Bent. I guess it really can happen to me.

[boulderjohn]

Just to clarify for my own knowledge, isn't ABT from beginning of descent to beginning of ascent? So shouldn't the time at the safety stop be subtracted from the total when using tables?

I was never taught to subtract safety stop time. And don't teach to do that either. And in this case 3 minutes is not going to make much difference. And remember the safety stop is optional so it may actually be skipped, so why subtract it? I teach students to err on the side of conservatism and to plan and track dives as square profiles as my agency requires me to. Even though we know they are not. Standards require me to teach them as such. My PADI classes were all based on square profiles when I got certified. I was not taught to fly the computer. In fact just the opposite. I guess now it's different.

If using the PADI tables exactly as intended, the bottom time begins as soon as you start your descent and ends as soon as you begin your direct ascent to the surface at 60 FPM. The ascent time and safety stop are not considered part of the bottom time.

So let's look at how this applies to what we know or do not know about this situation.

1. We do not know if the given times were total run times or bottom time as defined by the tables. We do not know if the ascent and safety stop were included in those times. We really can't make any real assessment of his dive in terms of tables because we don't know any of the real numbers for sure.

2. We do know that the ascent rates were slower than 30 FPM--apparently considerably so. The bottom times in the PADI tables were computed on the assumption that the diver will ascend at 60 FPM--ascending slower adds to the bottom time. We also know that the diver's ascent on the first dive included a barracuda-watching diversion that should be considered part of the bottom time. Since he did not begin his direct ascent until after that, then the barracuda watching time is part of the bottom time. If the times he gave us were actually run times and not just bottom times, then it doesn't matter.

 

[tc]

It's important for divers using computers to understand a bit about them. (Not implying that the OP does not BTW)

You need to understand a bit about the algorithm the computer uses and if it is on the liberal or conservative end or the spectrum. Knowing that can help you decide if you need to add any conservatism based on your personal conditions or the conditions of the dive.

Blind reliance on a computer isn't a good thing- but it's fine to use it as another tool in your toolkit for planning.

A good starting point is the computers manual, just about all of them are available on the internet if you've lost your copy. Just google the brand and model of the computer along with the word manual and it should turn up.

 

[chrpai]

I was taught the definition of bottom time "starts from the beginning of descent until the beginning of final ascent to the surface. It does not include the time spent during the final ascent and any safety stop."

 

[dumpsterDiver]

I was taught the definition of bottom time "starts from the beginning of descent until the beginning of final ascent to the surface. It does not include the time spent during the final ascent and any safety stop."

Yeah, but... the tables have a certain assumed ascent rate. If you dick around at 20-30 feet forever or go up super slow, then this is going to affect the slower tissue and may result in more nitrogen absorbed, which can be an issue on a repetitive dive. I think the right protocol would be to add to your bottom time any"delays" that occurred in the ascent which were not envisioned in the generation of the tables.

Again if it is your last dive of the day, chilling at 20 feet playing with jellyfish should not be a problem.

I myself was bent on a somewhat benign profile ('however I worked hard and was coming back from the flu)... and I too experienced significant numbness (but zero paralysis) and it was complete resolved in 25 minutes by breathing oxygen on the boat.

Rather than pissing and moaning about the details of this or that table or computer, the take home message should be that oxygen is good stuff.. Earlier is better...

 

[chrpai]

Yeah, but... the tables have a certain assumed ascent rate. If you dick around at 20-30 feet forever or go up super slow, then this is going to affect the slower tissue and may result in more nitrogen absorbed, which can be an issue on a repetitive dive. I think the right protocol would be to add to your bottom time any"delays" that occurred in the ascent which were not envisioned in the generation of the tables.
.

Sure, but that's not what Jim was saying. He was saying that he always uses total dive time.

 

[Tigerman]

As do I, but then again, I always "dick around at 20 feet forever" as well..

 

[Superlyte27]

Yikes! Based on what you've told us do far, other than the short interval, we should all be bent many times over. As others have asked what were you breathing? (Though you've referred to "air" numerous times in your post please confirm) Also do you recall the depth at which you stopped to look at the barracuda and duration thereof?

Glad that your symptoms abated and have not recurred but yes, this must be figured out.

Me thinks you don't understand how diving works if you think you can determine whether he should be bent from the info given. You have been given a max depth and the dive time, that's it. You don't know how long he was at that max depth. He could have been at 55' for 3 minutes and spent the remainder of the dive at 23'.

 

[redacted]

Sure, but that's not what Jim was saying. He was saying that he always uses total dive time.

SEI dive tables: http://www.humankinetics.com/AcuCustom/Sitename/DAM/040/Dive_tables.pdf

Includes their definition of bottom time. Greatly reduced pressure groups.

 

[Superlyte27]

Hey OP, upload your dive profile so we can eliminate some of this conjecture. I seriously doubt you were doing a square profile. But I could be wrong. Seriously guys, get out of the stone ages. There's nothing wrong with computers, just maybe the people programming or using them. GIGO

 

[flots am]

Me thinks you don't understand how diving works if you think you can determine whether he should be bent from the info given. You have been given a max depth and the dive time, that's it. You don't know how long he was at that max depth. He could have been at 55' for 3 minutes and spent the remainder of the dive at 23'.

It doesn't really matter. vPlanner is happy with that profile, with no deco and no safety stop and anything from a 10'/minute to 30'/minute ascent rate. I would have done that profile without a second thought.

There's something else going on.

flots.