HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 97/6/2284    most recent 00469.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Chakraborty, S. Articles by Bidani, A. Search for Related Content PubMed PubMed Citation Articles by Chakraborty, S. Articles by Bidani, A.

Diffusing capacity reexamined: relative roles of diffusion and chemical reaction in red cell uptake of O₂, CO, CO₂, and NO

¹Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Texas Medical School, Houston 77030, and ²Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4004

Submitted 4 May 2004 ; accepted in final form 16 August 2004

This paper presents an analytical expression for the diffusing capacity (_t) of the red blood cell (RBC) for any reactive gas in terms of size and shape of the RBC, thickness of the unstirred plasma layer surrounding the RBC, diffusivities and solubilities of the gas in RBC and boundary layer, hematocrit, and the slope of the dissociation curve. The expression for _t has been derived by spatial averaging of the fundamental convection-diffusion-reaction equation for O₂ in the RBC and has been generalized to all cell shapes and for other reactive gases such as CO, NO, and CO₂. The effects of size and shape of the RBC, thickness of the unstirred plasma layer, hemoglobin concentration, and hematocrit on _t have been analyzed, and the analytically obtained expression for _t has been validated by comparison with different sets of existing experimental data for O₂ and CO₂. Our results indicate that the discoidal shape of the human RBC with average dimensions of 1.6-µm thickness and 8-µm diameter is close to optimal design for O₂ uptake and that the true reaction velocity in the RBC is suppressed significantly by the mass transfer resistance in the surrounding unstirred layer. In vitro measurements using rapid-mixing technique, which measures _t in the presence of artificially created large boundary layers, substantially underpredicts the in vivo diffusing capacity of the RBC in the diffusion-controlled regime. Depending on the conditions in the RBC, uptake of less reactive gases (such as CO) undergoes transition from reaction-limited to diffusion-limited regime. For a constant set of morphological parameters, the theoretical expression for _t predicts that _t,NO > _t,CO2 > _t,O2 > _t,CO.

red blood cells; diffusing capacity; hemoglobin; oxygen; carbon monoxide; nitric oxide; carbon dioxide

This article has been cited by other articles:

				S. N. Glenet, C. De Bisschop, F. Vargas, and H. J. P. Guenard Deciphering the nitric oxide to carbon monoxide lung transfer ratio: physiological implications J. Physiol., July 15, 2007; 582(2): 767 - 775. [Abstract] [Full Text] [PDF]

				P. Pacher, J. S. Beckman, and L. Liaudet Nitric Oxide and Peroxynitrite in Health and Disease Physiol Rev, January 1, 2007; 87(1): 315 - 424. [Abstract] [Full Text] [PDF]

				C. Borland, H. Dunningham, F. Bottrill, and A. Vuylsteke Can a membrane oxygenator be a model for lung NO and CO transfer? J Appl Physiol, May 1, 2006; 100(5): 1527 - 1538. [Abstract] [Full Text] [PDF]