Detection, prevention and physiology of hypoxia, hypercapnia and nitrogen narcosis in rebreather div
Abstract
Rebreather underwater breathing devices are commonly used for military and scientific diving operations, and are also gaining popu,larity for recreational use. With its increased complexity and extended capabilities, the fatality risk for rebreather diving is sub,stantially greater than for open-circuit diving. Malfunctions and human errors often manifest through one of the so-called 3-Hs:,hypoxia, hyperoxia, and hypercapnia. Gas-induced narcosis during diving is an additional hazard that may predispose to the errors li,kely to result in 3-H problems. Many efforts aimed at preventing rebreather diving deaths have focused on engineering solutions and,monitoring of rebreather performance. Very limited research exists on directly monitoring the physiological manifestations of these,dangerous gas-related conditions or enhancing the ability of divers themselves to recognize them. In consideration of the above, we,plan to build on our existing work (monitoring inert gas narcosis using quantitative electroencephalography - qEEG) in two studies e,xamining whether prior open-label hypoxia and hypercapnia exposures enhance a divers ability to recognize these conditions and to m,ore expeditiously initiate self-rescue in a subsequent blinded exposure. At the same time, we will leverage the necessary exposures,to hypoxia and hypercapnia in human subjects to further explore the physiology of these conditions, and their independent detection,by three technologies: quantitative EEG analysis (qEEG); eye tracking (ET); and functional near infrared spectroscopy (fNIRS). Final,ly, our present program has identified a potential qEEG algorithm to measure the subtle cerebral electrophysiological changes associ,ated with nitrogen narcosis. We plan to put more subjects through the hyperbaric air protocol used in our present program to further, validate this algorithm, evaluate its sensitivity and specificity, and refine it for possible translation into a real-time diving m,onitor. The cumulative goal of this work is real-time detection of impending 3-H events and narcotic impairment that may predispose,to causative errors through either monitoring technologies or enhancement of diver recognition (or both). The work will afford a bet,ter understanding of the relationship between cerebral oxygenation and cognitive performance in human subjects, and may identify pot,ential real-time 3-H monitoring strategies in the form of eye tracking, qEEG and fNIRS. In the case of qEEG, this work will complete, the accumulation of indicative human EEG data in exposures to gas narcosis, hyperoxia, hypoxia, and hypercapnia, facilitating the p,ossibility of an integrative EEG-based monitoring package for all relevant gas effects / toxicities. In addition, the results will i,dentify (or refute) easily implemented strategies to improve diver recognition of critical 3-H events (such as prior exposures to hy,poxia and hypercapnia). This will also be of great interest to the military and civilian aviation communities who already conduct hy,poxia exposures for this purpose, largely without evidence of efficacy. The work will facilitate development of two early career sci,entists. Findings will be published in appropriate peer reviewed medical journals and presented at scientific meetings.Approved for,Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 10, 2021
- Source ID
- N629092212003
Entities
People
- Simon Mitchell
Organizations
- Office of Naval Research
- United States Navy
- University of Auckland