Aeromedical Flashcards
What are the 5 main layers of the atmosphere listed in order starting from the ground?
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Note There are other zones contained within these main layers that are not listed.
What factors lead to the vertical profile of the atmosphere?
Solar thermal radiation results in expansion of gas molecules, and expansion of the space filled by the atmosphere. The gravitational pull of the earth opposes this expansion of molecules, pulling them toward the earths surface.
When ascending through the troposphere, how quickly does the temperature drop?
The temperature drops with ascent approx -2c per every 1000 feet of elevation.
Where is the ozone layer
The ozone layer is in the stratosphere.
Briefly describe the stratosphere.
This is the layer directly above the troposphere and extends up about 50km. The temperature of the upper stratosphere remains constant at about -55c. There is no water vapor. Apparently swans, cranes, and vultures can fly this high.
Briefly describe the troposphere
The first layer of the atmosphere that is in contact with the earth. It extends to 50-60k feet at the equator and 25-30k feet at the poles. Water vapour reduces with ascent. Weather and turbulence are present. Transition to stratosphere is called the tropopause (jet streams). Temp drops about -2c per 1000 feet ascent.
Where do unpressurized aircraft fly?
Unpressurized aircraft fly in the troposphere, and generally within the first 10,000 feet of this layer.
What is an isobaric system?
It is what is used in most military and civilian aircraft to maintain
aircraft pressurization. It maintains a constant cabin pressure, while the atmospheric pressure falls. It is limited by the structural integrity of the aircraft to withstand a given differential pressure between ambient external pressure and that of the cabin.
Generally speaking, where in the atmosphere would a piston propeller aircraft, turbo prop aircraft, and jet fixed wing aircraft fly?
Most piston propeller aircraft will remain in the lower regions of the
troposphere. Turbo props will fly in the upper reaches of the troposphere, and occasionally may extend into the stratosphere. Jet fixed wing aircraft will fly in the upper reaches of the troposphere and commonly extend into the stratosphere.
What are the 4 basic variables of the gas laws?
- Temperature
- Pressure
- Volume
- Relative mass of gas or number of molecules
Boyle’s Law
The volume of a gas is inversely proportional to its pressure, temperature remaining constant.
Dalton’s Law
The total pressure of a gaseous mixture is equal to the sum of the partial pressures of the individual gases in the mixture. PO2 = 20.95 (21%) x 760 mmHg = 159.6
Charles’ Law
The volume of gas is proportional to its absolute temperature, when pressure and mass is constant.
Gay-Lussac’s Law
The pressure of gases is directly proportional to absolute temperature, for a constant amount of gas, when the volume remains constant.
Henry’s Law
The amount of gas that is dissolved in a solution and remains in solution is directly related to the pressure of the gas over the solution.
Graham’s Law
The rate of diffusion of a gas through a liquid medium is directly related to the solubility of the gas and is inversely proportional to the square root of its density.
What happens with a sudden loss of cabin pressure?
- Rapid temp drop
- Fogging due to rapid cooling of air
- Explosion or swish of air occurs d/t collision of two air masses
- Debris, dust, and unsecured items will often fly about
- Gases expend in body cavities
The pressure environment that surrounds the earth can be divided into four zones. What are they?
Physiologic zone – Sea level up to 10,000’
Physiologically deficient zone - 10,000 to 50,000’
Space equivalent zone: 50,000 to 250,000’
Space - Beyond 250,000’
Time of Useful Consciousness (TUC)
18,000’ or below: 30 minutes
25,000’: 3 - 5min normal, or 1.5 - 2.5min with rapid decompression
30,000’: 90sec normal, or 30 - 45sec with rapid decompression
35,000’: 30 - 60sec normal, or 15 - 30sec with rapid decompression
40,000 or above: 15sec normal, or 7 - 10sec with rapid decompression
There is a rapid decompression on your aircraft… what are you going to do?
All AMC need to apply O2 to their face and ensure the pilots have their masks on. Then ensure the patient has oxygen on. A rapid descent will bring the aircraft to a flight alt that is physiologically safe. Other equipment that will require attention during a rapid decompression would include any equipment with gas filled chambers.. ie ETT cuffs, Pressure bags, MAST, certain ventilators, NG tubes etc
Hypoxia
A general term that describes the state of oxygen deficiency in the tissues. It refers to a decrease in tissue oxygen or an oxygen supply inadequate to meet tissue needs. Hypoxia disrupts the intracellular oxidative process and impairs cellular function.
Hypoxemia
Refers to a decrease in arterial blood oxygen tension (PaO2). A normal
PaO2 doesn’t guarantee adequate tissue oxygenation conversely a low PaO2 may not indicate tissue hypoxia and may be clinically acceptable.
Hypercapnia
Refers to an increased amount of carbon dioxide in the blood.
Four Stages of Hypoxia (based on altitude)
- Indifferent stage
- Compensatory stage
- Disturbance stage
- Critical stage
Briefly describe the Indifferent stage of hypoxia
The physiologic zone for this stage starts at sea level and extends to 10 000’. In this stage the body reacts to the lessened availability of oxygen in the air with a slight increase in heart rate and ventilation. Night vision deterioration occurs at 5000’
Briefly describe the compensatory stage of hypoxia
The second stage of hypoxia which occurs from 10,000 to 15,000’.
In this stage the body attempts to protect itself against hypoxia by increasing BP, HR and depth/rate of respirations. Efficiency and performance of tasks that require mental alertness become impaired.
Briefly describe the disturbance stage of hypoxia.
This is the third stage of hypoxia which occurs between 15,000 and 20,000’. It is characterized by dizziness, sleepiness, tunnel vision and cyanosis. Thinking becomes slowed and muscle coordination decreases.
Briefly describe the critical stage of hypoxia.
This is the fourth stage of hypoxia and occurs between 20,000 and 30,000’. It features marked mental confusion and incapacitation followed by unconsciousness usually within a few minutes.
List the 4 main types of hypoxia
- Hypoxic hypoxia
- Hypemic hypoxia
- Stagnant hypoxia
- Histotoxic hypoxia
Briefly describe Hypoxic hypoxia
Deficiency in alveolar oxygen exchange. Causes include breathing air at reduced barometric pressure, resp arrest, severe asthma, malfunctioning oxygen delivery equipment. It is also referred to as altitude hypoxia because in this case its primary cause is exposure to low barometric pressure (so low PaO2). The blood oxygen sat which is 98% at sea level is reduced to 87% at 10 000’ and 60% at 22000’.
Briefly describe hypemic hypoxia
Decrease in oxygen carrying capacity of the blood. Even with normal ventilation and diffusion, cellular hypoxia can occur if the rate of delivery of oxygen doesn’t satisfy metabolic requirements. Think anemia, hemorrhage, hgb abnormalities, or intake of chemicals. Remember that CO binds to hgb 200 times more readily than O2 and its present in aircraft fumes.
Briefly describe stagnant hypoxia
Occurs when conditions result in reduced total cardiac output, pooling of blood with certain regions of the body, decreased blood flow to tissues or restriction of blood flow. Causes include heart failure, shock, continuous positive pressure ventilation, or PE. A reduction in regional or local blood flow may be caused by extremes of enviro temps, postural changes like prolonged sitting, bed rest, tourniquets, hyperventilation, embolism or CVAs.
Briefly describe histotoxic hypoxia
Occurs when metabolic disorders or poisoning of the cytochrome oxidase
enzyme results in a cells inability to use molecular oxygen. Causes include respiratory enzyme poisoning and intake of carbon monoxide, cyanide, or alcohol.
The primary treatment of hypoxia for any patient transported by air is?
PREVENTION - The transport team must remember that the patient’s condition is already compromised and that the stresses related to transport increase the risk of patient hypoxia unless the transport team continuously monitors the patient and accurately anticipates the oxygen needs of the patient during transport.
Stressors of Flight
Ghostban
- Gravitational Forces
- Humidity/hyperventilation
- Oxygen
- Shakes/Vibration
- Temperature
- Barometric Pressure
- Atmosphere
- Noise
Why is vibration a significant stressor of flight?
It increases metabolic rate, increases vasoconstriction, and overrides the body’s ability to cool itself, delaying cooling in hyperthermia, decreased ability to sweat, joint stiffness, headache nausea. The response to whole body vibration is an increase in muscle activity to maintain posture and to reduce the resonant amplification of the body structures. This response is reflected in an increase in metabolic rate and a redistribution of blood flow with peripheral vasoconstriction. The increase in metabolic rate during vibrations is comparable with that seen in gentle exercise. Respirations are increased to achieve the necessary elimination of carbon dioxide.
Dehydration during flight is influenced by?
- Relative humidity of aircraft cabin
- Cardiovascular status
- Hydration status of crew or patient pre flight which is affected by age, diet, and general health status
How many G’s can turbulence produce?
Turbulence can produce 1.5 to 2Gs of vertical acceleration and at high speeds up to 3 Gs.
How many Gs can people tolerate?
People have tolerated acceleration forces of 40G without injury, but protection is generally provided to a max of 25G’s.
Other than altittude, what else can affect barometic pressure?
Temperature and Humidity
How does moisture effect barometric pressure?
Water vapor is only 63% as heavy as ambient air. As the water vapor content of air increases barometric pressure falls.
How does temperature effect barometric pressure during flight?
The temp experienced by AMC normally changes from -45 to +45 C, representing a 31% change in gas volume.
Impact of noise include? (think stressors of flight)
- Distracting
- Contributes to fatigue and irritation
- Reduced ability to concentrate
- Interference with communications
- Interference with patient assessment
- Ear damage
Safe zones for noise intensity?
0-90 decibels
Frequency is the speed that soundwaves travel. What is it expressed in?
Hertz
Briefly describe Barotitis media. Why is there a difference between ascent and descent?
During ascent, air in the middle ear cavity expands but normally vents into the throat through the eustachian tub. However, during descent, the gas in the middle ear shrinks in size as external pressure increases. The eustachian tube does not allow for gas to readily enter the middle ear in order to equalize the pressure and so it can become quite painful.
What are some things that can be done to reduce pressure in the middle ear?
Valsalva maneuver, yawning, swallowing, moving the lower jaw, topical admin of vasoconstrictors, or use of the bag valve mask. Infants can bottle feed but watch for gastric distention and gas.
Barosinusitis
Inflammation of the soft tissues in the sinuses due to the positive and negative pressure changes that occur as the result of changes in barometric pressure. S/S include: Dull to sharp pain below one or both eyes or check bones, lacrimation, and epistaxis.
How can you manage barosinusitis?
- Decongestants
- Topical vasoconstrictors
- Utilize Valsalva on descent
- Avoid flying with an URTI
- Cabin altitude restriction and slow descent
Barodontalgia
Cavities in teeth or recent fillings may be sensitive to gas expansion during ascent. Tooth pain can result.
How can you manage barodontalgia?
- Preventative measures (dental care)
- Slow ascent
- Restrict flying for at least 24hrs following dental work
When was the first air medivac?
During the Prussian siege of Paris in 1870. The wounded were evacuated by hot air balloon.
Who was Marie Marvingt?
The first recorded flight nurse and probably the true founder of flight nursing. She was the most decorated woman in the history of France. She
was a surgical nurse and a pioneering aviator. In 1910 she designed the first air ambulance capable of carrying a stretcher. Between the two world wars, she worked as a medical officer with French forces in North Africa. While in Morocco, she invented metal skis and suggested their use on airplanes that landed in the sand
During the Korean war the corpsman evolved into what?
The field medic, whose rapid care and interventions included packaging the patient for helicopter evacuation.
What was used for medivac in the Vietnam war?
The medics worked out of helicopters to provide rapid transport and immediate care.
Which organization sets and enforces all airport safety and security standards, certifies and regulates all airports, and ensures that Canada’s civil aircraft conform to nation and international standards?
Transport Canada
Who is responsible for aircraft incident investigation in Canada?
Transportation safety board of Canada
What are the two main types of helicopters used for medivac in Canada?
Single engine and twin engine.
In a twin engine helicopter, what happens if you lose power to one engine?
When one engine goes out, the aircraft loses 80% of it’s power and so the pilot would have to make an emergency landing.
Fuselage
The fuselage is one of the major aircraft components with its long hollow tube that’s also known as the body of the airplane, which holds the passengers along with cargo. This area includes the cockpit, so the pilots are in the front of the fuselage. Despite there being different types of fuselages, they all connect the major parts of an airplane together.
Wings
Not surprisingly, the wings, also commonly known as foils, are aircraft parts that are imperative for flight. The airflow over the wings is what generates most of the lifting force necessary for flight. Along with the large wings that stem from the middle of the fuselage, the wings also include two smaller ones at the back of most aircraft, at the tail.
Empennage
The empennage is the tail end of the aircraft. It helps with the stability of the plane and has two main components called the rudder and the elevator. The rudder helps the aircraft steer from right to left, and the elevator helps with the up and down movement.
Power Plant
The power plant of an airplane structure includes the engine and the propeller. The engine itself is a complicated system comprised of many smaller parts like cylinders, fans, and pistons. Together, these aircraft engine parts work to generate the power or thrust of an aircraft.
Landing Gear
You cannot have a safe plane without having the landing gear. Not only are these parts imperative in order to land, but the landing gear is also used to help an aircraft take-off and taxi. The landing gear includes shock absorbers for a smooth landing and takeoff as well as the wheels on the plane.
What is meant by the gross weight of an aircraft?
The maximum total weight allowable for a safe flight.
What is meant by the operational weight of an aircraft?
The weight of the aircraft loaded with fuel, pilots and passengers.
Visual Flight Rules
Simply means that the aircraft is intended to operate in visual meteorological conditions (VMC, i.e. nice and clear weather). Clouds, heavy precipitation, low visibility, and otherwise adverse weather conditions should be avoided under VFR. Most general aviation flying and flight training occurs in visual meteorological conditions
Instrument Flight Rules
Implies that the flight may operate in instrument meteorological conditions (IMC, meaning cloudy or otherwise adverse weather conditions). However, many aircraft may operate under IFR while completing the entirety of the flight in VMC due to the efficiency provided by IFR flying as well as the safety of continuing to avoid bad weather. Just because you can fly in the clouds or less than acceptable weather under IFR doesn’t mean you should.
EMERGENCY LOCATOR TRANSMITTER (ELT)
Equipment that broadcasts distinctive signals on designated frequencies and may be automatically activated by impact or be manually activated.
FIXED VS ROTARY WING
Fixed wing is less susceptible to weather constraints with a decreased response time to patients with distances greater than 160km. Fixed Wing can travel greater distances faster.
What is the purpose of flaps. Where are they located.
Their purpose is to increase the wing surface area, providing additional lift
for takeoff and landing. Additional lift becomes necessary as the speed of the aircraft falls below normal cruising speeds. Flaps are located on the trailing portion of each wing, inboard of the ailerons.
What is the difference in movement between ailerons and flaps?
Flaps move in unison, where as ailerons move in opposition to one another.
What is the purpose of ailerons? Where are they located?
They are located distal to the flaps and are used to control the roll rate by moving in opposition to one another.
Flight deck
Cockpit
Which side is port? What colour is the port side light?
Port is the left side of the plane as viewed from the captains seat. The light on the port side is red.
Which side is starboard? What colour is the light on the starboard side?
Starboard is the right side of the aircraft as viewed from the captain’s seat. The light on the starboard side is green.
Where is the exterior white light located on an aircraft?
At the tail.
What are the forces of flight?
- Lift
- Thrust
- Drag
- Gravity
Lift opposes gravity and thrust opposes drag.
All disciplines should have ____ hours of uninterrupted rest before the beginning of a shift.
10 hours
PRE MISSION PLANNING
- Shift prep
- Vehicle inspection
- Flight briefings
- Team rest
- Weather check
- Risk analysis matrix
- Flight authorization
- Decline missions
- Vehicle walk around
