A PORTABLE DEVICE FOR ESTIMATING THE RATE OF CO2 PRODUCTION IN PRETERM INFANTS

We developed a simple flow-through system for measuring the net rate o f pulmonary excretion of CO2 (VCO2). Its components, connected in seri es by plastic tubing, are the following: plastic oxygen hood, suction flask used both as a mixing and sampling chamber, Brooks mass flow con troller, and wall suction. Gas aliquots withdrawn from the sampling fl ask are analyzed for CO2 concentration in the laboratory. The system w as validated by measuring over a 60-min period the evolution of CO2 fr om the reaction of sodium carbonate with phosphoric acid. In 9 trials, the mean recovery of CO2 was 99.8%. In 14 studies in 11 preterm infan ts, we evaluated the reproducibility of duplicate measurements of CO2 production on consecutive days; in 9 of the studies, the coefficient o f variation was <5 %, but in other 5 studies, it ranged from 7.7 to 35 .8%. We believe that this device might have both research and clinical applicability.