NICOP - Gas narcosis in hyperbaric environments
Abstract
gases breathed at high pressures. This can result in euphoria, inattention and poor decisionmaking which may increase the risk of a""ccidents. Although this is a well-recognizedphenomenon, there are many inadequately researched issues (such as the relative narcoti""cpotencies of relevant gases such as nitrogen, oxygen, helium, and carbon dioxide) andresearch is impaired by the lack of a repeat"able objective measurement of narcosis.The first goal of this project is to develop a novel means of quantifying narcosis using changesin the electrical activity of the brain measured by a technique known as quantitative electroencephalography(qEEG). We will record the changes in the qEEG that occur during breathingof different concentrations of a gas (nitrous oxide ~ ~laughing gas~) known to produce narcosiswhen breathed at the surface. We will benchmark the functional relevance of these qEEGchanges by measuring impairment in simple cognitive function tests administered at the sametime. This should allow development of a qEEG algorithm for quantifying narcosis that we canapply in subsequent experiments.The qEEG narcosis algorithm will then be benchmarked against the narcotic effect of nitrogen(the gas most widely recognized to produce narcosis under diving conditions). The qEEG willbe measured and simple cognitive function tests completed simultaneously in divers in ahyperbaric chamber breathing air at pressures equivalent to d"ives at 25 and 50m depth inseawater. With the qEEG ~calibrated~ against the effect of both nitrous oxide and nitrogennarcosis, it" will then be used to evaluate the narcotic potential of oxygen breathed at highpressures. There is unresolved debate about the extent to which substitution of nitrogen byoxygen can reduce narcosis in diving. Finally we will utilize the qEEG to determine whethercarbon dioxide (CO2) is narcotic by inducing hypercapnia (higher blood CO2 levels) throughrebreathing of exhaled CO2. This will be" undertaken initially at the surface, and thensubsequently during air breathing at pressure in the hyperbaric chamber to determine" whetherhypercapnia enhances nitrogen narcosis.We anticipate that the qEEG will provide a repeatable reliable means of quantifying changesin brain activity during narcosis. The project will also illuminate current controversy about therole of oxygen and CO2 in" narcosis during diving. Ultimately, it is conceivable that the qEEGmethod could be used as a monitoring system that is wearable un""derwater in the helmet ofthe diver, giving a real-time estimation of the narcosis in individual military divers.This work will be"" undertaken within the Department of Anaesthesiology, School of Medicine,University of Auckland under the supervision of Professor" Simon Mitchell. The measurementswith nitrous oxide and the development of the qEEG algorithm will be undertaken at theWaikato Clinical School (a satellite center for the department) under the supervision ofProfessor Jamie W. Sleigh. The hyperbaric measurements" will be undertaken at the SlarkHyperbaric Medicine Unit, Devonport, Auckland. There are no formal US collaborators. Theresults of" the project will be published in international peer-reviewed journals and presentedat international congresses.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 06, 2017
- Source ID
- N629091812007
Entities
People
- Simon Mitchell
Organizations
- Office of Naval Research
- United States Navy
- University of Auckland