[abstract] A NEW VPM ALGORITHM FOR REPETITIVE DIVES.

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[abstract] A NEW VPM ALGORITHM FOR REPETITIVE DIVES.

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Title: [abstract] A NEW VPM ALGORITHM FOR REPETITIVE DIVES.
Author: Yount, DE; Maiken, EB; Baker, EC
Abstract: BACKGROUND: Previous applications of the Varying Permeability Model to repetitive diving situations were accomplished by reducing the pressure gradients allowed by VPM for single dives by ad hoc factors. The purpose of this investigation was to determine whether the extension to repetitive dives could be accomplished on a more fundamental level by tracking microbubble nuclei and directly calculating the allowed supersaturation gradients. METHODS: As usual, the gradients allowed by VPM for single dives and for the first dive in a series were obtained from one setting of four global parameters that replace the matrix of critical tensions or M-values used in conventional tables. Three of these, including the minimum initial radius, are properties of the critical VPM microbubble nucleus. The fourth refers to the critical volume of released gas above which the risk of decompression illness becomes unacceptably large when the body's ability to dissipate free gas at a useful rate is taken into account. Called the "dynamic critical volume hypothesis," this decompression criterion allows the number of primary bubbles to vary from Nsafe, which can be tolerated under any circumstances, to Nactual, which can be much larger than Nsafe, particularly for dives of short duration. Values of the global parameters for subsequent dives were obtained by assuming that the new radial distribution of bubble formation nuclei has the same form as the initial radial distribution, but is corrected for the fact that Nactual is larger than Nsafe. RESULTS AND CONCLUSIONS: The new algorithm permits the allowed gradients for repetitive dives to be calculated directly from VPM. We compare the gradient reductions determined in this way to those found by other means. Additionally, we consider the viability of calculating a comprehensive set of diving tables from a bubble nucleation model and a modest number of assumptions, equations, and parameter values.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/6512
Date: 2000

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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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