Air integrated computer and tec diving

[Nasser]

Nasser,

I have lost two write-ups so this one will be short. Never said pre-planning was unimportant. It is critical in determining requirements and contingencies. Once the dive begins, you cannot change your equipment configuration with regards to supplies and any unforeseen or unplanned contingencies that may avail themselves. You have what you have. You might lose some supplies but you are unlikely to gain supplies. You still have options so a pre-plan that determined your supplies and dive profile is important but the dive profile in is control. You can go deeper, shallower, longer, shorter, abort etc. Once you start your ascent, you really cannot change much. Follow a GF99 value to reduce deco stops, use different gas switches etc but for the most part, your min deco obligation is what it is, your gas supply is what it is, your times to surface are what they are, your swim or other requirements are also what they are. So as you start your ascent your deco obligations are in control. It is possible for something else to take control, e.g. gas loss, gas exhaustion, thermal considerations, medical issue etc, but in a non-emergency ascent, deco obligations are in control. So it really does not matter what the pre-plan or even the dive plan states, as your deco obligations are what they are and you will either complete them or not with your current supplies (short of borrowing from buddies or the boat). Even if you run out of gas, only then is gas supply in more control than deco obligations. I may be concerned during deco but until I run out or nearly run out, gas is not in control. I have even seen it written and generally agree, although I do not do, deco bottles do not really need a pressure during the dive as it serves minimal purpose - all you can really do is watch your gas run out, hence you have what you have.

"You have what you have" during the dive is very largely predetermined by your dive plan and objectives... it doesn't exist within a vacuum. You are going to take down what you need for the dive and plan accordingly... and that can change depending on each dive's requirements.

"You have what you have" is intrinsically linked and predetermined to your present dive circumstances by this pre-dive plan and its ever-evolving and ongoing execution during the dive. However, you cannot separate the two and it is a direct function of causality. If you end up not having enough gas to complete your deco because of a flawed plan ... then you have what you have because of a flawed plan and you could have had a "better" have what you have with a better plan (barring any catastrophic failures - and even then, there's hopefully a plan to try to deal with that as well).

 

[packrat12]

"You have what you have" during the dive is predetermined by your dive plan and objectives... it doesn't exist within a vacuum. You are going to take down what you need for the dive... and that changes depending on each dive's requirements.

"You have what you have" is intrinsically linked and predetermined to your present dive circumstances by your plan. You cannot separate the two and it is a direct function of causality. If you end up not having enough gas to complete your deco because of a flawed plan ... then you have what you have because of a flawed plan and you could have had a "better" have what you have with a better plan (barring any catastrophic failures - and even then, there's hopefully a plan to try to deal with that as well).

But the original comment is that the computer has the actual representation of your dive profile, not your dive plan and that your ascent is controlled by your deco obligations (and yes even if it comes out of the pre-dive configured dive plan or from the computer).

A dive plan consists of limits, runtimes and a decompression schedule. The plan limits are Max depth and Max time. To build the dive plan, a pre-plan is considered with varying parameters, e.g. gas mix, desired depth, desired time, GF (or other conservative factors), etc. It also is considered with limits, e.g. gas quantity, gas availability, tank size, team configuration, thermal considerations etc. What comes out is a dive plan and typically contingencies. I might plan for a dive on the HydroAtlantic for 175' but not be sure how much deck time is going to be spent at 150' or at 165' etc. So my plan will be for the sand. This is not optimal but it will allow a safe ascent on loss of a computer.

Once the dive starts, the Dive Plan is in control. I have very little information from the pre-plan in my now processed plan. At the minimum I have a max depth, max time, runtime and a deco schedule + contingencies. So on my dive, I spent a lot of time between 150-170'. The dive plan still will be met, e.g. max depth, max time. Once the ascent begins, the deco schedule takes over, which is an approximation of my deco obligations. So back to the original statement, My Deco Obligations control my ascent, not my dive plan. Since by dive plan is NOT an accurate representation of my dive profile, my COMPUTER has the accurate representation of it and the Deco schedule on the computer is correct, NOT my dive plan. My Deco obligations are now the controlling factor in my ascent and they come from my computer, not my dive plan!

The only linking on ascent from my dive plan to my ascent is the time, although the max depth was never exceeded. My max depth and ave depth never followed my plan. So the plan is not accurate, the computer is, which is the primary statement I made at the beginning of this. While the pre-planning helped setup the max depth and max time limits (and yes a lot more including gas requirements), the actual dive did not follow it. They are not intrinsically linked as the only parameter used from the dive plan is the max time and not exceeding the max depth. My deco requirements are substantially less then required by the dive plan, my gas consumption is substantially less then anticipated by my dive plan, and my runtime in the end is less then anticipated by my dive plan.

If the computer fails, the dive plan is by alternate way out and the max parameters set by it can not be exceeded. They do not, however, need to be met. With a computer functional, I will use its deco schedule and as a result which still does not change, my Deco Obligations are in control of my ascent!

As an homage to Boulderjohn: This was a profile I dove with John Chatterton!

PS: A simple test is, if you have working computers and have significant Deco Obligations but are not around a contingency plan and your buddy suddenly starts feeling left should pain or otherwise is ill (but not immediately serious enough to risk DCS), are you going to wait out the dive plan OR are you going to use your computer's deco schedule and surface????? My bet is you will start your ascent . The only reason you cannot surface immediately is because of your Deco Obligations. You will follow your computer, which has the accurate representation of the dive profile. You are following your deco obligations, which are the controlling factor in your ascent....

 

[Nasser]

But the original comment is that the computer has the actual representation of your dive profile, not your dive plan and that your ascent is controlled by your deco obligations (and yes even if it comes out of the pre-dive configured dive plan or from the computer).

A dive plan consists of limits, runtimes and a decompression schedule. The plan limits are Max depth and Max time. To build the dive plan, a pre-plan is considered with varying parameters, e.g. gas mix, desired depth, desired time, GF (or other conservative factors), etc. It also is considered with limits, e.g. gas quantity, gas availability, tank size, team configuration, thermal considerations etc. What comes out is a dive plan and typically contingencies. I might plan for a dive on the HydroAtlantic for 175' but not be sure how much deck time is going to be spent at 150' or at 165' etc. So my plan will be for the sand. This is not optimal but it will allow a safe ascent on loss of a computer.

Once the dive starts, the Dive Plan is in control. I have very little information from the pre-plan in my now processed plan. At the minimum I have a max depth, max time, runtime and a deco schedule + contingencies. So on my dive, I spent a lot of time between 150-170'. The dive plan still will be met, e.g. max depth, max time. Once the ascent begins, the deco schedule takes over, which is an approximation of my deco obligations. So back to the original statement, My Deco Obligations control my ascent, not my dive plan. Since by dive plan is NOT an accurate representation of my dive profile, my COMPUTER has the accurate representation of it and the Deco schedule on the computer is correct, NOT my dive plan. My Deco obligations are now the controlling factor in my ascent and they come from my computer, not my dive plan!

The only linking on ascent from my dive plan to my ascent is the time, although the max depth was never exceeded. My max depth and ave depth never followed my plan. So the plan is not accurate, the computer is, which is the primary statement I made at the beginning of this. While the pre-planning helped setup the max depth and max time limits (and yes a lot more including gas requirements), the actual dive did not follow it. They are not intrinsically linked as the only parameter used from the dive plan is the max time and not exceeding the max depth. My deco requirements are substantially less then required by the dive plan, my gas consumption is substantially less then anticipated by my dive plan, and my runtime in the end is less then anticipated by my dive plan.

If the computer fails, the dive plan is by alternate way out and the max parameters set by it can not be exceeded. They do not, however, need to be met. With a computer functional, I will use its deco schedule and as a result which still does not change, my Deco Obligations are in control of my ascent!

As an homage to Boulderjohn: This was a profile I dove with John Chatterton!

PS: A simple test is, if you have working computers and have significant Deco Obligations but are not around a contingency plan and your buddy suddenly starts feeling left should pain or otherwise is ill (but not immediately serious enough to risk DCS), are you going to wait out the dive plan OR are you going to use your computer's deco schedule and surface????? My bet is you will start your ascent . The only reason you cannot surface immediately is because of your Deco Obligations. You will follow your computer, which has the accurate representation of the dive profile. You are following your deco obligations, which are the controlling factor in your ascent....

Your plan has tolerances and contingencies, and you dive within the plan - the real time feedback still falls within your plan that's all, they are not mutually exclusive. What you have is indeed intrinsically linked with your pre-plan... at least I would hope so.

P.S.

Would love to dive with John Chatterton - that is indeed very cool.

 

[CAPTAIN SINBAD]

As an aside... if someone wants to take steps to reduce narcosis at minimal depths... then a gym membership is a lot cheaper than a trade account with a helium supplier.

Id like to know how are these two interconnected. Is there any study done that shows that physical fitness levels effect narcossis?

 

[victorzamora]

Id like to know how are these two interconnected. Is there any study done that shows that physical fitness levels effect narcossis?

I think the theory is that better physical fitness will decrease your co2 loading which will reduce your susceptibility to narcosis. I believe it's almost purely anecdotal as a direct link, but CO2 is a known factor and fitness can reduce absorbed co2 levels....so there's a logical link pretty well established.

 

[packrat12]

Your plan has tolerances and contingencies, and you dive within the plan - the real time feedback still falls within your plan that's all, they are not mutually exclusive...

It does indeed fall within the dive plan and the dive plan does very much control the limits of the dive. All that I am trying to emphasize is that once the ascent begins, I am not concerned about my plan as it is a piece of paper or scratches on a slate. My deco schedule is based on real physiological requirements, e.g. my deco obligations that must be met before I can surface. These obligations are what really dictates my ascent. Whether I get the data from a piece of paper (the dive plan) or the computer does not really matter. The initial point of my entry into this thread was that the computer will, in the end, have a much more accurate representation of my profile and as a result, a much more 'realistic' deco schedule (assuming the same model and parameters were used, which is my case). They may exactly match the schedule in my dive plan, or not - but if the computer is working it has the better representation. The dive plan (table) deco schedule becomes a fall back if and only if my computer fails during the ascent.

---------- Post added January 8th, 2016 at 10:08 AM ----------

I think the theory is that better physical fitness will decrease your co2 loading which will reduce your susceptibility to narcosis. I believe it's almost purely anecdotal as a direct link, but CO2 is a known factor and fitness can reduce absorbed co2 levels....so there's a logical link pretty well established.

I have totally bought off on CO2 being a major cause of narcosis. A good article that was required reading during my trimix training:

https://www.globalunderwaterexplorers.org/carbon-dioxide-narcosis-and-diving

 

[The Chairman]

Id like to know how are these two interconnected. Is there any study done that shows that physical fitness levels effect narcossis?

Yeah, I'm not buying that being fit reduces narcosis one whit. That's a GI3 thing too, so it's kinda funny. I get the no brain, no pain mentality, but narcosis doesn't work that way. That being said, once on OC helium, being in shape makes a world of difference. The more you huff the more you spend. The better shape you're in, the easier it gets to rid yourself of CO₂. It's why getting a rebreather and I'm swimming in the pool everyday.

 

[DevonDiver]

I'm not sure what GI3 said about fitness and CO2, but I do recall comments about increasing vascularity to improve off gassing. I don't know of any scientific evidence that supports that.

Obesity is regularly stated as a DCS predisposing factor.

The role of CO2 in narcosis is also regularly mentioned. With respect to narcosis... improved cardiovascular fitness improves respiratory function... decreasing O2 demand/CO2 production for a given level of exertion. So, improved respiratory efficiency leads to reduced CO2 retention.

If CO2 plays a major role in exacerbating narcosis, as many believe, then cardiovascular fitness should indirectly reduce narcosis.

Either way, the main point is still that instinctive, ingrained, competencies are the least, or last, impaired by narcosis.

Ever see an MMA fighter get knocked down heavily? They continue fighting, even semi-consious, because they've ingrained their skills over thousands of hours and hundreds of thousands of repetitions.... They get knocked on their ass and don't know where they are, but are trying to leg-lock the referee, even whilst their opponent is celebrating victory on the other side of the cage. If you watch MMA, you'll have seen this...

That analogy explains, I believe, how experienced divers function under significant narcosis. Whereas a different diver, without ingrained skills or procedures, would make fundamental errors that jeopardised safety.

So, when someone tells me that they can't do x, y or z because of narcosis... It tells me they need more skill and procedural repetitions... more experience.

Narcosis merely exposes deficits in ingrained competencies; that are otherwise compensated for by disproportionate focus and concentration. Flaws that otherwise reduce situational awareness under normal, non-narcotic, circumstances.

What's sad is that, for some, there's a process of blame-shifting and denial. Ego dictates that it can't be a personal issue... so we see adamant arguments that ALL divers must suffer the same core skill and awareness degradation.

Caveat: That's not to justify deep air, or highly narcotic diving, at all... Because there's still plenty that can go wrong, outside of core functionality, that can get a narc'd diver in big trouble.

The initial point of my entry into this thread was that the computer will, in the end, have a much more accurate representation of my profile and as a result, a much more 'realistic' deco schedule (assuming the same model and parameters were used, which is my case). They may exactly match the schedule in my dive plan, or not - but if the computer is working it has the better representation.

Here's where I disagree:

1. Pre-dive planning functions to tie together all critical aspects of the dive... deco, gas and O2. If one aspect subsequently changes, the other two become compromised. Thus, an accident chain emerges...

2. Diving with 1 computer and a backup table is a proven method, however.... electing primacy of the computer must not allow the dive plan to become obsolete.

3. The dive plan is your assurance of all three elements; deco, gas and O2. If deco is exceeded, then deficit gas and/or increased O2 may/will harm the diver.

4. Whilst the backup plan/table may be reserve to your computer, it nonetheless represents a red-line that shouldn't be compromised.

5. If the computer deco exceeds the backup plan deco, you no longer have any backup. It's obsolete. You then have to pray your computer won't fail.

6. It is the technical divers' responsibility to ensure that their computer deco does not exceed their planned deco. To fail in this competency indicates they are unready for technical diving.

7. If pre-planned deco is disregarded on entering the water, then (even running the same algorithm) depth variations between team members may cause differing ascent schedules within the team. This compromises safety if the team elects to allow differing stop schedules to split them on ascent. If they elect to maintain cohesion, then some team members will be ignoring their computer calculated ascent schedule.... thus disappears any value of a "more realistic" schedule.

8. You cannot do too much deco, but you can do too little.

9. Cutting into planned gas reserves should be considered a 'failed' dive. It should be a warning sign...a lesson learned and should lead to refinement of future dives. Reserves aren't maintained to compensate for sloppy planning or sloppy diving. If a diver routinely consumes reserve gas, then they are routinely failing to retain proper, expected, support for their team.

10. Exceeding planned deco, gas consumption or O2 CNS/OTUs should never be deemed acceptable or expected. This is a process of complacency... a symptom of 'normalisation of deviance'.

Packrat13... This is what some of your comments indicate. I'm not sure if you meant that or not. Perhaps, I'm just misunderstanding your points..?

 

[Nasser]

It does indeed fall within the dive plan and the dive plan does very much control the limits of the dive. All that I am trying to emphasize is that once the ascent begins, I am not concerned about my plan as it is a piece of paper or scratches on a slate. My deco schedule is based on real physiological requirements, e.g. my deco obligations that must be met before I can surface. These obligations are what really dictates my ascent. Whether I get the data from a piece of paper (the dive plan) or the computer does not really matter. The initial point of my entry into this thread was that the computer will, in the end, have a much more accurate representation of my profile and as a result, a much more 'realistic' deco schedule (assuming the same model and parameters were used, which is my case). They may exactly match the schedule in my dive plan, or not - but if the computer is working it has the better representation. The dive plan (table) deco schedule becomes a fall back if and only if my computer fails during the ascent.

I don't know why you're under the impression that a plan needs to be executed strictly only by following RT's on a slate with pre-cut tables?

That is one way of doing it and probably the way the vast majority of us have been taught. But a plan is merely a predetermined set of parameters that are agreed upon based on the objectives and circumstances of the dive. It assists to set outer limits, figuring out gas requirements, what equipment is needed, and what your going to do if things go south.

You can establish all of these parameters and simply have your slate and tables as a backup - then dive freely off your computer with real time data and within your pre-established limits. In this case, not only is your ascent dictated by your realtime computer data, but the entire dive is - that is in fact how I conduct the vast majority of my dives.

Regardless of how you choose to execute the dive and what tools you choose to execute the dive... it is all informed and predetermined by your dive plan.

 

[boulderjohn]

Monitoring your depth and time is so extremely fundamental, I can't even get over it that were discussing it in the technical forum.

A a dive computer does not relive you of the responsibility of monitoring depth and time or understanding the relationship between depth, time, and decompression obligation.

Again, if you're so new that you can't do a task as fundamental to diving as monitoring depth and time, you have zero business in a technical environment. In my opinion you shouldn't even be training for technical dives if you're unable to do this. "Oh I have a dive computer, I can just 'go' and sort it out later" is backward and dangerous thinking.

Since by dive plan is NOT an accurate representation of my dive profile, my COMPUTER has the accurate representation of it and the Deco schedule on the computer is correct, NOT my dive plan. My Deco obligations are now the controlling factor in my ascent and they come from my computer, not my dive plan!

There seems to be a belief in this thread that the only reason humans ever make computational errors is because of narcosis. A lot of math teachers would disagree.

My first few years of technical diving were 100% DIR with dives conducted with only bottom timers and ratio deco. I then moved to planning dives with V-Planner and executing them with only a bottom timer. I observed a human propensity for making errors during that time that changed my thinking. The key thing is that for the most part the people did not realize they were making errors at the time. That means they could not adjust their dive plans because they did not realize they needed to adjust their dive plans.

I have observed that there is a strong tendency among tech divers to make three kinds of errors when diving like this:

Maximum Depth Errors: This is one of the errors the friends I mentioned earlier made when they got bent and looked at a computer log later to see why. They had planned the dive for a specific depth, and they tried to hold that depth as they swam along a rock wall in deep darkness. The computer profile showed that they would swim at that depth, gradually sink deeper as they swam, realize it, ascend to the planned depth, gradually sink deeper as they swam, realize it, ascend to the planned depth, gradually sink deeper,.... Their actual average maximum depth was more than 5 feet deeper than they thought it was. I also tagged along with a group of experienced divers going to 300 feet in Cozumel, and a subsequent analysis of the computer logs confirmed what I saw on the dive--they spent about half that planned 300 foot bottom time between 310 and 315 feet. They knew they had dipped below 300 and corrected it, but they had not realized the extent of that dip. I think this sort of thing happens frequently.

Early Ascent Rate Error: I recently spoke with a rebreather instructor trainer who had co-written her agency's curriculum for trimix diving on rebreather. We agreed that the most common error in decompression diving is ascending too slowly to the first stop. If you are at the end of a line of divers going up an ascent line from a wreck, and you ascend at 30 FPM, your biggest problem will be getting past all the people above you, for most of them will be ascending at about 10 FPM. I did a dive last year on a boat that included a pair of rebreather divers I knew pretty well. They were using the same computers my buddy and I were (Petrels), and they had the precise same GF factors and dive plan we did. They also had it written down for backup as we did. We all gave our planned run times to the DM and headed off. We arrived at the ascent line at almost the same time, and they began the ascent about 10 feet behind us. I noticed we were outpacing them as we ascended. When we reached the first stop, they were nowhere in sight, and I began to get worried. After a few stops were completed, they emerged from the gloom below. They did 10 minutes more deco than we did, and the DM asked what had happened. "I don't understand," he said. "The computer just kept adding deco time as we went up." I said I thought they had ascended awfully slowly, and he looked at me like I was crazy. "You're supposed to ascend slowly," he said.

In the case of my bent friends, they took about 3 minutes too long to get to the first stop and did not realize it.

Miscounting or Miscalculating Deco Times: In both cases above, the divers would have understood there was a problem if they had paid attention to the run times they had clearly written in their plans. They didn't. Instead they looked at the time of their arrival at the first stop and added the planned stop time there, making that the basis for their deco profile. As Packrat12 said above, they were following the deco profile for the dive they had planned rather than the dive they had done, but they did not know that. To compound the problem, they made a simple arithmetic error on the last deco stop and cut it short by a couple minutes, again without realizing it.

I don't think any of the problems identified above are caused by narcosis, but narcosis can make those problem more likely to occur. These are the kinds of errors we humans make, even humans who are completing their Ph.Ds in a math-related field, as one of my friends was when he got bent. I am sure there are people who are incapable of making those kinds of errors, but I will admit without embarrassment that I am not one of them.