Physiology And The Effect Of Flight

Question 1

What is the variation of pressure as altitude increases? (3) (ATPL/CPL)

Answer 1

• FL18 pressure is half of sea level
• FL335 pressure is quarter of sea level
• 100,000ft pressure is approx a 100th of sea level

Question 2

Describe the physiology of the respiratory system

Answer 2

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.

Question 3

Describe the role of the lungs in oxygen and carbon dioxide transfer

Answer 3

• 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.

Question 4

Define hypoxia

Answer 4

Hypoxia occurs when the oxygen available in the blood is inadequate for the demands of the tissues.

Question 5

Describe the partial pressure of oxygen both inside and outside the lungs at sea level.

Answer 5

• 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.

Question 6

What is the oxygen equivalent at certain altitudes? (4)

Answer 6

• 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.

Question 7

Describe the mechanical effect of the partial pressure of oxygen on oxygen transfer in the lungs

Answer 7

As altitude increases there’s a drop in oxygen, meaning less oxygen is in the lungs, therefore less oxygen in the blood flow

Question 8

Explain the causes of hypoxia

Answer 8

• 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’

Question 9

What are the different types of hypoxia? (4)

Answer 9

• Hypoxic - outside (atmosphere)
• Hypemic - blood
• Stagnant - g forces, circulation
• Histoxic - cell poisoning

Question 10

Describe the common symptoms of hypoxia (11)

Answer 10

• 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

Question 11

Describe the reason hypoxia symptoms are hard to detect.

Answer 11

• 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.

Question 12

Explain the relationship between hypoxic onset and both vision and cognitive performance.

Answer 12

• 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

Question 13

Describe how hypoxia can be prevented.

Answer 13

Providing a pressurisation system in aircraft

Question 14

State the factors that affect the likelihood of suffering from hypoxia.

Answer 14

• 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

Question 15

Describe how hypoxia can be treated

Answer 15

Giving the sufferer either pure oxygen or by descending to a lower altitude

Question 16

Define hyperventilation

Answer 16

Occurs when the breathing rate is greater than that required to expel the carbon dioxide produced in the body

Question 17

Explain the causes of hyperventilation (3)

Answer 17

• Anxiety or fear
• Mental tress of a sudden inflight emergency
• Turbulence can cause passengers with fear of flying to hyperventilate

Question 18

Describe the symptoms of hyperventilation (4)

Answer 18

• 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.

Question 19

Describe how hyperventilation can be treated (3)

Answer 19

• 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

Question 20

Describe the differences between hyperventilation and hypoxia.

Answer 20

• 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.

Question 21

When treating for hypoxia or hyperventilation what should you treat for first?

Answer 21

Hypoxia.

Question 22

Define barotrauma.

Answer 22

• 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

Question 23

Describe the symptoms of barotrauma

Answer 23

Discomfort and sometimes extreme pain in ears sinuses, teeth lungs and gastrointestinal tract

Question 24

Describe the effects of barotrauma on gastrointestinal tract of the body

Answer 24

intestines expand during ascend and are vented naturallly. Gases trapped in small bowel can be agonising

Question 25

Explain the causes of barotrauma

Answer 25

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.

Question 26

Describe the effects of barotrauma on the ears

Answer 26

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.

Question 27

Describe the effects of barotrauma on the Sinuses

Answer 27

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.

Question 28

Describe the effect of barotrauma on the teeth and lungs

Answer 28

Teeth - Gases can become trapped in incomplete fillings or abscesses

Lungs - If you fail to breath out during a sudden decompression, damage can occur

Question 29

Define decompression sickness

Answer 29

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)

Question 30

Causes of decompression sickness

Answer 30

Can result form flying after scuba diving buy not snorkelling

Question 31

Symptoms of decompression sickness (4)

Answer 31

Joints - the bends - aching joints
Skin - the creeps - tingling skin
Nervous system - the staggers - partial paralysis
Lungs - the chokes - possibly fatal

Question 32

Explain how decompression sickness can be prevented.

Answer 32

Avoid diving then flying in less than the recommended time

During diving make required recompression stops

Question 33

What are the minimum restriction times for diving and flying

Answer 33

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

Question 34

How can decompression sickness be treated.

Answer 34

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.

Question 35

What does the treatment for decompression do?

Answer 35

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.

Question 36

Explain the dangers of flying after diving

Answer 36

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

Question 37

The effects of an explosive decompression on the body

Answer 37

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.

Question 38

The actions that’s must be taken in the event of explosive decompression

Answer 38

Breathe out, Don nearest oxygen mask, Sit down, fasten seatbelt or grasp fixed objects

Question 39

Describe physiology of the circulatory system

Answer 39

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.

Question 40

34.6.6/46.6.4 Partial pressure of oxygen changes as altitude increases

Answer 40

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

Question 41

34.10.24/46.10.24 Time of useful consciousness and things that affect it

Answer 41

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

Question 42

34.10.26/46.10.26 The approximate time of useful consciousness at

Answer 42

(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!!

Question 43

34.10.28/46.10.28 Oxygen Paradox

Answer 43

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.

Question 44

46.10.30 Physiological effects of cabin pressurisation loss at 25,000ft and above (7)

Answer 44

• 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)

Question 45

What happens during slow decompression

Answer 45

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.

Question 46

46.10.32 Actions flight crew must take with high altitude cabin pressurisation failure

Answer 46

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.

Question 47

46.10.34 Principle features of supplemental oxygen systems to assist with in-flight pressurisation emergency

Answer 47

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.