Flying on air

Volume 48, No. 22, November 30, 2006

ALL GOOD: Pilot trainees FLGOFFs Jeremy Dutton, Michael Hannan and Nathan Thompson indicate all is going smoothly after 15 minutes breathing with their oxygen masks during the CADO validation study at AVMED. Photos by LAC Andrew Eddie

READY: WGCDR Greg Hampson in the control room of the hypobaric chamber.

By Hugh McKenzie

A GROUND-BREAKING research study by the Air Force Institute of Aviation Medicine (AVMED) will test the effects of high-altitude hypoxia on Air Force aircrew.

AVMED recently initiated the project to validate its Combined Altitude Depleted Oxygen (CADO) training program.

In February 2001, Air Force’s high-altitude hypobaric hypoxia training (25,000 and 45,000 feet) was cancelled after the Service received a Comcare Prohibition notice. This followed a number of cases of decompression illness in members undergoing high-altitude hypoxia training.

The Comcare directive significantly restricted AVMED’s hypobaric chamber operations, affecting its training and research capabilities.
As a result, AVMED developed its CADO training program.

“This system consists of an explosive decompression to 10,000 feet, followed by breathing a reduced oxygen gas mix equivalent to breathing air at 25,000 feet,” AVMED CO WGCDR Greg Hampson said.

“While the CADO system has provided all hypoxia training for the ADF since 2001, it has never been scientifically validated and its efficacy for military aircrew hypoxia training has been questioned.”

As the only institute of its kind using CADO, AVMED responded to these questions and is now conducting a research project to validate the system.

“This is ground-breaking research,” WGCDR Hampson said. “It directly compares a subject’s objective and subject’s performance during CADO and 25,000 feet hypoxia training.

“The results of the research will influence the safety and method of hypoxia training for current and future ADF aircrew.

“AVMED has Trials and Evaluation-tasking requiring altitudes above 18,000 feet. This is the capability AVMED and Aerospace Operational Support Group (AOSG) need to deliver to support ADF aerospace operations.”

In 2005, WGCDR Hampson approached Comcare to have the Air Force/AVMED high-altitude hypobaric capability restored. This occurred with the introduction of a process of requirement validation and risk management.

WGCDR Hampson explained that decompression illness (DCI) is a group of symptoms secondary to the effects of exposure to pressure changes at high altitude and at underwater depths. The most well-known types are the ‘bends’, which affect the body’s joints, and the ‘creeps’, which affect the skin. While the threshold for DCI is traditionally 18,000 feet, it is uncommon below 25,000 feet and rare below 22,000 feet.

WGCDR Hampson said the direct aim of this study is to clarify the direction of aircrew hypoxia/hypobaric training for the future.

“Validation of CADO will infer safe and effective hypoxia training. Also, with the chamber restrictions removed, there is scope for high-altitude training for specific platforms and/or roles, thus giving Air Force options for effective training and research,” he said. “This, I believe, represents world’s best practice for hypobaric chamber operations.

“Despite their [the volunteer subjects’] best efforts to date, they have not been able to differentiate reliably between CADO and the 25,000-feet runs. We’re looking forward to fully analysing the data when we have completed the study, with results expected to be published next year.”


Good medicine

AVMED has four main functions:

• Applied research, development, test and evaluation with respect to the military aviation environment, human performance, human system interface (human factors) and aircraft life support equipment.
• Aviation medicine/human factor training for ADF aircrew and aviation-related personnel such as AME crew and Special Forces.
• Clinical governance of ADF aircrew recruitment medical standards and medical employment category reviews.
• Specialist aviation medicine human factors’ services, such as accident investigation, motion sickness desensitisation and aircrew DNA repository.
  
  

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