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Medical and biological engineering

, Volume 4, Issue 6, pp 555–566 | Cite as

Analysis of expiratory airways collapse

  • R. McWilliam
  • J. M. Nightingale
  • A. B. Kinnier Wilson
Article

Abstract

A dynamic model of mechanical lung function has been made which displays the time variation of flow and pressure during a breathing cycle. It has shown how expiratory flow restriction can take place due to elastic instability of the “bronchial” walls. The model exhibits these characteristics over a wide range of operating conditions, and can describe both normal and diseased lungs. It is simple enough to form one element in an analogue computer simulation considered from a wider standpoint.

Keywords

Lung Volume Airway Resistance Lower Airway Intrathoracic Pressure Transverse Pressure 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Symbols

Pth

intrathoracic pressure referred to an arbitrary fixed level (cm H2O)

Pel

elastic pressure component referred to an arbitrary fixed level (cm H2O)

PA

alveolar pressure (cm H2O)

PL

pressure at collapsing region (cm H2O)

Pu

upper airway pressure drop (cm H2O)

Pt

transmural pressure drop (cm H2O)

Pc

transmural collapse pressure (cm H2O)

\(\dot V\)

flow rate (l/sec)

V

volume referred to an arbitrary level (l)

RL

flow resistance of lower airway (cm H2O/I/sec)

Ru

flow resistance of upper airway (cm H2O/l/sec)

x

mean diameter of airway throat λx=conductance (l/sec/cm H2O)

λ

conductance of throat per unit ofx λx=conductance (l/sec/cm H2O)

K

elastance of lungs (cm H2O/l)

Sommaire

Un modèle dynamique du fonctionnement mécanique du poumon a été réalisé qui met en évidence les variations du débit et de la pression au cours d'un cycle respiratoire complet. Il a été démontré comment une réduction excessive peut se manifester durant la phase respiratoire, dûe à l'instabilité élastique des parois des bronches. Le modèle montre ce fait caractéristique en opérant sur une gamme étendue et peut discriminer les poumons malades on en état normal. Le modéle est suffisamment simple pour être considéré comme un seul élément lors d'une simulation par calculateur analogique se déroulant dans un cadre plus général.

Zusammenfassung

Ein dynamisches Modell der mechanischen Lungenfunktion wurde hergestellt, das die zeitliche Änderung des Durchflusses und des Druckes während eines Atemzyklus darstellt. Es zeigte sich eine Behinderung des Ausatmungsflusses auf Grund einer elastischen Instabilität der “Bronchialwand”. Das Modell zeigt diese Charakteristika über einen weiten Bereich von Arbeitsbedingungen und kann die normale und die kranke Lunge beschrieben. Das Model ist einfach genug, ein Element in einer Analogrechner-Simulation ineinem größeren Zusammenhang zu bilden.

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Copyright information

© International Federation for Medical and Biological Engineering 1966

Authors and Affiliations

  • R. McWilliam
    • 1
    • 2
  • J. M. Nightingale
    • 1
    • 2
  • A. B. Kinnier Wilson
    • 1
    • 2
  1. 1.Medical Research Council, Centre for Muscle SubstitutesWest Hendon HospitalLondon
  2. 2.Department of EngineeringUniversity of LeicesterLeicester

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