INFLUENCE OF FLOW PATTERN ON THE PARAMETER ESTIMATES OF A SIMPLE BREATHING MECHANICS MODEL

The first-order model of breathing mechanics is widely used in clinica l practice to assess the viscoelastic properties of the respiratory sy stem, Although simple, this model takes the predominant features of th e pressure-flow relationship into account but gives highly systematic residuals between measured and model-predicted variables, To achieve a better fit of the entire data set, an approach hypothesizing determin istic time-variations of model parameters, summarized by information-w eighted histograms was recently proposed by Bates and Lauzon. The pres ent study uses Bow and pressure data measured in intensive care patien ts to evaluate the real potential of this approach in clinical practic e, Information-weighted histograms of the model parameters, estimated by an on-line identification algorithm, were first constructed by taki ng into account the parameter percentage standard deviations, Then, th e influence of the respiratory flow pattern on the calculated histogra ms was evaluated by the Kolmogorov-Smirnov statistical test, The resul ts show that the method gives good reproducibility under stable experi mental conditions, In addition, for a given airflow waveform, an incre ase in respiratory frequency shifts the histograms representing time-v arying viscous properties strongly versus lower values, whereas it shi fts the histograms representing time-varying elastic properties slight ly versus higher values, On the other hand, the same histograms were h ighly dependent on the airflow waveform, especially for the viscous pr operties, Even in a limited experimental work, in all the conditions c onsidered, the method provides results which agree well with the physi ological knowledge of nonlinear and multicompartment behavior of respi ratory mechanics.