Background In paediatric intensive care unit (PICU), the relationship between end-tidal partial pressure of carbon dioxide (PetCO2) and arterial partial pressure of carbon dioxide (PaCO2) may vary dramatically (PetCO2-PaCO2 difference between -36 and 63 mmHg) (1). The aim of our study was to develop a model using volumetric capnography (VolCap) to better predict PaCO2 in mechanically ventilated children.
Material and methods We conducted a prospective clinical study that included all children admitted at Ste-Justine hospital, age 3 kg, mechanically ventilated > 12 h, with an arterial cannula. After literature review, we collected specific data from medical record including demographic data, clinical informations, ventilation, VolCap (NM3, Respironics, Philips, USA) and biological parameters. VoCap was recorded 15 min before an arterial blood gas and analysed breath-by-breath using a specific software (FlowTool, Philips, USA). The predictive model for PaCO2 was developed using a linear multivariable regression with the best determination coefficient (R2).
Results 43 children (26 boys, 60%) age of 52 [9–137] months were included. Children with Tidal volume less than 30 ml were excluded because of technical bias in VolCap interpretation by the software. In linear multivariable regression, the best model included the mean airway pressure (p = 0.01), PetCO2 (p2 (p = 0.014) and the capnographic index (100*Slope SIII/Slope SII) (p = 0.003) with a R2= 0.85.
Conclusion Our preliminary results show that VoCap can help to improve the non-invasive estimation of PaCO2. Further research is necessary to validate the accuracy of our model.
McDonald et al. Pediatr Crit Care Med 2002;3:244-249