Scarica Aviation Physiology: Key Concepts in Flight Medicine e più Appunti in PDF di Medicina solo su Docsity!
Basics:
Latent threat: Cockpit design error Conceptual aspects of systems mismatch: Liveware – software James reason: Gathering information from accidents & investigations is informed
Atmosphere:
Heart muscles: Blood supply from coronary arteries Blood: Is lacking in oxygen & rich on CO 2 Pressoreceptors: Located in carotid & aortic arterial vessels Angina: Symptom of reduced oxygen to heart muscle , caused by narrowing/obstruction of coronary artery Circulation: O 2 & CO 2 transportation Gas exchange: Partial pressure of CO 2 in the alveoli is lower than in the blood Respiratory system: Oral nasal passage, pharynx, larynx, trachea, bronchi & alveoli Anaemia : Not enough functioning haemoglobin
Hypoxia:
- Histotoxic hypoxia: Alcohol increases physiological altitude, 1 ounce 2000ft
- Hypoxic hypoxia : Short term memory impairment starts at 12000ft
- Hypaemic hypoxia: Smoking
- Stagnant hypoxia: Excessive G-forces
- Can be experienced at 6000ft
- Night vision reduced at compensatory stage
- Dalton’s death
Hyperventilation:
- Causes CO 2 to be removed from the blood
- Lack/shortage of CO 2 in the blood
- Blood circulation to brain slowed down
- Jogging does NOT cause hyperventilation
- Running is voluntary hyperventilation
Decompression sickness:
- Primary symptom: The bends
- Nitrogen gas bubbles released
- Wait 12 hours before next flight
- Henry’s hole
Rate of depth of breathing:
- Controlled by pressure of CO 2 in the blood
- Increased rate = high level of waste CO 2 in the lungs
- Increased CO 2 causes shortness of breath
- Controlled by receptor cells in the brain
Respiratory control centre: Sensitive to carbon dioxide
Hypertension: Physiological condition involving increased pressure on the arterial walls
Hypothermia: Demand for oxygen initially increased
Low blood pressure:
- Arterioles constrict, cardiac output increase, heart rate rises
- Increased risk of low blood pressure when donating blood due to loss of blood volume
General gas law : Volume of a gas multiplied by pressure divide by its absolute temperature is constant Law of diffusion :
- Transfer of CO 2 to the alveoli
- Adjacent gases of different concentration mix until concentration is balanced Charles’ law: Volume of gas at constant pressure is proportional to absolute temperature Boyle’s law : Volume of a gas is inversely proportional to its pressure with temperature constant Henry’s law : Quantity of gas dissolved in a liquid is proportional to the partial pressure of the gas Dalton’s law:
- Partial pressure of gas is proportional to its fractional concentration in a gas mixture
- Total pressure = sum of partial pressures of the gas in the mixture
G-forces:
- Factors: Low blood sugar, obesity & hypoxia
- +Gz: Blood flow to brain decrease
Heart attack:
- Common for people above 40
- Total blockage of a coronary artery leading to the death of a piece of heart muscle
Random knowledge: Alpha radiation: Absorbed by thin sheet of paper or 0.2cm of water Cosmic radiation: Increases at higher latitudes Temperature increase RH decrease Ozone absorbs UVB better than UVA
Man environment & sensory systems
Eye: Iris: Control the size/diameter of pupils Pupil: Controls amount of light that strikes the eye Accommodation:
- Controlled by cilliary muscle around the lens
- Ability of the lens to change its shape Optic system : Cornea, lens, vitreous humour 3 coats of the eye: Sclera, uvea, retina Crystalline lens: Enables a clear image to be obtained Cornea: Part of the eye that bends the light the most Cornea & crystalline lens: Causes the convergence of light rays onto the retina Central vision : Enables details & colours to be seen, represents a zone where 150 000 cones/mm are located to give high resolution capacity Fovea : Area of best day vision & no night vision at all Foveal area is the only area where resolution is good enough to see clearly Retina: Rods in peripheral zone Central zone: Cones Optic nerve: Has no rods & cones
Vibrations cause blurred vision due to resonance of eyeballs When focusing shape of lens gets more spherical Glaucoma : Increase in pressure of the liquid within eye Eyes move in short jerky movements called saccades ; smooth vision is achieved in visual cortex Reading alphanumeric information limited to foveal area of the retina Refractive power: Variable from 16 – 30D Monocular depth cue: Linear perspective Sunglasses : Can have disadvantages Visual acuity: 1 minute of arc Visual acuity affected by: hypoxia, age & angular distance from the fovea
Presbyopia:
- Far sightedness due to age
- Common over the age of 50
- Decrease of accommodation
Short or near sightedness/myopia:
- Defective vision in the form of optical image in front of the retina
- Person will start experiencing problems at a later age with presbyopia than usual
Astigmatism: Misshaped cornea
Accelerations:
- Forward linear acceleration: Somatogravic/oculogravic
- Forward acceleration: Illusion of backward tilt it results in backward displacement of the otolithic membranes
Health & hygiene
Sleep:
- Orthodox – Deep sleep, physical recovery, refreshes body
- Paradox (REM) – Increases during night, regenerate mental functions (4-5 cycles)
- Time zone adjustment: 3-4 zones with 24 hour layover – keep in swing/rhythm of departure country as long as possible, maintain regular living patterns
- Duration depends on the point within your circadian rhythm at which you try to sleep Barotrauma:
- Reduction of hearing ability & feeling of increased pressure
- Affects facial sinuses, middle ear & dental cavities
- Pressure differentials between gases in hollow cavities of the body & the ambient pressure
- Causes pressure pains & flatulence Dysbarism:
- Refers to various medical problems caused by gas expansion induced by decreased barometric pressure Aerodontalgia/barodontalgia:
- Doesn’t occur at desert
- Arises especially with irritation of the sensitive tissues close to the root of a tooth Smoking:
- Lifts smoker physiological altitude
- Flying at 10000ft, oxygen content in blood equal to altitude above 10000ft
- Causes hypaemic hypoxia Alcohol:
- No alcohol should be consumed 8 hours prior for flight duty period or period of standby
- Does not promote barotrauma
- Degrades paradoxical sleep Hypoglycaemia/low blood pressure:
- Headache & lack of concentration Eustachian tube:
- Blocked = equalization of pressure is limited Cold:
- Pain & damage can occur to ear drum, particularly during fast descents
- Increased risk of barotrauma during climbs & descents Metabolic cell waste:
- Water & carbon dioxide Diabetes:
- Type 2: Caused by genetics & obesity ( Low physical activity?) Hyperthermia:
- Adjustment to hot country takes 14 days Tetanus:
- Bacteria in the form of spores via punctures
Others:
Rasmussen’s model :
- Errors in rule-based control mode are errors of technical knowledge
- Skill, rule & knowledge based models are associated with problem solving
Anderson model:
- Cognitive, associative & automatic
Rule allows situation to be resolved: Actions return to automatic mode
Attention:
- Detecting relevant information which is not presented in an actively monitored input channel = Attention
- Depends on level of automation of behaviour, salience of information, expectations
1 st^ stage of information process = sensory stimulation
Long term memory :
- Affected by expectation & suggestion , where motor programs are kept
- It is helpful to mentally rehearse information before it is needed Short term memory : 20 seconds
Mental training, rehearsal & cognitive pre- training is most important to acquire complex motor skills
Working memory: 5 – 9 items without rehearsing (About 7 maximum)
Experience & repetition may be beneficial & negative
Environmental capture: Tendency of a skill to be executed in an environment in which it is frequently exercised Tendency for a skill acquired in another aircraft executed in a new aircraft type even if it is inappropriate
Errors:
- Error tolerance: Error tolerance means minimizing the effects of errors by making a system as tolerant as possible towards errors
- Error results in cognitive sequence which makes it possible to modify behaviour with a view to adaptation
- Humans are fallible & system & procedures should be designed to minimize human error
- Error of commission: Taxiing to wrong runway
Decision making:
- Assertiveness makes crew decision making most effective
- Amount of time available has a large influence on analysis of the situation
- Pilot should take as much time as he needs & is available to make up his mind
- Intention of being integrated , to be recognized as leader or avoid conflicts: Attempt to agree on decisions made by other crew members
Time constraints: Preparation of the action & the prioritisation of tasks
Confirmation bias:
- Tendency to look for information that confirms the validity of the decision
- To avoid: Search for information that will falsify hypothesis
Groupthink: More or less unconscious support of a solution from group members
Professional language:
- Uses limited vocabulary & context provides meaning
- Quick comprehension & simplified grammar
Communications:
- Relies heavily on the sender
- TO make effective: Send information in line with receivers decoding abilities
- Loss of words & packaging more important as: Body language is lost
Information: Intended to reduce uncertainty, measured in bits
Coordination: Allows synergy between pilot & co-pilot , in this mode has the function of synchronizing actions & distributing responsibilities
Very high ambition & need for achievement disturbs climate of co-operation
Paralanguage: Pilots speak to a person which is outside aircraft
Democratic & co-operative style: Trying to clarify reasons & causes of the conflict with all persons involved
Co-action: Working parallel to achieve one common objective
CRM: Improves quality of crew performance
Invulnerability:
- Accidents can only happen to others
- “It will not happen to me”
“Personality”: Refers to unique psychological characteristics
Inspiratory volume: 3300ml Expiratory volume: 1000ml Residual volume: 1200ml
TUC:
- 25000ft: 3 – 5 minutes
- 30000ft: 45 seconds to 1 min 30 seconds
- 35000ft: 30 – 60 seconds (45 seconds)
- 43000ft: 30 – 45 seconds
Reaction threshold/compensatory reactions: 7000ft (Human organism starts remarkable measures) Disturbance threshold: 10000 – 12000ft Critical threshold: 22000ft (Non-pressurized 20000ft)
Hypoxia:
- Does not occur below 3000m
- Occurs at 38000 – 40000ft 100% oxygen without pressure
- Affects night vision at approximately 5000ft
Records of radiation kept above 29000ft After scuba diving wait 24 hours
Sight: 70 - 75% of knowledge from sight, 13% hearing Night vision: Degradation of night vision occurs from 1500m (5000ft) Visual acuity: Best within 2-3 degrees of the fovea & reduces rapidly towards periphery vision
Hearing: Frequencies: 20 – 20000Hz Hear/listen to 500 & speak 125
Alcohol: Slight lack of coordination starts at 0.05% blood alcohol No alcohol 8 hours before EASA blood/alcohol limit: 20 mg per 100mm of blood Rate of metabolism or digestion of alcohol: 0.01 – 0.015g/100g per hour (15mg/100ml/hour)
Smoking : One pack of cigarettes gives away 5 – 8% of total oxygen transportation
Time zone : Resynchronization time at a rate of 1 – 1.5 hours a day
Sleep: 5 stages of sleep REM sleep 4-5 bouts in 8 hours, Free running circadian rhythms: 25 hours Credit/debit system: 12 hours Normal sleep cycle every 90 minutes Human adults require 8 hours of sleep per night
BMI :
- Mass ÷ Height 2
- Normal 18 to 25 (Females just -1)
- Obese >30/
Breakfast = 25%
Caffeine in excess of 250mg/day is a problem
Errors: Simple repetitive tasks occur about 1 in 100 times Good & realistic error rates: 1 in 1000 times
Communications: 80% of communications is metacommunications
