Bent. I guess it really can happen to me.

[chillyinCanada]

Anatomy of a "HIT" • ADVANCED DIVER MAGAZINE • By John Rawlings

 

[Sevenrider860]

You were taught the rules correctly. General Rule #1 from the PADI RDP instructions...

"Bottom time is the total time in minutes from the beginning of descent until the beginning of final ascent to the surface or safety stop."

---------- Post added September 5th, 2013 at 07:37 AM ----------

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.

I don't think an ascent to the surface or safety stop at 60 FPM is assumed. General Rule #5 from the PADI RDP Instructions...

"Slowly ascend from all dives at a rate that does not exceed 60 feet per minute (one foot per second). Slower is acceptable and encouraged. Be a S.A.F.E. Diver - Slowly Ascend From Every Dive."

Also Bottom Time is not based on a direct ascent to the surface, it is based on the beginning of final ascent to the surface or safety stop.

If the "barracuda watching" occurred at the safety stop, per the PADI RDP instructions that did not contribute to total bottom time.

 

[Hickdive]

What happened - There was a delay as we waited for some divemasters to run lines out to some APCs that had been dumped at the site. I used this time to break down and pack up my gear. I had no indication of an issue until probably about 30 minutes after the last dive.

And there you have it. Did some lifting during that time?

Classic PFO. Dive within your computer limits, no neurological symptoms immediately on surfacing, bit of exertion on the surface and then sudden-onset, rapidly progressing neurological symptoms shortly after the exertion. The resolution of symptoms with O2 suggests it was a very minor shunt.

The algorithm, make or model of your computer or whether you dived tables and/or a square profile are irrelevant in this case.

PS Computers don't drag you along the raggedy edge of safe/unsafe (unless they're like an OSTC and you have programmed them to) even at their least conservative settings. The biggest driver of design safety is, unfortunately, litigation and it doesn't matter what disclaimers are in the manual, something that is of unsafe design will haul a manufacturer's ass into the courtroom by someone who gets injured by it.

 

[drbill]

Your dives seem awfully conservative to me even with just a 43 min SI. However other posters here are correct in that based on your original post there may be a lot of missing information regasrding both your physical starte of being and the actual profile.

I, too, use a computer (actually two) and have done many dives to depths up to 200 ft. I only use the computer as a guide though, not my definitive source. If the computer says I have a 5 min deco obligation, I normally double or triple it with multiple deep stops. However, given your max depth of 55.5 fsw, I wouldn't have flinched unless it was a totally square profile (here on Catalina we have steep sloping underwater profiles which make gradual ascents and multiple stops the norm).

 

[tracydr]

I think PFO is highly unlikely, given 20 years of successful dives.

 

[MMM]

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A ScubaBoard Staff Message...

The side discussion on air integrated computers, breath rate and DCI has been split off and placed here: http://www.scubaboard.com/forums/ba...air-integrated-computers-dci-correlation.html Marg, SB Senior Moderator

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[tracydr]

I watched a webinar by DAN on DCS and temperature. It was remarkable how much changing the temperature of the divers caused an increase in DCS symptoms, even when the divers stayed within NDLs.
PFO is certainly a possibility but wouldn't you think we'd seen other DCS cases in the past 20 years of the OP's diving career. Can't exertion after a dive cause DCS,even in people without DCS.

 

[flots am]

This "hit" was undeserved. However, if I were the OP, I would want to figure out how to avoid a future "hit".

I'm with Boulderjohn on this one. It's unexplained, but no hit is undeserved. It had a cause. The question is: "What was it?"

It would be interesting to see the graph from the dive computer.

flots.

---------- Post added September 5th, 2013 at 11:11 AM ----------

I watched a webinar by DAN on DCS and temperature.

Is there a link for that, or was it a one-time thing?

flots.

 

[iamjblevine]

I'm at work so I don't have any of my books, but I recall something in one class about a minimum SI when using a computer or ML dive of 1hr. I think the passage then went on to state the computer will give you bottom times for shorter, but it is outside the generally accepted safe practice for the computer. Wish I could remember if it was in the DM book, PADI adventures in Diving - ML chapter, or my computer manual. Anyone else remember anything like this?

 

[beaverdivers]

I'm at work so I don't have any of my books, but I recall something in one class about a minimum SI when using a computer or ML dive of 1hr. I think the passage then went on to state the computer will give you bottom times for shorter, but it is outside the generally accepted safe practice for the computer. Wish I could remember if it was in the DM book, PADI adventures in Diving - ML chapter, or my computer manual. Anyone else remember anything like this?

Yes, I stongly recommend at least an hour surface interval ( SI ) on dives that are deeper than 50' & longer than 40 minutes. If you are doing multiple dives a day then increasing your SI as the day continues is recommended.