Changes in clinical status and lung functions of patients with chronic respiratory diseases over 10 years.

After a period of 10 years the authors reexamined the respiratory health status of 381 dust-exposed males. Of the lung function values examined Raw, RV/TLC%, VC, TGV and PaO2 were found to be of significant prognostic importance. Among the radiological changes characteristic of silicosis the most serious B-C category, among the respiratory complaints dyspnoea accompanied by regular cough and expectoration, and among the physical changes extended rhonchi and rales accompanied by an emphysematous thorax are to be considered as most essential with respect to prognosis. Smoking habits significantly affected the total death rate, but did not prove to be significant with regard to respiratory death. In the development of bronchial obstruction recurrent febrile respiratory diseases proved to be more important than smoking habits and mild bronchitic complaints.

Parameter estimation of transpulmonary mechanics by a nonlinear inertive model.

Transpulmonary mechanics of anesthetized intubated dogs were studied during control breathing and hemorrhage-induced hyperventilation by least-mean-squares parameter estimation using several model versions. The classical elastance-resistance model was modified to include nonlinear elastic and viscous pressure terms with and without a linear inertive pressure component. Inclusion of the nonlinear terms decreased the root-mean-square error of fitting (q) of the classical model on the average to 67% in the control period and to 58% during hyperventilation. An additional decrease due to inertance was 4% (control) and 22% (hyperventilation) and was associated with acceptable estimates of inertance [0.056 +/- 0.02 (SD) and 0.063 +/- 0.008 cmH2O . l-1 . s2, respectively]. When inertance alone was added to the classical model, negligible improvement in q and unrealistic values of inertance were obtained. Conventional measures (Edyn and midvolume resistance) were close to the corresponding least-mean-squares estimates (E and R) of all model versions, except that in hyperventilation neglecting the inertance caused Edyn to markedly overestimate E of nonlinear inertive model.

Computation of the equivalent airway resistance: a comparison with routine evaluations of plethysmographic measurements.

Equivalent (effective) values of airway resistance were determined for total breaths, inspiration and expiration in spontaneously breathing patients by means of an off-line processing system. An improvement in the alveolar pressure determination was achieved by subtracting thermal pressure drifts of the pressure plethysmograph and by taking into account instantaneous values of the intrathoracic gas volume. Equivalent resistance values were compared with the results of several simulated routine evaluations. It was found that the equivalent resistance is best approximated by the graphical procedure using average pressure points at +/- 0.5 liter/sec flow levels.