The Underwater Handbook, 1976 A Guide to Physiology and Performance for the Engineer

This handbook attempts to translate data on various parameters of man's capability in underwater and hyperbaric environments for those without a background in the life sciences. Accomplishing any multifaceted task requires team work, and effective team work depends on facile communication among all participants. To communicate properly, all parties must understand each other's problems and be able to speak a similar language. To this end we believe that this publication will go a long way in furthering the understanding and communication necessary for maximum achievement. The U. S. Navy has a fundamental interest in all types of activities connected with the ocean and is especially interested in the growing field of manned underwater and hyperbaric activities. Thus, the manuscript for this comprehensive book was developed under Office of Naval Research contract N00014-67-A-0214-0013 with The George Washington University. We acknowledge with appreciation the financial support and technical guidance for this undertaking by the Naval Medical Research and Develop­ ment Command of the Bureau of Medicine and Surgery as well as by the Engineering Psychology Program and the Physiology Program of the Office of Naval Research. JOSEPH P. POLLARD Director Biological and Medical Sciences Division Office of Naval Research vii Preface A need was felt for a book that would document the relationship of the human being to the underwater hyperbaric environment in such a way that the individual unfamiliar with the psychological or biomedical jargon could still understand and appreciate the information.

I The Human Machine.- A. Introduction.- B. The Mechanics of Movement.- 1. Bones.- 2. Joints.- 3. Muscles.- C. The Production of Energy.- 1. The Fuel.- 2. The Chemical Laboratory.- D. The Transportation System.- 1. The Heart.- 2. Arteries, Capillaries, and Veins.- 3. The Blood.- 4. Blood Circulation.- E. Temperature Control.- F. Gas Exchange.- G. The Information Receptors.- 1. Vision and the Eye.- 2. Hearing and the Ear.- 3. Equilibrium and the Inner Ear.- 4. Taste and Smell.- 5. Touch.- 6. Kinesthetic and Organic Sensibilities.- H. Body Measurement (Anthropometrics).- I. Psychological Overlay.- 1. The Brain and Its Functions.- 2. Communication.- 3. Man-Machine Relationship.- 4. Memory.- 5. Motivation.- 6. Stress.- References.- II The Ocean as an Environment.- A. Introduction.- B. Physical and Chemical Properties of Sea Water.- 1. Pressure and Depth.- 2. Specific Gravity.- 3. Density.- 4. Salinity.- 5. Compressibility.- 6. Electrical Conductivity.- 7. Thermal Properties of Sea Water.- a. Temperature.- b. Thermal Expansion.- c. Thermal Conductivity.- d. Specific Heat.- e. Latent Heat of Evaporation.- f. Adiabatic Temperature Changes.- 8. Colligative Properties of Sea Water.- a. Vapor Pressure Lowering.- b. Freezing Point.- c. Osmotic Pressure.- 9. Transmission of Sound in Sea Water.- a. Dispersion, Scattering, and Reflection.- b. Absorption.- 10. Light Transmission in Sea Water.- a. Extinction Coefficient.- b. Absorption Coefficient.- c. Refractive Index.- 11. Summary.- C. Coping with Waves, Tides, and Currents.- 1. General Background.- 2. Waves.- 3. Surf.- 4. Currents.- a. Currents in Oceans and Large Lakes.- b. Rip Currents.- c. Tides and Tidal Currents.- d. Diving in Currents.- e. Effects of Currents on Undersea Operations.- 5. Shoreline Diving Entries.- a. Sand Beach Entry.- b. Rock Shore Entry.- References.- III Man in the Ocean Environment: Physical Factors.- A. Basic Concepts.- B. Gases.- C. Solubility and Partial Pressures.- D. Buoyancy.- E. Effects of Increased Pressure.- 1. Aural Barotrauma.- a. Aural Barotrauma of Ascent.- b. Aural Barotrauma of Descent.- c. External-Ear Barotrauma.- d. Prevention of Aural Barotrauma.- 2. Blowup.- 3. Gastrointestinal Barotrauma.- 4. Pulmonary Barotrauma.- 5. Sinus Barotrauma.- 6. Squeeze.- 7. Toothache.- 8. Vertigo.- References.- IV Man in the Ocean Environment: Physiological Factors.- A. Respiration in a Hyperbaric Environment.- 1. Introduction.- 2. Physiology of Respiration.- a. General Respiratory Function.- b. Oxygen Requirements.- c. Carbon Dioxide Elimination.- d. Control of Respiration.- e. Breath-Hold Diving.- f. Hyperventilation.- 3. Alveolar Ventilation.- a. Dead Space.- b. Ventilation and Carbon Dioxide.- c. Ventilation and Oxygen.- d. Exertion at Depth.- e. Gas Exchange.- 4. Respiratory Mechanics.- a. General Considerations.- b. Ambient Pressure Differences.- c. Pressure Differences Caused by Immersion.- d. Lung Volume Alterations Caused by Postural Changes.- 5. The Work of Breathing.- a. General Considerations.- b. The Breathing Mixture, Gas Density.- c. Flow Rates.- d. Maximum Breathing Capacity and Flow Rates.- e. Resistance to Breathing in Self-Contained Diving.- f. Respiratory Rate and Hyperbaric Environments.- 6. Conclusion.- B. Cardiovascular Factors.- 1. Immersion to the Neck.- a. Negative-Pressure Breathing.- b. Density.- c. Water Temperature.- d. Intrathoracic Blood Volume.- 2. Breath-Hold Diving.- a. Diving Bradycardia in Man.- b. Water Temperature.- c. The Role of Cold Receptors on the Face.- d. Cardiac Arrhythmia.- e. Cardiac Output.- f. Venous-Return Mechanism.- g. Effect of Changes in Ambient Pressure.- 3. Air Scuba Diving.- a. Effects of Oxygen at High Pressure.- b. Effects of Depth.- 4. Mixed-Gas Saturation Diving.- a. Changes in Heart Rate.- b. Effects of Gas Density.- c. Temperature.- d. Effects of Helium.- C. Oxygen Toxicity.- 1. Pulmonary Oxygen Toxicity.- a. Toxic Effects upon Lung Pathology.- b. Effects upon Pulmonary Function.- c. Signs and Symptoms of Pulmonary Oxygen Poisoning.- d. Tolerance.- e. Mechanisms.- f. Treatment.- g. Prevention.- 2. CNS Oxygen Toxicity.- a. Convulsions.- b. Mechanisms.- c. Treatment.- d. Residual Effects.- e. Prevention.- 3. Other Toxic Effects.- a. The Eye.- b. The Blood.- D. Physiological Aspects of Nitrogen Narcosis.- 1. Narcotic Potency and Possible Mechanisms.- 2. Interactions.- a. Carbon Dioxide.- b. Hypoxia and Hyperbaric Oxygen.- 3. Neurological Measurements.- a. EEG Activity.- b. Alpha Blocking and Critical Fusion Frequency (CFF).- c. Evoked Brain Responses.- 4. Predisposition.- 5. Adaptation.- E. The Physiology of Breathing Mixtures.- 1. General Planning Considerations.- 2. Properties of Gas.- 3. Factors Relating to Choice of Gas.- a. Oxygen: Metabolic Needs and Toxicity.- b. Inert Gas Narcosis.- c. HPNS and Hyperbaric Arthralgia.- d. Density and Viscosity.- e. Voice Distortion.- f. Thermal Properties.- g. Decompression Considerations and Counterdiffusion.- h. Fire Safety.- i. Cost and Logistics.- 4. Conventional Breathing Mixtures.- a. Air and Nitrogen-Oxygen Mixtures.- b. Helium (Mixed-Gas Diving).- c. Oxygen.- 5. Experimental Breathing Mixtures.- a. Hydrogen.- b. Neon.- c. Argon.- d. Other Gases.- e. Liquid Breathing.- 6. Breathing-Gas Purity Standards.- a. Purity Standards.- b. Contaminants.- c. Testing.- 7. Physiology of the Wrong Gas.- a. Low Oxygen (Hypoxia).- b. High Oxygen (Hyperoxia).- c. Lack of Inert Gas.- d. High Carbon Dioxide (Hypercapnia).- e. Low Carbon Dioxide (Hypocapnia).- f. Inert Gas Narcosis.- g. Carbon Monoxide.- F. The High Pressure Nervous Syndrome and Other High-Pressure Effects.- 1. History.- 2. The High Pressure Nervous Syndrome.- a. Tremor.- b. Convulsions.- c. Somnolence and EEG Changes.- d. Dizziness and Nausea.- 3. Hyperbaric Arthralgia.- 4. Hyperbaric Bradycardia.- 5. Etiology and Mechanisms.- a. HPNS.- b. Hyperbaric Arthralgia.- 6. Alleviation.- a. Compression Schedule.- b. Pharmacological.- 7. Areas in Need of Further Study.- G. Cold.- 1. Thermoregulation in Man.- a. The Role of the Hypothalamus.- b. Maintaining Body Temperature.- c. Effects of Thermal Stress.- 2. Problems of Cold Exposure in Underwater Work.- a. Immersion and Surface Swimming.- b. Shallow and Deep Dives Using Air or Helium-Oxygen.- c. Deep Saturation Diving, Dry Chambers.- d. Saturation Diving, Open-Sea or “Wet-Pot” Chambers.- 3. Methods of Measurement.- 4. Physiological Effects of Cold in Underwater Operations.- a. Nervous System.- b. Cardiovascular-Renal System.- c. Respiratory System.- d. Endocrine System.- e. Miscellaneous Effects of Cold.- H. Diet and Metabolism.- References.- V Man in the Ocean Environment: Psychophysiological Factors.- A. Vision.- 1. Basic Processes of the Eye.- a. Introduction.- b. Functioning of the Eye.- 2. Photopic or Daylight Vision.- a. Visual Acuity in Air.- b. Visual Acuity under Water.- c. Depth Perception.- d. Perception of Size, Shape, Position, and Color.- 3. Scotopic Vision.- a. Scotopic Vision under Normal Conditions.- b. Scotopic Vision under Water.- 4. Effect of Underwater Experience.- 5. Underwater Optical Equipment.- a. Masks.- b. Underwater Contact Lenses.- 6. Others Factors Affecting Vision under Water.- a. Effect of Confining Quarters on Acuity.- b. Effects of Pressure.- c. Effects of Oxygen.- d. Effects of Nitrogen.- e. Effects of Drugs.- B. Hearing.- 1. Underwater Hearing and Air- and Bone-Conducted Hearing.- 2. Absolute Thresholds of Underwater Hearing.- a. General.- b. Measurement of Threshold Values.- c. Effect of Air in External Auditory Meatus.- d. Effect of Depth.- e. Effect of Wearing a Hood.- 3. Underwater Auditory Discriminations.- 4. Localization of Underwater Sounds.- 5. Maximum Intensity for Safe Underwater Hearing.- 6. Human Auditory Responses to Air-Pressure Changes.- a. Pressure Equalized across the Eardrum.- b. Mild Differential Pressures across the Eardrum.- c. Occluded Eustachian Tube.- d. Middle-Ear Involvement.- e. Inner-Ear Involvement.- f. Central Nervous System Involvement.- 7. Incidence of Auditory Involvement.- a. Among Swimmers Generally.- b. Among Amateur Skin and Scuba Divers.- c. Among Caisson Workers.- d. Among Inexperienced Hyperbaric Chamber Subjects and Diving Trainees.- e. Among Professional Divers.- f. Among Breath-Hold Divers.- C. Vestibular Function.- 1. Introduction.- 2. Symptoms of Vestibular Problems.- a. Motion Sickness.- b. Nystagmus.- c. Vertigo.- 3. Vestibular Dysfunction in Diving.- a. Vertigo Associated with Inadequate Middle-Ear Clearing.- b. Vestibular Decompression Sickness.- c. Isobaric Vertigo.- D. Other Sensory Functions.- 1. Taste and Smell.- 2. Kinesthetic, Proprioceptive, and Organic Effects.- 3. Touch.- Terminology, Physical Constants, and Definitions of Terms.- References.- VI Man in the Ocean Environment: Performance.- A. Introduction.- B. Tests and Measures of Diver Performance.- 1. Tactile Sensitivity.- a. Vibratory Sensitivity.- b. Two-Point and Two-Edge Sensitivity.- c. Point-Pressure Sensitivity.- d. Pressure Reproduction.- e. Towse Touch Test.- 2. Biomechanical Forces.- a. Handgrip Strength.- b. Hand-Torqueing Strength.- c. Rotary and Linear Forces.- d. Lifting and Pulling Forces.- e. Multiple-Force Test Platforms.- 3. Steadiness and Tremor.- a. Tremor Transducers.- b. Paper/Pencil and Apparatus Tests.- c. Postural-Equilibrium Tests.- 4. Dexterity and Assembly.- a. Finger-Dexterity Tests.- b. Manual-Dexterity Tests.- c. Assembly Tests.- 5. Tracking and Coordination.- a. Rotary Pursuit Test.- b. Two-Hand Coordination Test.- c. Multidimensional Pursuit Test.- 6. Reaction Time and Vigilance.- a. Simple Visual Reaction-Time Test.- b. Choice Reaction-Time Test.- c. Peripheral Light-Monitoring Test.- 7. Perceptual Processes.- a. Postural-Orientation Tests.- b. Geographic-Orientation Tests.- c. Perceptual-Speed Tests.- d. Time-Estimation Test.- e. Hidden-Patterns Test.- f. Stroop Word-Color Test.- g. Wechsler Bellevue Digit-Symbol Test.- 8. Cognitive Processes.- a. Arithmetic-Computation Tests.- b. Memory Tests.- c. Free-Association Test.- d. Sentence-Comprehension Test.- e. Conceptual-Reasoning Test.- f. Navigation Problem-Solving Test.- 9. Mood and Adjustment.- a. Task Orientation.- b. Emotional Stability.- c. Social Compatability.- 10. SINDBAD Test Battery.- C. Summaries of Performance Research in the Diving Environment.- 1. Performance in Hyperbaric Air.- a. Cognitive-Task Performance.- b. Reaction Time and Perceptual Speed.- c. Dexterity-Task Performance.- d. Modifying Factors.- 2. Performance in Hyperbaric Heliox.- a. Tremor, Steadiness, and Dexterity Tasks.- b. Reaction Time and Perceptual Speed.- c. Cognitive Tasks.- 3. Work and Maneuver in a Tractionless, Viscous Medium.- a. Basic Force Production.- b. Swimming and Load Carrying.- c. Orientation and Maneuvering.- 4. Performance in the Cold.- a. Tactile Sensitivity.- b. Grip Strength.- c. Steadiness and Tremor.- d. Dexterity and Assembly.- e. Tracking and Coordination.- f. Reaction Time and Vigilance.- g. Memory and Other Cognitive Processes.- 5. Adjustment to Isolation and Confinement in Habitats.- a. Performance and Adjustment in SEALAB II.- b. Performance and Adjustment in TEKTITE.- 6. Reactions to Generalized Stress in the Diving Experience.- a. Dexterity and Assembly Tasks.- b. Vigilance Monitoring.- c. Time Estimation.- References.- VII Decompression Sickness.- A. Introduction.- B. Factors Relevant to the Pathogenesis of Decompression Sickness.- 1. Physical Factors.- a. Inert Gas Solubility.- b. Bubble Nucleation and Growth.- 2. Biological Factors.- a. Pulmonary Exchange.- b. Transdermal Exchange.- c. Blood Flow and Distribution between and within Tissues.- d. Site of Bubble Nucleation and Growth.- e. Diffusion and Convection in Tissues.- 3. Summary.- C. Diagnosis.- 1. Incidence of Decompression Sickness and Appearance of Symptoms.- 2. Major Symptoms.- 3. New Methods of Diagnosis.- a. Physical Methods.- b. Biochemical Methods.- D. Prevention.- 1. Preparation.- 2. Operational Factors that Influence Decompression Procedures.- 3. Decompression Schedules.- a. Models Utilized to Compute Decompression Schedules.- b. Decompression Schedules Available for Human Use.- c. Air Decompression Schedules.- d. Mixed-Gas Decompression Schedules.- E. Treatment.- 1. Diagnosis and Emergency Action during Transportation to a Recompression Chamber.- 2. Recompression Treatment.- F. Decompression Schedules.- 1. U. S. Navy Decompression Schedules for Subsaturation Air Diving.- a. Schedule 1.1: U. S. Navy Standard Air Decompression Table.- b. Schedule 1.2: No-Decompression Limits and Repetitive Group Designation Table for No-Decompression Air Dives.- c. Schedule 1.3: Surface Interval Credit Table for Air Decompression Dives.- d. Schedule 1.4: Repetitive Dive Timetable for Air Dives.- e. Schedule 1.5: U. S. Navy Standard Air Decompression Table for Exceptional Exposures.- f. Schedule 1.6: Surface Decompression Table Using Oxygen.- g. Schedule 1.7: Surface Decompression Table Using Air for Air Diving.- 2. Decompression Schedules for Compressed Air Work.- a. Decompression Tables.- b. Repetitive Diving Procedures.- c. Suggestions for the Guidance of Compressed Air Workers.- 3. Surface Decompression Table for Saturation Diving with Air (Schedule 3.1).- a. Limits.- b. Surfacing Instructions.- 4. Air Excursion Tables for Saturation Diving on Air or N2-O2 Mixtures.- 5. Decompression Schedules for Subsaturation He-O2 Diving.- a. Schedule 5.1: He-O2 Partial Pressures—40–380 ft.- b. Schedule 5.2: Helium-Oxygen Decompression Schedule (Normal and Exceptional Exposures).- c. Schedule 5.3: Emergency Schedule (He-O2).- d. Schedule 5.4: Emergency Schedule (Air).- e. Schedule 5.5: Helium-Oxygen Decompression Schedule for Mixed-Gas Scuba Using 68% Helium-32% Oxygen Supply Mixture.- f. Schedule 5.6: Helium-Oxygen Decompression Table for Mixed-Gas Scuba Using 68% Helium-32% Oxygen Supply Mixture and Oxygen Decompression.- g. Schedule 5.7: No-Decompression Limits and Repetitive Group Designation Mixed-Gas Scuba No-Decompression Table for Helium-Oxygen Dives.- h. Schedule 5.8: Surface Interval Credit Table for Mixed-Gas Scuba Helium-Oxygen Decompression Dives.- i. Schedule 5.9: Repetitive Dive Timetable for Mixed-Gas Scuba Helium-Oxygen Dives.- 6. Decompression Procedures for Excursion Diving from Saturation, While Breathing He-O2 Gas Mixtures.- a. Depth Limitations.- b. Habitat Pressure.- c. Habitat Atmosphere Control.- d. UBA Gas Mixture.- e. Description of Schedules.- f. Instructions for Use of Schedules.- 7. Emergency Abort Schedule (Schedule 7.1).- 8. U. S. Navy Treatment Schedules for Decompression Sickness.- a. Schedule 8.1: Air Treatment.- b. Schedule 8.2: Air Treatment.- c. Schedule 8.3: Air Treatment.- d. Schedule 8.4: Air Treatment.- e. Schedule 8.5: Oxygen Treatment.- f. Schedule 8.6: Oxygen Treatment.- g. Schedule 8.7: Oxygen Treatment.- h. Schedule 8.8: Oxygen Treatment.- References.- VIII Operational Safety Considerations.- A. Introduction.- B. Organization and Planning.- 1. General Safety Precautions.- a. Personnel.- b. Equipment.- c. Safety during Diving Operations.- d. Recompression Chambers.- e. Special Handling of Compressed-Gas Cylinders.- 2. Special Situations.- 3. Diving at Altitude.- 4. Polar or Ice Diving.- C. Predive Conditions.- 1. Age.- 2. Drugs.- 3. Alcohol.- 4. Cigarette Smoking.- 5. Diet.- 6. Obesity.- 7. Fatigue.- 8. Exercise.- 9. Emotional Instability.- 10. Respiratory Infections.- D. Underwater Blast.- 1. Physical Aspects of the Explosion.- a. The Initial Compression Wave.- b. Reflection of Primary Pressure Pulse.- c. The Gas Sphere and Subsidiary Pulses.- d. Surface Effects.- 2. Mechanisms of Injury.- a. Peak Pressure.- b. Momentum or Impulse.- c. Degree of Immersion.- 3. Clinical Aspects and Pathology.- a. Effect on the Lungs and Thoracic Cavity.- b. Effect on the Abdomen and Air-Filled Viscera.- 4. Treatment.- 5. Protective Measures.- E. Fire Safety.- 1. Introduction.- 2. History.- 3. Fire Aspects.- a. Ignition.- b. Atmosphere.- c. Materials.- 4. Methods of Fire Prevention and Control.- a. Fire Detection.- b. Fire Extinguishers.- c. General Safety Procedures.- d. Areas in Need of Further Study.- F. Electrical Safety.- 1. Physiology of Electric Shock.- a. General.- b. The Heart.- 2. Influencing Factors.- a. Body Pathway of Conduction.- b. Current Intensity.- c. Duration.- d. Type and Frequency of Current.- 3. Underwater Shock Hazards.- 4. Protective Measures.- 5. Treatment.- G. Drowning.- 1. Importance of the Problem.- 2. Causes of Drowning.- 3. Physiology of Drowning.- 4. Treatment.- 5. Prevention.- H. Other Hazards.- 1. Marine Life.- 2. Fouling.- 3. Infections.- 4. Fatigue.- 5. Flying after Diving.- I. Problems of Escape and Rescue.- 1. Submarines.- a. Escape.- b. Rescue.- 2. Submersibles and Habitats.- References.- IX Operational Equipment.- A. Hand-Held Tools.- 1. Underwater Tool Design.- 2. Survey of Tool Categories.- a. Standard Hand-Held Tools.- b. Special Hand-Held Tools.- c. Self-Contained Power Tools.- d. Remotely Supplied Power Tools.- 3. Torqueing Tools.- 4. Power Tools (Selected).- B. Power Sources and Requirements.- 1. Power Requirements.- 2. Hydraulic Power Sources.- 3. Batteries.- 4. Electrical/Electronic Equipment.- 5. Electrohydraulic and Cryogenic Pneumatic Power Sources.- 6. Fuel Cells as Power Sources.- 7. Comparison of Various Power Sources.- a. Power System Parameters.- b. Umbilical Power Supply.- c. Mission Parameters.- d. General Selection Guides.- C. Personal Equipment.- 1. Diving Suits.- a. Neoprene Suits.- b. Noncompressible Wet Suits.- c. Dry Suits.- d. Pressure-Compensated Constant-Volume Dry Suit.- e. Heating Systems for Divers’ Suits.- f. Unisuit.- g. The Armored, 1-atm Suit.- 2. Breathing Apparatus.- a. Air-Breathing Systems.- b. Mixed-Gas Systems.- c. Open-Circuit Underwater Breathing Apparatus.- d. Semiclosed-Circuit Breathing Apparatus.- e. Closed-Circuit Breathing Apparatus.- f. Cryogenic Breathing Apparatus.- 3. Ancillary Equipment.- a. Masks.- b. Fins.- c. Localization Equipment.- D. Human Engineering Factors.- 1. The Diver as a Resource.- 2. Evaluation Procedure.- 3. Biomechanical Capabilities.- E. Environmental Equipment.- 1. Diving Systems.- a. Advanced Diving System.- b. Deep Diving Systems.- c. The 1-atm Work System.- 2. Habitats.- 3. Swimmer Vehicles.- 4. Manned Submersibles.- a. Tethered Vehicles.- b. Self-Propelled Vehicles.- c. Lockout Capability.- d. Manipulator Capability.- e. Navigation.- 5. Unmanned Submersibles.- a. Towed Submersibles.- b. Cable-Controlled Submersibles.- c. Cableless Submersibles.- 6. Buoyancy Devices.- 7. Hyperbaric Facilities.- a. Design Factors and Certifications.- b. Examples of Hyperbaric Chambers.- c. Current Research Facilities.- 8. Environmental Control.- a. Maintenance of Desired Partial Pressure of Oxygen.- b. Removal of Carbon Dioxide and Trace Contaminants.- c. Temperature and Humidity Control.- d. Maintenance of Air Circulation and Extravehicular Support.- 9. Instrumentation.- Terminology.- References.- X Underwater Communications.- A. Introduction.- B. Normal Speech Generation Process.- C. Communication Systems.- 1. General.- 2. Underwater Communication Systems.- a. Acoustic Systems.- b. Hard-Line Systems.- c. Electromagnetic Radiation Systems.- d. Electric Field Potential Systems.- 3. Special Microphone and Earphone Considerations.- D. Factors Distorting Speech in the Underwater Environment.- 1. Noise Distortion Factors Due to Reverberation and Mouthpieces.- 2. Effects of Pressure upon Speech.- 3. Effects of Gas Mixtures.- a. Summary of Speech He-O2 Research.- b. Helium Unscramblers.- E. Human Factors Considerations in Underwater Communication.- 1. Psychological Factors.- a. Adaptation to Voice Changes.- b. General Intelligibility Interference Factors.- 2. Physiological Considerations.- a. Basic Factors.- b. Effects of Exertion.- 3. Packaging of Equipment.- 4. Design Problem Considerations and Recommendations.- F. Summary.- Terminology.- References.- XI Selection and Training of Divers.- A. Selection.- 1. Objectives of Selection.- 2. Medical History.- 3. Physical and Medical Examination.- a. Age.- b. Weight.- c. Vision.- d. Color Vision.- e. Teeth.- f. Ears.- g. Nose and Throat.- h. Respiratory System.- i. Cardiovascular System.- j. Gastrointestinal System.- k. Genitourinary System.- l. Skin.- m. Pregnancy.- 4. Requirements in Other Countries.- 5. Psychiatric Examination.- 6. Psychological Tests.- 7. Training Course as Selection Device.- 8. Pressure Test.- 9. Arctic, Antarctic, or Under-the-Ice Diving.- B. U. S. Navy Divers.- 1. Diver Designation.- a. Officers.- b. Enlisted Divers.- 2. Availability of Training.- a. Qualifying Criteria.- b. Selection Procedure.- 3. Naval Schools of Diving.- 4. Course Unit Contents.- C. Training—Civilian Sector.- 1. Background.- 2. Recreational Diver Training.- 3. Commercial Diver Training.- 4. College, University, and Institutional Programs.- a. Degree Programs in the Marine Sciences and Related Fields.- b. Nondegree Programs in Marine Sciences and Related Fields.- D. Training Pays Off.- 1. Safety.- 2. Productivity.- 3. Pleasure.- References.