[abstract] A DYNAMIC MODEL OF CNS O2 TOLERANCE BASED ON DEPTH, WORKRATE AND EXPOSURE TIME.

Rubicon Research Repository/Manakin Repository

[abstract] A DYNAMIC MODEL OF CNS O2 TOLERANCE BASED ON DEPTH, WORKRATE AND EXPOSURE TIME.

Show full item record


Title: [abstract] A DYNAMIC MODEL OF CNS O2 TOLERANCE BASED ON DEPTH, WORKRATE AND EXPOSURE TIME.
Author: Fairburn, SM; Morrison, JB
Abstract: Extensive research has been done on decompression models for divers while predictions of 02 tolerance limits are primitive in comparison. Current safety limits are confined to curves relating inspired 02 partial pressure (PI02) to CNS tolerance time when resting in a dry chamber or working underwater. No account is taken of changes in PI02, depth, workrate or breathing mixture during a dive or transfer from wet to dry conditions. Hence, limits can only be predicted for a constant PI02 during constant depth diving. In response, a theoretical model was developed for predicting onset of CNS 02 toxicity during dynamic exposures to hyperpoxic gas mixtures. The model is based on existing 02 tolerance curves, but combines a non-linear multiple regression model with the superposition theory of Hills (1977). The imminence of 02 toxicity is predicted utilizing depth (gas density), diver exertion, and PI02 as independent variables. Exposure is expressed in terms of a cumulative 02 toxicity index (COTi). Oxygen convulsions arc predicted when the COTi value exceeds 1.0. The model was evaluated using 9 casc studies of 02 toxicity provided in operational diving accident reports. All incidents occurred during excursion dives to 60 to 80 meters, with decompression stops in the water. Through computer simulation, the model yielded COTi values greater than 1.0 in all 9 cases, 8 of which were recorded as definite incidents of 02 convulsions. The model exhibited a fast and slow time constant. The value of COTi was found to be most sensitive to sudden changes in PI02, and less sensitive to continued exposure at constant conditions. When all 9 cases were considered, the mean COTi value was 1.32 (Sx=0.17), with individual values ranging from 1.03-1.55. The ability of the model to predict the imminence of CNS 02 toxicity during operational diving has been demonstrated within the scope of the present case studies.
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Joint Annual Scientific Meeting with the International Congress for Hyperbaric Medicine and the European Undersea Biomedical Society held 11-18 August 1990. Okura Hotel, Amsterdam, The Netherlands (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/7318
Date: 1990

Files in this item

Files Size Format View
abstract.txt 193bytes Text file View/Open

This item appears in the following Collection(s)

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

Show full item record

Browse

My Account