Advanced Nitrox Chapter 1-4 Flashcards
What % of gas exchange occurs in lower 1/3 of lungs?
70%
What is diaphragmatically initiated breathing?
‘ideal breathing’
Pull diaphragm down and away - pulls gas into lower lungs
Fill lungs to comfortably full
Pause and exhale, tongue to roof of mouth - exhalation should last longer than inhalation
Fill lungs from bottom and empty from top
What fundamental skills should you master?
Buoyancy, swimming, trim and breathing
What is the ideal swimming technique (working position)?
Don’t use hands
Allow time for glide after each kick
Use fins to make turns
Horizontal in water with slight arch to back so you can see forward, with knees slightly bent
When should you deviate from ideal breathing?
Using a rebreather - need shorter cycles
When correcting buoyancy - may need to cycle breathe quickly to keep lung volume high if suddenly descending
What is the ideal working position on descent?
Keep slightly negative
Angle head downwards
Planing of body will help with forward movement
Describe O2
Tasteless, odourless gas
Supports combustion
Diatomic molecule
How long can we live without O2?
4-6 minutes
Describe Boyle’s law
Inverse relationship between pressure and volume when temperature is constant
During descent, as a diver goes deeper, more gas is needed, volume gets smaller
Golden rule of diving (never hold breath) is related to Boyle’s law
Describe Dalton’s law
Each gas in a mixture will have a pressure that is directly related to its fraction in the mixture
Partial pressure of a gas is equal to its fraction of the total pressure of gas
What do we use Boyle’s law for?
Calculating pressure at any depth, amount of gas consumed at depth and how much the volume will increase by if they ascend from one depth to another
What do we use Dalton’s law for?
Calculating maximum operating depth, best mix and partial pressure calculations
Gas blending calculations
How much of each breathing gas a diver absorbs
What is EAD?
Equivalent Air Depth
Way for a diver to use any air table to calculate dive profiles
Dive profiles are linked to partial pressure of inert gases a diver breathes throughout dive
Increased O2 in mix reduces inert gas absorbed so the amount of nitrogen absorbed is the same as with air at a shallower depth
What is a hypoxic mix?
Mix with less than 0.21 ATA of oxygen
What low levels of oxygen become dangerous?
- 16 = hazardous
0. 12 = fatal
What does anoxic mean?
Gas absent mix
Why is the risk of hypoxia increased in shallow water?
Risk in CCR if oxygen is not being added to loop
Risk increased in shallow water as ppO2 can drop quickly
Can be accelerated during ascents due to drop in ppO2 caused by ascent
When must a diver track their oxygen exposure?
If they are exposed to over 0.5 ATA
Must track for each dive and for multiple dives through consecutive days
Why are you more at risk of oxygen toxicity in technical diving?
Exposure from air poses risk due to extended exposures and use of decompression gases
What are the 2 types of oxygen toxicity?
Short term high dose exposure
Long term lower dose exposure
Describe short term high dose exposure
Risk of dramatic problem - CNS toxicity
Tracked as a percentage of the allowed dose for each dive and the total of each day of diving