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BSAC Ocean diver UPDATED ACTUAL Questions and CORRECT Answers
Elected commitee Diving officer Training officer Chairperson Treasurer Secretary Equipment officer Branches vs BSAC centres Branches = local club (around 1000 branches around UK and overseas), BSAC centre are training centres i.e. professional diving schools BSAC organisation structure BSAC President, BSAC Council, National Diving Committee, Regional Coaching Team - BSAC council made up of elected members who manage BSAC for members - NDC members appointed for expertise - all unpaid volunteers Ocean diver aim Dive in open water to 20m under supervision of a dive manager in controlled conditions. Discovery diver aim 12m depth under direct in water supervision of a dive leader BSAC council committee that manages bsac on behalf of the members Atmospheric pressure Weight of 1 cm square column of air is 1 kg at sea level - - i.e. 1 bar at sea level Water pressure Water column with area of 1cm2 exerts downwards pressure of 1 bar for every 10 metres How to measure water pressure Depth gauges, gives reading in metres
10m water pressure and total pressure is 1 bar water pressure and 1 bar atmospheric pressure = 2 bar total pressure 20m water pressure and total pressure is 2 bar water pressure and 1 bar atmospheric pressure = 3 bar total pressure Effect of pressure on air spaces 2 bar, volume of air is halved. 3 bar reduces to 1 third original volume. 4 bar reduces to one quarter original volume Body water content 80 per cent Mask Rigid mask frame Tempered glass Flexible seal of silicone rubber Wash your mask in fresh water after each dive - avoid drying in direct sun as can affect flexibility of silicone rubber Fins Either shoe fin with foot pocket (in warm conditions) or strap fin (over boots, with strap or spring to keep in place) - wash in fresh water and dry standing on food pocket end SCUBA acronym self contained underwater breathing apparatus Scuba equipment Cylinder Buoyancy Compensator Regulator Cylinder working pressures 232/300 bar Cylinder material Aluminium/steel Must conform to PRESSURE EQUIPMENT DIRECTIVE (bears the CE mark) Type of gas it contains will be written on it SCUBA cylinder testing Visual check every 2.5 years Hydrostatic test every 5 years Cylinder care Wash in fresh water Store cylinder upright Nitrox 32 mix/Nitrogen 36 mix/air 32 - 32% oxygen and 68% nitrogen 36 - 36% O and 64% N Air - 21% O and 79% N Marking - WC how many litres of water the cylinder could hold WP or CP Working pressure - 232 bar or 300 bar TP Test pressure - used during hydraulic test CP Charging pressure
Buoyancy Neutral = In equilibrium with surrounding water - weightless state - need adjustment throughout, reduces physical effort Positive = when diver is too light, positive buoyancy and ensuing struggle to remain below water is physically tiring - being too light risks the possible over expansion of lungs Negative = too heavy - tiring - damage marine life and equipment - risk descending below safe depths Buoyancy in practice Input air into BC while descending as air compresses reducing buoyancy - remove gas while ascending to equalise buoyancy - Body temperature control Core body temperature - consists of main body arease g.. brain, chest organs and abdomen - surrounded by peripheral limbs skin and muscles - peripheral subject to greater variation - heat loss due to cool environment can cause reduced blood supply to periphery - can feel numb - muscles contract i.e. shiver - can lead to hypothermia
- Water conducts heat 25 times faster than air - need to insulate - more than 21 okay with minimal insulation - between 20 and 10 degrees wet or semi drysuit required at minimum - below 10 drysuit strongly recommended Wet/drysuits Wetsuits made of neoprene, as are hoods - drysuits can be made of neoprene or compressed neoprene and membrane - fit needs to allow for movement - drysuits use latex, neoprene or silicone seals at neck and wrists - waterproof entryzip Maintain drysuit = wash suit with fresh water after every dive and dry - mild disinfectant inside - use padded hanger - chalk on seals and wax on zips - leave zips open for storage Two vital systems Respiratory and circulatory - aid metabolic processes and carry gases and waste products around body - lungs transfer oxygen to blo od and carbon dioxide to expelled gas During breathing diaphragm flattens and muscles lift ribs up and out - increases lung volume and draws in gas - as inhale, should feel movement - inhaled air on land made up of 21 percent oxygen and 79 percent nitrogen - exhaled air contains 17 percent oxygen
- nitrogen stays at 79 - exhaled air contains 4 percent carbon dioxide therefore Vital capacity =Maximum usable lung volume - four and a half litres - normal quiet breathing uses only around half a litre (tidal volume) - lungs always retain air, called residual volume which is one and a half litres Describe gas exchange and skip breathing Air passes from airway into bronchi - enters lung and subdivides into bronchioles and alveoli - large surface area for gas exchange - on inhalation the alveoli contain oxygen at a higher concentration than blood, diffuses into blood, carbon dioxide diffuses into air - stimulus to breathe comes from high carbon dioxide levels
- Skip breathing (i.e. skipping breaths) can result in carbon dioxide building up in the body
Describe circulation transfers oxygen and carbon dioxide between cells and lungs Breathing rate (^) Greater physical demand = more oxygen required - higher levels of CO2 also increase breathing rate - stress or nervousness can increase breathing rate - results in more gas being used - must montior use of gas Fit to dive Exhaustion = inability to meet physical demands - beneficial to maintain fitness - underwater work caused by hard finning rapidly cause elevated breathing rates - cold water can reduce ability to function underwater - no drinking night before - also diving when unwell can increase breathing rate, dehydration risk and loss of concentration - colds can prevent equalisation of pressure in ears - need to be well rested and fit to dive - need to assess fitness and avoid being pressured What airspaces in body can be affected by diving Flexible air space - middle ear, lungs, gut Rigid - sinuses and breathing airways - also mask airspace (breath to avoid mask squeeze) How to equalize pressure in ears (^) open eustachian tube e.g. by performing valsalva maneuver by breathing out against pinched nose - if ears can't clear should ascend or abort - colds can prevent equalisation due to mucus congestion - tight hood can cause pressure in ear canal - do not wear ear plugs Sinuses (^) Hollows in bones - normally equalises - can fill with mucus - hence do not dive with cold or congestion Nitrogen absorption - Increasing pressure can result in increased absorpotion of gases
- At surface body is in equilibrium with nitrogen in atmosphere
- On dive increase in ambient pressures results in more nitrogen dissolving (nitrogen on gassing) - going deeper or staying under for longer increases on gassing
- different tissues absorb nitrogen at different rates - if good blood supply e.g. brain or heart absorb quickly (fast tissues) while if poorer blood supply or high fat content absorb more slowly (slow tissues) - eventually would all become saturated at new ambient pressure Nitrogen release During ascent, process of nitrogen absorption reversed - nitrogen released from tissues (off-gassing) - just as nitrogen on-gasses at different rates, also off gasses at different rates - body can tolerate some excess but once exceeded will come out of solution to form bubbles in blood
- Means rapid ascents should be avoided - dissolved gas will rapidly come out of solution and bubbles of nitrogen gas will begin to form in body tissues
- Bubbles can slow off gassing and distort or damage tissues, or block blood vessels - can cause oxygen starvation which can result in decompression illness (DCI)
- To manage nitrogen exposure use decompression look-up tables, dive computers and software programs
- Tools are models incorporating parameters of depth (pressure), time and gas mix How to dive with table (^) Need depth guage (to monitor depth), diving watch (to monitor time) and diving slate (to write down plan)
Organisation of BSAC branch 1. Diving officer - accountable to BSAC national diving officer for maintaining safety and diving standards - accountability for diving safety - ensures safety standards complied with
- Dive manager appointed by diving officer (can be for one dive, day or ongoing)
- DM will agree objectives for dives with DO and divers - DM responsible for diving on site, can cancel diving if required - Dive buddy pairs form final link in triangle of responsibility - all persons have duty of care to themselves, buddy and whole group Role of a DM Select dive site and depth (i.e. formulate dive plan) Timetable of the day Provision of gas / boats Gives a dive brief Confirms dive plan before entry - will also collect details upon exit What should you tell the Dm after a dive Maximum depth reached Amount of gas remaining Dive time Any problems Buddy dive plan after dive brief Discuss objectives, planned depth (within maximum depth), dive duration
- Consider how to manage risks (e.g. if poor viz or snagging risk), and how will navigate Gas consumption rules Shallow dives in sheltered conditions, ascend when 70 bar reached so exit water with 50 bar reserve - on deeper dives use Rule of Thirds - one third of gas for descent and outward leg, second third for return leg and ascent, leaving third for reserve SEEDS brief - After planning and just before getting ready to enter water - SEEDs Safety - confirm fit to dive, ensure within capabilities, understand specific hazards Exercise (gas type, length, depth and aims) - Equipment - ensure all equipment prepared Discipline - confirm who is dive leader - important to eliminate uncertainty in decision making Signals Up, down ok, no, gas check, Dive flags A flag flown on boats to indicate divers below- blue and white with triangle cut out of blue half red and white flag American equivalent of divers down below flag Buddy check BAR - Buoyancy (check inflating and oral inflate, dump valves) Air (breathe - free from smell and taste? monitor for fluctuation in gauge. check buddy octopus and ease of release) Releases- (how to get buddy out)
Entering water - ensure air in BC and demand valve and mask in place - on most shore dives can wade into water - fins can be fitted before entry or after wading into water - use a large stride forward to enter from large drop - need to ensure sufficient depth and no divers
- From small boat, use backwards roll entry
- Signal ok upon surfacing Descent Can follow slope if sloping seabed - can follow shot line - give ok and down signal - stay together - equalise pressure - stop after a few metres and make checks, including computer or depth guage - check gas level and ensure no leaks
- continue descent - hover clear of seabed - checking process repeated on bottom - now is time to fine tune buoyancy - check gas supplies and confirm satisfactory to dive - check all equipment in good order During dive Communicate - point out items - swim side by side - monitor conditions including tides - monitor depth (do not exceed maximum depth) monitor breathing gas - monitor buddy with ok signals - make sure to easily locate alternative supply - keep to plan
- Note passing features to aid return to start point (pilotage) - create mental map - remember to monitor depth while using pilotage, as it is easy to become distracted - underwater compasses can be used Separation procedure Stop, carry out complete turn looking for buddy or bubbles - If cannot see buddy ascend and look for bubbles - if carrying torch look for flashes of light - limit time looking for 30 - 60 seconds - then do controlled ascent and signal to surface cover that both are okay - if only one appears signals may be problem Trio diving Buddy diving safest - trio increases risk of separation - need strong leadership and constant monitoring to avoid risk of separation Underwater environment Blue penetrates best so deeper = bluer - visibility reduced compared to land due to reduced light, also turbidity reduces light levels
- Hearing unreliable - less able to identify source of sound as sound travels faster
- water temperature can vary - thermocline is transition layer between warm surface water and cooler deeper layer - can have blurry boundary Ascent Ascent depends on type of dive - can gradually swim up shore or up shot line - when ready to ascend exchange ok and up signals - start to ascend - control ascent rate while controlling buoyancy, i.e. dumping gas - monitor ascent with depth guage slow down for six metre check - at 6 metres, stop and check dive parameters such as depth and time still within planned limits - from there take 1 min to reach surface
- Check free from hazards e.g. boats and inflate BC - use Ok signal to buddy and then to surface cover - keep regulator in mouth Exiting water Ensure gas in BC - avoid tripping on rocks - walking backwards better with fins - can use ramp or ladder - exits on large boats normally via powered lift or ladder to help up - fins need to be removed before climbing steps but ladders often designed for use with fins - small boats often requires dekitting e.g. removing weights and scuba equipment
Table levels Level 1 used at sea level 9pressure greater than 984 millibar) - table sets for levels two, three and four - higher altitude
- Should be used when living or diving at altitude or when travel to or from dive sites causes changes in altitutde
- Diving protected inland sites at sea level when a low-pressure weather system is present might mean planning dives on level two tables Diving and flying - in pressurised aircraft the ambient pressure is reduced compared with atmospheric pressure at sea leel - standard commercial aircraft cabins during flight would be at a pressure equivalent to level four - should not dive after flight until feel physically rested - unless surface interval off 10 hours has elapsed betwee nshort flight of less than 90 minutes in pressurised aircraft and diving, need to use table B
- Recommended that divers do not fly within 24 hours of last dive - needs to return to B for pressurised aircraft and A for unpressurised - reduced pressure can increase risk of DCI by causing nitrogen bubbles in blood to expand Oxygen toxicity planning When breathed at high partial pressure can be toxic - oxygen toxicity determines MOD for particular nitrox mix - but staying within MOD does not guarantee freedom from oxygen toxicity - length of time breathed is also major consideration - nitrox contan higher oxygen - reduces nitrogen absorption and DCI risk but increases risk of oxygen toxicity - Ocean divers limited to max depth of 20m - minimises risk of oxygen toxicity when using nitrox mixes containing up to 36 pe cent oxygen
- Using air table for nitrox mix gives safety margin - reduces risk of DCI Gas consumption planning Rule of thirds - one third used for descent and first half of five, second third used for second half and ascent - should arrive at surface with one third remaining as reserve - always aim to surface with one-third of your gas in reserve (minimum of 50 bar)
- Gas monitoring - gas should be monitored during a dive to ensure everything is within the plan - gas consumption increases with effort, or when cold or anxious - should shorten or terminate dive if gas consumption higher than planned triangle of responsibility Divee manager, diver leader - Individual divers are responsible for diving safely within the limits of the plan and taking corrective action in the event of problems - referred to as dive safely within limits of plan take corrective action of problems Hazards Entanglement, separation underwater, surface separation (can mitigate by using inflatable marker buoy) - variety of alternative emergency signalling devices available including flags, torches, strobes Early resolution of hazards Prevention better than cure - resolve probles - buddy monitoring important - practice dive skills Incident pit - incidents usually result of combinatin of factors - in isolation innocuous but as combination builds stress on diver inceases until beyond capabilities - effect likened to pit whose sides become steeper and steeper the further one descends
Managing decompression illness - nitrogen uptake during a dive it is important to control rate of nitrogen release - dive planning is done to reduce risk of DCI - good diving practice includes careful control of buoyancy especially on ascents and avoidance of saw tooth profiles - using a nitrox mix and air tavles, divers can reduce DCI exposure DCI gas bubbles - Condition includes formation of gas bubbles in body Causes of gas bubbles = inadequate elimination of nitrogen during ascent or lung damage from expanding gas during ascent
- Both bubbles can have similar effects 0 bubbles form in tissues as a result of gas coming out of solution when surrounding pressure rduced - body tissues may be damaged and forced out of shape, compressing nerves and causing pain and weakness - bubbles within tissues can apply pressure on blood vessels causing damage and reducign blood flow - reduce oxygen delivery to cells downstream - bubbles can form in or enter blood - can cause damage to lining of vessels and hinder uptake of oxygen by surrounding tissues Lung damage can result not only in gas bubbles passing into bloodstream but also in gas pockets between tissues and organs in chest - two causes of lung damage - excessive ascent speeds and breath holding on ascent - divers should carefully control their ascent speed and adhere to recommendations provided by the BSAC tables or a dive computer - gas escapng from damaged air sacs can pass through thin membrane surrounding lungs into chest cavity - expansion can then cause lung collapse - gas can also travel between tissues around lungs and heart into chest cavity up to the neck - gas bubbles can also pass through the damaged lung tissue and enter blood supply resulting in gas embolism DCI treatment Recompression chamber Divers use first aid tool on dive sites, oxygen - increases oxygen levels in blood and helps oxygen delivery to damaged tissues - speeds up elimination of nitrogen from body - by removing nitrogen from gas breathed in - fluids also required to ensure good flow of blood (do not apply if risk of unconciousness or surgey may be required) Nitrogen narcosis Nitrogen affects tranmsission of impulses in nerve cells - only noticed when go beyond 30m - similar to effects of alcohol - solve by ascending DCI signs and symptons rashes nausea headaches confusion breathing difficulties crepitation = bubble formation in the tissues aches in joints visual disturbances bad dci = changes to voice Oxygen toxicity Toxic when breathed at high pressures - determines MOD of particular diving gas
- MOD must be observed Signs/symptoms = visual or auditory disturbance, dizziness of nausea, muscular twitching in face, lips or fingers - convulsions or fits, can lead to significant risk of drowning when underwater
- Prevention is better than cure - return to surface and abort dive
