Trapped Gas and Decompression Sickness Flashcards
What are the 2 aircraft pressurization techniques? Give an aircraft for both
Isobaric Control (constant value over altitudes, C-17)
Differential Control (>23,000 ft 5 psid difference, Oxygen mask at all times, CF-18)
What cabin altitude is maintained by most transport and commercial aircraft?
6,000-8,000ft
What is one advantage and disadvantage of aircraft pressurization?
Pro: Reduce risk of hypoxia/DCS
Con: Increased weight reduces efficiency
What are two types of decompression?
Rapid (loud, 2-15 seconds, compounds hypoxia effect)
Slow (insidious, difficult to notice)
What is Boyle’s Law?
Volume of a gas is inversely proportional to pressure (balloon becomes bigger as we rise in altitude, less pressure means more gas moves around)
What are 3 factors determining decompression rate?
Cabin volume (large cabin takes longer)
Orifice area (bigger hole, faster decompression)
Pressure ratio (between cabin and outside air)
What are 4 physical indications of decompression?
Loud noise
Drop in temperature
Objects moving around, may depart
Fog
Rapid Decompression can shorten EPT by _________
1/3 to 1/2 (so 3-5 mins can suddenly become ~1-2)
Why is slow decompression so dangerous?
It is insidious
What are 5 areas in the body affected by Trapped Gas?
Gastrointestinal
Ears
Sinuses
Teeth
Lungs
If you experience pain on descent, what maneuver can you do?
Valsalva manuever
If you experience pain on ascent, what maneuver should you NOT do?
Valsalva maneuver
What are the 3 maneuvers?
Valsalva (most effective), Toynbee, Frenzel
What is the Valsava maneuver?
Pinch your nose and try to blow through it (with HA/LP mask, close right port and cough)
What law governs Decompression Sickness?
Henry’s Law
What is Henry’s Law?
Amount of gas in a solution varies with partial pressure (opening a carbonated beverage, the gases get excited and exit, making a hissing sound)
Are Trapped Gas and DCS the same thing?
No, Trapped Gas is gas stuck inside (compression) whereas DCS is gas unable to leave (forming nitrogen bubbles in body)
What is the most common symptom of DCS?
The Bends, 80%, affects joint or muscle pain
What factors affect DCS?
- Altitude (18,000 ft)
- Level of activity (moving around)
- Exposure time
What are prevantative measures to DCS
- Denitrogenation (Pre-breathe, have 100% O2 for a while)
- Aircraft pressurization
T or F: If you experience DCS, any airfield is good to land at
False, land at the nearest airfield with a Hyperbaric Treatment chamber
What are 3 ways to treat DCS?
- Descend as soon as practical
- 100% Oxygen (stay on)
- Hyperbaric treatment
