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Aviation Safety 2005

Aero Medical BriefingAero Medical Briefing

Larry R Boehme, MDLarry R Boehme, MD

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Civil Aeromedical Institute 04/21/23

Altitude Physiology

Physics of the atmospherePhysics of the atmosphere Respiratory physiologyRespiratory physiology Trapped gasTrapped gas

Required by FM-301Required by FM-301 aero medical training for flight personnelaero medical training for flight personnel

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Air

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Air

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

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Altitude Physiology

Physics of the atmospherePhysics of the atmosphere Respiratory physiologyRespiratory physiology Trapped gasTrapped gas

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Physics Of The Atmosphere

• The atmosphere is a gaseous envelope that covers the earth

• It extends from sea level up to 1000 nautical miles

Definition and Boundary

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Physics Of The Atmosphere

• Oxygen - 20.95%

• Nitrogen - 78.08%

• Trace Gases - .97%

Gaseous Content

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Civil Aeromedical Institute 04/21/23

Physics Of The Atmosphere

• The weight of all atmospheric gases creating a measurable force at any given point on the surface of the earth

Atmospheric Pressure

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Physics Of The Atmosphere

• 14.7 psi • 760 mm of Hg • 29.92 inches of Hg

Atmospheric Pressure (continued)

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Physics Of The Atmosphere

• Provides Protection

• Supports animal and plant life

Benefits

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Physics Of The Atmosphere

• Troposphere - Sea level to 30,000 feet at poles

- Sea level to 50,000 feet at the equator

• Tropopause - Not considered a major division

Divisions

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Physics Of The Atmosphere

• Stratosphere - Tropopause to 50 miles

• Ionosphere - 50 miles to 600 miles

Divisions (continued)

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Physics Of The Atmosphere

• Exosphere - 600 miles to 1000 miles

Divisions (continued)

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Physics Of The Atmosphere

• 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

Physical Gas Laws

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Civil Aeromedical Institute 04/21/23

Physics Of The Atmosphere

• 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

Physical Gas Laws (continued)

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Physics Of The Atmosphere

• Physiological Efficient Zone - Ranges from sea level to 10,000 feet

• Physiological Deficient Zone - Ranges from 10,000 feet to 50,000 feet

Physiological Zones

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Altitude Physiology

Physics of the atmospherePhysics of the atmosphere Respiratory physiologyRespiratory physiology Trapped gasTrapped gas

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Respiration & Circulation

• 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

Definition of Respiration

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• Atmosphere/Lungs - External Respiration

• Lungs/Blood - Internal Respiration

• Blood/Body Cells - Cellular Respiration

3 Phases of Gas Exchange

Respiration & Circulation

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• Oral/Nasal passages • Trachea • Bronchi

• Bronchial

Respiratory System Components

Respiration & Circulation

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• Alveolar Ducts

• Alveoli - Air Sacs

- 300 million

- Surrounded by capillaries

- 1 cell thick

Respiratory System Components(continued)

Respiration & Circulation

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Civil Aeromedical Institute 04/21/23

• 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

Internal Respiration

Respiration & Circulation

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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.

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Dalton’s Law

Ptotal = P1 + P2 + P3 ---

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• 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

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• Partial pressure of oxygen at sea level maintains an arterial oxygen saturation of 96% - 98%

Internal Respiration (continued)

Respiration & Circulation

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• 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

Internal Respiration (continued)

Respiration & Circulation

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• The circulatory system is responsible for transportation of blood through out the body

Circulatory System

Respiration & Circulation

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• Plasma - 90% water

• Solids - Primarily Red Blood Cells

Bloods Components

Respiration & Circulation

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• 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

The Red Blood Cell (continued)

Respiration & Circulation

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• 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

Respiration & Circulation

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• 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)

Cellular Respiration (continued)

Respiration & Circulation

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Graham’s Law

A Gas Will Diffuse From an Area of High Concentration to an Area of Low Concentration.

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• Blood supplies each cell with - Food

- Water

- Oxygen

• Blood transports waste material from cells

Bloods Function

Respiration & Circulation

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• 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

The Red Blood Cell

Respiration & Circulation

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Altitude Physiology

Physics of the atmospherePhysics of the atmosphere Respiratory physiologyRespiratory physiology Trapped gasTrapped gas

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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

Intro to Trapped Gas

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Boyle’s Law

A Volume of Gas Is Inversely Proportional to the Pressure Exerted on the Gas, With Temperature

Remaining Constant.

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Civil Aeromedical Institute 04/21/23

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

Intro to Trapped Gas

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Trapped Gas

• Gas cavities - Middle Ear

- Sinuses

- Stomach and Intestines

- Teeth

Intro to Trapped Gas

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Trapped Gas

• During the ascending phase of flight you more likely to develop problems with the gastrointestinal tract, and on rare occasions, the teeth

Ascending Phase

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Trapped Gas

• 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

Ascending Phase

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Trapped Gas

• With advances in modern dentistry, problems with trapped gas in the teeth are rare

Ascending Phase

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Trapped Gas

• 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

Ascending Phase

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Trapped Gas

• 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

Descending Phase

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Trapped Gas

• 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

Descending Phase

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Trapped Gas

• 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

Descending Phase

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Trapped Gas

• 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

Descending Phase

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Trapped Gas

• 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

Descending Phase

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Trapped Gas

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

Descending Phase

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Civil Aeromedical Institute 04/21/23