A new paediatric 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 metabolic monitor (Datex Instrumentarium, Finland) to use in ventilated and spontaneously breathing children. This paper describes a laboratory validation of the paediatric option for ventilated children with regard to the influence of respiratory variables.

DESIGN

Respiratory variables were varied within the following ranges: FIO2 0.21-0.8, FIO2-FEO2 (DFO2) 0.01-0.05, FECO2 0.01-0.05, VE 300-6000 ml/min, VT 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 simulated by injection of nitrogen and CO2 at a RQ close to 1.

PATIENTS OR PARTICIPANTS

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 result in a range of 8 to 210 ml/min of VO2 and VCO2.

MEASUREMENTS AND RESULTS

Reference measurements were carried out by mass spectrometry and wet gas spirometry. The mean VCO2 difference for all tests ranging from 20 ml/min to 210 ml/min was -2.4% (2SD = +/- 12%). The respective VO2 difference was -3.2% (2SD = +/- 23%). Measurement agreement for VO2 in neonatal respirator treatment (20-50 ml/min) compared to older children (50-210 ml/min) showed a mean difference of -3.9% (2SD = +/- 26%) versus -2.8% (2SD = +/- 20%). The respective differences for VCO2 were -7.1% (2SD = +/- 7%) versus +0.4% (2SD = +/- 10%). The mean difference for VO2 as well as VCO2 indicated a high systematic agreement of both 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 FECO2 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.