A NEW PEDIATRIC METABOLIC MONITOR

Objective: A paediatric option for the measurement of VO2 and VCO2 (20 to 150 ml/min) has recently been introduced for the adult Deltatrac m etabolic monitor (Datex Instrumentarium, Finland) to use in ventilated and spontaneously breathing children. This paper describes a laborato ry validation of the paediatric option for ventilated children with re gard to the influence of respiratory variables. Design: Respiratory va riables were varied within the following ranges: FIO2 0.21-0.8, FIO2,- FE0(2) DFO2) 0.01-0.05, FECO(2) 0.01-0.05, V-E 300-6000 ml/min, V-T 8- 300 ml, RR 10-50/min, P-aw 10-60 mbar, relative humidity 10% and 60%, and resulted in 107 test situations. Setting: Gas exchange was simulat ed by injection of nitrogen and CO2 at a RQ close to 1. Patients or pa rticipants: Different situations of paediatric patients ventilated in controlled mode were simulated on a gas injection model. Interventions : Respiratory and metabolic variables were varied independently to res ult in a range of 8 to 210 ml/min of VO2 and VCO2. Measurements and re sults: Reference measurements were carried out by mass spectrometry an d wet gas spirometry. The mean VCO2 difference for all tests ranging f rom 20 ml/min to 210 ml/min was -2.4% (2SD = +/-12%). The respective V O2 difference was -3.2% (2SD = +/-23%). Measurement agreement for VO2, in neonatal respirator treatment (20 - 50 ml/min) compared to older c hildren (50-210 ml/min) showed a mean difference of -3.9% (2SD = +/-26 %) versus -2.8% (2SD = +/-20%). The respective differences for VCO2 we re -7.1% (2SD = +/-7%) versus +0.4% (2SD = +/-10%). The mean differenc e for VO2 as well as VCO2, indicated a high systematic agreement of bo th methods. The variability (+/-2SD) in VCO2 measurement is acceptable for all applications. The overall variability in VO2 measurement (2SD = +/-23%) can be reduced by exclusion of all tests with a FECO(2) and DFO2 below 0.03. This results in a mean difference of -3.2% (2SD = +/ -13.7%). Conclusion: Within this limitation the paediatric measurement option seems to introduce a valuable method for clinical application in paediatric intensive care medicine.