Bent. I guess it really can happen to me.

[jbomb001]

True story!

Sent from my SPH-L720 using Tapatalk

 

[diveDavedive]

Being new to diving I want to learn so I plugged TechDeep's numbers into PADI's eRDPml (I know, I know, square profile vs dive computer). The eRDPml would not allow me to plan that dive.
First dive of 43 minutes @ 55' the diver would have an NDL of 65 minutes and a pressure group of P at end of dive. A 44 minute SI drops pressure group to H. Entering the second dive to 55' I now see an ANDL of 40 minutes so the eRDPml errors when a 46 minute ABT is entered.
I bumped the SI up to one hour, it allowed me to plan the dive and the pressure group at the end of the second dive is W. I would say that yes, there was a lot of residual nitrogen by square profile theory.

This made me curious as to what the eRDPml would say about my recent three dive (Blue Hole, Half Moon Wall, Westpoint Wall) day trip to the Blue Hole in Belize. I dove with a Wisdom3 but I used square profiles on the planner. The three dives were 130' for 10 minutes, 60' for 37 minutes and 55' for 35 minutes. I ended the dives with pressure groups of H, T and Q, respectively. My first SI was 80 minutes and the second lunch time SI was 120 minutes. I started both 2nd and 3rd dives at a pressure group of B.

This is a very simplistic way of looking at it but by the standards I was recently taught, I would say TechDeep did "deserve it", if you will, because of a short SI.

Just my two cents

 

[kidsdream]

Jim,

Just wondering if you have any cave certifications and have done any significant overhead/cave diving. If so, how do you practically or "realistically" use tables for those dives as a planning tool?





Jeff

What was your back up plan? IS your computer set to take into account your body type, whether or not you were dehydrated, your age, your general physical health, or your level of fitness? If not why would you blindly rely on it?

As long as it doesn't indicate deco it's ok? Not a good way to conduct dives.

There's a reason why we say to plan your dives. I'll use this as a prime example of why I do not teach computers in the OW class and insist students plan their dives on tables and try to do that whenever possible. And use a computer as a back up.

Let's see on the SEI tables we have

42:49 rounded up to 45:00 @ 60 ft gives pressure group H

SI 43:55 takes you to pressure group H (well whaddaya know)

RNT of 46 minutes

Next dive

44:21 rounded up to 45:00 @ 60 ft

Add in your RNT and your TBT is 91:00 minutes! At a depth with an NDL of 51 minutes. But hey what's 40 minutes? You got lucky the last time (or times) you did this.

91 minutes @ 60 ft puts you well into deco. On our tables you end up in fact with a 1:20 ascent to 20 feet where you then get to spend 57:00 minutes if decoing on air.

Had you planned this dive out on tables would you have done it? I

I'd throw that damn computer in a box until until I'd developed the discipline and good sense to plan my dives as square profiles beforehand and then MAYBE allow a little extra for the computers sampling rate.

Yeah I'd call that a deserved hit.

And another huge reason DM's should be required to take an actual tech course before starting DM. Even if it's an intro to tech. A good one will put the proper amount of fear in you and go a long way towards reinforcing planning over all.

 

[nimoh]

Jim,

Just wondering if you have any cave certifications and have done any significant overhead/cave diving. If so, how do you practically or "realistically" use tables for those dives as a planning tool?

Jeff

I think cave diving is a little off topic for this discussion

 

[kidsdream]

Jim,

Made a comment that strongly indicated that diving using your computer as your primary reference was not suggested or even fool hardy. My inference that you apparently did understad was that a high percentage of cave divers do in fact dive using their computers as their deco reference (based on the variation and nature of a multilevel dive profile host often accompanies and cave dive)

Tyocially for dives not involving trimix, most cave divers do dive using their computer's deco schedule as their primary/sole reference. It is each diver's comfort/ risk profile that becomes the basis of their time and any additional safety stops or deco profiles.

I think cave diving is a little off topic for this discussion

 

[flots am]

But my COMPUTER can be adjusted to be more or less conservative. Just some food for thought;-)

More or less conservative than what?

 

[jbomb001]

More or less conservative than the tables witch let's face it all computers are initially based on . Not that you can not dive tables conservatively. Just from what I've seen most people that choose to use tables consider them to be as conservative as they need. For instance I've never seen someone say I was at 48ft but am Going to figure my ndl. For 60 where as if I program my computer for 50 ft with a conservative level of 3 out of the possible 5 levels it'll give me the ndls. As if I were at 60ish

if im on this fourm i must be at work. if not id be having way more fun out doors

 

[Dauntless]

Had you any injury that would be described as a "whip Lash" prior to the incident?

 

[TechDeep]

Yes, I have, but it was 3 years prior. Would that make a difference?

 

[boulderjohn]

Had you any injury that would be described as a "whip Lash" prior to the incident?

Yes, I have, but it was 3 years prior. Would that make a difference?

Great question! This could really send this thread into a very interesting and potentially very useful direction!

This past October, a study was released and discussed in this thread. It concluded there is a possible significant increase in DCS risk in people who suffered from spinal stenosis in the cervical area, an age-related problem that narrows the space for the spinal chord and the nerves extending to the arms. It can produce problems similar to whiplash.

Not long after that, someone started another thread in which he was attacking DAN as a corrupt organization. His position is not getting much support, but he did publish a letter from DAN to someone in which they were arguing for highly qualified people on site at a chamber. One of the reasons was to prevent people from getting unnecessary chamber rides for problems that presented as DCS but were actually something else. That letter cited spinal stenosis as a problem that can create DCS symptoms following a dive. As someone who suffers from spinal stenosis, I assure you that if I did not know I had this problem, I would have been heading for the chamber on a number of occasions. When it happens, my symptoms are much the same as yours. (I can get them in non-diving situations as well, such as when carrying heavy loads on my back. It appears that carrying of weight on the shoulders--like scuba tanks--is the problem.)

So I went back to the study mentioned above and looked at their methodology, which I found to be suspect. They studied a group of people who had been treated for DCS in the past and found that they had a much higher incidence of spinal stenosis than a control population. They assumed that meant that they were more susceptible to DCS. The problem is that they also assumed that because they were treated for DCS, they actually had it. There could have been a high number of cases of people being treated for DCS when they actually were having problems with stenosis. An alternative conclusion from their study might be that a large number of people are getting treated for DCS when they actually don't have it.

So your whiplash offers two new intriguing possibilities that I would hope would lead to further scientific study.

1. It is possible that your whiplash injury makes you more susceptible to DCS.
2. It is possible you did not have DCS but instead got an unnecessary chamber ride for symptoms related to your whiplash injury.