Abstract Rationale Lung mechanical power (MP, the energy per unit time transmitted to alveoli) of mechanical ventilation (MV) correlates with mortality in both adult and pediatric patients. The calculation of MP requires knowledge of the lung compliance (C), resistance (R), and inductance (L) effects of airflow through lung tissue. In conventional MV, calculations of MP ignore L due to relatively low flow velocities. However in high frequency oscillatory ventilation (HFOV), this assumption may not be valid. In this in silico study, we compared the traditional RC-circuit used in MP models for conventional MV with two models that incorporate the L of bulk air flow for healthy and diseased states: the RLC-model; and the Mead’s model (i.e., a two-compartment model of lung tissue in which connected alveoli of different C are considered). Methods In silico modeling was performed in MATLAB (MathWorks, Natick, MA). We simulated a pediatric patient with acute respiratory distress syndrome (ARDS) undergoing MV with HFOV, with mean airway pressure 25 cmH2O, 1:1 inspiratory to expiratory ratio, and delta pressure of 50 cmH2O. Frequencies were tested from 8-15 Hz. The RC and RLC models were implemented using physiological estimates for R, C, and L described in the literature; additionally, the Mead’s model was used. Results The difference in MP between the RC model and RLC model increased as frequency increased. But, the MP for the RLC model, over the range of 8-15 Hz, was proportionately 0.6-0.8 of the MP for the RC model. In the Mead’s model of ARDS, the MP was 1.1-1.5 times of value of the RC model and 1.8-2.4 times the estimate of the RLC model. Conclusion In silico, in simulated pediatric patients undergoing MV with HFOV, the RC and RLC models of MP show increases in value as frequency increases. In the clinically relevant ranges of HFOV frequencies (8-15 Hz), however, the difference between the single compartment models was relatively small. This difference increased as compartments with varying C were considered. These findings suggest that while air flow L may not significantly affect MP in healthy pediatric patients, its effect may become increasingly significant in diseased states. This abstract is funded by: None
Luchette et al. (Fri,) studied this question.