Book contents
- Frontmatter
- Contents
- Preface
- Notation
- 1 Introduction
- 2 Collecting data
- 3 The linear single-compartment model
- 4 Resistance and elastance
- 5 Nonlinear single-compartment models
- 6 Flow limitation
- 7 Linear two-compartment models
- 8 The general linear model
- 9 Inverse models of lung impedance
- 10 Constant phase model of impedance
- 11 Nonlinear dynamic models
- 12 Epilogue
- References
- Index
7 - Linear two-compartment models
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Notation
- 1 Introduction
- 2 Collecting data
- 3 The linear single-compartment model
- 4 Resistance and elastance
- 5 Nonlinear single-compartment models
- 6 Flow limitation
- 7 Linear two-compartment models
- 8 The general linear model
- 9 Inverse models of lung impedance
- 10 Constant phase model of impedance
- 11 Nonlinear dynamic models
- 12 Epilogue
- References
- Index
Summary
We now come back to the general question of how the single-compartment linear model can be extended to provide a more realistic representation of the lung. Even this simple model has proven extremely useful for describing the behavior of the lung (Chapters 3 and 4). It does even better when extended to include nonlinearities related to flow and volume (Chapters 5 and 6). Nevertheless, a model with only one alveolar compartment just seems too simplistic. It is obvious from considerations of anatomy that a real lung can never be perfectly homogeneous, even when healthy. Structural asymmetries in the airway tree alone make it easier for inspired air to reach some alveolar regions than others. It is also hard to imagine that any disease process affecting mechanical function would strike the lung in a geographically uniform manner. It is therefore natural to think that a realistic model of lung mechanics should account for regional differences in mechanical properties. Indeed, one does not have to look far to find examples of significant departure from single-compartment behavior in the lung.
Passive expiration
One source of experimental evidence for the presence of more than one compartment in the lung comes from passive expiration. Here, the lungs are inflated to some volume V0 above functional residual capacity, and then suddenly allowed to exhale solely under the influence of the elastic recoil forces of the respiratory tissues.
- Type
- Chapter
- Information
- Lung MechanicsAn Inverse Modeling Approach, pp. 108 - 126Publisher: Cambridge University PressPrint publication year: 2009