Fitting nonlinear time-domain models of respiratory mechanics to pressure-flow data from an intubated patient

The mechanical status of the respiratory system in intubated mechanically ventilated patients is conveniently assessed from the dynamic relationships between the pressure and flow of gas measured at the entrance to the endotracheal tube. A model of respiratory mechanics is fit to the data, and the parameters of the model are then taken to be measures of important physiological quantities. The authors demonstrate here how a nonlinear lumped-parameter model is required to fit pressure-flow data from a patient with acute respiratory distress syndrome. The model describes the curvilinear dynamic pressure-volume relationship of the lung, knowledge of which may be clinically useful in avoiding overinflation injury.