ENERGY LOAD IN MECHANICALLY VENTILATED PAEDIATRIC LUNGS: A BENCH STUDY
- Stavroula Ilia, Greece
- Stavroula Ilia, Greece
- Alette A. Koopman, Netherlands
- Robert Blokpoel, Netherlands
- Martin Kneyber, Netherlands
Abstract
Background
Mechanical ventilator energy is transferred to the respiratory system and mainly spent to expand the lung parenchyma and overcome resistance of the airways. This has never been measured in mechanically ventilated children.
Objectives
To determine the tidal mechanical energy imparted to the lungs under different conditions in terms of lung size, respiratory mechanics and ventilator settings.
Methods
A bench study was designed to simulate age groups from newborn (endotracheal tube (ETT) 3.0mm) to adolescent (ETT 8.0mm). Pressure (PC) and volume (VC) controlled modes were tested. All possible combinations of respiratory mechanics were simulated. PEEP was set at 5cmH20. Airway and intrapulmonary pressure, including plateau pressure (Pplat) measured at zero-flow state, tidal volume (VT) and flow were recorded. Elastic energy applied to the lung (ELUNG) per breath normalised to body weight was measured from the dynamic pressure –volume curve.
Results
2,652 measurements were performed. ELUNG was higher in VC (p<0.001) and in small ETT sizes (p<0.001). ELUNG was positively correlated with driving pressure (DP) and inflated volume (VT/kg) (r2=0.87 and r2=0.65, respectively, all p<0.001). Best fitting model for predicting ELUNG was a linear combination of DP and VT/kg (R2 = 0.934, p<0.001). ELUNG differed between ventilation modes after stepwise change of compliance (p<0.001). ELUNG was negatively associated with stepwise increase of resistance only in PC ventilation (p<0.001).
Conclusion
DP and inflated volume were the leading mechanical lung energy coefficients. Further studies are needed to delineate the clinical significance of energy load in children and define the “bearable” range as to cause the least lung damage.