GUE - Fundamentals - Decompression Flashcards
Why does the body absorb inert gasses (on gas) during the decent and bottom phases of a dive and release inert gasses (off gas) when we ascend?
Because of the changing pressure gradient or tissue tension between the gas and the tissues of the body.
Why does oxygen not cause decompression issues?
Because it is used by the body for metabolism.
What determines the rate and amount of inert gasses absorbed by the body? (Select all of the correct answers).
The pressure gradient (differential pressure) or depth in diving terms.
The tissue itself.
The amount of blood perfusion through the tissue.
The amount of time the body is under pressure.
What happens when a diver ascends from a decompression perspective?
The ambient pressure reduces meaning that the gas pressure or tissue tension is greater than that of the gas breathed so the body off gasses.
What happens if the diver ascends too quickly?
Bubbles can form that then present a possible decompression sickness problem.
What causes decompression sickness?
The presence of bubbles, which causes physical tissue damage and blocks the flow of blood around the body.
Which of the following are symptoms of decompression sickness? (select all correct answers).
Muscle & Joint Pain
Itching
Numbness
Tingling.
Paralysis
Breathing Problems
Unconsciousness.
How do we as divers reduce the likelihood of a decompression sickness problem whilst diving?
By controlling our ascent.
What is the term used to describe the ascent profile used by GUE divers when conducting recreational dives?
Minimum decompression ascent.
What ascent rate should a diver use from the maximum depth of a minimum decompression dive up to half the maximum depth? e.g. for a 30m dive, during the ascent from 30m to 15m.
9 meters per minute.
What ascent rate should a diver use from 50 percent of the maximum depth up to the surface?
3 meters per minute.
When ascending at 3 meters per minute how is the ascent broken up to make it more manageable?
The diver should use approx 30 seconds to move the 3 meter distance and then 30 seconds to stabilise before moving again.
How do GUE divers determine how long they can stay at a given depth during recreational diving?
Either using decompression software / tables or through the rule of thumb provided by GUE for dives using 32 percent nitro in the 30m range.
What does staying within the Minimum Decompression Limit allow a diver to do?
Make a controlled, minimum decompression, ascent to the surface without the need for mandatory decompression stops.
Which of the following are true of the GUE rule of thumb for minimum decompression limits? (Select all the correct answers).
A set point of 30 minutes at 30m is used.
For every 3m shallower than 30m an extra 10 minutes can be added to the 30 minute minimum decompression limit. i.e at 27m the MDL is 40 minutes.
The rule of thumb assumes that the diver will make a minimum decompression ascent once the minimum decompression limit is reached.
