Aero Medical Briefing Larry R Boehme, MD Aviation Safety 2005 Aero Medical Briefing Larry R Boehme, MD

Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas Required by FM-301 aero medical training for flight personnel

Air

Air What is it? Where is it? How do we use it as individuals? Why is it important in aviation safety?

Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas

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

Physics Of The Atmosphere Gaseous Content Oxygen - 20.95% Nitrogen - 78.08% Trace Gases - .97%

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

Physics Of The Atmosphere Atmospheric Pressure (continued) 14.7 psi 760 mm of Hg 29.92 inches of Hg

Physics Of The Atmosphere Benefits Provides Protection Supports animal and plant life

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

Physics Of The Atmosphere Divisions (continued) Stratosphere - Tropopause to 50 miles Ionosphere - 50 miles to 600 miles

Physics Of The Atmosphere Divisions (continued) Exosphere - 600 miles to 1000 miles

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

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

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

Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas

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

Respiration & Circulation 3 Phases of Gas Exchange Atmosphere/Lungs - External Respiration Lungs/Blood - Internal Respiration Blood/Body Cells - Cellular Respiration

Respiration & Circulation Respiratory System Components Oral/Nasal passages Trachea Bronchi Bronchial

Respiratory System Components Respiration & Circulation Respiratory System Components (continued) Alveolar Ducts Alveoli - Air Sacs - 300 million - Surrounded by capillaries - 1 cell thick

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

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.

Dalton’s Law Ptotal = P1 + P2 + P3 ---

Internal Respiration (continued) 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

Internal Respiration (continued) Respiration & Circulation Internal Respiration (continued) Partial pressure of oxygen at sea level maintains an arterial oxygen saturation of 96% - 98%

Internal Respiration (continued) 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

Respiration & Circulation Circulatory System The circulatory system is responsible for transportation of blood through out the body

Respiration & Circulation Bloods Components Plasma - 90% water Solids - Primarily Red Blood Cells

The Red Blood Cell (continued) 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

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)

Cellular Respiration (continued) 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)

Graham’s Law A Gas Will Diffuse From an Area of High Concentration to an Area of Low Concentration.

Respiration & Circulation Bloods Function Blood supplies each cell with - Food - Water - Oxygen Blood transports waste material from cells

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

Altitude Physiology Physics of the atmosphere Respiratory physiology Trapped gas

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

Boyle’s Law A Volume of Gas Is Inversely Proportional to the Pressure Exerted on the Gas, With Temperature Remaining Constant.

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

Trapped Gas Intro to Trapped Gas Gas cavities - Middle Ear - Sinuses - Stomach and Intestines - Teeth

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

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

Trapped Gas Ascending Phase With advances in modern dentistry, problems with trapped gas in the teeth are rare

Trapped Gas Ascending Phase Teeth - Dental problems that can cause pain on ascent a. A cavity b. Bad dental work c. An abscess d. Swollen maxillary sinus from impacted wisdom tooth - Treatment a. Land and see your dentist b. Maintain a schedule of good dental hygiene

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

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

Trapped Gas Descending Phase Middle Ear - Middle ear block symptoms (continued) e. Pain f. Dizziness g. Nausea h. Eardrum rupture - Middle ear block treatment a. Yawning b. Swallowing c. Chewing d. Perform a Valsalva e. Climb

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

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

Trapped Gas Descending Phase Sinuses - Sinus block treatment a. Level off from descent b. Perform a Valsalva maneuver c. Gradual descent d. Stair step down