Can Deco-Sickness occur during the dive?

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The dive in question is a 100ft air dive for 40minutes. (The 10msw 7min stop is ignored) Followed by a repetitive dive (SI=01:00) of 70ft 45 minutes and so is definitely an academic concern rather than something I actually want to do..
I'm looking at getting certified before I even think of conducting a 100ft dive.

When you get certified, you'll learn how to plan dives that don't go into decompression. Without extended training, you'll always be diving in a situation where you have a no-decompression limit (NDL). That keeps your saturation low and will always enable a direct ascent to the surface.

Most divers conduct 'safety' stops. These aren't mandatory - they just add a level of conservatism. In contrast, a deco stop is mandatory - on the basis that you have an unreasonable likelihood of getting DCS if you don't complete it.

I'm focusing on a dive where safety is completely ignored. More specifically I am focusing on DCS due to ignored safety stops.

As mentioned above.. there's a difference between a safety stop and a deco stop. You shouldn't get DCS from ignoring a safety stop. You may well get DCS from ignoring a deco stop. Recreational divers don't do dives that require deco stops... such dives are covered by 'technical diving' courses.

If a diver did go into a deco situation...and then fail to carry out the required stops..... I think Darwin's Law is more applicable than any of the Gas Laws.
 
When you get certified, you'll learn how to plan dives that don't go into decompression. Without extended training, you'll always be diving in a situation where you have a no-decompression limit (NDL). That keeps your saturation low and will always enable a direct ascent to the surface.

Most divers conduct 'safety' stops. These aren't mandatory - they just add a level of conservatism. In contrast, a deco stop is mandatory - on the basis that you have an unreasonable likelihood of getting DCS if you don't complete it.



As mentioned above.. there's a difference between a safety stop and a deco stop. You shouldn't get DCS from ignoring a safety stop. You may well get DCS from ignoring a deco stop. Recreational divers don't do dives that require deco stops... such dives are covered by 'technical diving' courses.

If a diver did go into a deco situation...and then fail to carry out the required stops..... I think Darwin's Law is more applicable than any of the Gas Laws.

In reference to my reply if you accidentally missed it:
"http://www.scubaboard.com/forums/basic-scuba-discussions/402722-can-deco-sickness-occur-during-dive.html#post6123617"

The Deco stop in this dive is mandatory (sorry I confused it with safety stops). You stated that its highly unlikely that DCS would develop if the mandatory stop was missed. How would you modify the dive so that the likelihood of DCS is high?

Also, I'm a bit lost on the Darwin's law part, do you mean Dalton's?

Thanks for the reply !!!
 
The Deco stop in this dive is mandatory (sorry I confused it with safety stops). You stated that its highly unlikely that DCS would develop if the mandatory stop was missed. How would you modify the dive so that the likelihood of DCS is high?

You are confusing a DECO stop and a SAFETY stop.

Two very different things (as I described). You shouldn't get DCI from a missed safety stop. You probably would get deco from a missed deco stop.The dives you describe would require deco stops.

The dive in question is a 100ft air dive for 40minutes. (The 10msw 7min stop is ignored).Followed by a repetitive dive (SI=01:00) of 70ft 45 minutes

How I would do that dive:

1. I would use desktop dive planning software to calculate the parameters of the dive/s, including decompression schedule required.
2. I would calculate my gas requirements for that schedule, using observed SAC/RMV and allowing a 1/3rd gas reserve for contingencies.
3. I would confirm that my cylinders held enough gas for that schedule of decompression, in accordance with my gas plan.
4. I would select appropriate equipment and procedures, including equipment redundancy, to ensure that I could maintain the deco schedule precisely - without recourse to surfacing in the event of a problem.
5. I would conduct the dive, in accordance with my detailed planning, with an emphasis on precision, awareness and control - knowing that any deviation would potentially take me beyond the scope of my calculated deco schedule and subject me to unreasonable risk of DCS.

The answers you've been given regards the onset of DCI are correct. You would expect to get DCI if you completed your hypothesised dive without conducting any stops on ascent. The severity of that DCI might vary, but the likelihood is moderate-high.

I'm a bit lost on the Darwin's law part, do you mean Dalton's?
More specifically I am focusing on DCS due to ignored [-]safety[/-] deco stops
I'm focusing on a dive where safety is completely ignored.

No, I definitely mean Darwin's.

Put simply, any diver that choose to complete a series of dives that put them into a state requiring decompression... and who then choose, or was not reasonably trained, equipped and prepared to complete that decompression - is just an example of how nature eliminates the weakest links within a species.
 
You are confusing a DECO stop and a SAFETY stop. Two very different things (as I described).

How I would do that dive:

1. I would use desktop dive planning software to calculate the parameters of the dive/s, including decompression schedule required.

2. I would calculate my gas requirements for that schedule, using observed SAC/RMV and allowing a 1/3rd gas reserve for contingencies.

3. I would confirm that my cylinders held enough gas for that schedule of decompression, in accordance with my gas plan.

4. I would select appropriate equipment and procedures, including equipment redundancy, to ensure that I could maintain the deco schedule precisely - without recourse to surfacing in the event of a problem.

5. I would conduct the dive, in accordance with my detailed planning, with an emphasis on precision, awareness and control - knowing that any deviation would potentially take me beyond the scope of my calculated deco schedule and subject me to unreasonable risk of DCS.



No, I definitely mean Darwin's.

Put simply, any diver that choose to complete a series of dives that put them into a state requiring decompression... and who then choose, or was not reasonably trained, equipped and prepared to complete that decompression - is just an example of how nature eliminates the weakest links within a species.

Thank you for the amount of effort put into the answer you provided.

About the way you would do the dive, I was asking how the risk of NCS can be increased in the dive technically (not decreased)
So, do you know what you would change about the dive in order to Increase the NCS risk??
Here is the dive schedule again:
1st. 40 minutes at 100ft (Mandatory 7minutes stop at 10msw is ignored)
2nd. 45 minutes at 70ft

Btw, the entire dive is conducted with Standard Normoxic Air.

About that Darwin thing, that is deep but truthful.
The dive I am speaking of is, in essence, supposed to be foolish and deemed to failure.

Thank You!!
 
I dont understand what you are trying to accomplish.. the 1st dive, ignoring the stop, is already dangerous, possible for DCS.. I'm very new and here yrying to learn also...
 
How to INCREASE the risk of decompression sickness, if that's your thing:

Do the dives that you describe, only deeper and longer. Ignore mandatory decompression. Stay dehydrated and generally out of shape. Since the dives of yours are air dives; switch to a high helium mix on decompression. Have a PFO. Do yoyo profiles. Be cold. Work hard, and after the dive; wait for a couple of minutes and then go back down to loosen the ancer:)

You should now get bent.


Best,
Bjørn
 
There ARE mathematical tools to calculate the likelihood of symptomatic DCS with certain profiles, but I don't know what they are or where you can find them. They're complex, and no one uses them in daily diving.

The more mandatory decompression you ignore, the more likely you are to be symptomatic. But ascent RATE is involved, too; you can be symptomatic with a low or nonexistent deco obligation, if the ascent rate of the model you are following is violated.

As I mentioned before, decompression ILLNESS exists in two forms. One is physical harm related to oversaturation of nitrogen in the body, and inadequate decompression. This form is rarely fatal, except in the most egregious cases (which your example is not). Arterial gas embolism CAN be, and often is fatal, but tends to be related to ascent rates and breathing patterns, rather than total body nitrogen saturation.

It sounds as though you are writing a book . . . If you want someone dead underwater, have them get oxygen toxicity and seize, have a heart attack, or have an embolism and surface and die. Fatal decompression sickness from nitrogen is more typical of deep technical dives. (This is not to say that the results of DCS from dives like you are describing cannot be devastating, with severe neurological sequelae. They are just unlikely to be fatal.)
 
How to INCREASE the risk of decompression sickness, if that's your thing:

Do the dives that you describe, only deeper and longer. Ignore mandatory decompression. Stay dehydrated and generally out of shape. Since the dives of yours are air dives; switch to a high helium mix on decompression. Have a PFO. Do yoyo profiles. Be cold. Work hard, and after the dive; wait for a couple of minutes and then go back down to loosen the ancer:)

You should now get bent.


Best,
Bjørn

As weird as it sounds, something like this is what I was looking for.
With the standard dive profile that is set before any changes, ignoring the short 7min deco, what would you classify the chances of DCI as? Wait TSandM answered this. Thanks for the help anyways!!

There ARE mathematical tools to calculate the likelihood of symptomatic DCS with certain profiles, but I don't know what they are or where you can find them. They're complex, and no one uses them in daily diving.

The more mandatory decompression you ignore, the more likely you are to be symptomatic. But ascent RATE is involved, too; you can be symptomatic with a low or nonexistent deco obligation, if the ascent rate of the model you are following is violated.

As I mentioned before, decompression ILLNESS exists in two forms. One is physical harm related to oversaturation of nitrogen in the body, and inadequate decompression. This form is rarely fatal, except in the most egregious cases (which your example is not). Arterial gas embolism CAN be, and often is fatal, but tends to be related to ascent rates and breathing patterns, rather than total body nitrogen saturation.

It sounds as though you are writing a book . . . If you want someone dead underwater, have them get oxygen toxicity and seize, have a heart attack, or have an embolism and surface and die. Fatal decompression sickness from nitrogen is more typical of deep technical dives. (This is not to say that the results of DCS from dives like you are describing cannot be devastating, with severe neurological sequelae. They are just unlikely to be fatal.)

I'm not writing a book, its personal research with a friend. (the reverse of safety)
Your reply really helped with my understanding though, nice and clear! Basically your reply and opperud's answered my initial questions.

Can I ask though, say the cause of death was due to a case of oxygen toxicity,
How would the dive be altered? Where would symptoms occur?

Thanks!!
PS: The diver is diving with atmospheric air.
 
So, do you know what you would change about the dive in order to Increase the NCS risk??


As others have said; Depth + Time = Nitrogen Absorption

Here's a very simplistic explanation:

Speed of ascent dictates how nitrogen is released. A recreational diver is limited to dives where nitrogen absorption is sufficiently low to enable a direct ascent to the surface. However, that direct ascent must be completed at a specific speed (typically slower than 18m/60ft per minute). A technical diver is trained and equipped to complete dives that do not have a direct ascent to the surface - the amount and location of absorbed nitrogen dictates a much slower speed of ascent - this results in a 'staged' ascent, where the diver has to pause at pre-calculated depths to ensure that sufficient nitrogen is released. These 'pauses' are known as decompression stops.

Too Fast Ascent = Nitrogen cannot be removed quickly enough by the cardio-vascular system, thus it de-saturates inside the body, forming bubbles.

The speed of ascent is determined by the amount of nitrogen absorbed and where it is absorbed into within the body.

More depth = more pressure. More pressure = more nitrogen. More time at pressure = even more nitrogen
As depth and time increase, the nitrogen is 'pushed' deeper in the body tissues. We categorise this absorption in terms of hypothetical 'tissue compartments'. There are 'fast' tissues and 'slow' tissues.

A recreational diver (shallow + short) is mainly going to absorb nitrogen into 'fast' tissues. These absorb nitrogen quickly, but also release it quickly. The recreational diving 'No-Deco Limits' ensure that the ascent/release of nitrogen is only limited by 'fast tissues'. The speed of ascent reflects the faster release of nitrogen from the body.

A technical diver (deep and/or long) will absorb more nitrogen into 'slow' tissues. These release nitrogen slowly - which require the diver to make a much slower ascent to de-saturate. The very slow speed of that ascent dictates the need for 'stops'.

Killing the 'ficticious' diver:

Here is the dive schedule again:
1st. 40 minutes at 100ft (Mandatory 7minutes stop at 10msw is ignored)
2nd. 45 minutes at 70ft
....the entire dive is conducted with Standard Normoxic Air.

Those dives would have a requirement for deco stops, but missing those stops would not necessarily indicate DCI. They are relatively 'lightweight' deco dives. If there was DCI - it would be relatively mild, would probably onset shortly after surfacing. Most likely symptoms would be acute localised pain in one or more joints/limbs, possibly coupled with a slight skin rash. It would be treated by hyperbaric treatment with a high likelihood of complete recovery.

You've given us time, depth and breathing gas... and also defined that they 'missed' their deco stops. The only other variable would be their ascent speed. Even with a fast ascent - it'd be unlikely to be fatal.

So... to make the diver 'die'... you'd need to add something like this:

Now... given the dive you've described... to have the diver 'die', you could look at one of the following circumstances:

1. Diver completed the ascent on Dive 2, from 70ft to the surface, at an extremely fast pace. Possible cause of this would be panic; as divers are trained to share air with their buddy and/or complete a 'Controlled Emergency Swimming Ascent' to the surface where they maintain a safe ascent speed. The diver would have to panic to ignore either of those options. Panic would mean 'kicking for the surface as fast as humanly possible'. Panic does kill divers. Another alternative for fast ascent would be a buoyancy malfunction. Maybe a stuck inflator button on a dry-suit or BCD that wasn't quickly dealt with (diver train to resolve this also). If the diver was raising an item from the sea-bed using a 'lift-bag', then they could get tangled in the bag and pulled up by it. Another option would be that the diver got caught in a fishing net/line and dragged up to the surface. The ascent to the surface would need to be in seconds, to have the level of severity that you are looking for.

2. Diver made a rapid ascent from Dive 2, but somehow failed to breath/exhale on the way up. Air trapped in their lungs would expand (due to decreasing ambient water pressure). That expanding air would burst their lungs, resulting in a potentially fatal complication. The 'most lethal' complication from a Lung Over-Expansion Injury is an Arterial Gas Embolism (AGE) where air enters the circulatory system. There are other possible complications - just ask if you need more details on those.

3. Diver had a Patent Foramen Ovale (PFO). A medical condition otherwise known as a 'hole in the heart'. I believe that up to 1/4 of people have this (?). The PFO allows blood to re-circulate through the body without passing the lungs. This means that nitrogen is released from the body, but a significant percentage of it won't pass the blood-lung barrier for release. Consequently, it accumulates...and is known to cause significantly higher risk of DCI.

4. The diver might have other pre-disposing factors for DCI. Known pre-disposing factors would include: dehydration, exhaustion, lack-of-sleep, illness and injury or diving in extremely cold water. These conditions basically interfere with the cardio-vascular system - meaning the nitrogen 'off-gassing' would be slower than predicted. They'd increase the chance of DCI, but wouldn't necessarily make the DCI substantially more severe.
[h=3][/h]Otherwise... there's just no way to make your hypothetical dive more lethal. It's a bad dive plan - that could cause harm - but is likely to be survivable if medical care were forthcoming within a few hours of the incident. As it is, without an 'extra' factors - it wouldn't kill you in the water.
 
It sounds as though you are writing a book . . . If you want someone dead underwater, have them get oxygen toxicity and seize, have a heart attack, or have an embolism and surface and die. Fatal decompression sickness from nitrogen is more typical of deep technical dives. (This is not to say that the results of DCS from dives like you are describing cannot be devastating, with severe neurological sequelae. They are just unlikely to be fatal.)

I had a similar thought. :D
Or it could be just a fun, creative writing assignment for school.

The OP did state that he/she was trying to "teach" someone about decompression sickness. :shocked2:
That seems to be a rather ambitious endeavor.
 

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