- Graham found that the rates at which gases diffuse is inversely proportional to the square root of their densities.
- The heavier the weight (Molar Mass) the slower the gas diffuses.
- (Inhaling Heium, a light gas, moves faster than room air making the voice higher in pitch. A heavier gas would make the voice lower.
- The amount of a gas dissolved at equilibrium in a given quantity of a liquid is proportional to the pressure of the gas in contact with the liquid
- Opening a can of soda= when opened pressure equalizes with the atmosphere. Pressure becomes less than gas disolved and gas is released.
- In transport think the bends, also Nitrogen release from fat tissues during ascent.
- Assuming constant pressure, temperature will affect the volume of a gas.
- Heat expand
- cool contract
Total pressure of a gas mixture is the total of the pressures of each type of gas in the mixture.
at constant temperature for a fixed mass, the absolute pressure and the volume of a gas are inversely proportional
- P1V1 = P2V2
- Think of a hellium balloon. If you release it at sea level it as a certain shape. As it rises the outside pressure becomes less, and the balloon expands.....The higher you go the more trapped gas tires to expand. Think about sinuses, a chest tube should bubble more on ascent, etc...
- Key Points:Volume and moles of gas are constant
- Pressure and temperature are directly proportional to each other
Application: Heating an oxygen cylinder will increase pressure (Closed system)
A sinus infection may cause pain on:
Ascent: Trapped gases expand on ascent and can not escape causing pain/pressure
At 760 torr 50% FiO2 would be____mm Hg
P torr X gas concentration = Partial Pressure
Altitude above sea level
Altitude above the ground
ELT stands for:
Typical G forces to trigger
Emergency Locator Transmitter
- 121.5 Civil
- 243 Military
- New Sat system: 406 Hz
4 G impact to device to trigger
greater changes in atmospheric pressure occur nearest
Anticipated Temperature change for each 100 meters of ascent
Decrease 1 degree C
- 0 to 10,000' MSL
- Most humans can function normalls
Physilogic Deficient Zone
- 10,000 to 50,000'
- Supportive or protective suppliments needed to survive
- -Causes hypoxic hypoxia
The weight of air in a 1" coloum that goes from sea level to top of atmospere at 59 degrees F.. 14.7 lbs = 760 torr.
Decompression that occurs in < 0.1 second.
This is a lack of oxygen as a result of a high altitude (decreased oxygen pressure)
malfunction of the circulatory system resulting in a decrease in blood flow. Causes include high g-loading, exposure to extreme hot or cold temperatures, or by shock
This form results from tissue poisoning such as from alcohol, narcotics, and certain poisons
Inability to carry adequate oxygen. (low H & H). Effects greatly affected by decreased atomspheric partial pressures (altitude)
Time of useful conciousness
- amount of time an individual is able to perform flying duties efficiently in an environment of inadequate oxygen supply
- FL 150 30 min or more
- FL180 20 to 30 min
- FL 250 3 to 6 min,
- FL 2802.5 to 3 mins
- FL 3001 to 3 mins
- FL 350 30 sec to 60 sec
- FL 400 15 to 20 sec
- FL 430 9 to 15 sec
- FL 500 and above 6 to 9 sec
The only adverse effect is on dark adaptation (Night vision)
Physiological compensations provide some defense against hypoxia
- physiological compensations do not provide adequate oxygen for the tissues
- Symptoms may include fatigue, lassitude,somnolence , dizziness, headache, breathlessness, and euphoria. Both the peripheral and central vision are impaired and visual acuity is diminished. Extraocular muscles are weak and incoordinate– Touch and pain are diminished or lost. Hearing is one of the last senses to be impaired or lost. Intellectual impairment is an early sign Thinking is slow. Calculations are unreliable. .
In the critical stage consciousness is lost. Death follows shortly
Calculation for FiO2 with pressure changes
- P1 (Bara 1) X FiO2/ P2 (Bara2)= FiO2
- Starting 700 torr x 0.25O2 /destination 650 torr=0.27 FiO2
Attitude that affects nights vision in healthy person
Night Vision in the eye
rods in periphery of the retina
Shut down procedure post crash
Throttle,fuel,Battery, rotor brake,oxygen
Stressors of Flight
- D rugs
- E xhaustion
- A lcohol
- T obacco
- H ypoglycemia
Maintained during all critical phases of flight