Annals of Biomedical Engineering

, Volume 19, Issue 6, pp 679–697 | Cite as

Sensitivity of CO2 washout to changes in acinar structure in a single-path model of lung airways

  • Jeffrey D. Schwardt
  • Sherif R. Gobran
  • Gordon R. Neufeld
  • Stanley J. Aukburg
  • Peter W. Scherer
Article

Abstract

A numerical solution of the convection-diffusion equation with an alveolar source term in a single-path model (SPM) of the lung airways simulates steady state CO2 washout. The SPM is used to examine the effects of independent changes in physiologic and acinar structure parameters on the slope and height of Phase III of the single-breath CO2 washout curve. The parameters investigated include tidal volume, breathing frequency, total cardiac output, pulmonary arterial CO2 tension, functional residual capacity, pulmonary bloodflow distribution, alveolar volume, total acinar airway cross sectional area, and gas-phase molecular diffusivity. Reduced tidal volume causes significant steepening of Phase III, which agrees well with experimental data. Simulations with a fixed frequency and tidal volume show that changes in blood-flow distribution, model airway cross section, and gas diffusivity strongly affect the slope of Phase III while changes in cardiac output and in pulmonary arterial CO2 tension strongly affect the height of Phase III. The paper also discusses differing explanations for the slope of Phase III, including sequential emptying, stratified inhomogeneity, and the issue of asymmetry, in the context of the SPM.

Keywords

Convection Diffusion Pulmonary gas exchange Numerical model Phase III slope 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Bates, D.V.; Macklem, P.T.; Christie, R.V. Pulmonary emphysema. Philadelphia: W.B. Saunders Co.; 1971.Google Scholar
  2. 2.
    Buohuys, A. Respiratory dead space. In: Fenn, W.O.; Rahn, H., eds. Handbook of Physiology. Section 3: Respiration, Vol. I. Washington, D.C.: Am. Physiol. Soc.; 1964: pp. 699–714.Google Scholar
  3. 3.
    Cerretelli, P.; DiPrampero, P.E. Gas exchange in exercise. In: Fishman, A.P., ed. Handbook of Physiology, Section 3: The Respiratory System, Vol. IV. Washington, D.C.: Am. Physiol. Soc.; 1987: pp. 297–307.Google Scholar
  4. 4.
    Cherniak, R.M.; Cherniak, L. Respiration in health and disease. Philadelphia: W.B. Saunders Co.; 1983.Google Scholar
  5. 5.
    Chilton, A.B.; Stacey, R.W. A mathematical analysis of carbon dioxide respiration in man. Bull. Math. Biophysics. 14; 1952.Google Scholar
  6. 6.
    Cumming, G.; Horsfield, K.; Jones, J.G.; Muir, D.C.F. The influence of gaseous diffusion on the alveolar plateau at different lung volumes. Respir. Physiol. 2:386–398; 1967.PubMedGoogle Scholar
  7. 7.
    DuBois, A.B.; Britt, A.G.; Fenn, W.O. Alveolar CO2 during the respiratory cycle. J. Appl. Physiol. 44:325; 1981.Google Scholar
  8. 8.
    Fletcher, R. The single breath test for carbon dioxide. Arlöv, Sweden: Gerlings; 1986. Thesis.Google Scholar
  9. 9.
    Haefeli-Bleuer, B.; Weibel, E.R. Morphometry of the human pulmonary acinus. Anatom. Rec. 220:401–414; 1988.Google Scholar
  10. 10.
    Hansen, J.E.; Ampaya, E.P.; Bryant, G.H.; Navin, J.J. Human air space shapes, sizes, areas, and volumes. J. Appl. Physiol. 38:990–995; 1975.PubMedGoogle Scholar
  11. 11.
    Horsfield, K.; Cumming, G. Morphology of the bronchial tree in man. J. Appl. Physiol. 24:373–383; 1968.PubMedGoogle Scholar
  12. 12.
    Luijendijk, S.C.M.; Zwart, A.; de Vries, W.R.; Salet, W.M. The sloping alveolar plateau at synchronous ventilation. Pflügers Arch. 384:267–277; 1980.CrossRefPubMedGoogle Scholar
  13. 13.
    Marthar, R; Castaing, Y; Manier, G.; Guenard, H. Gas exchange alternations in patients with chronic obstructive lung disease. Chest 87(4): 470–475; 1985.Google Scholar
  14. 14.
    Neufeld, G.R.; Gobran, S.; Baumgardner, J.E.; Aukburg, S.J.; Schreiner, M.; Scherer, P.W. Diffusivity, respiratory rate, and tidal volume influence inert gas expirograms. Respir. Physiol. 84:31–47; 1991.CrossRefPubMedGoogle Scholar
  15. 15.
    Paiva, M. Gas transport in the human lung. J. Appl. Physiol. 35:401–410; 1973.PubMedGoogle Scholar
  16. 16.
    Paiva, M.; Engel, L.A. The anatomical basis for the sloping N2 plateau. Resp. Physiol. 44:325–337; 1981.Google Scholar
  17. 17.
    Rohen, J.W.; Yokochi, C. Colar atlas of anatomy. New York: Igaku-Shoin; 1988.Google Scholar
  18. 18.
    Scherer, P.W.; Gobran, S.; Aukburg, S.J.; Baumgardner, J.E.; Bartkowski, R.; Neufeld, G.R. Numerical and experimental study of steady-state CO2 and inert gas washout. J. Appl. Physiol. 64:1022–1029; 1988.PubMedGoogle Scholar
  19. 19.
    Scherer, P.W.; Neufeld, G.R.; Aukburg, S.J.; Hess, G.D. Measurement of effective peripheral bronchial cross section from single-breath gas washout. J. Biomech. Eng. 104:290–293; 1983.Google Scholar
  20. 20.
    Scherer, P.W.; Haselton, F.R. Convective mixing in tube networks. AIChE J. 25:542–544; 1979.CrossRefGoogle Scholar
  21. 21.
    Scherer, P.W.; Haselton, F.R. A network theory of bronchial gas mixing applied to single breath nitrogen washout. Lung. 158:201–220; 1980.PubMedGoogle Scholar
  22. 22.
    Scherer, P.W.; Shendalman, L.H.; Greene, N.M. Simultaneous diffusion and convection in single breath lung washout. Bull. of Math. Biophys. 34:393–412; 1972.Google Scholar
  23. 23.
    Smidt, U.; Worth, H. Diagnostik des Lungenemphysems auf expiratorischen CO2-Partialdruckkurven mit Hilfe eines Mikroprozessors. Biomed. Technik. 22:357; 1977.Google Scholar
  24. 24.
    Ultman, J.S.; Blatman, H.S. Longitudinal mixing in pulmonary airways: Analysis of inert gas dispersion in symmetric tube network models. Resp. Physiol. 30:349–367; 1977.Google Scholar
  25. 25.
    Weibel, E.R. Morphometry of the human lung. Berlin: Springer-Verlag; 1963.Google Scholar
  26. 26.
    West, J.B. Respiratory physiology—The essentials. Baltimore: Wiliams and Wilkins; 1985.Google Scholar
  27. 27.
    West, J.B. Pulmonary pathophysiology—The essentials. Baltimore: Williams and Wilkins; 1987.Google Scholar
  28. 28.
    West, J.B.; Fowler, K.T.; Hugh-Jones, P.; O’Donell, T.V. The measurement of the inequality of ventilation and perfusion in the lung by analysis of single espirates. Clin. Sci. 16:549; 1957.PubMedGoogle Scholar
  29. 29.
    Worth, H.; Piiper, J. Diffusion of helium, carbon dioxide, and sulfur hexafluoride in gas mixtures similar to alveolar gas. Respir. Physiol. 32: 155–166; 1978.PubMedGoogle Scholar

Copyright information

© Pergamon Press plc 1991

Authors and Affiliations

  • Jeffrey D. Schwardt
    • 1
  • Sherif R. Gobran
    • 1
    • 3
  • Gordon R. Neufeld
    • 2
    • 3
  • Stanley J. Aukburg
    • 2
  • Peter W. Scherer
    • 1
    • 2
  1. 1.Department of Bioengineering, School of Engineering and Applied ScienceUniversity of PennsylvaniaPhiladelphia
  2. 2.Department of AnesthesiaUniversity of Pennsylvania, School of MedicinePhiladelphia
  3. 3.Philadelphia Veterans Affairs Medical CenterPhiladelphia

Personalised recommendations