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Aviation Safety 2005 Aero Medical Briefing Larry R Boehme, MD Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas Required by FM-301 Civil Aeromedical Institute aero medical training for flight personnel 5/6/2017 Air Civil Aeromedical Institute 5/6/2017 Air What is it? Where is it? How do we use it as individuals? Why is it important in aviation safety? Civil Aeromedical Institute 5/6/2017 Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Definition and Boundary • The atmosphere is a gaseous envelope that covers the earth • It extends from sea level up to 1000 nautical miles Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Gaseous Content • Oxygen - 20.95% • Nitrogen - 78.08% • Trace Gases - .97% Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Atmospheric Pressure • The weight of all atmospheric gases creating a measurable force at any given point on the surface of the earth Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Atmospheric Pressure (continued) • 14.7 psi • 760 mm of Hg • 29.92 inches of Hg Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Benefits • Provides Protection • Supports animal and plant life Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Divisions • Troposphere - Sea level to 30,000 feet at poles - Sea level to 50,000 feet at the equator • Tropopause - Not considered a major division Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Divisions (continued) • Stratosphere - Tropopause to 50 miles • Ionosphere - 50 miles to 600 miles Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Divisions (continued) • Exosphere - 600 miles to 1000 miles Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Physical Gas Laws • Boyle’s Law - A volume of gas is inversely proportional to the pressure exerted on the gas, with temperature remaining constant • Henry’s Law - When the pressure over a liquid is decreased, the gas in the liquid will also decrease Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Physical Gas Laws (continued) • Daltons’s Law - The total pressure of a mixture of gas is equal to the sum of the partial pressure of each gas in the mixture • Graham’s Law - A gas will defuse from an area of high concentration to an area of low concentration Civil Aeromedical Institute 5/6/2017 Physics Of The Atmosphere Physiological Zones • Physiological Efficient Zone - Ranges from sea level to 10,000 feet • Physiological Deficient Zone - Ranges from 10,000 feet to 50,000 feet Civil Aeromedical Institute 5/6/2017 Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Definition of Respiration • Respiration is the exchange of gases between an organism and its environment - Supplies body cells with Oxygen - Removes Carbon Dioxide from cells • Oxygen is used by the body for metabolism - The burning of food material by the cells to produce energy Civil Aeromedical Institute 5/6/2017 Respiration & Circulation 3 Phases of Gas Exchange • Atmosphere/Lungs - External Respiration • Lungs/Blood - Internal Respiration • Blood/Body Cells - Cellular Respiration Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Respiratory System Components • Oral/Nasal passages • Trachea • Bronchi • Bronchial Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Respiratory System Components (continued) • Alveolar Ducts • Alveoli - Air Sacs - 300 million - Surrounded by capillaries - 1 cell thick Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Internal Respiration • An exchange of gases between the lungs and blood • All gas movement is dependent on the difference in the partial pressure of that particular gas - Dalton’s Law Civil Aeromedical Institute 5/6/2017 Daltons’s Law The Total Pressure of a Mixture of Gas Is Equal to the Sum of the Partial Pressure of Each Gas in the Mixture. Civil Aeromedical Institute 5/6/2017 Dalton’s Law Ptotal = P1 + P2 + P3 --- Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Internal Respiration (continued) • There are 4 major gases always present in the lungs - Nitrogen @ 573 mm of Hg - Water Vapor @ 47 mm of Hg - Carbon Dioxide @ 40 mm of Hg - Oxygen @ 100 mm of Hg Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Internal Respiration (continued) • Partial pressure of oxygen at sea level maintains an arterial oxygen saturation of 96% - 98% Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Internal Respiration (continued) • High partial pressure of oxygen (100 mm) diffuses through the air sac wall into the blood • High partial pressure of carbon dioxide diffuses from the blood to the alveoli Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Circulatory System • The circulatory system is responsible for transportation of blood through out the body Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Bloods Components • Plasma - 90% water • Solids - Primarily Red Blood Cells Civil Aeromedical Institute 5/6/2017 Respiration & Circulation The Red Blood Cell (continued) • The ability of the hemoglobin to become oxygen saturated is dependent on alveolar oxygen partial pressure - Which is dependent on the ambient barometric pressure • Normal oxygen saturation goes down as a result of decreasing atmospheric pressure Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Cellular Respiration • The exchange of gases between the blood body cells • Partial pressure of oxygen in the cells is lower than the partial pressure of oxygen in the blood - Oxygen is off- loaded to the cells (Graham’s Law) Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Cellular Respiration (continued) • Partial pressure of carbon dioxide in the cells is higher than the partial pressure of carbon dioxide in the blood - Carbon Dioxide is off- loaded to the blood (Graham’s Law) Civil Aeromedical Institute 5/6/2017 Graham’s Law A Gas Will Diffuse From an Area of High Concentration to an Area of Low Concentration. Civil Aeromedical Institute 5/6/2017 Respiration & Circulation Bloods Function • Blood supplies each cell with - Food - Water - Oxygen • Blood transports waste material from cells Civil Aeromedical Institute 5/6/2017 Respiration & Circulation The Red Blood Cell • Responsible for transporting oxygen to body cells • Each red blood cell contains hemoglobin - Contains iron - Each red blood cell has over 250 million hemoglobin molecules Civil Aeromedical Institute 5/6/2017 Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas Civil Aeromedical Institute 5/6/2017 Trapped Gas Intro to Trapped Gas • Gases within the body are governed by physical and chemical laws that describe how a volume of gas changes in response to changes in pressure and temperature - Boyle’s Law • Body cavities each have openings that allow the gas to enter or exit Civil Aeromedical Institute 5/6/2017 Boyle’s Law A Volume of Gas Is Inversely Proportional to the Pressure Exerted on the Gas, With Temperature Remaining Constant. Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Trapped Gas Intro to Trapped Gas • Problems arise when these openings are reduced in size or closed, the gas is then considered trapped • Gas expansion occurs within the natural gas cavities of the body that contains varying amounts of gas Civil Aeromedical Institute 5/6/2017 Trapped Gas Intro to Trapped Gas • Gas cavities - Middle Ear - Sinuses - Stomach and Intestines - Teeth Civil Aeromedical Institute 5/6/2017 Trapped Gas Ascending Phase • During the ascending phase of flight you more likely to develop problems with the gastrointestinal tract, and on rare occasions, the teeth Civil Aeromedical Institute 5/6/2017 Trapped Gas Ascending Phase • Gastrointestinal Tract - Relieve by burping and passing gas - Pilots should watch their diet and avoid foods that cause excess gas formation - If you encounter any abdominal pain on ascent you should a. Treat as soon as the symptoms appear b. Relieve internal pressure by belching or passing gas c. Massage affected area d. Descend Civil Aeromedical Institute 5/6/2017 Trapped Gas Ascending Phase • With advances in modern dentistry, problems with trapped gas in the teeth are rare Civil Aeromedical Institute 5/6/2017 Trapped Gas Ascending Phase • Teeth - Dental problems that can cause pain on ascent a. b. c. d. - A cavity Bad dental work An abscess Swollen maxillary sinus from impacted wisdom tooth Treatment a. Land and see your dentist b. Maintain a schedule of good dental hygiene Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • During the descending phase you are more likely to develop problems in the middle ear and sinuses • During descent as ambient pressure increases, air must forcibly enter the middle ear through the eustachian tube Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • Middle Ear - Normal ear clearing accomplished by a. Swallowing b. Exaggerated jaw movement - Upper respiratory infections may cause the eustachian tube to become blocked Middle ear block symptoms a. Sensation of fullness b. Minor hearing loss c. Discomfort d. Ringing in the ears Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • Middle Ear - Middle ear block symptoms (continued) e. f. g. h. - Pain Dizziness Nausea Eardrum rupture Middle ear block treatment a. Yawning b. Swallowing c. Chewing d. Perform a Valsalva e. Climb Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • Sinuses blockage can occur on ascent or descent, however, problems are more likely to occur on descent • The most commonly affected sinuses are the frontal and maxillaries Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • Sensation of fullness may or may not appear before the onset of pain • Onset rate can occur faster than middle ear problems and can be incapacitating Civil Aeromedical Institute 5/6/2017 Trapped Gas Descending Phase • Sinuses - Sinus block treatment a. b. c. d. Level off from descent Perform a Valsalva maneuver Gradual descent Stair step down Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017 Civil Aeromedical Institute 5/6/2017
