Technological Solutions to Chronic Hypoxia Amongst Aviators Gp Capt (Retd) Dr V N Jha; Sc F MBBS, AMD, MD DEBEL, DRDO, Bangalore, India

Hypoxia amongst Aviators Hypoxia defined as inadequate supply of oxygen at tissue level. Increasing altitudes adversely affects:- Night visual Fn beyond 4-5Kft AMSL Novel Task Fn Cognitive Fn, Skilled task Fn, Physical performance, Effects of dysbarysm beyond 18Kft. Life sustenance becomes difficult beyond 20Kft.

Hypoxia amongst Aviators By Defn, Hypoxia is prevalent in almost all aviation flights exceeding 4-5kft cabin altitude. Standard acceptable values varies:- Aircrew Night Ops without O2 <5000 ft Aircrew Day Ops <10000 ft Aircrew Day Ops <12000 ft (for <30 min) No Std acceptable values laid down for acclimatised aircrew.

The requirements of supplemental O2 Aviation standards mandate usage of supplemental oxygen for aircrew above 10000 ft AMSL to prevent hypoxia whether ‘acute’ or ‘acute-on-chronic’. Oxygen systems for aircrew mandate the requirement of a technology that provides sea level oxygenation and is approved by appropriate Certification Agencies.

Aviation Breathing systems Helicopter Oxygen System Consists of following LRUs:- Oxygen gas source :GASOX/LOX/OBOGS/Chemical Breathing regulator:- Continuous flow or demand type. With or without dilution function. With or without pressure breathing functions Personal equipment connector Oxygen mask Hoses and connectors

Integrated Life Support System of Fighters

Oxygen Gas Source LOX system consists of :- GASOX system Consists of :- High / Low Pressure cylinder: Steel / Aluminum / Composite Reducer Head Aviation Std Oxygen gas LOX system consists of :- LOX & its converter OBOGS consists of air separation technologies:- PSA through MSOC (single / dual stage) Hollow Fiber membrane (HFM) Ceramic membrane Chemical Oxygen from Na/K Chlorate, Super-oxide

Pressure Reducer Valve It reduces the service pressure of the high pressure cylinder to a value required for the optimum functioning of the DDOR hence, it is design specific. It is also designed to meet the specific flow & pressure requirements of the DDOR. Apart from charging & output ports, it has pressure gauge, safety valve and an on-off switch. Various design specs available:

Performance Tests : HPOS 11

Oxygen Gas Aviation grade O2 to be used. Mil-PRF-27210G (Type-I) Purity >99.5%; -Moisture <7 ppm vapour CO2 <10 ppm -Methane <50 ppm N2O <4 ppm -Ethane <6 ppm Filter 10 & 40 micron nominal & absolute. No discernable odour.

DDOR : The requirements Prevent hypoxia upto specified altitude. O2% raised up to 100% by 28-33 Kft. Provide PBA beyond 37-39 Kft. Provide gas flow with minimal resistance, within the specified limits of physiological requirements. Provide 100% O2 breathing option. Flow indication to be provided. Redundancy for gas supply in pneumatic failure. Provide safety pressure breathing.

Performance Tests : DDOR 14

DEBEL DDORs Dilution Demand Oxy Regulator (DDOR). Man / Harness clipped. Low Pr Br Regulator (2.8 bar). Performance meets Defence Std 00-970 & Mil-R-6018C. Has ‘Air Mix’ and 100% modes of breathing. DDOR certified for Hptr upto 25000 ft AMSL.

DEBEL DDOR Aircraft mounted DDOR. Low Pr Br Regulator (2.8 bar). Performance meets Defence Std 00-970 & Mil-R-6018C. Has ‘Air Mix’, 100% and Emergency modes of breathing with safety pressure. It has electronic flow sensor imparting night O2 capability.

Performance Tests : Flexible hoses

Performance Tests : PMA Passengers’ Mask 19

Hptr Oxy Systems in diff configurations Mod-A Hose PBC HPOS Passengers’ Mask DDOR 20

HELICOPTER OXYGEN SYSTEM OXYGEN MASK DILUTION DEMAND OXYGEN REGULATOR SEAT SIDE INSTRUMENT PANEL SIDE OXYGEN HOSES CARBON COMPOSITE CYLINDER PRESSURE REDUCING VALVE

Actual Flight Trials Ground trials of fitment & interface – Satisfactory. In-flight trials – Satisfactory In-flight sPO2 upto 18kft in air-mix mode -99% Extensive flight trials carried out over 6 months and accepted for introduction in services.

conclusion Aviators are always at the risk of ‘acute’ or ‘acute-on-chronic‘ hypoxia in-flight. Supplemental oxygen is mandatory for flights above 10000 ft AMSL thru’ dedicated systems. The systems consist of high Pr O2 gas source, a Pr reducer, a breathing regulator and delivery sys. Aviation Oxygen Systems are specially certified. DEBEL has successfully designed and developed the oxygen systems which in various configurations, can sustain aircrew operations within large envelop of aircraft Ops.

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