Effect of normobaric hypoxia on psychomotor pilot performance

Effect of normobaric hypoxia on psychomotor pilot performance
Bc. Lukas Novak
Department of Air Transport
CTU in Prague, Faculty of Transportation Sciences
Prague, Czech Republic
[email protected]
and
Ing. Vladimír Nemec, Ph.D.
Department of Air Transport
CTU in Prague, Faculty of Transportation Sciences
Prague, Czech Republic
[email protected]
and
Doc. Ing. Radovan Sousek, Ph.D.
University of Pardubice, Jan Perner Transport Faculty
Pardubice, Czech Republic
[email protected]
Abstract - The diploma thesis deals with the effects of
normobaric hypoxia on psychomotor performance of pilots.
The aim was to create a model that could serve as a preselection of suitable candidates for training of commercial
pilots. The methodology is based on a simple flight
simulator that allows you to check the reaction time to
unexpected events of probands with insufficient oxygen
supply. The attention was paid to the description of existing
knowledge of the problems and testing process itself,
including evaluation of measured data. The results of
measurement confirmed our assumptions, namely that is
able to quickly and efficiently assess the suitability of
candidates at minimum funds.
Keywords - Atmospheric pressure, hypobaric hypoxia,
classification, oxygen, method, model, normobaric hypoxia,
organism, proband, system, tension, test, pressure,
hyperbaric chamber, Institute of Aviation Medicine in
Prague.
INTRODUCTION
One of the most serious risk factors in aviation is the
issue of hypoxia - a lack of oxygen in the blood, cells and
tissues which may cause dysfunction or limited
functionality. This dysfunction affects numerous
biological functions in the foreground with the central
nervous system, which is on the regular supply of oxygen
entirely dependent. The result is a gradual degradation of
logic and rational thinking and an overall reduction in
performance. Therefore it is undeniable that hypoxia is
very insidious condition and airline staff should have a
good theoretical and practical knowledge about it. There
is the issue of preventive and regular testing to the benefit
of increased safety.
The aim of this study is to create a pre-selection test
model, which can be used for clearly choose of ideal
candidates to start training for the position of commercial
pilot. An advantage is the relatively low cost of
mentioned test thus can be used for regular control
measurements of aviation personnel. Among other things,
the study also could very well serve as an informative
insight into the issue, leading to a form of awareness
among the public, which is often distorted images.
PROBLEMS OF HYPOXIA AND OVERVIEW OF CURRENT
KNOWLEDGE
The goal of this chapter is to describe accurately the
issue of hypoxia, including all connections from the air
psychophysiology, which are necessary for the
understanding of this topic. However, priority was a good
clarity of the whole text. It also includes a brief
characterization of the Institute of Aviation Medicine in
Prague and especially Flight Safety department which
allowed all this research.
A. The physical properties
The first part is devoted to the physical properties of
the atmosphere. In broader sense is the atmosphere
working environment for the pilots. With increasing
height are changing properties and thus effect of the
atmosphere on function of the human body.
The chemical composition of the atmosphere is
almost unchanged as a result of vertical mixing of air to
an altitude of about 100 km. Given the nature of
temperature changes occur to the vertical division into
four basic layers, which are separated by 1 - 2 km strong
transition layers.
Atmospheric pressure decreases with increasing
altitude. The oxygen permanently occupies about 21% of
the total gas content located in the air which is connected
with proportional descent of partial oxygen pressure.
Boundaries are constantly moving and therefore occurred
a problem of decrease partial oxygen pressure in the
atmosphere and lungs. The lack of oxygen negatively
affected human performance, which was cause of much
aviation disaster. Obviously, there were two possible
solutions to this problem obviously:
• breathing of air enriched with oxygen during the
flight. There is also the possibility to breathe pure
oxygen, because with decreasing barometric
pressure gradually decreases its toxicity to
disappear completely,
• airtight cabin destined for people where will be
demonstration of the symptoms of altitude hypoxia and
represents an important and unique practical experience
increasing flight safety.
C. Hypoxia and its influence on the organism
With increasing height due to declining oxygen
tension in atmospheric air is unprotected body influenced
of decrease the partial pressure of oxygen in arterial
blood. This specific type of inadequate supply of blood,
cells and tissues by oxygen is called hypoxia, and the
result is a gradual degradation of their functionality.
Type
hypoxia
Hypoxic
Anemic
Stagnation
maintained normal barometric pressure.
B. Institute of Aviation Medicine in Prague Department of Flight Safety
Institute of Aviation Medicine in Prague is a
specialized, diagnostic and therapeutic medical facility,
which is only one in the Czech Republic authorized to
issue certificates for staff aircraft. Specific procedures
and medical examinations are carried out at the
Department of flight safety. In the vacuum chambers are
tested individuals exposed to different levels of vacuum,
simulating stay at altitudes ranging from 0 to 13 000
meters above sea level. During testing are monitored
physiological data reflecting the subsequent response of
the human organism to changes in atmospheric pressure
respectively the height. The exposure also serves as a
Histotoxic
Characteristics and causes
The decrease in partial pressure of
oxygen (piO2) at arterial blood in the
drop in atmospheric pressure with
increasing height
Decrease in oxygen concentration in the
inhaled mixture below 21 °%
Faults of oxygen transport into the lungs
(insufficient ventilation of the lungs,
reducing airway patency, etc.)
Reducing the
number of red
blood cells
Reduced ability of Deterioration of
blood to carry
haemoglobin in
oxygen due to:
oxygen transport
Decrease in
haemoglobin
concentration
Own transport
Narrowing of the
mechanism of
arterial bed
oxygen is not
(illness, injury)
disturbed
Heart failure and
seriously, however
shock
the blood supply to
tissues stagnate as
+GZ forces
a result of:
The inability of
Alcohol
tissues to utilize
Some drugs
supplied oxygen
and perform
metabolism caused Cyanide
by:
The study of the physiological effects of hypoxia
began more than 100 years and at first sight it may seem
that this issue is not a problem for aviation. The opposite
is true despite a significant technical progress is hypoxia
still one of the highest risk factors. The first significant
signs of hypoxic condition are reflected in the decrease in
the partial pressure of oxygen at 9,3 to 8,0 kPa, which
corresponds approximately to a height between 3 000 - 4
000 m. For some of the less resistant individuals first
defensive reactions can be observed at the border 2 500
m. Causes of lack of oxygen can be divided into three
basic groups:
• reduction partial pressure of oxygen in the inhaled
air,
• failure in a part of the oxygen transport
mechanism,
• combination of both these causes when one can
damage other parts of the oxygen transport
mechanism.
Hypoxia affects the human body on several levels
simultaneously. Each area of the human body react
differently, and therefore it is necessary to pay close
attention. Most affected are the following systems:
•
•
•
nervous system,
circulatory system,
respiratory system.
An important term is the time of useful consciousness
which precisely defines the maximal time interval in
which the pilot is capable of rational and conscious
thought.
Altitude [m]
Time of useful consciousness - TUC
The Air
O2
5 500
20 - 30 min
unlimited
7 500
3 - 5 min
unlimited
9 000
45 - 90 s
unlimited
10 600
30 - 60 s
6 min
12 000
25 s
17 s
13 000
5 - 15 s
seconds
13 500
5 - 15 s
seconds
15 000
5 - 15 s
seconds
DESIGN OF MODEL AND TESTING METHODOLOGY
Hypoxic tests are important part of a complex testing
of natural resistance towards fundamental risk factors
emerging during flying. Demonstration effects of hypoxia
in connection with central nervous system are realized
through physiological tests based on simple mathematical
operations and drawing tasks. The big advantage is
simplicity but on the other hand it does not correspond to
character of the flying pilot activities.
A. The final developed methodology
The aim of this work was to replace the mentioned
tests. Solution is simple visualization system in which
displayed a natural symbols associated with their spatial
orientation for pilots. The basic premise for this system
was to use the joystick (analogy with control of airplane)
and computer with appropriate software, allows
interactive control of the system, displays necessary
elements and stores the results. The system was
developed for the realistic simulation effects that occur in
flight. Therefore pilots during hypoxic test react to two
variable parameters and solve described tasks:
• move the joystick to correct the deviation of
analogue pointer indicators,
• press a button integrated in the joystick to respond
to stimuli displayed on a digital device.
B. Technical description of the device
A system for testing psychomotor function is located
in a hypobaric chamber, however a hypoxic condition is
achieved with a device that allows breathing air mixture
containing reduced amount of oxygen without changing
the atmospheric pressure hypoxic. The system is
designed so that pilot controls joystick through which
keeps the deflection of pointer at the marked position to
simulate steady horizontal flight. Deflection of the meter
pointer is realized by a pseudorandom signal. Except the
joystick must tested person follow continuously changing
the numerical value of numbers on the screen. On the
basis of the individual assigned number must indicate by
pressing the button on the joystick. The system
continuously measures and retrieves deviation.
The entire test cycle consists of three five-minute
stages, where each stage starts with one-minute tutorial
interval and followed by a four-minute measured interval.
Tutorial interval is used for familiar with the operation
and prepare for measured attempt. The final outcome is
evaluation of performance expressed as the integrated
error in stage during and after hypoxia and mutual
comparing of these results.
Throughout the duration of the test is a doctor present
and closely follows screens of physiological system and
response to psychomotor test of tested persons. In case of
any serious complications test is prematurely terminated
regardless to the importance of the measured data. The
output of the program is the trend of integrated error
compared with measurements in various stages.
ANALYSIS AND
MEASUREMENTS
EVALUATION
OF
TESTS
AND
Whole test was carried out according to the described
methodology. To verify predetermined hypotheses and
thus confirm the goals, it was necessary to test the
equipment at full load with a human crew.
Data stored on the disk are processed using the
program and the output is represented by a table and
graph. Both clear and unambiguous manner summarizes
the course of the entire test and together with the record
of biosignals physiological functions are guide in the
final assessment of the specific resistance of the tested
person to hypoxic effects.
Tabular output:
To test psychomotor performance during normobaric
hypoxia was chosen set of individuals who could be
potential applicants for the course of commercial pilot.
Given this assumption, it was necessary to comply with
two conditions:
• very good health (First class medical certificate),
• appropriate age.
Attribute
Value
Total number
22
Number of women
5
Number of men
17
The highest age
26
The lowest age
20
The average age
23,68
Standard deviation of age
1,55
Modus age
24
Median age
24
CONLUSION
Graphical output:
The output of this study is the statistical evaluation,
which was prepared on the basis of 22 tested individuals.
The main objectives of this statistical analysis are:
• evaluate the effect of hypoxia on the testing role,
• evaluation of the statistical distribution of the
calculated coefficient of influence of hypoxia,
• evaluate the correlation of physiological
parameters (oxygen saturation and heart rate) in
relation to the size of the integrated error,
respectively the coefficient of influence of
hypoxia.
The measurement results confirmed the assumptions
and hypotheses. By using this method it is possible
quickly and efficiently determines the effect of hypoxia
on the psychometric performance of pilots at minimal
financial resources. This can advantageously be used for:
• training of pilots with problems of hypoxia and its
effect on the human body,
• testing of pilot resistance to manifestations of
hypoxia may exclude individuals with extremely
low natural resistance of flight training,
• testing the level of psychomotor performance
affected by hypoxia with the possibility to
quantify the potential effect of hypoxia on the
allocation and distribution of attention,
• training of pilots in the early detection of this
phenomenon and familiarity with the possibilities
of preventive measures.
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