The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

Qualification Of Multiple Metabolic Systems For Use In The Pediatric Clinical Setting

Timothy C. Lovelady, BA, RRT, RPFT All Children's Hospital, St. Petersburg, Florida

INTRODUCTION: With the clinical use of multiple metabolic measuring devices in a single hospital facility, it may be necessary, based on availability, to use a combination of these devices for serial measurements on individual patients. Under these circumstances it becomes important to systematically compare the results of these devices to some standard and included this information in metabolic study interpretations. This will provide a more cohesive uniform longitudinal quality to metabolic results.

METHOD: The conformity of three Metabolic measurement systems in the Canopy Mode (the MGM JR-Life Systems Industries, the Deltatrac-Sensormedics Corp., and the 2900-Sensormedics Corp.) were evaluated in a pediatric range of use for VO2 and VCO2 (13-75 ml/minute) by applying gas dilution method. Factory calibrated Cole-Parmer Flowmeters were used to titrate known quantities of CO2 and Nitrogen into a pediatric Deltatrac Canopy system connected to the measuring port of each instrument via wide bore corrugated tubing. Flows were set at specific levels and each instrument was calibrated according to manufacturer's recommendations immediately before each test run. Once the metabolic device was flushed with the titrated gases via the canopy flow (after steady state was achieved), 5 one minute measurements of VO2 and VCO2 were obtained over a 5 minute interval and averaged. At each level of flow, an interval of data was obtained on each instrument while maintaining consistent flows during that interval. Canopy flows were selected to develop physiologic RQ's and FeCO2 values between .5 and 1%.

Results: Statistical analysis using Paired T-Test with standard deviation and variance of individual sample intervals on each instrument were obtained. The probability of Conformity with range of % Error for the Deltatrac, MGM jr, and Sensormedics 2900 were 0.9917 (0-5%), 0.6368 (0-29%), and 0.6968 (1.7-21.5%) respectively. Average sample standard deviations and variances for these instruments were (S.D. 1.01, 1.47,& 1.17)(VAR 1.15, 2.98, & 1.88) as well.

Conclusions: Of the Systems evaluated for pediatric metabolic use, the Deltatrac produced the most consistent results in the Canopy mode. With the MGMjr and the Sensormedics 2900, although each instrument developed stable interval results; in general, their results were alinear, their relative error was high, and conformity to standard was low (up to 29% lower than expected values). These two systems if used in the pediatric setting should be closely scrutinized for variations in calibration routine and placed on a stringent quality assurance regiment.


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