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.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bates, D.V.; Macklem, P.T.; Christie, R.V. Pulmonary emphysema. Philadelphia: W.B. Saunders Co.; 1971.
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.
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.
Cherniak, R.M.; Cherniak, L. Respiration in health and disease. Philadelphia: W.B. Saunders Co.; 1983.
Chilton, A.B.; Stacey, R.W. A mathematical analysis of carbon dioxide respiration in man. Bull. Math. Biophysics. 14; 1952.
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.
DuBois, A.B.; Britt, A.G.; Fenn, W.O. Alveolar CO2 during the respiratory cycle. J. Appl. Physiol. 44:325; 1981.
Fletcher, R. The single breath test for carbon dioxide. Arlöv, Sweden: Gerlings; 1986. Thesis.
Haefeli-Bleuer, B.; Weibel, E.R. Morphometry of the human pulmonary acinus. Anatom. Rec. 220:401–414; 1988.
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.
Horsfield, K.; Cumming, G. Morphology of the bronchial tree in man. J. Appl. Physiol. 24:373–383; 1968.
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.
Marthar, R; Castaing, Y; Manier, G.; Guenard, H. Gas exchange alternations in patients with chronic obstructive lung disease. Chest 87(4): 470–475; 1985.
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.
Paiva, M. Gas transport in the human lung. J. Appl. Physiol. 35:401–410; 1973.
Paiva, M.; Engel, L.A. The anatomical basis for the sloping N2 plateau. Resp. Physiol. 44:325–337; 1981.
Rohen, J.W.; Yokochi, C. Colar atlas of anatomy. New York: Igaku-Shoin; 1988.
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.
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.
Scherer, P.W.; Haselton, F.R. Convective mixing in tube networks. AIChE J. 25:542–544; 1979.
Scherer, P.W.; Haselton, F.R. A network theory of bronchial gas mixing applied to single breath nitrogen washout. Lung. 158:201–220; 1980.
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.
Smidt, U.; Worth, H. Diagnostik des Lungenemphysems auf expiratorischen CO2-Partialdruckkurven mit Hilfe eines Mikroprozessors. Biomed. Technik. 22:357; 1977.
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.
Weibel, E.R. Morphometry of the human lung. Berlin: Springer-Verlag; 1963.
West, J.B. Respiratory physiology—The essentials. Baltimore: Wiliams and Wilkins; 1985.
West, J.B. Pulmonary pathophysiology—The essentials. Baltimore: Williams and Wilkins; 1987.
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.
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.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Schwardt, J.D., Gobran, S.R., Neufeld, G.R. et al. Sensitivity of CO2 washout to changes in acinar structure in a single-path model of lung airways. Ann Biomed Eng 19, 679–697 (1991). https://doi.org/10.1007/BF02368076
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02368076