Physiologic Basis for CO2 Limits Within Semiclosed and Closed-Circuit Underwater Breathing Apparatus

Abstract

Semiclosed- and closed-circuit underwater breathing apparatus (UBA) incorporate a canister filled with carbon dioxide (CO2) absorbent material. As the absorbent becomes expended, the CO2 level within the breathing loop will rise. Currently, CO2 absorbent canisters are considered expended when the effluent CO2 is 0.5% Surface Equivalent Value (SEV). In the past, this value often represented the threshold between the linear and the exponential rise in effluent CO2. The 0.5% SEV limit was used to reduce the diver's risk for experiencing excessive levels of CO2. However, with advances in absorbent canister design, this value may be overly conservative. Because the overall respiratory load of a UBA can compound the effect of the inspired CO2, the improved breathing performance of some current UBAs also warrants reevaluating the current limit. This literature review specifically looked at low levels of CO2 affecting work and mental performance, nitrogen narcosis, decompression sickness and central nervous system (CNS) oxygen toxicity to determine if the breakthrough limit could be changed.

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Document Details

Document Type
Technical Report
Publication Date
Aug 01, 2000
Accession Number
ADA383684

Entities

People

  • M. E. Knafelc

Organizations

  • United States Navy Experimental Diving Unit

Tags

DTIC Thesaurus Topics

  • Blood
  • Blood Chemistry
  • Blood Flow
  • Breathing Apparatus
  • Breathing Gases
  • Carbon Dioxide
  • Central Nervous System
  • Decompression Sickness
  • Divers
  • Diving
  • Greenhouse Effect
  • Literature Surveys
  • Nervous System
  • Partial Pressure
  • Respiration Disorders
  • Respiratory Physiological Phenomena
  • Underwater Breathing Apparatus

Readers

  • Cardiovascular Physiology
  • Materials Science
  • Systems Analysis and Design