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. REFERENCES [1] BERNE, R., M.; LEVY, M., N. Physiology. 4th ed. St. Louis: Mosby, 1998, 1131 s. ISBN 0-8151-0952-0.

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