Diving Flashcards
1
Q
Scuba diving
A
Self-contained underwater breathing apparatus
2
Q
Free diving
A
Breath-holding
Spearfishing, photography etc
3
Q
Free diving mechanism
A
Reduced HR
Blood flow and volume is redistributed towards vital organs by means of a reflex vasoconstriction, body cooling
Risk of hypoxic blackout and drowning
4
Q
Competitive apnoea
A
Free diving
Attempt to attain great depths, times or distances on single breaths
11 disciplines, pool (apnoea) and depth (using weights etc)
5
Q
AIDA records- depth
A
253.2m
6
Q
AIDA records- time
A
11 mins 35s
7
Q
AIDA records- distance
A
30m
8
Q
DAN
A
Annual number of breath-hold competitive and non-competitive incident cases captured from 2004 through 2013 (mean±standard deviation) was 65±18 (range 30-82).
Majority fatal incidents (2010-2013: 81% fatal)
9
Q
Scuba diving buoyancy equipment
A
Buoyancy compensator or buoyancy control device (BCD)
Buoyancy controlled by adjusting the volume of air in the jacket
10
Q
Scuba diving breathing equipment- Diving cylinders
A
Usually contain air (mixture 21% )2, 78% N, 1% other gases mainly argon) or pure oxygen or nitrox (mixture of O2 and air)
Regulator mechanism to control gas pressure
Submersible pressure gauges
Open circuit used more commonly (exhausts exhaled air to the environment)- exhale through mouth
11
Q
What happens to vol. of gas in your lungs or BCD jacket as you descend deeper in water
A
It decreases (Boyle’s)
12
Q
What happens to vol. of gas in lungs or BCD jacket as you descend in colder water
A
Drops
charles
13
Q
What happens to gas pressure of cylinder when you enter into cold water?
A
Drops
gay loussac
14
Q
Ideal gas law
A
Pv=nRT
15
Q
Ideal gas law- what is P
A
Absolute pressure
16
Q
Ideal gas law- what is v
A
Volume
17
Q
Ideal gas law- what is N
A
Number of moles
18
Q
Ideal gas law- what is R
A
Universal gas content
19
Q
Ideal gas law- what is T
A
Temperature
20
Q
Boyle’s law
A
P and V inversely related
21
Q
Gay-Lussac’s law
A
P and T directly related
22
Q
Charles law
A
V and T directly related
23
Q
Implications of gas law in diving
A
Temp gets colder –> pressure of cylinder may drop + vol of air in lungs/BCD drops
As pressure increases in deeper diving, vol of air in lungs/BCD drops
More gas will diffuse into tissues as depth of diving increases
24
Q
Dalton’s law
A
Total pressure exerted by a mixture of gases is equal to the sum of pressures that would be exerted by each of the gases if it alone were present and occupied the total volume
PTotal=Pp1+Pp2+…+Ppn
25
Henry's law
The amount of any given gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of the gas that is in contact with the liquid and the solubility coefficient of the gas in the particular liquid
26
Pressure vs depth
As depth increases, gas pressure increases
--> partial pressures of the O2 and N in the breathing air increase
As depth increases, more gas will dissolve into the blood and body tissues
27
For every 33 feet depth in sea water, the pressure increases by
1 bar
28
Nitrogen narcosis
Increased nitrogen into the blood stream can lead to a narcotic feeling at depth
29
How many feet is equivalent to effects of 1 alcoholic drink
Every 50ft (15m)
30
What can divers experience at 150ft (46m)
Alterations in reasoning, memory and response time
Idea fixation
Overconfidence
Calculation errors
31
Nitrogen narcosis physiology
As diver descends and pressure increases, increasing amounts of N dissolve and accumulate in lipid component of tissues
As long as pressure is maintained, regardless of quantity of gas that has dissolved in tissues, gas will remain in solution
32
Nitrogen narcosis ascending
When diver ascends, a lag occurs before saturated tissues start to release nitrogen back in blood
When critical amount of N is dissolved in tissues, ascending too quickly causes dissolved N to return to its gas form while still in blood or tissues, causing bubbles to form
33
Nitrogen narcosis bubbles
If bubbles still in tissues, can cause local problems
If in blood, embolization may result
Further reductions in pressure while flying or ascending to higher altitude also contribute to bubble formation
34
Diving safety
Tables/dive computers used to show relationship between given depth of water + time diver can stay down
Safety stop every 5 metres, and not to ascend at pace more than 10m/min
35
Safety stop every ... metres
5
36
Don't ascend at a pace more than
10 metres/min
37
DCS stands for
Decompression sickness
38
Type I DCS sympoms
Pain (the bends) occurs in most patients (70-85%)
Pruritus, or 'skin bends'
Oedema
Anorexia or excessive fatigue
39
Type I DCS- pain- what joint is most affected
Shoulder
40
Type I DCS- what is pain like
Initially mild
Slowly becomes more intense
Many divers attribute early DCS symptoms to overexertion or a pulled muscle
41
Type II DCS Symptoms categories
Pulmonary
Circulatory
Nervous system involvement
Pain
42
Type II DCS- Pulmonary
Burning
Sub-sternal discomfort on inspiration
Non-productive coughing that can become paroxysmal
Severe respiratory distress (2% of all DCS and can cause death)
43
Type II DCS- Circulatory
Hypovolaemic shock
44
Type II DCS- NS involvement
Low back pain may start within few mins to hours after dive
May progress to paresis, paralysis, paraesthesia, loss of sphincter control, headaches or visual disturbances, dizziness, tunnel vision, and changes in mental status
45
Type II DCS- Pain
Reported in only about 30% of cases
| Because of anatomic complexity of the central and peripheral NS, S+S are variable and diverse
46
Type II DCS Symptom onset
Usually quick
60% within 3 hours and 98% within first 24 hours
Can be delayed as long as 36 hours
Increased risk if diver went on high altitude within 24 hours of a deep dive
47
Arterial Gas Embolization (AGE) physiology
Pulmonary over-pressurization can cause large gas emboli to enter into the pulmonary vein + systemic circulation
gas emboli can lodge in coronary, cerebral, and other systemic arterioles
These gas bubbles continue to expand as ascending pressure increases --> increased severity in clinical signs
48
AGE symptoms and signs
Depend on where emboli travel
49
AGE- coronary artery embolization
Can lead to MI or dysrhythmia
50
AGE- Cerebral artery emboli
Can cause stroke or seizures
51
AGE symptoms occur
Within 10-20 minutes of surfacing (usually)
52
AGE symptoms
Multiple symptoms may be involved
Clinical features may occur suddenly or gradually
Dizziness, headache, profound anxiousness
Unresponsiveness, shock, and seizures
Death
53
AGE vs. Neurological DCS II
Based on suddenness of symptoms
AGE- Any type of dive can cause it, onset is immediate (<10-120 min) + neurologic deficits manifest mainly in brain
DCS- dive must be of sufficient duration to saturate tissues, onset is latent (0-36h) + neurological deficits manifest in spinal cord + brain
54
AGE neurological deficits manifest mainly in
Brain
55
DCS II neurological deficits manifest mainly in
Spinal cord and brain
56
Treatment of AGE + DCS II
Both require re-compression
| Therefore differentiating between them not great importance
57
DCS management
Do not delay HBO therapy
Administer 100% oxygen
Do not put patient in Trendelenburg position
Consider IV fluids if available
Transfer to nearest ED + hyperbaric facility- try to keep all gear to use for clues as to why problems
Transfer to HBO facility even if improvements, as can relapse
If shock- resuscitation
In-water recompression not believed to be safe, but do if in remote areas without reachable HBO chamber support
58
Predisposing factors DCS- Diving factors
Inadequate decompression or surpassing no-decompression limits (includes increased depth + duration of dives, + repeated dives)
Inadequate surface intervals (i.e. failure to decrease accumulated N)
Failure to take recommended safety stops
Flying or going to higher altitude soon (12-24hrs) after diving
Rapid ascent can be due to panic- identify anxiety traits
59
Predisposing factors DCS- individual
```
Obesity (N is lipid soluble)
Fatigue
Age
Poor physical condition
Dehydration
Illness affecting lung or circulatory efficiency
Prior musculoskeletal injury
Smoking
```
60
Dehydration
Study found significant decrease in venous bubble formation with pre-dive hydration
61
Illness affecting lung or circulatory efficiency
Patent foramen ovale
62
Prior musculoskeletal injury
Scar tissue decreases diffusion
63
Predisposing factors DCS- environmental factors
Cold water
Heavy work
Rough sea conditions or poor buoyancy
Heating diving suits
64
Cold water
Vasoconstriction decreases nitrogen offloading
65
Heavy work
Vacuum effect in which tendon use causes gas pockets
66
Heated diving suits
Leads to dehydration
67
Cylinders- Air
```
21% O2
78% N
1% other traces, mainly argon
Safety depth limit about 40m
Max operating depth is 66.2m
```
68
Cylinders- pure O2
Mainly used to speed the shallow decompression stops (military + commercial dives)
Only safe down to depth of 6m before O2 toxicity sets in
69
Cylinders- nitrox
Mixture of O2 and air
Can be used to accelerate in-water decompression stops or decrease risk of decompression sickness
Has shallower max operating depth than air
70
Oxygen toxicity
Harmful effects of breathing molecular O2 at elevated pressures
71
O2 toxicity symptoms
```
Disorientation
Seizures
Breathing problems
Vision changes (retinal detachment)
Death
```
72
O2 toxicity pathophysiology
```
Collapse of alveoli in lungs
Hypoxia
Destruction of cell membrane which can lead to chemical toxicity and haemolysis
Hepatic + retinal damage
Neural toxicity
```
73
Ear barotrauma
Can affect external, middle or inner ear
74
Middle ear barotrauma
Most common being experienced between 10-30% of divers
| Due to insufficient equilibration of middle ear
75
External ear barotrauma
May occur on ascent if high pressure air is trapped in external auditory canal either by tight fitting diving equipment or ear wax
76
Inner ear barotraums
Less common
Can lead to varying degrees of conductive and sensori-neural hearing loss as well as vertigo and auditory hypersensitivity
77
Pulmonary barotrauma
Usually caused by breath holding on ascent
Compressed gas in lungs expands as ambient pressure decreases, causing lungs to over expand and rupture unless diver breathes out
No associated pain
78
Buoyancy
An object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object
Maintaining neutral buoyancy is key to easy diving
79
Adjust buoyancy before dive
Weights
wetsuit
water temp
80
Adjust buoyancy during dive
BCD
Exhale/inhale
Swimming position
81
Too buoyant
Harder work to stay done
| can't do safety stop on ascent
82
Too heavy
Difficult adjusting buoyancy at different depths
| Constantly having to add or remove air using BCD
83
Divers Alert Network
169 deaths involving recreational scuba diving during 2016
Diving fatalities are a global hazard, occurring in tropical seas and colder waters alike.
In 2016, 4 out of 5 decedents were male-similar to previous years
In 2016 the leading cause of death was drowning, and the leading disabling injury that led to death was cardiovascular-related problems
84
Mortality and morbidity
Fewer than 1% of divers experience DCS
Most common cause of dive-related death is drowning (80%)
Asphyxia (due to entrapment and insufficient gases): common cause of death
85
AGE death causes
Overwhelmingly caused by emergency assent with insufficient gases as key contributing factor
For those older than 40, association with CV disease
86
AGE- HBO treatment
Mortality + morbidity directly related to HBO treatment
If recompression within HBO occurs within 5 mins, death rate 5% with little residual morbidity in survivors
If delayed 5 hours, mortality increases o 10% with residual symptoms in half the survivors
87
How many deaths
Fewer than 2 deaths per million recreational scuba divers
88
Absolute contraindictions
Epilepsy controlled by medication
Unexplained syncopal episodes
Stroke and TIA
Intracranial aneurysm, arterial-venous malformation or tumour
Progressive neurological problems- severe MS, Parkinson's, MND
Severe heart disease
Post coronary bypass surgery with violation of pleural spaces
Lung problems
Blood disorders
Pregnancy
Severe mental health problems + drug abuse
Inability to equalize pressure in middle ear by auto-inflation or acute perforation of the tympanic membrane
89
Severe heart disease
Congenital heart defects
Severe valve problems
Severe ischaemic heart disease especially when not fully controlled
Post MI with LV dysfunction
Congestive HF
Dependence on medication to control dysrhythmias
90
Lung problems
```
Bullae (large air sacs)
Severe asthma
Chronic obstructive pulmonary disease
Certain types of lung surgery
Past history of spontaneous pneumothorax
```
91
Blood disorders
Severe bleeding disorders e.g. haemophilia
| Blood cancers e.g. leukaemia
92
Temporary contraindications
Any illness requiring drug treatment may constitute a temporary disqualification if either the illness or drug may compromise diving safety
Sedatives, tranquilisers, antidepressants, antihistamines, steroids
93
Saturation diving
Diving technique that allows divers to reduce risk of decompression sickness (the bends) when work at great depth for long periods of time
Divers live in pressurized environment
May be maintained for up to several weeks
Diver's tissues absorb max partial pressure of breathing gas possible for that depth + decompressed to surface pressure only once, at end of their tour of duty
Limit no. of decompressions, so risk of decompression sickness v reduced
94
Saturation diving record
Scientific dive in 1992
701m
43 days
95
Saturation diving risk
Exposure to high pressure can have negative effects on NS and risk of osteonecrosis
96
Atmospheric diving suit
Maintains internal pressure 1 atmosphere
Used for v deep dives up to 700m for many hours
Eliminates majority of physiological disorders associated with deep diving
Divers don't need to decompress, no need for special gas mixtures, no danger decompression sickness or nitrogen narcosis
97
ADS used by US navy since
2006
