Physiology And The Effect Of Flight Flashcards
What is the variation of pressure as altitude increases? (3) (ATPL/CPL)
- FL18 pressure is half of sea level
- FL335 pressure is quarter of sea level
- 100,000ft pressure is approx a 100th of sea level
Describe the physiology of the respiratory system
Air enters through nose mouth, travels to lungs via trachea which divides into two bronchi, each then divides into bronchioles and then once again into the alveoli.
The alveoli are responsible for the diffusion of oxygen into the bloodstream where it is taken up by the haemoglobin in the red blood cells and transported throughout the body.
Describe the role of the lungs in oxygen and carbon dioxide transfer
- Lungs are housed in the chest cavity as we breath in and out, the diaphragm expands and contracts
- Low pressure in the chest cavity as we exhale, draws air down the bronchial passage to the alveoli allowing the diffusion of oxygen.
Define hypoxia
Hypoxia occurs when the oxygen available in the blood is inadequate for the demands of the tissues.
Describe the partial pressure of oxygen both inside and outside the lungs at sea level.
- Partial pressure of oxygen at sea level is 150mmHg
- In lungs this drops to 102mmHg, this reduction is due to the presence of water vapour and carbon dioxide.
What is the oxygen equivalent at certain altitudes? (4)
- 10,000ft partial pressure of oxygen is half the mean sea level I.e 52.5 mmHg.
- At 34,000 ft on 100% oxygen pressure is equal to that of the mean sea level value
- 42,000ft on 100% oxygen the pressure is equal to that of 10,000ft above mean sea level
- Above 42,000ft pressure breathing equipment is required.
Describe the mechanical effect of the partial pressure of oxygen on oxygen transfer in the lungs
As altitude increases there’s a drop in oxygen, meaning less oxygen is in the lungs, therefore less oxygen in the blood flow
Explain the causes of hypoxia
- Flying, most likely due to reduced atmospheric pressure at altitude, therefore reduced oxygen
- Inhalation of carbon monoxide
- Restricted movement of oxygen enriched blood as a result of sustained high ‘G’
What are the different types of hypoxia? (4)
- Hypoxic - outside (atmosphere)
- Hypemic - blood
- Stagnant - g forces, circulation
- Histoxic - cell poisoning
Describe the common symptoms of hypoxia (11)
- Increased breathing rate
- light headedness or dizziness
- tingling or warm sensations
- sweating
- reduced vision (tunnel vision especially)
- sleepiness
- blue Colour on skin, fingernails and lips (cyanosis)
- behaviour changes (euphoric and very confident)
- loss of concentration
- impaired reasoning
- attention and memory failure
Describe the reason hypoxia symptoms are hard to detect.
- Because victims are seldom able to judge how seriously they are affected
- Unpleasant sensations experienced in suffocation are absent in the case of hypoxia. Blurring of vision, slight shortness of breath, a vague, weak feeling, and a little dizziness are the only warnings. May be absent or very slight.
Explain the relationship between hypoxic onset and both vision and cognitive performance.
- Hypoxia reduce both vision and cognitive performance, the sufferer mat experience tunnel vision and clumsiness and even simple tasks become difficult
- Night vision is susceptible to hypoxia especially above 4000ft, snooker has a blood stream equating to partial hypoxia and so reduced night vision
Describe how hypoxia can be prevented.
Providing a pressurisation system in aircraft
State the factors that affect the likelihood of suffering from hypoxia.
- If body needs more oxygen, then the lack of it becomes more acute.
- in cold conditions or during high activity or if a person is sick with a cold or flu, has fatigue is under the influence of drugs, alcohol or smokes, they’ll have increased susceptibility to hypoxia
Describe how hypoxia can be treated
Giving the sufferer either pure oxygen or by descending to a lower altitude
Define hyperventilation
Occurs when the breathing rate is greater than that required to expel the carbon dioxide produced in the body
Explain the causes of hyperventilation (3)
- Anxiety or fear
- Mental tress of a sudden inflight emergency
- Turbulence can cause passengers with fear of flying to hyperventilate
Describe the symptoms of hyperventilation (4)
- Dizziness and tingling in the hands and feet
- Visual disturbances and hot and cold sensations
- Anxiety and loss of muscular coordination and impaired performance
- Increased heart rate and muscle spasms.
Describe how hyperventilation can be treated (3)
- Calm victim down
- Person may become unconscious, which wil causer the rate and depth of breathing to return to normal and they’ll recover.
- Have person breath into a paper bag to re-breath some of the expelled CO2 and therefore raising the acidity levels back to normal
Describe the differences between hyperventilation and hypoxia.
- Early symptoms of them are similar and treatment should be based on the assumption that the patient is hypoxic until it can be eliminated
- If treated initially for hyperventilation but was hypoxic it’ll accelerate the effects as oxygen intake is further being reduced.
When treating for hypoxia or hyperventilation what should you treat for first?
Hypoxia.
Define barotrauma.
- The pain which can result from excessive pressure differential caused by barometric changes.
- Experienced when the Eustachian tube becomes blocked, causing the ear to be unable to equalise the pressure inside, pushing the eardrum
Describe the symptoms of barotrauma
Discomfort and sometimes extreme pain in ears sinuses, teeth lungs and gastrointestinal tract
Describe the effects of barotrauma on gastrointestinal tract of the body
intestines expand during ascend and are vented naturallly. Gases trapped in small bowel can be agonising
Explain the causes of barotrauma
There are a number of cavities within the body, which naturally contain gas and unless vented, these gases will expand and contract as ambient pressure changes.
Describe the effects of barotrauma on the ears
Eustachian tube acts as a non-return valve. During a climb it opens to equalize pressure, but can close during descent under increasing pressure. This is otic barotrauma.
Describe the effects of barotrauma on the Sinuses
Can usually cope with decreasing pressure from ascent, but descending can pose a problem. The problem is aggravated by cold/flu which blocks sinuses and eustachian tube.
Any trapped gases in the nasal passages may cause pain behind the nose and eyes. It can be described as a sharp stabbing like pain which can affect your ability to see.
Describe the effect of barotrauma on the teeth and lungs
Teeth - Gases can become trapped in incomplete fillings or abscesses
Lungs - If you fail to breath out during a sudden decompression, damage can occur
Define decompression sickness
Caused by nitrogen (normally dissolved into body fluids) coming out of solution and forming bubbles throughout the nervous system and else where
DCS (divers disease)
Causes of decompression sickness
Can result form flying after scuba diving buy not snorkelling
Symptoms of decompression sickness (4)
Joints - the bends - aching joints
Skin - the creeps - tingling skin
Nervous system - the staggers - partial paralysis
Lungs - the chokes - possibly fatal
Explain how decompression sickness can be prevented.
Avoid diving then flying in less than the recommended time
During diving make required recompression stops
What are the minimum restriction times for diving and flying
Wait a minimum of 12 hours if you scuba dive up to and including 10 metres
Wait a minimum of 24 hours if you dive beyond 10 metres
How can decompression sickness be treated.
Emergency - involve maintains blood pressure and administering oxygen. The key to treatment is the use of a (recompression chamber), a high pressure chamber in which the patient receives 100% oxygen.
What does the treatment for decompression do?
Reverses the pressure changes that allowed gas bubbles to form and it drives nitrogen back into its liquid form so that it can be cleared more gradually over a period of hours.
Explain the dangers of flying after diving
Diving uses air under pressure and increases the quantity of nitrogen in solution in the body
Flying after diving increases the pressure differential a person is exposed to, and increases the risk of decompression sickness
The effects of an explosive decompression on the body
Occurs art a rate swifter that at which air can escape from the lungs 0.1-0.5 seconds
Risk of lung trauma is high, as in the danger from any unsecured objects that ca become projectiles because of the explosive force, which may be likened to a bomb detonation.
The actions that’s must be taken in the event of explosive decompression
Breathe out, Don nearest oxygen mask, Sit down, fasten seatbelt or grasp fixed objects
Describe physiology of the circulatory system
Oxygen rich blood travels from the lungs through the pulmonary vein to the left atrium
- Through the heart from the left atrium to the left ventricle
- Then through the aorta to the arteries and arterioles which distribute oxygenated blood to all parts of the body via the tissue capillaries
Oxygen poor blood travels from the capillaries, through the venules and then veins to the right atrium
- Then through the heart, from the right atrium to the right ventricle
- Back to the lungs via the pulmonary artery, where the blood is re-oxygenated.
34.6.6/46.6.4 Partial pressure of oxygen changes as altitude increases
The pressure of the atmosphere at sea level is 760 mmHg (millimetres of mercury) therefore the partial pressure of oxygen at sea level is 159 mmHg. (760 x 21%)
•At 18,000ft the partial pressure of oxygen is 79.5 mmHg
34.10.24/46.10.24 Time of useful consciousness and things that affect it
This is the time available to recognise that hypoxia exists and to do something about it. After these times the sufferer will still be conscious however they will not be able to engage in any meaningful activity
Warmer cockpit will make it longer and so will staying still and quiet, moving around reduces it
34.10.26/46.10.26 The approximate time of useful consciousness at
(a) 18,000ft – 15 - 30 minutes
•(b) 25,000ft – 3 – 5 minutes
•(c) 35,000ft - 30 – 45 seconds
•At 45,000ft the time of useful consciousness reduces to about 12 seconds – not alot of time to get your oxygen mask on!!
34.10.28/46.10.28 Oxygen Paradox
When a person is suffering from hypoxia, often symptoms will actually get worse for a few seconds after they are given oxygen.
This is due to the sudden affects of oxygen on blood vessels to the brain, this only lasts around 15 seconds. The oxygen mask should NOT be removed during this period.
46.10.30 Physiological effects of cabin pressurisation loss at 25,000ft and above (7)
- Rapid/Explosive – sudden loss in cabin pressure due to damage to the aircraft e.g. loss of window
- A loud bang/thump/clap as internal air meets external air
- Cloud/fog/mist in the cabin due to drop in temperature
- Rush of air
- Decrease in temperature
- Debris may fly around the cabin
- Oxygen masks drop from Passenger Service Units (PSU)
What happens during slow decompression
very gradual decrease in cabin pressure due to faulty door seal, malfunction in the pressurisation system or cracked window
●May be not always be obvious
●First sign could be the oxygen mask dropping
●Unusual noise, such as whistling or hissing sound around door area
●Occupants may have ear discomfort or ‘popping’, joint pain or stomach pain due to gas expansion.
46.10.32 Actions flight crew must take with high altitude cabin pressurisation failure
IMMEDIATLEY don Oxygen masks
•Rapid descent to reduce the aircraft altitude to 10000’or less, (suitable level if over mountainous terrain)
•If no structural damage the aircraft should be flown at VMO/MMO
- A descending 90 degree turn to vacate the airway
- MAYDAY call.
46.10.34 Principle features of supplemental oxygen systems to assist with in-flight pressurisation emergency
Most large aircraft are fitted with two fixed oxygen systems. One for crew and one for passengers. In addition portable bottles are located throughout the aircraft.
- Passenger Oxygen System – masks automatically fall if cabin altitude is approximately 14000’. Oxygen flows for 12minutes and cannot be shut off.
- Flight Crew Oxygen System – The mask can supply 100% on the regulator or a mixture (NORMAL). An EMERGENCY switch supplies 100% under pressure to purge smoke or fumes.
