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1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2007 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA)
4、 Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org AIR825/2 AEROSPACE INFORMATION REPORT Issued 2007-07 Effects of Acute Altitude Exposure in Humans: Requirements for Physiological Protection RATIONALE This document is written to provide information on the physiologi
5、cal modifications of humans exposed to altitude and the limits of his/her adaptation. This information is useful to establish the principles of the protection of humans during the flight. TABLE OF CONTENTS 1. SCOPE3 1.1 Purpose.3 2. BIBLIOGRAPHICAL REFERENCES3 3. GENERAL.4 3.1 Units4 3.2 Mean Values
6、 and “Safe“ Values.4 4. ATMOSPHERE.5 4.1 Atmospheric Pressure.5 4.2 Temperature6 4.3 The Composition of the Atmosphere 6 5. CARDIOVASCULAR AND RESPIRATORY ANATOMY AND PHYSIOLOGY.8 5.1 Blood Circulation.8 5.1.1 Anatomy8 5.1.2 Physiology.9 5.2 Ventilation .10 5.2.1 Anatomy10 5.2.2 Mechanical Aspects o
7、f Pulmonary Ventilation11 5.2.3 Pulmonary Gaseous Exchanges 11 5.2.4 How Oxygen is Carried by the Blood13 5.2.5 How Carbon Dioxide is Carried by the Blood and its Relationship with pH14 5.3 Relationship Between Oxygen Consumption and Workload14 6. HYPOXIA 14 6.1 Background.15 6.2 Main Mechanisms and
8、 Classifications15 6.2.1 Classification of the Different Types of Hypoxia.15 6.2.2 Time-based Classification of Types of Hypoxia15 6.3 Effects of Acute Altitude Hypoxia on the Major Vegetative Functions16 6.3.1 Effects of Hypoxia on Ventilation16 6.3.2 Effects on Blood Circulation16 6.4 Effects of H
9、ypoxia on the Relation Functions.16 6.4.1 Effects of Hypoxia on the Physiology of the Neurons.16 6.4.2 Changes in the Motor Function.16 6.4.3 Sensory Organs18 6.4.4 Effects of Acute Hypoxia on the Psychic Functions18 6.5 Tolerance to Altitude Hypoxia.19 6.5.1 Tolerance in Relation to the Altitude Re
10、ached .19 Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 20:46:43 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/2 - 2 - 6.5.2 Development of Hypoxia Over Time.20 6.5.3 Toleranc
11、e to Hyperacute Hypoxia and Time of Useful Consciousness .21 6.6 Physiological Principles of Protection Against Altitude Hypoxia.21 6.6.1 General Case21 6.6.2 Case of Rapid Decompression at High Altitude .23 6.7 Rules of Protection Against Hypoxia 23 7. HYPERVENTILATION25 7.1 Physiological Mechanism
12、 of Hypocapnia .25 7.2 Clinical Symptoms of Hypocapnia 25 7.3 Causes of Hyperventilation During Flight .26 7.4 Procedure to Follow During Flight 26 7.4.1 Recognizing the Problem26 7.4.2 Sedation of Malaise During Flight.26 7.5 Specific Case: The Hyperventilation of a Subject Using a PBE (Protective
13、Breathing Equipment).27 7.6 Conclusion 27 8. GAS DILATION AND COMPRESSION27 8.1 ENT Barotraumas .27 8.2 Barotraumas of the Digestive System 28 8.2.1 Aeroodontalgia28 8.2.2 Digestive Pain.28 8.3 Pulmonary Barotraumas .28 9. DECOMPRESSION SICKNESS.31 9.1 Physical Principles32 9.2 Physiological Mechani
14、sms32 9.3 Symptoms of Decompression Sickness .33 9.3.1 Benign Decompression Sickness .33 9.3.2 Severe Decompression Sickness.33 9.3.3 Delayed Decompression Sickness.33 9.4 Decompression Sickness Risk Factors 33 9.5 Protection Methods.34 TABLE 1 COMMON CONVERSION FACTORS4 TABLE 2 COMPOSITION OF AMBIE
15、NT AIR 7 TABLE 3 TIME OF USEFUL CONSCIOUSNESS .21 FIGURE 1 5 FIGURE 2 6 FIGURE 3 7 FIGURE 4 9 FIGURE 5 11 FIGURE 6 13 FIGURE 7 17 FIGURE 8 20 FIGURE 9 22 FIGURE 10 24 FIGURE 11 28 FIGURE 12 30 FIGURE 13 30 FIGURE 14 34 Copyright SAE International Provided by IHS under license with SAELicensee=Defens
16、e Supply Ctr/5913977001 Not for Resale, 12/04/2007 20:46:43 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/2 - 3 - 1. SCOPE The intent of this SAE Aerospace Information Report (AIR) is to describe the effects of the environmental changes on human physiology and
17、the protection required to avoid negative consequences resulting from altitude exposure. A brief presentation of basic terms and considerations required to discuss the topic of human physiology at altitude are followed by an overview of the cardiovascular and respiratory systems. Issues specifically
18、 related to human exposure to altitude are then discussed. Hypoxia, hyperventilation, barotrauma, and decompression sickness (DCS) are each addressed: hypoxia is defined as an insufficient supply of oxygen to the tissues, hyperventilation is an excessive rate of ventilation with ultimate consequence
19、s on acido-basic equilibrium, barotrauma is injury caused by pressure: most commonly referencing injury to the walls of the Eustachian tube and the ear drum due to the difference between atmospheric and intratympanic pressures, and DCS is related to an excess of nitrogen in the body tissues. One goa
20、l of this AIR is to demonstrate the necessity of oxygen use for prevention of physical and psychological problems, or loss of consciousness in an aircraft pilot, flight crew, or passengers. Hopefully, this will provide a clear understanding as to why the use of supplemental oxygen is required for fl
21、ight crew and passengers at altitudes greater than 12,000 ft (3650 m). 1.1 Purpose The purpose of this AIR is to establish the physiological requirements for protection of humans against altitude in aviation. 2. BIBLIOGRAPHICAL REFERENCES a. General References: 1. Ernstings Aviation Medicine, Rainfo
22、rd DJ and Gradwell DP Ed., Hodder Arnold, London , UK, and Oxford University Press Inc., New York, USA 2. A Textbook of Aviation Physiology, J.A. Gillies Ed., Pergamon Press 1966, (1226 pages) b. Regulation Texts: 3. 14 CFR, Part 25: Airworthiness Standards: Transport Category Airplanes, 4. CS-25 (E
23、ASA): Certification specifications for large aeroplanes. 5. NATO NSA STANAG 3198AMD: Physiological Requirements For Aircraft Oxygen Equipment And Pressure Suits. c. Books or Papers: 6. Bert P. La pression baromtrique (The Barometric Pressure). Redited by CNRS Paris, Masson, 1979. 7. Gaume JG. Factor
24、s influencing the time of safe unconsciouness (TSU) for commercial jet passengers following cabin decompression. Aerosp Med 1970, 41 (4):382-385 8. Luft UC, Bancroft RW. Transthoracic pressure in man during rapid decompression. J Aviat Med, 1956, 27:208- 220 9. Luft U. Aviation physiology: the effec
25、ts of altitude. Handbook of Physiology Respiration, Fenn WO and Rahn H Ed. - Am. Physiol. Soc. 1965, WASHINGTON D.C.: t.2, 44:1099-1145 10. Marotte H, Tour C, Clre JM, Vieillefond H. Rapid decompression of a transport aircraft cabin: protection against hypoxia. Aviat Space Environ Med 1990, 61 (1):2
26、1-27 11. Marotte H, Tour C, Florence G, Lejeune D, Kergulen M. Transport aircraft crew and decompression hazards: study of a positive pressure schedule. Aviat Space Environ Med 1990, 61 (8):690-694 Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/59139770
27、01 Not for Resale, 12/04/2007 20:46:43 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/2 - 4 - 12. Otis A.B. Quantitative relationships in steady-state gas exchange. Handbook of Physiology Respiration, Fenn WO and Rahn H Ed. - Am. Physiol. Soc. 1965, WASHINGTON D
28、.C.,: t. 1, 27:681-698 13. Ruff S, Strughold H. Grundri der Luftfahrtmedizin. Johann Ambrosius Barth, 1939, Verlag Leipzig 14. Violette F. Les effets physiologiques des dcompressions explosives et leurs mcanismes. Rev. Md. Aro., 1954, 223-271 3. GENERAL 3.1 Units In any serious discussion of altitud
29、e exposure, quantitative descriptions are required. The variables of primary interest being altitude, pressure, and temperature, a variety of units are commonly used with each of these parameters. Table 1 presents conversion factors for some of the most frequently used units for each of these parame
30、ters. In addition, the term Flight Level (FL) is commonly used in aeronautical practice. It is a valid reference for discussions of physiological limitations since it provides a common reference for the effects of pressure changes on the human body. It is, however, a valid means to determine absolut
31、e altitude with reference to sea level. Flight level is defined as the conventional altitude, expressed in feet, divided by 100 (for instance: FL 300 is 30,000 ft). TABLE 1 - COMMON CONVERSION FACTORS Pressure to mm Hg In H2O hPa psi From Multiply by mmHg 0.5353 1.3333 0.0193 in H2O 1.8683 2.4909 0.
32、0361 hPa 0.7500 0.4014 0.0145 psi 51.7149 27.7000 68.9476 Length to Feet Meters From Multiply by Feet 0.3048 Meters 3.281 Volume: 1 L = 1 dm3 Temperature Fahrenheit (F) Centigrade (C) Kelvin (K) F = 9/5 C + 32 C = 5/9 (F - 32) K = C + 273 3.2 Mean Values and “Safe“ Values In many instances, data wil
33、l be presented in this paper to demonstrate the concepts and issues being discussed. Confusion could result regarding the interpretation of these numbers if the differences between “mean“ and “safe“ values are not recognized. The mean of a set of data is the average value of all the observations. Us
34、ually, a measure of variability, such a standard deviation, among observations is also calculated. These measures are most meaningful when the observations are distributed in a manner that is referred to statistically as normal. For example, if one were to measure the height of 1000 individuals, the
35、 distribution of heights between the tallest and shortest individual would be expected to resemble that presented in Figure 1. Most biological data can be described or summarized in this manner. The sections of this AIR which address the fundamental functioning of human body, will often utilize mean
36、s and standard deviations to describe responses. Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 20:46:43 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/2 - 5 - FIGURE 1 - Gauss
37、curve, “mean and “safe“ values. This curve describes the probability to observe a given value. The number of subjects, which are above this value, is in relation with the area under the curve. “Safe value“ must leave less than 10-7 of subjects under the curve, at the left of this value. When the top
38、ic of discussion is the adaptative and performance limits of humans at altitude, a different perspective and analysis must be utilized. The objective is flight safety. Therefore, statistically unusual responses must be considered. In the case of “safe“ data, the occurrence of responses at a probabil
39、istic risk at of least 10-7/10-9 are considered. The part of this AIR which discusses data directly related with aviation safety will use “safe“ data. Regulatory bodies often utilized “safe“ data as the basis for their requirements. Although “safe“ data can be described in statistical terms, mean da
40、ta and “safe“ data are not necessarily the same across the human population as a whole. For instance, subpopulations such as military people versus older passengers on commercial airline flights may be characteristically different for a given response. 4. ATMOSPHERE As a biological species, humans a
41、re predominantly aerobic (i.e., dependent upon oxygen for metabolic energy production) requiring relatively specific environmental conditions for survival and comfort. Due to intelligence, humans have developed technologies that allow them to live in an extreme range of environments. Included within
42、 this range are the atmospheric changes associated with ascent to altitude in aircraft. If not controlled and regulated, the environmental changes associated with flying will result in physical and mental performance deficits that represent a serious threat to survival. 4.1 Atmospheric Pressure Baro
43、metric pressure (PB) decreases with altitude in an exponential relationship (Figure 2). Just a few key values are required to show how fast the atmospheric pressure decreases as the altitude increases: - standard value at sea level (PB0): 1013 hPa (760 mm Hg), - PB0/2, i.e., 506 hPa (380 mm Hg) at a
44、bout 5500 m (18,000 ft), - PB0/4, i.e., 253 hPa (190 mm Hg) at about 10,200 m (33,500 ft), - PB0/10, i.e., 101.3 hPa (76 mm Hg) at about 16,100 m (52,800 ft), - PB0/100, i.e., 10 hPa (7.6 mm Hg) at about 30,500 m (100,000 ft). Copyright SAE International Provided by IHS under license with SAELicense
45、e=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 20:46:43 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR825/2 - 6 - FIGURE 2 - GRAPH INDICATING ATMOSPHERIC PRESSURE (PB) IN RELATION TO ALTITUDE (Z) 4.2 Temperature The temperature of the atmosphere decreas
46、es as altitude increases, up to about 37,000 ft (11,300 m) where temperature reaches a mean value of approximately -56 C (-69 F, 217 K). Above this altitude, and at all flight levels used in aeronautics, the temperature remains constant (Figure 3). 4.3 The Composition of the Atmosphere For the major
47、ity of gases, the composition of the atmosphere is constant at all the flight levels operated in aeronautics. The primary exceptions are water vapor and carbon dioxide. Table 2 lists the components normally found in the lower layers of the atmosphere. Ozone is situated mainly between 50,000 and 150,
48、000 ft (15 and 50 km), with a maximum at 100,000 ft (30 km). For human respiration, the most important element in the atmosphere is oxygen. On a percentage basis, oxygen makes up 21% of the gas in air. This percentage is important in that it is used in calculating the partial pressure of oxygen (P O2). It is the P O2 that provides the force to drive oxygen into the body. Since the percentage of oxygen in the air remains relatively constant, the P O2 varies in direct proportion with the atmo