Diffusion - dependence of pulmonary gas mixing at 5.5 and 9.5 ATA

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Diffusion - dependence of pulmonary gas mixing at 5.5 and 9.5 ATA

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Title: Diffusion - dependence of pulmonary gas mixing at 5.5 and 9.5 ATA
Author: Van Liew, HD; Thalmann, ED; Sponholtz, DK
Abstract: Gas-phase diffusivity is inversely proportional to pressure, so mixing of inspired gas in the lung can be expected to be poor in hyperbaric environments. Subjects performed multiple-breath wash-in of a mixture (4percent each of SF6, Ar, Ne, and He; 21percent O2, 63percent N2) at 1.5, 5.5, and 9.5 ATA. At the higher pressures there were marked differences of concentrations between the indicator gases, measured by mass spectrometer at the mouth during a single expiration. Compared to heavier gases, light gases fell from dead space concentration to the "alveolar" level sooner, had a flatter plateau, and had a lower average expired concentration, indicating that more of the light gases were retained in the Functional Residual Capacity (FRC) after the breath. However, wash-in rates for the indicators were about the same; a rapid initial rate for He diminished so that it was about the same as the SF6 rate, because in later breaths a back pressure developed for He. The findings illustrate the basic principle that the amount of gas that diffuses from one location to another in a container depends not only on diffusivity, but also in an interdependent manner on concentration gradient, time for diffusion, and configuration of the container. Argon/diagnostic use Diffusion Helium/diagnostic use Human Male Mathematics Neon/diagnostic use Pressure/adverse effects *Pulmonary Diffusing Capacity Sulfur Hexafluoride/diagnostic use Support, U.S. Gov't, Non-P.H.S. Support, U.S. Gov't, P.H.S. Time Factors
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: PMID: 524527
http://archive.rubicon-foundation.org/2863
Date: 1979

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  • Undersea Biomedical Research Journal
    The Undersea Baromedical Research journal was published by the Undersea Medical Society, Inc. (now the Undersea and Hyperbaric Medical Society) quarterly from 1974 to 1992 when the name changed to the Undersea and Hyperbaric Medicine Journal.

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