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Cardiogenic oscillation and phase III caused by pressure-volume heterogeneity: a model
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 1, 1986
Summary
Mathematical lung models reveal how pressure-volume behavior and heart pulsations affect expired nitrogen. Heterogeneity in lung compliance compartments influences the alveolar plateau shape and cardiogenic oscillations during expiration.
Area of Science:
- Pulmonary physiology
- Mathematical modeling
- Respiratory mechanics
Background:
- Lung heterogeneity in pressure-volume (PV) behavior impacts gas exchange.
- Cardiac pulsations can influence gas washout dynamics in the lungs.
Purpose of the Study:
- To mathematically model the effects of lung unit PV heterogeneity and cardiac pulsations on expired nitrogen (N2) after a single oxygen (O2) breath.
- To investigate how different lung compartment compliances and their interactions affect the alveolar plateau and cardiogenic oscillations.
Main Methods:
- A mathematical lung model with three compartments: high compliance (HC), low compliance (LC), and non-oscillatory (NC).
- Sigmoid PV curves assigned to compartments, with total compliance of 200 ml/cmH2O.
- Cardiac pulsations incorporated to simulate alternate flows and cardiogenic oscillations (CO).
Main Results:
- The ratio of steepness constants (KHC/KLC) determined the alveolar plateau shape: sloping for 1:1, concave for KHC/KLC > 1, and convex for KHC/KLC < 1.
- Cardiogenic oscillations (CO) were produced by alternate flows from different lung compartments.
- CO diminished during rapid expiration, and a phase shift between heart pulsation and CO was observed, consistent with experimental data.
Conclusions:
- Lung unit heterogeneity significantly influences the shape of the expired N2 plateau.
- Cardiac pulsations are a source of cardiogenic oscillations in expired N2, with dynamics dependent on lung compartment properties and expiratory flow rate.