HYPOXIA
Hypoxia results when the body lacks oxygen. Hypoxia tends to be associated with flights at altitudes. However, many other factors such as alcohol abuse, heavy smoking, & various medications interfere with the blood’s ability to carry oxygen.
INDIVIDUALS PHYSIOLOGICAL ALTITUDE.
Drugs. Many medications have an unexpected effect when combined with high altitudes. Never self-medicate, even w/ over the counter drugs.
Alcohol. 1 ounce of alcohol can give the body a physiological altitude up to 2000’.
Smoking. The hemoglobin molecule of RBCs has a 200-300 times greater affinity for CO than for O2. Smoking 3 cigarettes in rapid succession or 20 to 30 cigarettes w/ in a 24 hr period gives a physiological altitude of 5000’ at sea level & a 20% reduction of night vision.
CLASSIFICATIONS:
Hypoxic.Occurs when not enough O2 is in the air or when decreasing atmospheric pressures prevent the diffusion of O2 from the lungs to the bloodstream. Typically, Occurs at higher altitudes.
Hypemic. or anemic, hypoxia is caused by a reduction in the oxygen-carrying capacity of the blood. Anemia & blood loss are the most common causes. CO,nitrites, & sulfa drugs also cause this by forming compounds w/ hemoglobin & reducing the hemoglobin that is available to combine w/ O2.
Stagnant.O2 carrying capacity of the blood is adequate, but circulation is inadequate. Conditions as heart failure, arterial spasm, & occlusion of a blood vessel predispose the individuals to stagnant hypoxia. More often, a crew member experiences extreme gravitational forces, causing the blood to be stagnant.
Histotoxic. Results when there is interference with the use of O2 by body tissues. Alcohol, narcotics, & certain poisons-cyanide- interfere the cell’s ability to use an adequate supply of oxygen.
STAGES
Indifferent.(0’ – 10,000’)
Night vision deteriorates at about 4000’. When approaching 10,000’ visual acuity begins to decrease.
Compensatory.(10,000’ – 15,000’)
The circulatory & the respiratory system provide some defense against hypoxia at this stage. The pulse rate, systolic blood pressure, circulation rate, & cardiac output increase. Respiration increases in depth & sometimes in rate. At 12,000’ to 15,000’ the effects of hypoxia on the nervous system become increasingly apparent. After 10-15 min, impaired efficiency is obvious. Crew members may become drowsy & make frequent errors in judgment. May become difficult to do even simple task. Easy to overlook these symptoms.
Disturbance.(15,000’ – 20,000’)
The physiological responses can no longer compensate for the O2 deficiency. Subjective symptoms include fatigue, sleepiness, dizziness, headache, breathlessness, & euphoria. Objective symptoms include:
Senses: peripheral & central vision are impaired, & visual acuity is diminished. Weakness & loss of muscular coordination are experienced. Sensations of touch & pain are diminished or lost. Hearing is one of the last senses lost.
Mental Processes: Intellectual impairment is an early sign that often prevents the individual from recognizing disabilities. Thinking is slow, & calculations are unreliable. Short-term memory is poor, & judgment & reaction time is affected.
Personality Traits: Person may display traits & emotions much the same as with intoxication. Euphoria, aggressiveness, overconfidence, or depression can occur.
Psychomotor Functions: Muscular coordination is decreased, & delicate or fine muscular movements may be impossible. Stammering & illegible handwriting are typical impairments.
Cyanosis: the skin becomes bluish in color. This effect is caused by O2 molecules failing to attach to hemoglobin molecules.
Critical(20,000’ and above)
Within 3 to 5 minutes, judgment, & coordination usually deteriorate. Subsequently, mental confusion, dizziness, incapacitation, & unconsciousness occur.
PREVENTION of HYPOXIC HYPOXIA
Education is the greatest prevention. Hypoxic hypoxia is the type most often encountered in aviation. The other 3 may also present danger to aviators.
HYPERVENTILATION
An excessive rate & depth of respiration leading to abnormal loss of CO2 from the blood. Condition occurs more often among aviators than generally recognized. The human body reacts under conditions of stress & anxiety. Often, a marked increase in breathing occurs. This leads to a significant decrease in the CO2 content of the body & a change in the acid-base balance.
SIGNS & SYMPTOMS
Dizziness, muscle spasms, unconsciousness, visual impairment, tingling sensations, & hot/cold sensations.
TREATMENT
The most effective method is reduction in the affected individuals rate of respiration. However, an extremely apprehensive person may not respond to directions to breathe more slowly. The normal rate is 12 to 16 breaths per minute. Treat by controlling breathing & go to 100% O2. If symptoms continue & conscious control of respiration is not possible, the individual should talk or sing. It is physiologically impossible to talk & hyperventilate at the same time.
PRESSURE CHANGE EFFECTS
DYSBARISM
The human body can withstand enormous changes in barometric pressure as long as air pressure in the body cavities equals ambient air pressure. Difficulty occurs when expanding gas cannot escape. DYSBARISM- refers to the various manifestations of gas expansions induced by decreased barometric pressures.
Boyle’s Law:states that the volume of a gas is inversely proportional to its pressure, with temperature remaining constant.
Trapped Gas Disorders.
Free gas normally present in various body cavities expands. If the escape of the expanded volume is impeded, pressure builds up and pain is experienced. Greater pressure changes occur from 15,000’ down to 0’ PA, especially 5000’ to 0’ PA.
Gastrointestinal
Gas expansion in digestive tract. Not serious most of the time, unless above altitudes of 25,000’.
☺Preventive measures: avoid eating high
gas foods, such as: onions, cabbages, raw apples,
radishes, dried beans, cucumbers, & melons.
Chewing the food well is important. Avoid
carbonated drinks & chewing gum during ascent.
☺Relief: belching or passing flatus, if pain persist,
descent to lower altitude is necessary.
Middle Ear Discomforts
The Eustachian tube normally allows air to pass outward from the middle ear. However, with an increase in pressure during descent, the pressure of the external ear is higher than the pressure in the middle ear & the ear drum is forced inward. If the pressure differential increases appreciably, it may be impossible to open the eustachian tube. Very painful & eardrum can rupture if the pressure is not equalized.
Blocked Eustachian Tube
☺Relief: Normally you can equalize pressure by
swallowing, yawning, or tensing the throat muscles.
If this fails, perform the valsalva maneuver. If the
pain increase with further descent, relief can only be
obtained by ascending to an altitude where the
pressure can be equalized. Then a slow descent is
recommended.
Sinus Pain
Sinus openings may become obstructed when the mucous membrane lining swells as a result of an infection or allegoric reaction. Viscous secretions may also cause the openings to be covered. These conditions may make it impossible to equalize pressure. Change of altitude produces a pressure differential between the inside & the outside of the cavity, sometimes causing severe pain. Unlike, the ears, the sinuses are equally affected by ascent & descent. Could involve any three of areas of the sinuses: ethmoid, frontal, & Maxillary.
SINSUS AREAS
☺Avoid flying with a cold or congestion & valsalva
often during descent.
Evolved Gas Disorders
Occurs inflight as a direct result of a reduction of atmospheric pressure. Also known as decompression sickness. Typically, pressure altitudes over 18,000’.
Henry’s Law:states that the amount of gas dissolved in a solution is directly proportional to the pressure of the gas over the solution.
Bends
At the onset, pain in the joints & related tissues may be mild, but it can become deep, gnawing, penetrating, & eventually intolerable. The pain is progressive & gets worse if ascent is continued.
Chokes
Symptoms occurring in the thorax are caused by innumerable small bubbles that block the smaller pulmonary vessels. At first, a burning sensation is citied under the sternum. As the condition progresses, the pain becomes stabbing & inhalation is markedly deeper. There is almost uncontrollable desire to cough. Finally, there is a sensation of suffocation; breathing becomes more shallow & the skin bluish. An immediate descent is imperative.
Paresthesia
Tingling, itching, cold, & warm sensations that are believed to be caused by bubbles formed locally or in the CNS where they involve nerve tracts leading to the affected areas in the skin.
CNS
In rare cases when aircrews are exposed to high altitude, symptoms may indicate that the brain or the spinal cord is affected by nitrogen bubble formation. The most common symptoms are visual disturbances such as the perception of lights flashing or flickering when they’re actually steady.
STRESS
Stress is the nonspecific response of the body to any demand placed upon it.Stress is a physiological phenomenon involving actual changes in the body’s chemistry & function, and Stress involves some perceived or actual demand for action. Any event which requires you to adjust or adapt in some way is a source of stress, also called a stressor.
TYPES OF STRESSORS
Psychosocial.These stressors may trigger adaptation or change in one’s lifestyle, career, and/or interaction with others. Positive or negative. Job stress: low morale/unit cohesion/boredom/fatigue/over-tasking/poorly defined responsibilities, Illness: organic diseases/fatigue, & Family issues: family commitments/spousal relationships.
Environmental. Those things found in our every day job. Altitude: altitudes below 5000’/ trapped gas causing ear or sinus problems. Speed: associated with speeds > than those experienced in every day life cause a higher degree of alertness & concentration over long periods. Hot or Cold: use proper clothing or equipment. Aircraft Design: cockpit illumination/instrument location/seat comfort/heating & ventilating systems/visibility/noise level. IMC conditions: increased vigilance & accuracy reading, following, monitoring flt instruments are very stressful.
Physiological.Self-imposed stressors or maladaptive behaviors that are potentially debilitating & threaten aviation safety. Acronym DEATH.
- Drugs. Self-medication: may incur unwanted side-effects. Caffeine most commonly ingested. Limit or avoid drugs unless prescribed by a flt surgeon.
- Exhaustion. Lack of rest and poor sleep. Lack of exercise impairs circulatory efficiency, reduces endurance, & increases likelihood of illness.
- Alcohol. Affects of alcohol depend on: the amount of alcohol consumed/the rate of absorption from the stomach & small intestines/the body’s rate of metabolism, 1 oz every 3 hrs.
- Tobacco. Use of any tobacco product is detrimental.
- Hypoglycemia. maintain a well-balanced diet to avoid low blood sugar, which could cause weakness or fainting, , fatigue, & inefficiency’s.
Cognitive.How one perceives a given situation or problem is a potentially significant & frequently overlooked source of stress. Pessimism, obsession, failure to focus on the present, and/or low self-confidence can create a self-fulfilling prophecy that will ensure a negative outcome. Musts & Shoulds: lack of flexibility in thinking causes problems when reality does not accommodate one’s wishes. Failure to accept the possibility that things may happen contrary to one’s wishes leaves one unprepared, frustrated, & dysfunctional.Failure to Focus on the Here & Now: living in the past or future & overemphasizing what should have been or what could be, can increase one’s overall stress.
STRESS RESPONSE
Emotional Responses. Ranges from increased anxiety, irritability, or hostility to depressed mood, loss of ones self-esteem, hopelessness, & inability to enjoy life.
Behavioral Responses.High stress can adversely affect one’s work performance, decrease motivation, & increase the likelihood of conflict, insubordination, & violence in the workplace. Some individuals become socially isolated. Others may abuse drugs or alcohol.
Cognitive Responses.Stress can significantly affect one’s thought processes. It can decrease attention & concentration, interfere with judgment & problem solving, & impair memory.
Simplification Heuristic: under high stress conditions, people tend to oversimplify problem solving & ignore important relevant information, taking the easy way out.
Stress-Related Regression:individualsunder high-stress conditions will forget learned procedures & skills & revert to bad habits.
Perceptual Tunneling:individual or an entire crew under high stress becomes focused on one stimulus, & neglects to attend to other important task/information such as flying the aircraft. A similar situation may occur when an aviator realizes during flight that he or she overlooked some aspect of flight such as missing a radio call. The stressed aviator may then overattend to rectifying this problem/become emotionally & mentally fixated on the error & fall “behind the aircraft.”
Physical Responses.involves overall heightened arousal of the body. Increased heart rate, increased blood pressure, more rapid breathing, tensing of the muscles, & the release of sugars & fats into circulation to provide fuel for “fight or flight.” Prolonged stress & its continuous effects: muscle tension & pain, headaches, high blood pressure, decreased immunity to infectious diseases.
Stress Underload. Too little stress may be dysfunctional as having too much stress. A lack of challenges: complacency, boredom, & impulsive risk taking.
STRESS & PERFORMANCE
Physical Characteristics of the Individual. Differences in strength, endurance, & physical health effects stress performance.
Psychological Makeup of the Individual. Individuals with good coping, problem solving, & social skills will cope more efficiently.
Mental Skills Required by the Task or Situation. Attention, concentration, memory, problem solving, or spatial orientation will influence the extent to which stress will degrade performance.
Stress Characteristics of the Individual. Taking a stressful, timed problem-solving test in a quiet comfortable room is much easier & will result in fewer errors than taking the same test in a hot, noisy room.
STRESS MANAGEMENT
Avoiding Stressors.Most powerful mechanism. Avoid with good planning, foresight, realistic training, good time management, & effective problem solving. Stay physically fit & eat right. Good crew coordination & communication.
Changing Your Thinking.Practice positive self-talk, taking responsibility for your actions, avoiding perfectionism & inflexibility in thinking, focusing on the here & now rather than the past or future.
Learning to Relax. Use breathing exercises, meditation, or regularly engaging in a quiet hobby, greatly reduces stress.
FATIGUE
The state of feeling tired, weary, or sleepy that results from prolonged mental or physical work, extended periods of anxiety, exposure to harsh environments, or loss of sleep.
Acute Fatigue.Associated with physical or mental activity between 2 regular sleep periods. Loss of awareness of errors & coordination first to develop. Crew members feel this tiredness at night after being awake for 12 to 15 hrs in a day. Characterized by: inattention, distractibility, errors in timing, neglect of secondary task, loss of accuracy & control, lack of awareness of error accumulation, & irritability.
Chronic Fatigue. Result of inadequate recovery from successive periods of acute fatigue. It may take several weeks of rest to completely eliminate chronic fatigue & there may be underlying social causes, such as family or financial difficulties. Characterized by: insomnia, depressed mood, irritability, weight loss, poor judgment, loss of appetite, slowed reaction time, poor motivation & performance on the job.
Motivational Exhaustion or Burnout.If chronic fatigue proceeds untreated for too long, the individual will eventually “shut down” & cease functioning occupationally & socially.
DIURNAL (CIRCADIAN) RHYTHMS & FATIGUE
We have an intrinsic biological clock with a cycle of roughly 24 to 25 hours, & many important bodily functions such as core body temperature, alertness, heart rate, & sleep cycle occur along these diurnal rhythms.
Circadian Desynchronization (Jet Lag)
Rapid travel from one time zone to another causes the body to resynchronize its diurnal rhythms. Sleep disorders & fatigue will prevail. Resynchronization occurs more rapidly when traveling west.
THE SLEEP CYCLE
The sleeping brain cycles between rapid eye movement & non-REM sleep through five stages. Cycling occurs every 90 minutes. The duration & quality sleep depend on body temperature. It is the timing of sleep, not the amount that matters. A sleep schedule that is inconsistent w / ones circadian rhythm & the light & social cues of the environment will ultimately result in fatigue. Frequent changes in sleep patterns may also result in fatigue. Sleep efficiency deteriorates with age.
SLEEP REQUIREMENTS
During operations in which sleep loss is expected, aircrew members should closely monitor each others behavior for indications of fatigue. Avg person sleeps 7 to 9 hrs per day. Sleep length can be reduced 1-2 hrs without performance decrement over an extended period. As a RULE, five hours of sleep per night are the minimum for continuous operations (for example 14 days).
PREVENTION OF FATIGUE
Control the sleep environment, adjust to shift work, maintain good health & physical fitness, practice good eating habits, practice moderate controlled use of alcohol & caffeine, plan & practice good time management, practice realistic planning, maintain optimal working conditions, & Take naps.
Treatment of Fatigue.The most important action is to get rest & natural (not drug induced) sleep. Alcohol is the number one sleep aid in the U.S., but it suppresses REM sleep. If you find yourself lying awake more than 30 minutes; get out of bed & read a boring book or listen to some relaxing music. When attempting to recover from 24 to 48 hrs of sleep deprivation; do not sleep longer than 10 hrs.
TOXIC HAZARDS IN AVIATION
The greatest toxicological risk during flight is short-term, high level exposure to toxic agents. Ground support personnel may be affected by chronic exposure to toxic agents. These agents can be inhaled, ingested, or absorbed into the body. The two most common entry points are the repiratory tract & the skin.
AIRCRAFT CONTAMINATION
Normally results from exhaust gases, tetraethyl lead, fuel, carbon monoxide, engine lubricants, & oxygen contaminants in the cockpit.
Carbon Monoxide.A colorless, odorless gas that is lighter than air. The effects are subtle & deadly. Results from incomplete combustion. It is the most common gaseous poison in aviation.
ACCELERATION
Change in velocity with respect to time.
Linear.A change in speed without a change in direction/heading.
Radial, or Centripetal.A change in any direction w/ out a change in speed.
Angular.A change in both speed & direction simultaneous. ie..Aircraft in a tight spin.