Gliding Aviation Medicine,
High Altitude Aspects and
 Mountain Wave Project 1999,
St. Martin de los Andes, Argentina

Juergen K. Knueppel, Flight Surgeon; German Aero Club (DAeC), DGLRM, DFV, ASMA
34613 Schwalmstadt, aeromednews@t-online.de / 9.2000

Summary

Mountain Wave Project 99 in Argentina was a scientific, Hi-Tec first time high altitude wave glider-flying excursion. Next to overall mission planning and management tasks was the human factors part, with its life- and human performance related aeromedical concerns, an extraordinarily demanding business. These experiences are summarized as follows:

1. Flying at altitudes above 3000 m / 10000 ft in gliders requires general medical considerations, e.g. hypoxia.
2. Wave Flying at altitudes above 6000 m / 20 000 ft requires special high altitude preparations.
3. High altitude scientific literature studies, basic instruction and hypobaric chamber training were performed.
4. Technical planning, O2 requirement calculation and emergency training had to be done.
5. If both oxygen systems (EDS & Bendix) are used properly as required, O2 supply is provided in a safe manner.
6. At lower altitudes EDS provided sufficient O2 support, but battery function had to be watched closely.
7. O2 -systems must work reliably; they need professional maintenance.
8. Most used O2 -systems are not state of the art. Also EDS systems have to be technically improved.
9. Technical support and manpower for servicing O2 -equipment in the gliders must be provided at local airfield.
10. Available oxygen stores are not sufficient for long duration flights of more than 3 hours and performed at altitudes above 20 000 ft / 6000 m. – All compromises in flight are disabling and dangerous for flight safety.
11. Hypothermia, Hypoxia, Hyperventilation and DCS are the physiological threats.
12. Timely sufficient O2 - pre-breathing during ascent prevented all but one flight up to 27 000 ft / 8000 m from DCS symptoms, probably for the reason that the duration of stay at this altitude would only be a few minutes.
13. Flight safety and altitude physiology rules were known due to prior intensive basic training.
14. All flight safety related concepts were key elements for the success of MWP 99.

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I. Introduction to Mountain Wave Project 99

1. OSTIV and some other highly committed glider pilots, some of them scientists and meteorologists, travelled in Nov 1999 to Argentina to study the rule of the "Wave in the Andes". They also anticipated the opportunity to head for new Long Distance World records in gliders of their class.
2. In the wave a glider can be climbed at a rate of 1 to 10 m/s / 200 to 2000 ft/min or even more. In this type of forceful lift, which is usually associated with high velocities of wind and often signaled by a formation of lenticular clouds, it is possible to easily gain several thousand metres of altitude up to 50 000 ft /15 Km.
3. Such life threatening high altitude flights require aviation and space medicine considerations, flight-physiology training and technical support by aviation medicine trained specialists! The author, also a glider pilot and military trained flight surgeon took part in the preparation phase of this project and accompanied the excursion to San Martin de Los Andes.
4. The Andes extend 7000 Km in a nearly true north-south direction. The prevailing wind direction is primarily from the west. This wind creates large powerful mountain waves, which was the reason for exploring this remote area. Two groups of about 15 experienced pilots were accompanied by three powered high performance gliders, a double seated Stemme SV 10, an ASH 25 M and a single seat Nimbus 4 M.
5. Supported by local Argentinean pilots, they flew more than 100 flights totaling several hundred flying hours and at times covered long distances of more than 1800 Km / 1000 NM with some world records.

II. History of High Altitude Glider Flying and its Medical Aspects

Wave Flying has become increasingly important in recent times, as equipment and knowledge have improved over the last ten to fifteen years. Long Distance Wave Flights in the European Alps now happen regularly. In New Zealand and France during the last world championships the competitors had to prepare for wave flights at altitudes of up to 23 000 ft / 7000 m.

1. At altitudes of more than 20 000 ft / 6000 m, flying is lethal without oxygen. Decompression Sickness (DCS) with Types I and II (minor symptoms up to CNS and cardiovascular collapse) can readily occur and may destroy the health of a pilot.
2. Adequate oxygen equipment and hypobaric chamber-training should be mandatory for this type of rigorous and demanding glider flying. It is imperative for flight safety. In the USA altitude records of about 50 000 ft / 15000 m and recent speed records (Jim Payne) were all done with aid of the wave!
   In the USA, Poland, and the former GDR, hypobaric chamber training along with hyperbaric chamber facilities were widely supported by the authorities, even demanded in some places, prior to wave flying.
3. For a long time in Germany there has been a general lack of knowledge about oxygen needs when flying above 10 000 ft / 3000 m, with obvious detrimental influences on flight safety. This was the case for many years and no action was taken to improve this situation, even though expert opinion and knowledge in this field was available. One famous "Alpensegelflieger", Jochen von Kalkreuth, died at high altitude several years ago of hypoxia in his glider, apparently due to confusion about high altitude limits.
   The common situation was that expensive oxygen equipment was rarely bought or used.
4. With intensive support by the German Armed Forces, namely by Rainer Wienzek from Bueckeburg, the Military Flying Club and the knowledge and training by the Institute of Aviation Medicine, this situation in Germany has improved during the last ten years. It has focused on the following main subjects:
   1. OXYGEN DEFICIENCY AT ALTITUDE
   2. DECOMPRESSION SICKNESS (DCS)
   3. OXYGEN SYSTEMS.
5. Inexpensive, newly developed, Oxygen Demand Systems, like "EDS" from Mountain High/USA and "FLOWTIMER" from Spiegelberg in Hamburg have helped to resolve the problems of the limited stores of oxygen that can be carried aboard a glider. Now it is possible to fly for more than 11 hours with a 5 ltr bottle up to 18 000 ft / 5500 m.
6. At altitude new "PULSE OXYMETRY" devices can measure the amount of oxygen available in the pilot’s body, more commonly known as the oxygen saturation of hemoglobin, using a sensor clip on the finger. This measurement shows the pilot that he is either in a "safe" range or that he is becoming hypoxic.

III. High Altitude Physiology Training and Preparation for MWP 99

A team of flight surgeons discussed and proposed the following detailed plan to prepare for this expedition in the Argentinean Andes. In fact, not all of the preparation could be completed in time before the expedition started.

1. Flight medical exams prior to travel with emphasis on heart, lung and hematological functions.
   - Focusing on health problems that could be exacerbated at high altitudes. Those were addressed in advance to provide a margin of safety for the participants.
2. Review of the basic literature to understand altitude physiology concerning gas, pressure, and diffusion laws.
   - This is mandatory to understand high altitude dangers including the planned hypobaric chamber training.
3. Calculate oxygen requirements for the planned flight duration at different altitudes to be flown.
   - As a rule at altitude O2 consumption is 1 ltr oxygen at 200 bar / ATA, per hour, per person.
4. Prepare life support equipment for each glider to meet oxygen needs, including possible emergency situations.
   - This had to be done a long time in advance in order to design systems and organize the equipment. One unsolved problem exists for altitudes above 20 000 ft / 6000 m, as a "rule of thumb" there is not enough space in the glider to store sufficient oxygen for this altitude.
5. Lectures in Altitude Physiology: (+ Pressure changes in the body + oxygen deficiency at altitude + type of oxygen deficiencies + time reserve (TUC) + decompression sickness (DCS) + thermophysiology and others) and a practical hypobaric chamber ride, version No.1. - This is the first chance to experience hypoxic symptoms at 25 000 ft / 7500 m during a routine chamber run. The pilots had to get used to the chamber routine, to gain basic experience and learn O2 -discipline, like PRICE-Check (Pressure, Regulator, Indicator, Connections, Emergency Equipment) etc.
6. Hypobaric chamber ride, version No. 2. Introduction and training-practice of the O2 -equipment used in the glider, redundant additional systems and review in-flight emergency procedures. It was important to learn, plan and discuss different emergency options during flight, like O2 -system failure.
7. Documentation of all flights. Logger, paper, standardized questionnaire.
8. Pre- and post-flight briefings conducted by a flight surgeon. This exchange of experience helps to establish safe flying criteria.
9. Plan Search and Rescue Emergency Procedures (SAR), find local support, like a hyperbaric chamber, qualified hospitals, rescue systems, emergency phone numbers.
10. Technical equipment needed for Oxygen refills and additional technical supplies and support available at local airport.

IV. Practical Experiences during MWP 99

1. Oxygen Equipment

EDS (Electronic Oxygen Delivery System), nasal cannula, System No. I

1. All gliders carried EDS from Mountain High as the primary oxygen system. These systems had their own O2 -bottle, independent of a second system.
2. Stemme had two EDS Systems attached to one 5 ltr bottle. It seemed to work correctly, but it had to be routinely checked for proper operation. It consisted of two systems connected to one valve.
3. All bottles used were German Standard with 200-bar / 200 ATA pressure carrying a 3 or 5 ltr bottle.
4. EDS worked excellently in most of the flights excellently.
5. In a few cases EDS was likely to run low on battery power, without the pilot noticing and without realizing the audio-warning, if not monitored closely! This was dangerous and a point of concern!
6. If more than one pilot is flying in an aircraft, some additional cross checking has to be done to insure adequate battery power. Alternate options should be discussed, like regular battery change or another permanent power resource such as solar panels.
7. There has to be some technical test capability on the site available to be able to check such an apparatus, especially when it ages and more malfunctions occur. These systems have no regular "Quality Test Regimen", as other aircraft equipment and technical maintenance rules require.

Diluter Demand Systems , with face mask; system No. II

1. Stemme S10 VT,115 hp, had a certified Bendix diluter demand system, the standard system GAF F4F/ Alpha Jet.
2. The Bendix system met all legal technical and maintenance requirements.
3. It was equipped with masks, which were attached with Velcro tape on German military textile caps. This seems to be an excellent solution and fits tightly.
4. There were long elongated hoses for convenience.
5. The system is built into the panel (one for each crew member), so it can be operated individually.
6. The 5-ltr bottle was the primary O2 resource.
7. For higher or longer flights there was a battery of six individual 1 ltr bottles, which fitted behind one seat with specially constructed attachments and pressure valves.
8. Some pilots stated that they put the mask on in case of use at high altitude above 20 000 ft / 6000 m sometimes over the "nasal-cannula" of the EDS. They considered this a "Backup-System", in case the diluter demand system ran out of oxygen.
9. ASH25 M, 54 hp, had two EDS Systems attached to the one EDS valve on two connected 3-ltr bottles.
10. A big 5 ltr bottle was positioned parallel to the front of the aft seat. It served two Draeger diluter demand systems, similar to the Stemme System.
11. Nimbus 4 M, 40 hp, single seat, was equipped with EDS and a small independent diluter demand system, two independent 5 and 2 ltr O2 -bottles.

2. O2 -Resources

1. O2 -resources for flights up to 20 000 ft / 6000 m were sufficient, and in the case of higher altitudes there were time limits for its use.
2. Officially recognized standards for oxygen supplies that can provide up to 15 hours flying time at higher altitudes were not met! (Klaus Ohlmann’s single seat, 15-hour flight on S 10 was double seat equipped!)
3. Draeger Company states: Calculate altitude 6 to 11 Km: 1 ltr (bottle pressurized 200 bar) per hour, per person)!
4. To carry more oxygen bottles is nearly impossible, as there is also an engine and fuel tanks which take up space.
5. There has to be some invention to increase the oxygen stores in these gliders. In technical terms, a bottle should be light weight, and small in size or the fuselage has to be adapted for O2 -tanks. - This is also a concern for regular sport gliders.
6. Oxygen equipment/material is of military origin and often old and outdated. Technical testing cannot be done easily. This is a stringent safety concern!
7. As long as this equipment is the only one primarily used, trained personnel and test equipment have to be available at the site by some means to keep the life support systems in first rate condition.

3. DCS Prevention

1. "Preventive Decompression Sickness (DCS) Oxygen Breathing" before and during flight cannot be done sufficiently at the moment, due to lack of oxygen stores in the glider.
2. In case of a preplanned, rapid climb to more than 20000 ft / 6000 m (e.g. to 8500 m) altitude, this cannot be done without danger. 100% oxygen is already needed before take off and right from the start during the climb. This is mandatory to prevent Type II DCS Illness of a neurological nature, like severe headache, stroke, hearing loss, or partial blindness.
3. The ground calculation is 15 ltr 100% O2 per min (1 breath 750 ml times 20 per minute), which results in about 600 ltr O2 in 40 min, which amounts to a 3 ltr container. See also Annex 1: Practical Preventive Measures and Treatment of DCS in High Altitude Glider Flying above 22000 ft / 6000 m , J.Knueppel, 11/1999.
4. Some team members did three flights on three consecutive days up to: No 1= 8000 m, No 2=5500 m, No 3= 8500 m. The flights lasted from 9 to eleven 11 hours, higher altitudes climbed in about three hours. Even though the pilots flew several times at this high altitude, in these specific cases on three consecutive days, they experienced no signs of DCS-symptoms at all. This was not the expected finding, but probably due to the fact that pilots stayed at high altitude only a short time to exchange higher glider velocities in favour of longer flight distances.
5. Additional O2 was provided through EDS above 10 000 ft / 3000 m and through Bendix Diluter Mask above 20 000 ft / 6000 m. This regimen was used in most flights.
6. Logger data have to be analyzed exactly! But the conclusion was with the empirical experience up to this point, from O2 / time schedules of oxygen-use during the performed flights in 1999, that DCS seems to be sufficiently preventable!
7. In contrast, one experienced Argentinean pilot suffered in and after flight with severe headache and bends, which cleared over night. He used only the EDS-system in a rapid ascent to about 8000 m / 27 000 ft. -This really gives some evidence of the dangers of DCS.
8. Further data will be needed to prove all these experiences.
9. In case of a DCS emergency it would have been necessary to fly the pilot in 1ATA cabin pressure to La Plata to the Navy hospital, because the hyperbaric chamber at ALICURA was not available to the pilots.

V. Reference List

1. Evolved Gas, Pain, the Power Law, and Probability of Hypobaric Decompression Sickness, John Conkin et al.: ASEM, Vol. 69, No. 4, April 1998.
2. Paradigms for the Treatment of Hypobaric Decompression Sickness, Todd S. Dart et al.: ASEM, Vol. 69, No. 4, April 1998.
3. Guidelines for Treatment of Decompression Illness, Richard M. Moon et al.: ASEM, Vol. 68, No. 3, March 1997.
4. 1990 Hypobaric Decompression Sickness Workshop: Summary and Conclusions, Andrew Pilmanis: AL/CFTS, Brooks AFB, TX 78235, NATO AGARD Panel, April 1991.
5. Towards New In-flight De-Nitrogenisation and Altitude Decompression Sickness Risk, Andrew Pilmanis: AL/CFTS, Brooks AFB, TX 78235, Feb. 1992.
6. An Abrupt Zero-Pre-Oxygenation Altitude Threshold for Decompression Sickness Symptoms, James T. Webb et al.: ASEM, Vol. 69, No. 4, April 1998.

Annex 1:

Practical Preventive Measures and Treatment of DCS in High Altitude Glider Flying above 22000 ft / 6000 m

By
Juergen K. Knueppel, Flight Surgeon; German Aeroclub (DaeC), DGLRM, DFV, ASMA
34613 Schwalmstadt, aeromednews@t-online.de / 11.1999

Glider pilots, who fly above 20 000 ft / 6000 m must understand the basic principles of Henry’s Gas Law in order to be prepared to counter and treat DECOMPRESSION SICKNESS (DCS). - Reviewing the latest literature in ASMA Journal, Vol. 69, April 1998 (Aviation Space and Environmental Medicine), some new scientific articles were presented on DCS, also called "Divers Sickness". They highlight some valuable points worth considering, as follows:

1. Nitrogen bubble formation in the human body is generated through hypobaric pressure; as a rough rule above 1/2 of the original permanent pressure. This is e.g. if 1 Atmosphere at sea-level with 29,92 inch / 760 mm Hg is reduced to 14,96 inch / 380 mm Hg at an altitude of 18 000 ft / 5500 m . (This is to compare with the generation of CO2 bubbles, when a bottle of carbonated water is opened.- "Hypobaric" pressure is below atmospheric pressure and allows air bubbles to be released from the blood serum.)
2. The formation of gas bubbles is dependent of ascent rate, time at altitude and De-Nitrogenisation before the climb with 100% oxygen. (For example: One half atmosphere is reached in 18000 ft / 5500 m, or diving in water from 33 ft / 10 m to sea-level.)
3. Scientifically there are great interpersonal differences and situational variations, which contribute, like age, weight, muscle activity, recurrence of ascent, time at altitude or other individual predispositions.
4. Scientific knowledge is still under consideration, as many problems are still not completely understood and solved (space suits, space travel). Nevertheless, several empirical limits and insights have to be followed to prevent possible disastrous health consequences!
5. It is possible to be killed through DCS!
6. DCS in glider flying is a new subject. The professional aviation world knows how to deal with DCS, but it wasn't considered to be a problem in the glider world. In 1994 LTC Bob Weien, MD, FS USARMY discussed the first time high altitude glider flight and DCS risk. Symptoms were reported regularly, but not identified as DCS. -Scientifically Glider Flying DCS is a new problem.
7. The scientific barrier for DCS Symptoms without pre-breathing oxygen and with a climb of 5000 ft per minute / 25 m per second is 21000 ft / 6300 m.
8. Above this altitude about 5% of pilots without a pressurized cabin will experience DCS Symptoms (which are muscular, skeletal, pulmonary, and minor or major neurological symptoms). Most pilots below this won’t experience any symptoms at all.
9. In case of pre-breathing 100% oxygen, depending also on the time flown at lower altitude, the barrier goes up. The longer 100% oxygen is administered on the ground, the higher you can go without DCS.
10. The two main DCS symptoms must be differentiated as follows:
    Type I DCS: Symptoms are primarily bends; pain in the joints; considered minor!
    Type II DCS: Symptoms are of neurological nature, brain and nerve-malfunction, considered severe!
11. Most important are the variables, like elapsed time, altitude, intensity, quality of onset etc., which determine outcome!
    - Sudden incapacitation in flight, like hearing-loss or striking headache with vision-problems need immediate care and special medical treatment for survival! (Hyperbaric Pressure Chamber! " Hyperbaric "pressure is above atmospheric pressure and forces air bubbles into the blood serum. See also No 1!)
    - Bends at altitude slowly developing with minor intensity, disappearing at descent requires 100% oxygen!
12. All DCS symptoms need to be surveyed as they can return in the next 24 h and might require hyperbaric pressure therapy to resolve.
13. Hyperbaric pressure chambers exist, -portable and fixed based-, with the Navy, Airforce and with Diving Companies. They can save life and provide routine therapy in diver / DCS accidents.
14. First Aid, if DCS symptoms appear, is:
    a. always 100% OXYGEN,
    b. HYDRATION by drinking isotone solutions (water with 1/3 apple-juice, 1/2-teaspoon saline).
    c. transport to a HYPERBARIC CHAMBER, "dive" to 3 ATA for 2 to 5 hours, which hopefully will resolve the problem!
15. In-flight pre-breathing times of 100% oxygen, between 13-16 000 feet (not higher!) don’t prevent minor DCS symptoms, but prevent the most dangerous Type II DCS symptoms. The longer 100% O2 is inhaled, the more useful is it for the body!
16. High altitudes above 30 000 ft / 10 Km require as a rule 1 to 2 hours pre-breathing 100% O2 on the ground. One hour breathing 100% O2 flying at an altitude of 13 000 ft / 4000 m seems to have a similar effect!
17. If glider pilots fly high above 20 000 ft / 6000 m, it is important to go higher stepwise by ascending slowly, preferably for hours, than only in a few minutes. This reduces the DCS Risk!
18. Going up fast, staying up long at high altitude (i.g. 4 hours over 25000 ft / 7500 m) without pre-breathing will most probably cause DCS to develop.
    75% of all U 2 Pilots who fly at cabin altitudes of 30 000 ft / 9000 m experienced DCS at least once in their flying career, even with 100% oxygen breathing and with part time pre-breathing in advance!
19. DCS develops in general after one hour after ascent! If it is experienced, the pilot must descend immediately!
20. After DCS-symptoms have appeared, pilots have to descend and breath 100% oxygen, for 2 hours or even longer, after landing. This method should also be applied as a safety procedure, even when symptoms disappeare during descent.
21. Rule is: No Flight the Next Day, after a high altitude flight and if DCS Symptoms occurred during flight!
22. For follow up of DCS mishaps it is essential to document all important data on a protocol. Debriefing after flight and a second protocol the next day is recommended.
23. If in doubt: Ask a doctor/diving doctor or flight surgeon over the phone for consultation, (Airforce, Navy) or over one of the 24 hours worldwide civilian DCS emergency numbers: like DAN Suisse 0041 32-3223823 or DAN Europe 0039 085 8930333 (all languages)!

Last, but not least!
(Quoted from: Clinical Aviation Medicine; Rayman,R  2000)
The Breakoff Phenomenon

Rayman and Gillingham and Previc describe a rare event experienced by Pilots at very high altitudes who feel they have indeed “slipped the surly bonds on earth”.The term breakoff covers a variety of high altitude flight experiences, from simply feeling good through euphoria to psychological detachment. As noted by Rayman,it is important to advise pilots flying at high flying altitudes of the phenomenon and the need to report any such unusual experience. Psychiatric consultation should be requested if the event degrades flying performance or if the pilot is negativeley influenced by the experience after return to earth.