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Chapter 3: KISS CCR Physiology: The Good and the Very Bad

Chapter 3: KISS CCR Physiology: The Good and the Very Bad. Respiratory Physiology The Human Oxygen Range Hyperoxia Hypoxia Hypercapnia Hypocapnia Caustic Cocktail Arterial Gas Embolism Squeezes Decompression Sickness Narcosis Carbon Monoxide Discipline

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Chapter 3: KISS CCR Physiology: The Good and the Very Bad

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  1. Chapter 3: KISS CCR Physiology: The Good and the Very Bad • Respiratory Physiology • The Human Oxygen Range • Hyperoxia • Hypoxia • Hypercapnia • Hypocapnia • Caustic Cocktail • Arterial Gas Embolism • Squeezes • Decompression Sickness • Narcosis • Carbon Monoxide • Discipline • The “Good Stuff”

  2. Chapter 3: KISS CCR Respiratory Physiology • Inhale 21% O2 @ sea level this is equivalent to 0.21 atm of O2 • Exhale 16% O2 and approximately 3-4 % CO2 • In physiologically normal humans the desire to breath is triggered by CO2 • Increases in CO2 cause the respiratory center in the brain to increase breathing in an attempt to lower the CO2 level

  3. Chapter 3: KISS CCR Respiratory Physiology • Each diver (human) has a RMV (respiratory minute volume) • This RMV is the volume of gas inhaled / exhaled per minute at one atmosphere • Each diver (human) also has a metabolic O2 requirement • On OC increasing depth will increase the mass of gas consumed (wasted) RMV • On CCR increasing depth does not increase the mass of gas wasted • On CCR it is the divers metabolic oxygen rate that is important

  4. Chapter 3: KISS CCR Respiratory Physiology A general guide for Oxygen metabolism For the KISS target flow rate for orifice/IP between 0.6-1 L/min, must be lower than divers actual metabolic oxygen requirement

  5. Chapter 3: KISS CCR Respiratory Physiology

  6. Chapter 3: KISS CCR Respiratory Physiology • For every liter of oxygen metabolized by the body we produce about 0.8 – 1 L of CO2 • Here is where the OC light breathers may use more oxygen than the OC heavy breathers • On CCR we are not concerned about mass like on OC • The oxygen metabolic rate of the light breathersmay be higher than the heavy breathers thus they may use more oxygen in the CCR arena

  7. Chapter 3: KISS CCR The Human Oxygen Range • PO2 0.16 – 1.6 atm (human range) • PO2 < 0.16 atm = hypoxia and unconsciousness • PO2 > 1.6 atm = hyperoxia and seizures • Two forms of Oxygen toxicity • CNS (central nervous system) seizures • Pulmonary (whole body) lung toxicity • CNS toxicity is from PO2 exposure (i.e. PO2 > 1.6 atm) and also the clock (time at various PO2) • Avoid OC PO2 exposures > 1.6 atm • Avoid CC PO2 exposures > 1.3-1.4 atm • Avoid running the clock past 80%

  8. Chapter 3: KISS CCR Hyperoxia • CONVENTID: lets just accept that the first sign of O2 toxicity may be convulsions • Previously on OC PO2 of 1.4 atm for dive and 1.6 atm for decompression was allowed • With a CCR the constant nature of the PO2 demands a lower safe dive PO2 limit • If you remember a PO2 of 1.6 atm allows for a clock of 45min, 1.5 atm=120min, 1.4 atm=150 min and so on • If you ran your dive at a PO2 of 1.6 atm (remember this is now CCR and constant PO2 ) your total dive time can not be above 45min and should not be above (80% of clock) = 36 min

  9. Chapter 3: KISS CCR Hyperoxia • A 36 minute dive on a CCR seems short • Oxygen toxicity due to violating the “O2 clock” now becomes a real possibility, careful planning is essential • Hyperoxia induced myopathy (near sightedness) has been implicated in CCR divers • It is in your best interest to run dives at a set point of no more than 1.3 atm • A compounding issue is CO2 buildup, if you experience “breakthrough” then you have just lowered your threshold for O2 toxicity • The first signs of CNS O2 toxicity maybe a seizure

  10. Chapter 3: KISS CCR NOAA Guidelines • Single dive greater than 80% of CNS clock: Minimum Surface Interval of 2 hrs • The NOAA 24 hrs limit reached: Minimum Surface Interval of 12 hrs

  11. Chapter 3: KISS CCR Hyperoxia: CNS • CAUSES: • Rapid descents can cause PO2 spikes • Erroneously manually adding O2 can cause PO2 spikes • A incorrect O2 flow for a divers metabolism can cause PO2 increases • A stuck O2 addition valve, damaged o-rings in the manual oxygen add valve, or a faulty HP seat • Poor oxygen clock management

  12. Chapter 3: KISS CCR Hyperoxia: CNS • ALWAYS KNOW YOUR PO2 • At first sign of a high PO2 lower it by : • Slow/stop descent • Switching to OC bailout • Access situation • Add diluent • See emergency procedures section for more detail

  13. Chapter 3: KISS CCR Hyperoxia: Pulmonary Oxygen Toxicity • Long term exposure to increased PO2 can cause inflammation of the lungs, pulmonary congestion, dry non-productive cough, edema, and shortness of breath • Maximum OTU (oxygen tolerance units) 1440 / day • Save 750 OTU for chamber ride • Leaves 690 OTU for a single day / single dive • For multi dives over multi days use a maximum of • 300 OTU per day

  14. Chapter 3: KISS CCR Hypoxia • ALWAYS KNOW YOUR PO2 • This can be caused by rapid ascents • Forgetting to open the O2 supply cylinder • before the dive • Running out of O2 (or plugged valve/filter) • Not monitoring PO2 displays often enough • Working hard • Lucky divers may experience symptoms of • hypoxia before blackout (not the norm) • These may include tingling, and visual disturbances • Remember if something appears wrong IT IS, DEAL WITH IT

  15. Chapter 3: KISS CCR Hypoxia • ALWAYS KNOW YOUR PO2 • This is one of the most seriousmaladies for the • CCR diver (death is usually assured) • There is usually no warning • The first symptom is often unconsciousness • At the first sign of anything wrong, it is, go to OC • immediately • Access situation • The repair is to manually add O2, and always • monitor PO2 during a dive • NEVER DIVE a CCR alone • See emergency section for more information

  16. Chapter 3: KISS CCR Hypercapnia • This is CO2 build up • Causes: • Over using a scrubber (pushing the time limits) • Incorrectly packing the scrubber / settling (channeling) • Working hard • Water in scrubber • Skip breathing / improper breathing • Starting a deep dive on used sorb

  17. Chapter 3: KISS CCR Hypercapnia • Results in: • Unconsciousness = death • Decreased threshold for CNS oxygen toxicity • Increased nitrogen narcosis • CO2 is not your friend • Very important to breath regularly deep & slow with a CCR • DO NOT SKIP BREATH, all this does is build up CO2

  18. Chapter 3: KISS CCR Hypercapnia • PCO2 = 0.01-0.02 atm = first signs of distress • PCO2 > 0.03 atm = distress • PCO2 > 0.06 atm = unconsciousness • Increased CO2 levels in the body may cause symptoms • including: • Headache • Anxiety / confusion • Feelings of inability to breath • Weakness in legs

  19. Chapter 3: KISS CCR Hypercapnia • In a perfect world this would be the case • Problem: the higher PO2 can cause the above symptoms to not appear, and the first sign of hypercapnia may be unconsciousness

  20. Chapter 3: KISS CCR Hypercapnia • Like hypoxia unconsciousness may • likely be the first sign of hypercapnia • Never dive alone • Never push the limits of the scrubber • (sorb is relatively cheap compared to • your life) • If you are lucky to sense a problem, • immediately switch to OC, assess situation • If it is hypercapnia, stop work, use OC bail • out and end dive • See emergency procedures section

  21. Chapter 3: KISS CCR Hypocapnia • Decreased CO2 in body • This is not usually an issue with CCR, but is still • worth mentioning • Deep rapid breathing (hyperventilation) will • cause the PCO2 in the body to decrease • Remember PCO2 controls the bodies drive to • breath • A decreased PCO2 will signal the body to slow • down breathing lowering O2 levels, leading to • blackout • KEY: deep slow regular breathing like on OC

  22. Chapter 3: KISS CCR Caustic Cocktail • If water is allowed into the loop, it may dissolve the sorb creating a corrosive solution “caustic cocktail” • Avoid by properly preparing KISS • Completing pre-dive safety checks • (positive &, negative pressure tests) • Perform in water bubble check • Fill scrubber with a slight breeze to help eliminate sorb dust • Be aware of bubbling / gurgling sounds in breathing hoses • Increased breathing resistance, loss of buoyancy, metallic taste, slippery feeling, over pressure relief valve opening on every breath

  23. Chapter 3: KISS CCR Caustic Cocktail • If you get a bad taste in your mouth immediately rinse with water, and switch to OC, the dive is over • If you suspect water in the loop, the best choice is to finish the dive in OC • Caustic cocktail is very corrosive, it may burn your mouth, close up your airway, and is highly corrosive to the lungs • DO NOT BREATH IN OR GET IT IN YOUR MOUTH

  24. Chapter 3: KISS CCR Arterial Gas Embolism • The loop is at a constant volume • If you rapidly ascend, the gas will expand, the over pressure relief valve may be activated (if it is adjusted properly), but if the expansion is to great the weakest part of the loop will give (your lungs!!) • Ascend slowly • If you experience “chipmunk” cheeks vent excess gas through your nose or mouth • Watch out for large surge

  25. Chapter 3: KISS CCR Squeeze • Hyperoxic ear squeeze • Post dive especially with CCR due to the increased PO2 • Increased PO2 in middle ear space, gets metabolized slowly resulting in a decreased number of molecules resulting in a slow and perhaps unnoticed onset of ear squeeze • Solution: surface equalization post dive

  26. Chapter 3: KISS CCR Squeeze • Ear squeeze: if the counterlungs are significantly lower or higher than ears, this will cause an increased/ decreased static pressure inside the ear causing the eardrum to bulge in/out • May result in ear discomfort / infections especially on long dives • Lungs: maintain proper CCR orientation and trim in the water

  27. Chapter 3: KISS CCR Decompression: Quick Review • On Descent increased pressure, increases inert gas on-gassing into tissues (Henry Law) • On Ascent decreased pressure, increases inert gas release into the blood from the tissues until exhaled • KEY CONCEPT: inert gas is dissolved in the blood / tissues, as long as it stays dissolved in solution everything is okay • If there is to much inert gas or to great of a decrease in pressure the dissolved inert gas will skip out of solution phase (critical super saturation) and form bubbles in the tissue / blood = DCS

  28. Chapter 3: KISS CCR Decompression: quick review • If critical super saturation is not exceeded then the inert gas will stay in solution dissolved in the blood / tissues, and move from high concentration in the tissue into the blood then to the lungs and then innocently exhaled “blown off” without DCS • On CCR we strive to set the PO2 high enough to decrease this inert gas on-gassing, but it is also a fine line, as we do not want too much oxygen leading to oxygen toxicity

  29. Chapter 3: KISS CCR Decompression Sickness • ALWAYS KNOW YOUR PO2 • If your set-point PO2 is allowed to vary from your actual dive plan, then DCS is a much greater risk (or if the sensors are improperly calibrated the same situation may occur) • Ex.) set-point of 1.3 atm, diver does not maintain a 1.3 atm and looks at PO2 30 minutes into dive and discovers a PO2 of 1.0 atm, but planned dive and has tables for a constant PO2 of 1.3 atm. • The diver has taken on a considerable amount of extra inert gas that was not accounted for, DSC is likely

  30. Chapter 3: KISS CCR Decompression Sickness: Prevention • Maintain planned PO2 and proper dive planning • Always keep hydrated drink lots of water the day before, day of , and day after dives (# 1 non-diving measure) • Avoid strenuous exercise after diving • Avoid getting cold on dives • Pad the tables!!

  31. Chapter 3: KISS CCR Decompression Sickness: Signs • Type 1: • Itchy,inflamed, mottled skin, joint pain • Type 2 (neurological): • Tingling, numbness, paralysis, hearing • problems, ringing, difficulty voiding, • difficulty breathing • Treatment: • 100% oxygen and EMS, hydrate

  32. Chapter 3: KISS CCR Narcosis: IMPERIAL • The greater the amount of nitrogen in the mix the increased • PN2 and increased state of narcosis • END is a concept not to be overlooked • PG = FG x Data 99’=4 ata 132’=5 ata • PG = 0.79 x 4 ata PG= 0.79 x 5 ata • PG = 3.2 atm PG = 4.0 atm • Each diver must decide on their own MOD for N2 (i.e. MND) • Usually between 100-130 fsw • Avoid deeper than 130 fsw

  33. Chapter 3: KISS CCR Narcosis: METRIC • The greater the amount of nitrogen in the mix the increased • PN2 and increased state of narcosis • END is a concept not to be overlooked • PG = FG x Data 30 =4 ata 40 =5 ata • PG = 0.79 x 4 ata PG= 0.79 x 5 ata • PG = 3.2 atm PG = 4.0 atm • Each diver must decide on their own MOD for N2 (i.e. MND) • Usually between 30-40 msw • Avoid deeper than 40 msw

  34. Chapter 3: KISS CCR Narcosis • Factors affecting the decision include: visibility, temperature, stress level, task loading, darkness, rapid descents, increased CO2 • In warm tropical 100 ft (30 m) visibility, fun dive a diver may choice 130 fsw (40 msw) as their END • Where as a diver in cold murky water will likely opt for 100 fsw (30 msw) END.

  35. Chapter 3: KISS CCR Narcosis • Along with the increased risk of DCS another problem with letting the PO2 fall below the planned levels is: increased narcosis • Lets assume a diver has a PO2 1.3 atm, starts the dive at a safer PO2 of 0.7 atm, gets to the bottom (99 fsw or 30 msw) and forgets to adjust PO2 to 1.3 atm • Continues to dive at a PO2 of 0.7 atm vs 1.3 atm • PG=FG x Data • 0.7 atm = FG x 4 ata= 18% O2, and 82% N2 • He will experience more narcosis (deco implications also)

  36. Chapter 3: KISS CCR Carbon Monoxide • Results from fossil fuel combustion • Always ensure the compressor has the air intake far away and up wind of the exhaust from any engines including its own • Always analyze supply tanks filled with a gas driven compressor or around gas driven engines for Carbon Monoxide (CO) before use • From smoking cigarettes or second hand smoke or boat exhaust • This CO is inhaled by the diver then exhaled into the loop and is compounded with depth

  37. Chapter 3: KISS CCR Discipline • If you do not have the discipline to do pre-dive maintenance, dive monitoring, and post-dive maintenance, then the KISS CCR is NOT FOR YOU • Neither is any form of CCR diving • As stated right on the unit “this device is capable of killing you without warning” • You must accept that this is a whole new form of diving, and as such you are a beginner again • Take it slow • Live by “if something appears wrong IT IS”

  38. Chapter 3: KISS CCR The Good Stuff • There must be some reason for this?? • Gas efficiency (cheaper trimix dives etc.) • Near silent operation (great for photography) • Warmth and hydration • Decompression efficiency • Almost unlimited depths • Longer dive times

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