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Interdependence of regional expiratory flows limits alveolar pressure differences
G P Topulos1, G J Nielan, G M Glass
1Harvard School of Public Health, Boston, Massachusetts 02115.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1990
Summary
Interregional alveolar pressure differences in canine lungs reach limiting values during forced deflation, independent of initial lung volume. This suggests lung interdependence balances regional emptying variations.
Area of Science:
- Pulmonary Physiology
- Respiratory Mechanics
Background:
- Regional differences in alveolar pressure can arise during forced lung deflation.
- Interdependence of regional expiratory flows may limit these pressure differences.
Purpose of the Study:
- To test the hypothesis that limiting interregional alveolar pressure differences develop during forced lung deflation.
- To investigate the influence of initial transpulmonary pressure on these limiting differences.
Main Methods:
- Excised canine lungs were subjected to complete and partial maximal forced deflations.
- Regional alveolar pressures were monitored in six lobes using alveolar capsules.
- Deflations were initiated at various transpulmonary pressures (30, 20, 15, 10 cmH2O).
Main Results:
- Interregional heterogeneity of alveolar pressure increased early in deflation but stabilized later.
- In 16 of 24 maneuvers, pressure heterogeneity became independent of the initial transpulmonary pressure.
- Alveolar pressures relaxed to limiting interregional differences, independent of deflation time.
Conclusions:
- Data provide strong evidence for the existence of limiting interregional alveolar pressure differences during forced deflation.
- Lung interdependence balances regional emptying nonuniformities, leading to pressure stabilization.
- Maximum expiratory flow-volume curves are insensitive to underlying regional lung emptying patterns.