The endotracheal tube biases the estimates of pulmonary recruitment and overdistension.
To assess the impact of the endotracheal tube (ETT) and of different flow waveforms on estimates of alveolar cyclic recruitment (CR) and overdistension (AO). Numerical simulation of the respiratory system plus ETT (inertance L plus a flow-dependent resistance, K (1) and K (2)), with the following non-linear equation of motion PAW(t)= ((K1 + K2 x/V(t)/) x V(t) + L x V(t)) + Rrs x V(t) + (E1 + E2 x V(t) x V(t) + P0 (PAW pressure at the airways opening, V volume), under volume-controlled mechanical ventilation. An index %E2 = 100 x (E2 x V(T))/(E1 + E2)x V(T)) can be calculated where %E(2) > 30% represents AO and %E(2) < 0% represents CR. Parameters were estimated by the least-squares method, either with the complete equation or suppressing L, K(2) or both. %E(2) is always underestimated (down to -152 percent points) with incomplete equations of motion. The estimation of %E (2) may be strongly biased in the presence of an ETT excluded from the estimation model.
Jandre
Frederico C
FC
Biomedical Engineering Program, Federal University of Rio de Janeiro, Graduate School of Engineering, COPPE, Rio de Janeiro, Brazil.
Modesto
Felipe Cardozo
FC
Carvalho
Alysson Roncally Silva
AR
Giannella-Neto
Antonio
A
D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D008170:Lung Compliance / Q000502:physiology; D008954:Models, Biological; D012121:Respiration, Artificial / Q000295:instrumentation*; D015656:Respiratory Mechanics / Q000502:physiology