Modelling and estimation of respiratory mechanics in presence of gas leakage

This paper focuses upon the use of simple mathematical models in estimating total pulmonary compliance for clinical investigation and attempts to quantify the estimation errors that may be expected in presence of significant and sustained gas leakage from lungs. To this end, simulation experiments were made and mechanically ventilated patients were analyzed. The results obtained in both cases demonstrate that, in spite of good reproducibility, systematic overestimation of the compliance (ranging from 6% to 50% for normal and stiff subjects, respectively) occurs when the presence of gas leakage is neglected. Consequently, a monocompartmental extended model of respiratory mechanics is proposed and tested. This model provides reproducible and unbiased estimation of compliance and can be seen as an appropriate representation of respiratory mechanics also in presence of gas leakage.