The accuracy of hypoxia awareness training in military aircrew'

1
The accuracy of hypoxia awareness training in
military aircrew.

• Adrian Smith
• Specialist Aviation Medical Officer (Army)
• RAAF Institute of Aviation Medicine
• Formerly, BAE Systems Saudi Arabia

2
Symptoms of hypoxia

• Hypoxia symptoms vary from person to person
• Range of symptoms experienced
• Severity of individual symptoms and
• Order in which symptoms appear.
• Believed to be relatively stable over time
  (Pickard 2002 Gradwell 2005).
• Each person has a hypoxia signature.

3
Hypoxia awareness training

• Integral component of physiological training for
  military (and civil) aircrew.
• Allows aircrew to experience hypoxia in a
  controlled training environment.
• Enables aircrew to recognise their hypoxia
  signature early enough to react within their
  time of useful consciousness.

4
Is hypoxia awareness training effective?

• Hypoxia incidents in the Australian Defence
  Force, 76 of aircrew recognised their symptoms.
  (Cable 2003)
• 31 of military aircrew who experienced hypoxia
  during accidental loss of cabin pressure
  recognised their symptoms. (Files et al 2005)
• High rate of recognition of hypoxia attributed to
  effectiveness of hypoxia awareness training.
• Hypoxia-naïve aircrew more likely to lose
  consciousness during hypoxia than hypoxia-trained
  aircrew, presumably due to delayed recognition of
  hypoxia. (Island Fraley 1993, cited in Cable
  2003)

5
But, on the other hand

• 25 - 70 of aircrew who have experienced
  in-flight hypoxia have not recognised hypoxia.
• Explosive decompression in a commercial aircraft
  (bang, misting)
• Cabin oxygen masks deployed
• Captain elected to NOT use oxygen mask
• Co-pilot despite feeling light-headed held
  the oxygen mask to his face as needed. (AAIU
  Report 2001/0014)
• Explosive decompression failure of rear
  pressure-bulkhead.
• FE queried Captain 4 times about need to don
  oxygen masks.
• Loss of cabin pressure, cabin oxygen masks
  dropped.
• Captain Theoretically, we should be on oxygen
  (AAIU Report 2001/0018)

6
But, on the other hand

• 1999 commercial flight with two former-RAF
  pilots.
• Pilot became hypoxic and fell unconscious.
• Neither crew fully appreciated the nature of
  hypoxia or urgency to respond.
• Even those crew who have had the benefit of
  training in a hypobaric chamber in the past may
  not be immune from failing to recognise the
  importance of immediate action.
• 2001 civil-register RAAF-operated Super King
  Air failed to pressurise
• Three military aircrew, all hypoxia experienced.
• The pilot and passengers had all undertaken
  regular hypoxia training. Despite this they
  did not identify the onset of symptoms of
  hypoxia until one person became unconscious.

7
For hypoxia awareness training to be effective

• Aircrew must remember their symptoms of hypoxia
• Amnesia, confusion, and drowsiness during acute
  hypoxia
• Remember these symptoms until next refresher
  training (3-5 years)
• Natural decay of non-refreshed memory
• The symptoms aircrew remember must reflect
  their hypoxia signature.
• Classroom knowledge overlaying imprecise memory
  of true symptoms.
• Aircrew must
• recognise symptoms as being hypoxia
• appreciate the significance of in-flight hypoxia
• carry out immediate corrective action.

8
Aims
9
Method

• Hypoxia awareness (refresher) training.
• 22 hypoxia symptoms, completed twice
• Before the hypoxia lecture (What symptoms do you
  remember)
• After hypoxia awareness training (What symptoms
  did you experience).
• Analyses
• Distribution of hypoxia symptoms
• Level of agreement
• the symptoms remembered and those experienced
  (overall)
• 5 dominant symptoms on each survey

10
Results

• 58 consecutive students - 85 effective response
  rate (n49)
• All exhibited signs of hypoxic impairment SpO2
  60-65
• 53 Pilots
• 47 Loadmasters, flight engineers, mission
  specialist crew
• 33.7 years old
• 2048 hrs flying experience

11
Symptoms of hypoxia - collective
12
Level of agreement memory and experience?
16 symptoms
13 symptoms
13
Did they experience the symptoms they remembered?
14
Did they remember the symptoms they experienced?
15
Recency of training
N10
N15
p 0.36
16
Age
p 0.25
17
Recency of training
p 0.16
18
Summary

• High level of agreement between
• Symptoms remembered and those actually
  experienced and
• Symptoms experienced and those remembered from 3
  years earlier.
• Recognition of hypoxia signature remains high up
  to 3 years, and is unaffected by age.
• Emphasis of hypoxia awareness training
• Be aware of symptoms.
• Recognise hypoxia signature, and appreciate its
  significance.
• Decide to act.
• Hypoxia awareness training an effective and
  valuable tool for demonstrating hypoxia
  signatures to aircrew.

19
Questions

• adrian.smith14_at_defence.gov.au
• Smith, A. M. (2008). Hypoxia symptoms in military
  aircrew long-term recall vs acute experience in
  training. Aviation, Space, and Environmental
  Medicine, 79, 54-57.