I https://ntrs.nasa.gov/search.jsp?R=19690004637". 2020-03-23T22:37:56+00:00Z LOAN CQPY: RETURN TO AFWt (WLIL-2) KIRTLAND AFB, ME>( t- N $- j !:> I$& -, RAPID (EXPLOSIVE) pP1 DECOMPRESSION EMERGENCIES 1i IN PRESSURE-SUITED SUBJECTS i I'; by Emanuel M. Rotb i ' Prepared by THE LOVELACE FOUNDATION I Albuquerque, N. Mex. ! for j NATIONALAERONAUTICS AND SPACE ADMINISTRATION WASHINGTON,D. C. NOVEMBER 1968 w TECH LIBRARY KAFB, NM OOb031& NASA CR-1223 RAPID (EXPLOSIVE) DECOMPRESSION EMERGENCIES IN PRESSURE-SUITED SUBJECTS By Emanuel M. Roth, M.D. Distribution of this report is provided in the interest of informationexchange. Responsibility for the contents resides in the author or organization that prepared it. Prepared under Contract No. NASr- 115 by THE LOVELACE FOUNDATION FOR MEDICAL EDUCATION AND RESEARCH Albuquerque, N. Mex. for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - CFSTI price $3.00 FOREWORD This study of explosive decompression emergencies in vacuum test chambers was performed upon request of Dr. E. L. Beckman, Acting Chief, Preventive Medicine Office, Manned Spacecraft Center, Houston, Texas, and submitted through the Directorate of Space Medicine, Headquarters Office of MSF, NASA. I wish to acknowledge the aid given by Dr. William V. H. Mason, Dr. UlrichLuft, Dr. Archer S. Gordon,Mr. Gerald Bowen, Dr. Royce Fletcher,and Mr. Ronald'Rietz of the Lovelace Foundation and Dr. Rodger E. MacQuigg of the Lovelace Clinic through their critical review of the manuscript and suggestions made in analysis of the problem. Many of the data used in evaluation of current space suits were obtained by verbal communication with several different groups. The individuals who contributed to this analysis were Messrs. Edward Michel, JosephKosmo, M. I. Radnofsky, C.C. Lutz,and J. H. Chappee of the Manned Spacecraft Center, Houston and Mr. Pierre Brousseau of the Space Sciences Laboratories, Litton Industries. Any errors of omission or commission are the fault of the author in misinterpreting these un- published data. Thanks are also due Drs. Richard Bancroft and Fritz Holmstrom of the USAF, SAM, Brooks AFB for Air Force data and Dr. Karl Schaefer of the U. S. Naval Research Laboratory, New London, and Captain R. D. Workman of theNMRI, Washington, D. C., for their interpretation of U. S. Navy diving experience. I also wish to gratefully acknowledge the task performed by Miss Dorothy Tyson, Mrs. Irene Brian, Mrs. Marjorie Wilson, and the members of the Document Library of the Lovelace Foundation in the preparation of this report. iii TABLE OF CONTENTS I . Physical Considerations in Damage to the Lung During ExplosiveDecompression ............ 1 I1 . Evaluation of Decompression Hazards Following Specific Suit Failures .............. 17 A . SoftSuit ..................... 18 B . HardSuit ..................... 22 C . Time of Decompressionand Hazard Analysis ... 25 I11 . Pathological Phvsiology of Explosive Decompression to a Vacuum .................. 34 Contusionand Disruption of Lung Parenchyma ..... 34 Pneumomediastinumand Pneumothorax ........ 36 Aeroemboli ...................... 38 Ebullism ....................... 40 Review of Human Accidents Involving Explosive Decompression ................. 43 IV . Therapyin Explosive Decompression Emergencies ..... 49 A . Prophylacticand Preventive Measures ....... 49 B . Treatment of Subjects Showing Symptoms afterExplosive Decompression ......... 51 1 . LungContusion ............. 51 2 . Pneumomediastinum.Pneumothorax. andHemopneumothorax ....... 54 3 . Aeroembolism ............. 59 4 . Ebullism ................ 74 V . TherapeuticEquipment and Supplies ............ 77 VentilationKit .................... 78 Intubation Kit ..................... 78 DrugKit ...................... 79 Injection/InfusionKit ................. 80 SpecialEquipment .................. 81 Summary ............................ 83 References ........................... 87 Appendix V Rapid___ "_(Explosive) ~ Decompression~ ~ Emergencies in Pressure-Suited Sub.jects Exposure of humans to the vacuum of space simulation chambers has become a requirement in the development of full pressure suits and extravehicular assemblies. One of the hazards of such studies is rapid or explosive decompression damage to the lungs brought about by catastro- phic failure of any one of several components of the extravehicular assembly. The present analysis will cover the physical factors determining lung damage after explosive decompression of any pressurized structure sur- rounding a human; the modes of failure and physical processes in the disruption of space suits; the pathological physiology of lung damage by explosive decompression; and the therapeutic considerations in handling such emergencies in vacuum simulation chambers. I. Physical Considerations in Damage to the Lung During ExplosiveDecompression The following discussion is adapted directly from the excellent sum- mary of Luft (1 23 The severity of mechanical effects on the body in rapid decompres- sion is dependent on the change in absolute pressure, the ratio of initial to final pressure, and the rate of decompression. The latter can be defined , rather precisely on the basis of physical theory if the pressure conditions, the volume of the cabin, (suit) and the size of the aperture are known or can be (71 , 77 , 82 ,136 ) assumed . Inpresence the of humidity,decom-the pression is neither an adiabatic nor an isothermal process, but is poly- .I tropic in character. The rate of flow through the orifice may be of sub- 1, sonic or sonic velocity, according to the pressure ratio across the orifice ( 77 ' 136 ). If the critical ratio of approximately 2 to 1 is exceeded, the !I L esdape flow will be constant at the speed of sound regardless of how high the pressure head may be. The initial rate of change in pressure is deter- minedby the absolute magnitude of theinitial cabin pressure. For all 1 practical purposes, the complex factors that define the decompression transient can be resolved into two principal determinants (82 I. The first of these, which sets the absolute time scale of decompression, will be referred to as the time constant (t,) It is defined by the ratio between cabin volume (V) and the effective area of the decompression orifice (A). The velocity of sound (C) is introduced as a characteristic of flow that eliminates the effect of density. It will be seen that t must appear in units of time, all other units canceling out. C The time constant is independent of pressure. The chart in Figure 1 is a graphic solution of equation (1) relating cabin volume and effective orifice to the time constant in metric units. The second determinant is the pressure factor (P,) derived for a polytropicprocess under subsonic or sonic conditions of flow. P is a 1 function of the initial cabin pressure (P.)and the final pressure of equi- 1 librium with the environment (P ), and is independent of the- absolute pres- f sur e (82) p1 = f(+) The values for P can be read for any desired pressure ratio from the 1 curve in Figure 2. The total duration of decompression (t ) is the product d of the time constant (t ) and the pressure factor P C 1' td = tc PI The relationships expressed in equations (1) and(3),which have been verified in numerous experiments, are convenient for estimating the decom- pression time on the basis of an aircraft cabin volume..and the configuration of windows, doors, or canopy for various cabin pressures at altitudes, Similarly, the volume to orifice ratio and the time constant of any decom- pression situation can be estimated if the elapsed time of decompression 2 TlME CONSTANT .4." ,4SG AREA OF ORIFICE. m2 Figure 1. The volume of the pressure cabin relative to the effective area of the decompression orifice deter- mines the time constant of decompression. For the respiratory tract this depends on the lung volume and the flow resistance of the airways at the time of decompression. (After Luft ( 123)) and the pressure ratio P./P are known. 1f Under vacuum conditions, the duration of decompression becomes extremely long because the final equalization of pressure is very slow. Under these circumstances, the initial part of the transient where the rate of decompression is constant (constant rate time) is more meaningful, as far as biological effects are concerned, than the total duration of de- compression. As shown on Figure 3 the line of initial rate of change is extendeduntil it intersects theambient pressure P Thepoint of inter- ao' section marks a time which is evidentiy related to the initial rate of pres- sure change and the pressure difference. This "constant rate time" (tcr) can be calculated fromthe time constant (t ) and another pressure factor C 3 Figure 2. The pressure function P1 for the total time of decompression and for the L'constant rate time" (P3) as derived from the pres- sure ratio (Pc/P ) or (Pi/Pf). a (After Bancroft (12 )) (P,) which may be read from the curve so designated on Figure 2 for the appropriate decompression ratio: t = tc P3 cr If an individual were decompressed from an initial cabin pressure, Pi, to a final pressure, Pf, at altitude with closed airways in the absence of any change in his lung volume the pressure in his lungs, PL, would remain equal to P and the pressure gradient, APL, sustained byhis i' lungs and chest would be equal to the total pressure difference of decom- pres sion. APL = PL - Pf = Pi - Pf On the other hand, if the gas in