Dynamic and Quasi-Static Lung Mechanics System for Gas-Assisted and Liquid-Assisted Ventilation

Our aim was to develop a computerized system for real-time monitoring of lung mechanics measurements during both gas and liquid ventilation. System accuracy was demonstrated by calculating regression and percent error of the following parameters compared to standard device: airway pressure difference (DeltaP_aw), respiratory frequency (f_R ), tidal volume (V_T), minute ventilation (V´_E), inspiratory and expiratory maximum flows (V´_ins,max, V´_exp,max), dynamic lung compliance (C_L,dyn), resistance of the respiratory system calculated by method of Mead-Whittenberger (R_rs,MW) and by equivalence to electrical circuits (R_rs,ele), work of breathing (W_OB), and overdistension. Outcome measures were evaluated as function of gas exchange, cardiovascular parameters, and lung mechanics including mean airway pressure (mP_aw). DeltaP_aw, V_T, V´_ins,max, V´_exp,max, and V´_E measurements had correlation coefficients r = 1.00, and %error < 0.5%. f_R, C_L,dyn, R_rs,MW, R_rs,ele, and W_OB showed r ges 0.98 and %error < 5%. Overdistension had r = 0.87 and %error < 15%. Also, resistance was accurately calculated by a new algorithm. The system was tested in rats in which lung lavage was used to induce acute respiratory failure. After lavage, both gas- and liquid-ventilated groups had increased mP_aw and W_OB, with decreased V_T, V´_E, C_L,dyn, R_rs,MW, and R_rs,ele compared to controls. After 1-h ventilation, both injured group had decreased V_T, V´_E, and C_L,dyn, with increased mP_aw, R_rs,MW, R_rs,ele, and W_OB. In lung-injured animals, liquid ventilation restored gas exchange, and cardiovascular and lung function- - s. Our lung mechanics system was able to closely monitor pulmonary function, including during transitions between gas and liquid phases.