Aeromedical
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Presentation Transcript
Aeromedical Factors Technical Subjects, Task A Jeppesen, Chapters 1, 10
Objective • This section will instruct the student on the recognition, symptoms, and treatment of some common medical problems that may occur during flight.
Motivation • During flight, aeromedical problems may develop rapidly in you or your passengers. Prompt identification and corrective action may actually spell the difference between life and death.
Overview • This lecture will cover the definition, symptoms, effects, and corrective actions of the following: • Hypoxia • Hyperventilation • Middle ear and sinus problems • Spatial disorientation • Motion sickness • Carbon monoxide poisoning • Decompression sickness • Fatigue
Hypoxia • Hypo (below normal, deficient) + oxia (oxygen) • Hypoxia: The body (generalized hypoxia) or parts of the body (tissue hypoxia) are deprived of oxygen • Hypoxia can be classified into four groups, based on their causes: • Hypoxic • Hypemic • Stagnant • Histotoxic
Hypoxia • Hypoxic – Inadequate oxygen supply to the body as a whole • Not enough partial pressure of O2 to sustain life (also known as “altitude sickness” or “altitude hypoxia”) • Or, enough O2 in the air, but it is not making it into the body (blocked airway, COPD, drowning) • Onset may occur suddenly (explosive decompression) or gradually (climbing a mountain) • The most lethal factor of all physiological causes of accidents
Hypoxia • Hypemic – hypo (deficient) + -emia (blood) • Though there is an adequate supply of O2 in the air, the blood cells are not absorbing it properly • Most commonly occurs due to CO poisoning (faulty heating duct, cigarette smoke) • Donating blood removes red blood cells, which may lead to hypemic hypoxia during flight • May also occur because of bleeding
Hypoxia • Stagnant – sufficient O2 in the air, and the blood is absorbing enough… but the blood is not reaching the cells • May occur due to shock (after a fright), constricted arteries, weak heart, positive G-forces, or cold temperatures
Hypoxia • Histotoxic – Histo- (tissues) + toxic (poisonous) • Adequate O2 in the air, blood is absorbing enough, and blood is delivering it to the cells… but the cell is unable to accept it or use it • Most common causes are alcohol, narcotics, and cyanide (from the combustion of plastics)
Hypoxia - Symptoms • No matter the type of hypoxia, the symptoms are usually the same: • Headache • Lightheadedness • Drowsiness • Fatigue • Shortness of breath • Feeling of euphoria • Nausea • Cyanosis • Similar to drunkenness • In the case of sudden onset of hypoxia, symptoms may also include: • Unconsciousness • Seizure • Coma • Death
Hypoxia - Effects • Hypoxia may cause any or all of the following: • Confusion • Visual impairment (dim, blurry vision, or loss of night vision) • Loss of sense of time • Poor reaction time • Hypoxia affects judgment, and thus is difficult (or impossible) to self-diagnose
Hypoxia – Effects • When O2 is removed, you have a finite period of time with which to make a rational decision that may save your life. • This is the Time of Useful Consciousness (a.k.a. Effective Performance Time) • Explosive decompression may halve these values
Hypoxia - Treatment • Get more oxygen into the body! • Use supplemental O2 if available • Descend to under 10,000 feet, if possible to do so safely • Because hypoxia affects judgment, the best approach is prevention
Hypoxia - Prevention • Everyone is susceptible to hypoxia • Monitor yourself and your passengers carefully • Symptoms will vary in different people, or even in the same person on different flights • FAA recommends a session in an altitude chamber to familiarize yourself • Use supplemental O2: FAR Part 91.211
Hypoxia - Prevention • Tolerance to hypoxia can be increased by: • Keeping in shape • Eating nutritiously • Avoiding alcohol and smoking • Living at high altitude • Keeping the aircraft at a comfortable temperature • Rapid ascension will decrease tolerances
Hyperventilation • Hyperventilation – unusually rapid or deep breathing, caused by emotional tension, anxiety, or fear • Normal breathing rate: • 12-20 bpm • Why do we breathe? • Secondary drive – low levels of O2 • Primary drive – high levels of CO2
Hyperventilation - Symptoms • Hyperventilation “blows off” CO2 in the blood, raising the blood’s pH. Low blood acidity reduces the blood’s calcium levels • Result: extremities may feel hot/cold, tingly, or numb • The brain, sensing low CO2 levels, assumes that O2 levels are high and constricts arteries to the brain • Result: lightheadedness
Hyperventilation - Symptoms • Other symptoms include: • Headache • Euphoria • Visual impairment • Numbness • Muscle spasms • Pale, clammy appearance • Tightness in chest • Frequent yawning or sighing • Feeling that you can’t get enough air
Hyperventilation - Effects • Like hypoxia, hyperventilation affects brain function: • Impaired judgment • Decreased reaction time • Dizziness • In severe or untreated cases, unconsciousness will result • Pilots who have never experienced hyperventilation before may confuse symptoms with those of a heart attack, adding to their panic and complicating matters
Hyperventilation - Treatment • Slow the rate of breathing • Concentrate on maintaining a normal rate • Talk (or get the victim to talk) aloud in long sentences. Use reassuring words and tone (“You’re not having a heart attack. Just keep breathing. So, you’re from Michigan? What’s it like this time of year?”) • Restore proper CO2 blood levels by rebreathing into a paper (not plastic) bag or cupped hands
Hyperventilation vs. Hypoxia • Because the symptoms of both are similar, correct diagnosis may be difficult • If using supplemental O2, check equipment and flow rate • Take 3-4 deep breaths of O2. If hypoxia, recovery will be rapid • If symptoms are accompanied by lethargy - hypoxia • If symptoms are accompanied by nervousness - hyperventilation
Middle Ear/Sinus Problems • The Eustachian Tube connects the middle ear to the throat • Normally closed, its purpose is to equalize middle ear pressure with outside pressure • Usually automatic • “Ears popping”
Middle Ear/Sinus Problems - Causes • Eustachian tubes may become blocked or inflamed during illness (colds, sinus infections) or as a result of mucus buildup (smoking) • Pressure differences can occur during ascent (higher pressure in middle ear) or descent (lower pressure)
Middle Ear/Sinus Problems - Effects • Blocked tubes will not automatically relieve pressure differences • Sensations of popping, clicking, and ear fullness • Sounds become muffled • Moderate to severe ear pain
Middle Ear/Sinus Problems - Treatment • Eustachian Tubes can be opened manually: • Chewing gum, swallowing • Yawning • Valsalva Maneuver: forcible exhale against a closed airway. • Shut mouth, pinch nose, and exhale • Open jaw is more effective, as closed jaw pinches the tubes
Spatial Disorientation • Occurs when perception of position, movement, and/or altitude does not match reality • Usually occurs when outside reference is lost (flying into IMC) or during night flights over featureless terrain • 5-10% of GA accidents are attributed to spatial disorientation – 90% of these are fatal
Spatial Disorientation - Causes • Semicircular canals in the middle ear perceive motion and gravity • Otoliths – nerve endings in the canals that register position and balance • Otoliths can be “fooled” by G-forces, prolonged, steady turns, or rapid head movements (a.k.a. vestibular disorientation)
Spatial Disorientation - Effects • Otoliths can tell the brain that you are turning when you are not. Without outside reference, you may put the craft into dangerous attitudes trying to correct the perceived problem
Spatial Disorientation - Treatment • If not instrument rated and current, STAY OUT of IMC. • Rely on the instruments, even (or especially) if they conflict with what your body tells you
Motion Sickness - Causes • Vestibular disorientation produces feelings of instability, which often leads to motion sickness • Eyes and ear send conflicting messages to the brain • Because may passengers focus their attention inside the craft to a greater degree than pilots, they are more susceptible to motion sickness
Motion Sickness - Effects • Motion sickness may cause: • Nausea (you may have figured this one out beforehand) • Dizziness • Sweating/Cold Sweating • Paleness • Vomiting • Vertigo • Headache • Confusion • Fatigue • General discomfort
Motion Sickness - Treatment • Motion sickness is a normal reaction • Put head back and attempt to relax (reclined head increases tolerance to up-and-down movement) • Reduce passenger anxiety by keeping them informed on flight’s progress • Have passengers focus on things outside the cabin • Avoid steep banks and aggressive maneuvers • Avoid turbulent air if possible • Open fresh-air vents • Loosen clothes around neck • Medications (ex. Dramamine) may help • Ginger (root or extract) may also help • If nothing else…
Alcohol and Drugs • Alcohol use can result in: • Poor decision-making • Increased reaction time • Decreased inhibitions • Loss of attention • Impaired memory and comprehension • Loss of motor control
Alcohol and Drugs • Illegal drugs should be avoided (duh) • Even over-the-counter drugs may impair pilot performance • Drug effects may become unpredictable at lower air pressures • Antihistamines can cause drowsiness, dizziness, and blurred vision • Aspirin can cause nausea and hyperventilation
Alcohol and Drugs • FAR 91.17 • No person may act or attempt to act as a crewmember of a civil aircraft-- (1) Within 8 hours after the consumption of any alcoholic beverage (“8 hours from bottle to throttle”); (2) While under the influence of alcohol; (3) While using any drug that affects the person's faculties in any way contrary to safety; or (4) While having an BAC of 0.04% or greater
Alcohol and Drugs • Prevention is the best remedy – do not fly after drinking or while taking medication • Though you can legally fly 8 hours after drinking, hangover effects may persist for up to 24 hours • Ask an aviation physician if any medications that you take may cause problems during flight
Carbon Monoxide Poisoning • Colorless, odorless, tasteless gas • Formed during the incomplete combustion of carbon compounds (gasoline, aviation fuel) • CO-hemoglobin bonds are 230 times stronger than O2-hemoglobin bonds • Hemoglobin bound with CO will not deliver O2 to the body
Carbon Monoxide Poisoning - Symptoms • Symptoms vary with concentration:
Carbon Monoxide Poisoning - Effects • CO Poisoning may cause: • Shortness of breath • Impaired judgment • Confusion • Agitation • Drowsiness • Hallucinations • Vomiting • Seizures • Unconsciousness • Most common type of death by poisoning in the U.S.
Carbon Monoxide Poisoning - Treatment • Because the gas is undetectable by humans, early symptoms may resemble the onset of the flu • In aviation, CO poisoning may occur when heating a cabin with air drawn from around a leaky exhaust system • If you smell exhaust, immediately close the heater vents and open fresh air vents • Make sure the CO detector is functional (if installed) • High-flow oxygen (if available) can purge CO from the body • Land and seek medical treatment
Decompression Sickness • Inhalation of gases under high pressure (SCUBA tanks) causes inert gases (usually nitrogen) to dissolve into the blood • Henry’s Law: Solubility of a gas in a liquid is proportional of the pressure of that gas. If pressure decreases, amount of dissolved gas will also decrease (ex. soda cans) • Thus, when pressure is reduced (divers returning to the surface, or ascending in an aircraft), gases come out of solution
Decompression Sickness • Normally, gases coming out of solution are breathed out • However, if outside pressure decreases too rapidly, gases will form bubbles in the body and not escape through the lungs (the “bends”) • Divers avoid this by making decompression stops during ascent
Decompression Sickness - Symptoms • If bubbles occur in the joints (60-70% of cases): • Mild to excruciating deep pain • If bubbles occur in the brain (10-15% of cases): • Headaches • Dizziness • Nausea • Seizures • Memory loss • Impaired vision • Unconsciousness • Death • If bubbles occur in the skin (10-15% of cases): • Itching, burning sensations • Mottled skin • Sensation of insects crawling under skin
Decompression Sickness - Prevention • Decompression sickness is extremely rare in healthy adults (who have not been diving) under 18,000 feet • People should not fly above 8,000 feet if they have made any dives within the last 12 hours • If the dives included decompression stops (deep dives), should not fly within 24 hours
Decompression Sickness - Treatment • Bring the craft as low as safely possible • If oxygen is available, use it • If joint pain is present, do not move the joint to “work out” the pain • Do not ignore symptoms that go away during the flight • The Bends require medical treatment; victim must be brought to a hospital • If you experience DCS, do not fly again unless cleared by an aviation medical examiner
Fatigue • Fatigue - a non-pathologic state resulting in a decreased ability to maintain function or workload due to mental or physical stress • In other words, feeling tired, sleepy, or exhausted • One NTSB study on major air carrier accidents from 1979-1990 found that, in half of all accidents, the captains and first officers had been awake for more than 11 hours
Fatigue - Causes • Fatigue is most commonly associated with: • Lack of sleep • Disruption of circadian rhythm cycle (shift work, jet lag) • Other factors that contribute to fatigue: • Long periods of strain (physical, mental, or emotional) • Long periods of immobility • Heavy mental workload • Monotony (sorry)
Fatigue - Effects • Fatigue may cause: • Sleepiness (did you need to be told this?) • Difficulty concentrating • Apathy • Feelings of isolation, annoyance • Increased reaction time • Slowing of higher-level mental functioning • Decreased vigilance • Memory problems • Fixation on tasks • Especially dangerous for GA pilots, who often do not have a co-pilot
Fatigue - Treatment • Ideally, get more sleep (7 - 8 hours per night if possible) • Establish sleep patterns • Take naps (up to 30 minutes) • Maintain a healthy lifestyle (proper nutrition and exercise) • Don’t take medications before flying – some may cause drowsiness
