ALTITUDE PHYSIOLOGY

OUTLINE The Atmosphere Hypoxia Types Stages Hyperventilation Trapped Gas Disorders Evolved Gas Disorders

REFERENCES FM 1-301, Aeromedical Training for Flight Personnel, May 1987 FM 1-204, Night Flight Techniques and Procedures, October 1983

TROPOSPHERE Sea level to flight level depending on temperature, latitude and season. Physical Divisions Physical Divisions of the Atmosphere STRATOSPHERE IONOSPHERE EXOSPHERE MOUNT EVEREST 29,028 FEET 1200 miles 600 miles 50 miles Tropopause

Physiological Zones of the Atmosphere EFFICIENT ZONE: SEA LEVEL TO 10,000 FEET SPACE EQUIVALENT ZONE: 50,000 FEET AND ABOVE DEFICIENT ZONE: 10,000 TO 50,000 FEET 10,000 50,000

78 % Nitrogen (N 2 ) 21 % Oxygen (O 2 ) 1 % Other (.03 % CO 2 ) Composition of Air

14.7 PSI Sea Level Pressure Scale lbs 760 mm Hg OR in. Hg Barometer / Altimeter

PERCENT COMPOSITION OF THE ATMOSPHERE REMAINS CONSTANT BUT PRESSURE DECREASES WITH ALTITUDE

SIGNIFICANT PRESSURE ALTITUDES ALTITUDE PRESSURE FEET mm/HG ATMOSPHERES , /2 34, /4 48,000951/8 63,000471/16

Partial Pressure (Dalton’s Law) 760 mm Hg mm/Hg % O2O2 78% N 2 1% Other

The pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture. Pt = P 1 + P Pn (Dalton’s Law)

Hypoxia State of oxygen [O 2 ] deficiency in the blood cells and tissues sufficient to cause impairment of function.

Types of Hypoxia l Hypemic l Stagnant l Histotoxic l Hypoxic

Hypemic Hypoxia Inability of the blood to accept oxygen in adequate amounts

Stagnant Hypoxia Reduced blood bloodflow Blood moving slowly adequateoxygen Red blood cells not replenishing tissue needs fast enough

Red blood cells Red blood cells retain oxygen retain oxygen Inability of the cell to accept or use oxygen Histotoxic Hypoxia Poisoned tissue adequateoxygen

Hypoxic Hypoxia Reduced pO 2 in the lungs (high altitude) Body tissue Red blood cells

Hypoxia Symptoms Subjective: Feel Air hunger Hot and Cold Flashes Apprehension Euphoria Fatigue Belligerence Nausea Blurred vision Headache Numbness Dizziness Tingling Denial Air hunger Hot and Cold Flashes Apprehension Euphoria Fatigue Belligerence Nausea Blurred vision Headache Numbness Dizziness Tingling Denial

Hypoxia Signs Objective: See HyperventilationCyanosis Mental confusion Poor Judgment Lack of muscle coordination

Stages of Hypoxia l Indifferent Stage l Compensatory Stage l Disturbance Stage l Critical Stage

Indifferent Stage l Altitudes Air: ,000 FEET l Symptoms: decrease in night 4000 feet

Compensatory Stage l Altitudes Air :10, ,000 FEET l Symptoms: impaired efficiency drowsiness poor judgment decreased coordination

CAUTION! Failure to recognize symptoms and take corrective action may result in an aircraft mishap Failure to recognize symptoms and take corrective action may result in an aircraft mishap

Disturbance Stage l Altitudes Air:15, ,000 FEET

Disturbance Stage symptoms W Sensory l Vision l Touch & pain l Hearing

Disturbance Stage Disturbance Stage symptoms W Mental l Memory l Judgment l Reliability l Understanding

Disturbance Stage symptoms W Personality l Happy Drunk versus the l Mean Drunk

Disturbance Stage symptoms W Performance l Coordination l Flight Control l Speech l Handwriting

put back on oxygen Time off Oxygen 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 6 minutes

CAUTION!CAUTION! Failure to recognize symptoms and take corrective action may result in an aircraft mishap Failure to recognize symptoms and take corrective action may result in an aircraft mishap

Disturbance Stage W Signs l Hyperventilation l Cyanosis

Critical Stage l Altitudes Air:20,000 FEET and above l Symptoms: loss of consciousness convulsions death

WARNING! When hemoglobin saturation falls to serious cellular dysfunction occurs; and if prolonged, can cause death WARNING! 65%

Factors modifying hypoxia symptoms l Pressure altitude l Rate of ascent l Time at altitude l Temperature l Physical activity l Individual factors l Physical fitness l Self-imposed stresses

Alcohol it’s a no brainer! Tobacco keep self imposed stresses out of the aircraft Drugs Exhaustion Hypoglycemia

2000 feet B U Z Z 1 ounce = alcohol

Expected Performance Times FL 430 & above9-12 seconds FL seconds FL seconds FL minutes FL /2 - 3 minutes FL minutes FL minutes FL minutes

Expected performance time for a crew member flying in a pressurized cabin is reduced approximately one-half following loss of pressurization such as in a: RD rapid decompression

Hypoxia u Prevention limit time at altitude breathing oxygen l pressurized cabin

Hypoxia u Treatment oxygen descend to a safe altitude

Hyperventilation definition an excessive rate and depth of respiration leading to the abnormal loss of CO 2 from the blood.

n Emotional (fear, apprehension, excitement) n Pressure breathing n Physical stress n Hypoxia HyperventilationCauses

Hyperventilation Symptoms l tingling sensations l muscle spasms l hot and cold sensations l visual impairment l dizziness l unconsciousness

Hyperventilation reason for symptoms:  loss of carbon dioxide [CO 2 ] ê shift in pH balance

Hyperventilation significance * incapacitation of an otherwise outstanding, healthy aviator. * confusion with hypoxia

n Don’t Panic n Control your breathing Hyperventilationprevention Check your oxygen equipment - it may be hypoxia

n above 10,000 feet possible hypoxia n below 10,000 feet probable hyperventilation Hyperventilation corrective action

Dysbarism syndrome resulting from the effects, excluding hypoxia, of a pressure differential between the ambient barometric pressure and the pressure of gases within the body syndrome resulting from the effects, excluding hypoxia, of a pressure differential between the ambient barometric pressure and the pressure of gases within the body

Boyle’s Law The volume of a gas is inversely proportional to its pressure; temperature remaining constant.

DRY GAS EXPANSION WET GAS EXPANSION 1.8X 2.0X 16, X 25, X, 34, X 43, X 9.5X 6.0X Gas Expansion

l Watch your diet, don’t eat too fast l Avoid soda and large amounts of water just prior to going to altitude l Don’t chew gum during ascent l Keep regular bowel habits; eat your fiber Gas Expansion prevention of abdominal gas pains

Middle Ear Opening to throat Eustachian tube External ear Middle ear Ear drum Semicircular canal Cochlea Auditory nerve

Middle Ear Cavity Eustachian Tube Atmospheric Pressure Tympanic Membrane External Ear Middle Ear Cavity Eustachian Tube Blocked / Infected Tympanic Membrane External Ear Atmospheric Pressure Pressure Effect Ear Block Clear

Normal tympanic membrane (ear drum) Inflamed ear drum Infected ear drum

Frontals Ethmoids Maxillary Sphenoids The Sinuses

Treatment of an Sinus/Ear Block 1. Stop the descent of the aircraft and attempt to clear by valsalva. 2. If unable to clear, climb back to altitude until clear by pressure or valsalva. 3. Descend slowly and clear ear frequently during descent.

Barodontalgia l Tooth pain due to: l Gum abscess: dull pain on ascent l Inflamed pulp: sharp pain on ascent l Inflamed maxillary sinus: pain primarily on descent

Decompression Sickness

Henry’s Law l The amount of gas dissolved in solution is directly proportional to the pressure of the gas over the solution

WARNING Evolved gas disorders are considered serious and medical treatment and advice must be sought immediately.

Evolved Gas Disorders l The Bends l Paresthesia l The Chokes l Central Nervous System-CNS

Evolved Gas Disorders l N2 bubbles become trapped in the joints. Onset is mild, but eventually painful! l The Bends

Evolved Gas Disorders l Paresthesia l N2 bubbles form along nerve tracts. Tingling and itchy sensation and possibly a mottled red rash.

Evolved Gas Disorders l The Chokes l N2 bubbles block smaller pulmonary vessels. Burning sensation in sternum. Uncontrollable desire to cough. Sense of suffocation ensues.

Evolved Gas Disorders l CNS l N2 bubbles affect spinal cord. Visual disturbances, paralysis, one sided tingling.

Evolved gas factors l Rate of ascent l Altitude l Body fat content l Age l Exercise l Duration of exposure l Repeated exposure

l Descend l 100% Oxygen Decompression Sickness treatment l Land at nearest location where qualified medical assistance is available. l Compression greater than 1 atmosphere (absolute).

Scuba Divers Beware! 2 4 H o u r r e s t r i c t i o n b e t w e e n d i v i n g a n d f l y i n g ! ! ! ! ! or be bent!

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