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 functions. Our lung mechanics system was able to closely monitor pulmonary function, including during transitions between gas and liquid phases.