[abstract] DEADSPACE, BREATHING GAS DENSITY AND THE HALDANE EFFECT

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[abstract] DEADSPACE, BREATHING GAS DENSITY AND THE HALDANE EFFECT

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Title: [abstract] DEADSPACE, BREATHING GAS DENSITY AND THE HALDANE EFFECT
Author: Moon, RE; Baek, PL; Mummery, HJ; Lanzinger, MJ; Stolp, BW; Dear, GdeL; Carraway, MS; Piantadosi, CA; McMahon, TJ
Abstract: INTRODUCTION and METHODS: A contributing cause of hypercapnia in divers is an increased pulmonary deadspace. This has been attributed to increased gas density, causing maldistribution of ventilation, increased anatomic deadspace due to higher FRC, carbonic anhydrase inhibition and the effect of greater PO2, causing a reduction in blood CO2 solubility (Haldane effect). This proposed mechanism has been shown to be responsible in large part for the hypercapnia induced by O2 administration to patients with severe airways obstruction (Hanson CW. Crit Care Med 24:23, 1996). To analyze the effects of gas density and PO2 on deadspace in diving, 22 sets of measurements of Bohr dead space (requiring arterial and mixed expired PCO2) obtained from six studies of normal subjects at rest were examined (Saltzman, 1971; Salzano, 1984; Morgan, 1996; Moon, 1998; McMahon, 1998; Mummery, 2001). RESULTS: The 22 data sets encompassed a range of gas densities from 0.3-17.1 g/L. These measurements were obtained over a pressure range from 1-68 ATA. Inspired PO2 ranged from 0.2-3 ATA. Results are shown on the graph, on which is plotted Bohr deadspace (Vd) vs. gas density (rho). Each point on the graph represents the mean of several subjects. Least squares best fit was used to derive the regression equation: Vd = 0.19 + 0.28rho (R = 0.82, P less than 10-5). Whereas there was a good correlation between deadspace and density, inspection of the graph reveals no significant relationship between deadspace and PO2. Vd at the highest PO2 (100percent O2 breathing at 3 ATA, N = 13 subjects) was within the normal range breathing air at 1 ATA. CONCLUSIONS: We conclude that the increased Bohr dead space during diving is predominantly due to the effect of high breathing gas density, and that the effect of hyperoxia mediated via the Haldane effect does not contribute. deadspace, haldane effect, gas density, diving
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/1222
Date: 2002

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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