"Riding your Computer Up" vs. "Lite Deco"

[Edward3c]

Two comments.

1. a severe DCI was diagnosed. Once again: DCI means Decompression Illness, a diagnosis that includes both Decompression Sickness (DCS) and lung overexpansion injury. The symptoms for the two are are similar, but since the treatment is the same, the need to make a true differentiation in the diagnosis is unnecessary. A lung overexpansion injury can happen on any dive, including a shallow end of the pool training session. According to a joint DAN-PADI study, it is the most common accident-related insjury in scuba.

2, As I said in a recent post in one of these maddening threads, a private statement by DAN released in a thread a couple of years ago indicated that a large number of people treated for DCI did not in fact have DCI but were misdiagnosed and treated anyway. Many such ailments misdiagnosed heal with time--the time spent in a recompression chamber would be just about right.

You need more than an anecdote here or an anecdote there to build a case.

There is a language issue here between the US and the UK.

The term DCS was dropped it favour of DCI a number of years age because sickness implied the condition was unavoidable, illness meant it was preventable. But both terms are effectively the same thing.

 

[Storker]

This is big boy diving - at least in the NorthEast. We dive same ocean - this is not a warm water 100 foot viz vacation dive. If you carry a pony - that is your business - if you don't I will help you if you come find me but I am not following you to make sure you are safe.

We obviously have very different philosophies about what buddy diving means. In fact, I think our philosophies are so different that I wouldn't want to buddy up with you.

 

[Basking Ridge Diver]

We obviously have very different philosophies about what buddy diving means. In fact, I think our philosophies are so different that I wouldn't want to buddy up with you.

That is fair enough - however you will know all of this when we decide to dive together or not dive together - there will not be any doubt how the dive will go before you get on the boat or we do a shore dive. Pre-dive conversations start before we even get to the location, generally a few days prior.

You can always back out - some folks have backed out. There is no shame if you or someone are not comfortable - at that point either I or you need to decide if we are going to alter the plan. Spearing or hunting lobster generally is a solo activity. Diving a new location or destination will determine how we approach it - on Vacation I tow the Buddy line as needed so I can dive off the boat.

The exception to the rule is when I dive with my son. I play the helicopter Buddy with him. Hover around him so he knows where I am.

 

[Neilwood]

My take on the different DC/NDL situation is similar to someone's analogy of the cliff earlier.

Someone decides to draw a line at a distance from the edge of the cliff that they deem safe (based on training and experience from other cliffs).
Different people have different ideas how to decide on where the safety line is drawn (depending on what method they choose to create the safe distance.
There is a statistical chance that even staying inside that line you might get hurt.
The edge of that particular cliff and how dangerous that cliff edge is is unknown (until you go over that line). As a lay person, you have no idea how dangerous that edge might be. You trust the person definining the edge to make it safe.
Without that skill and training, you might overstep the edge and fall.
With skill & training, you might be able to step over the line and negotiate your way back recognising the hazards that are there.

Similar with NDL:
Someone sets a No Deco Limit (based on their study of the issues) and deems that limit safe.
They will have made a number of tests and assumptions to achieve that line but different studies will achieve different lines due to the different assumptions.
There is a statistical chance that even diving within NDL you might get hurt.
No one knows how each persons body will respond on a particular day with regards to DCS/DCI even if you have dived a hundred times before. You might get hit due to a PFO, dehydration, tiredness, stress etc. As a diver you trust the person that made the study and set the NDL to make it a safe limit.
Without skill and training, you have to trust that limit to be safe.
With skill and training, you can go over the limit and get yourself back safely. You recognise the danger signs and know what to do to avoid them.

Until decompression experts develop a better understanding of DCS/DCI (which the true experts admit is still a grey area), all they can do is come up with models that are "best fit" for statistical analysis of available data. There is no right answer to how to model DCS/DCI (and can't be until there is an absolute understanding of it - which most experts would probably agree is a long way off).

What using a specific algorithm allows you to do is ride a statistical curve that says you shouldn't get hurt if you stick to the parameters it is based on. There is no guarantee that comes with it. The analogy of "measure with a micrometer, mark with chalk and cut with an axe" comes to mind. The NDL put out by the algorithm is very exact but it does not reflect that it is based on a statistical analysis of a large number of divers and not a personal one generated at that time based on the exact circumstances of the dive.

What agencies could probably do better IMHO with regards to NDL is to better equip their non tech trainees with an understanding of what each system (DSAT, RGBM, Buhlman etc) is based on, how choosing it could affect them and how conservatism can be decided upon (fitness, weather, hydration etc). That would better equip divers to pick an algorithm that suits them and their diving. I have certainly picked up a huge amount here and reading books that has helped me realise where I probably sit on the bell curve and how that should affect my choices.

 

[Lorenzoid]

A little off topic, but can anyone point me to a layperson-level explanation of how hyperbaric treatment affects lung overexpansion injuries? It's a little more intuitive how recompression helps treat DCS.

 

[Killerflyingbugs]

overexpansion causes an arterial gas embolism(AGE), and the treatment of AGE is re-compression therapy.

 

[boulderjohn]

The term DCS was dropped it favour of DCI a number of years age because sickness implied the condition was unavoidable, illness meant it was preventable. But both terms are effectively the same thing.

The PADI OW course I teach, with the manual that teaches more than half the new divers in multiple languages around the world, still differentiates between the two terms. DCS means decompression sickness; DCI means Decompression Sickness OR lung overexpansion injury. In each of the cases presented here as evidence of DCS, I would first suspect lung overexpansion. They would both receive the same treatment, and they would respond to treatment the same way. How do you know they were not cases of lung overexpansion?

 

[uncfnp]

A little off topic, but can anyone point me to a layperson-level explanation of how hyperbaric treatment affects lung overexpansion injuries? It's a little more intuitive how recompression helps treat DCS.

Until someone more knowledgable pops in I will give it a try in layman's terms. Just like DCS bubbles, plumonary lung over expansion injuries creates tears in the vascular tissue in the lungs and allows air (bubbles) to enter the pulmonary capillaries and eventually the arterial blood stream and from there it can enter the heart circulation (mimics a heart attack) or more likely the brain (mimics a stroke). Its the same as DCS injury when venous bubbles are able to enter the arterial circulation via right to left shunt. So the same treatment applies, HBOT to reduce bubble size and resolve embolism, whether from supersaturation bubble formation or lung trauma allowing bubbles in the blood.

 

[scubadada]

A little off topic, but can anyone point me to a layperson-level explanation of how hyperbaric treatment affects lung overexpansion injuries? It's a little more intuitive how recompression helps treat DCS.

Hi Lorenzoid,

DCS is due to bubble formation from dissolved inert gas. AGE is introduction of bubbles into the arterial system by pulmonary barotrauma. Recompression reduces the size of bubbles and may relieve obstruction whether the bubbles are from DCS or AGE. The higher oxygen pressure may aid hypoxic tissue, and accelerates nitrogen elimination. Oxygen is the emergent treatment and recompression with 100% oxygen breathing is the definitive threatment of DCS or AGE.

Good diving, Craig

I see I was 2 minutes late and @uncfnp beat me to it

 

[Lorenzoid]

For some reason, I was thinking the hyperbaric therapy was intended to help heal the lung injury itself. I get it that it reduces the bubbles. That makes sense.