABLE METABOLIC SYSTEM FOR MEASUREMENT OF BASAL METABOLIC RATE - T.P. Olson, J. Tracy, D.R. Dengel, FACSM. University of Minnesota, Minneapolis, MN and the VA Medical Center, Minneapolis, MN

The accurate measurement of physiologic variables at rest is essential for the determination of basal metabolic rate (BMR). This measurement often requires subjects to come into a laboratory or stay over night in a metabolic ward. Advances in technology have led to the development of portable metabolic measurement systems which would allow researchers to take these systems into homes for the determination of BMR, however the low flow volume produced during measurement of BMR have often proved difficult for these portable devices to accurately measure. Recently a pneumotach was developed for use with a portable metabolic measuring system for the purpose of measuring oxygen consumption (VO₂), carbon dioxide production (VCO₂) and minute ventilation (V_E) at rest.

PURPOSE: The purpose of this study was to investigate the validity of the MedGraphics VO2000 portable metabolic measurement system coupled with a Low Flow Pneumotach (Medical Graphics Corp., St. Paul, MN) for the determination of VO₂, VCO₂, and V_E 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 male, 12 female) young (24±6 yrs) healthy participants volunteered for this study. The mean height and weight were 173.2 cm (±10.2) and 73.5 kg (±10.9), respectively. The protocol consisted of each subject 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 V_E. These findings coincide with significant(P<0.05) correlation coefficients of 0.78, 0.78, and 0.71 for VO₂, VCO₂, and V_E, respectively. Bland-Altman plots indicated a good agreement between the two systems for VO₂, VCO₂ and V_E.

CONSLUSION: The results of this study indicate that the MedGraphics VO2000 fitted with a Low Flow Pneumotach produces comparable results for VO₂, VCO₂, and V_E to that of the gold standard MedGraphics CPX/D unit for measures of BMR.