PD87 <audio>

Divers Alert Network:  2008 Technical Diving Conference. The two-day conference, planned for Jan. 18-19, 2008, in Durham, N.C., will feature four half-day workshops. Discussions will include the operational and medical aspects of technical diving. The forum will also address ways to improve effectiveness and safety.

Workshops Overview
Normal respiration and gas exchange at sea level with emphasis on oxygen uptake, CO2 elimination, and ventilatory control. Dependency of CO2 elimination on ventilation. CO2 retention and individual susceptibility. Effects of tidal volume and dead space on alveolar ventilation. Hypo- and hyperventilation. Ventilatory capacity, physical fitness, and respiratory muscle fatigue. Effects of immersion and gas density. Airway collapse and effort independent expiratory flow. Equipment dead space, static lung load, breathing resistance, and work of breathing. Effect of HPNS on respiration. Case reports.

CNS Oxygen Toxicity
Relevant mechanisms of CNS toxicity: free radicals, ventilation, CO2 retention, cerebral blood flow. Risk factors and individual susceptibility. Donald’s WWII studies. Estimating CNS toxicity risk in relation to O2 exposure, review of O2 exposure guidelines, and the O2 clock. O2-CO2 interactions and “Shallow Water Black-Out.? Mixed-gas O2 exposure limits. Recovery from CNS toxicity risk during underwater air breaks. Case reports.

Narcosis and HPNS
Signs and symptoms of nitrogen narcosis; individual susceptibility, accommodation and adaptation to narcosis; effects on narcosis of rate of compression, oxygen and carbon dioxide; onset depths of narcosis; narcotic potencies of N2, He, Ne, Ar, Xe, O2and CO2; oxygen narcosis; recommended depth limits for air diving; mechanism of narcosis; pressure reversal; utility of EAD/END (equivalent air depth/equivalent nitrogen depth). Signs and symptoms of HPNS; individual susceptibility; depth of occurrence; effect on HPNS of compression rate and time at depth; effect of trimix; effect of hydreliox; mechanisms of HPNS; options for reducing HPNS effects given obligatory fast descent rates.

Thermal Mechanisms of heat transfer (radiation, conduction, evaporation, and convection) with application to divers. Physiological temperature control and consequences of heat transfer (work; shivering; regional vasoconstriction; stages of hyperthermia and hypothermia; freezing and non-freezing injury). Respiratory heat transfer (inert gas and density effects). Rewarming and thermal afterdrop (“warm and dead?). Drysuit insulation properties of Ar, He, CO2, air and O2 (is this safe?). Insulation properties of wet undergarments. Tools for thermal modeling. Hotwater suits for shallow in-water decompression stops vs. insulation for dry decompression. (Thermal effects on decompression will be covered in the Decompression Workshop.) Current and new active and passive technologies (power sources, hydrogen thermal batteries, hydrogen catalytic heating, regional rewarming, aerogel garments).

  2. DCI Pathophysiology
  3. DCI signs, symptoms and pathophysiology. Paradoxical thromboembolism and cryptogenic stroke. AGE: pulmonary barotrauma, ASD, PFO, and transpulmonary passage, Type III DCS. PFO detection and diver evaluation. Transpulmonary passage and bubble size. Evidence associating DCS with PFO. Skin bends and PFO. Exercise and pulmonary shunt. PFO correction. Case reports.
  4. DCS Risk Factors
  5. VGE as a measure of decompression stress. Environment: temperature, immersion, exercise. Influence of dive phase (pre-, bottom, deco, post-). Individual: obesity, gender, age, aerobic fitness, individual susceptibility. Adaptation, hydration, alcohol, previous DCS, injury.
  6. Deep Stops
  7. History and theory of deep stops. Empirical methods and rules. Supporting evidence and experimental data. Validation of methodology.
  8. In-Water Recompression
  9. Review of IWR experience. Appropriate signs and symptoms for IWR. Equipment and procedures to minimize IWR risk in event of decompression emergency with no access to recompression chamber. Training requirements. Environmental conditions. Depth measurement and control. Diver monitoring and tending. Surface support. Emergency procedures. Outcome reporting.
  10. DCS Risk Assessment
  11. DCS probability and severity in air and nitrox diving. DCS severity and acceptable DCS risk. Technical diving database, risk analysis and dive condition effects. Examples of tech dive profiles and outcome data. Diver Health Status Form (DHSF). Uploading dive profile and DHSF data to DAN Website. Are technical divers self-selected?
  13. US Navy and UK/EU Perspectives on Rebreather Test Methods and Standards
  14. Rebreather divers must overcome the work of breathing due to breathing resistance, static lung load, and elastance. Inspired CO2 amplifies these effects by increasing ventilation. CO2 sensors and scrubber gauges would decrease this risk. CO2 canister duration is tested as a function of temperature, workload, and depth. O2 control accuracy is assessed.
  15. Testing should be performed on breathing machines and by divers. What US and EU labs are qualified to test rebreathers? What is the role of failure mode effect and criticality analysis (FMECA) in rebreather design? New U.S. Navy performance standards are based on diver tolerance. U.S. Navy and EU rebreather test standards should not differ, but do.
Direct download: PD087.mp3
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