Some antidotal stuff from a novice at this tek thing.... 

I've been finding that long dives ( on air ) are harder on me than short
dives.  The typical TriMix training dive I hear about is a 20mins at
depth and about 90 mins of deco.  The middle tissue compartments are the
ones loaded during the longer dives.  These to me are far harder to me
than the short, fast ones.  If I bounce quickly deep, it's much less
tiring than the 45 mins at 100 ft dives.  

The DCS cases I hear about repetitive dives at medium (60-100 ft) sorts
of  depths to the limits of the tables.  Maybe there is something wrong
with the way we model those mid-range tissues?  

Tom Mount posted a while back about a study that was done where deco on
air for 100 ft dives > 60 mins caused symptomatic bubbling.  Better deco
gases solved the problems, but I still wonder what's wrong with model
that we didn't predict the bubbles better.

>----------
>From: 	Richard Pyle[SMTP:deepreef@bi*.bi*.Ha*.Or*]
>Sent: 	Wednesday, May 08, 1996 2:34 PM
>To: 	David Wilkins
>Cc: 	techdiver@terra.net
>Subject: 	Re: TWO trimix dives a day ?
>
>
>> For me, it all started from two factors some 10-15 years ago, when 
>> 'deep' dives were 50-55m. It was customary to do a main (deep) dive out 
>> in the English channel, then do a 20m or shallower dive close inshore 
>> on the way in.
>
>[...]
>
>> Anyway, a few people got 'niggles', generally a few hours after the 
>> second dive, and there was one or two cases of arm joint/ muscle bends 
>> that required recompression. The Royal Navy 'pot' at Portland Bill 
>> forcibly told these unfortunates that they thought two dives in one day 
>> was a very bad thing to do when one or more was 'deep'. (They also 
>> thought that letting divers control their own decompression stops was 
>> crazy). The second dives were phased out after deep first dives, and 
>> the niggles stopped occurring.
>
>Interestingly, in the old days I would tend to have problems much more
>frequently on days when I did a deep (>55m) dive followed by a
>shallowish
>(20-30m) second dive, than on days when I would do two or more deep
>dives. 
>Surface interval was the same, decompression "conservatism" (staying
>20ft
>below the ceiling, clearing at 20 feet, staying 15 extra minutes, etc.)
>
>was the same. Go figure...
>
>> 2. If you subscribe to the micro-bubble theory, you need to have a 
>> long-enough surface interval such that no micro-bubbles remain in the 
>> blood at the start of the second dive. Anyone know how long this is?
>
>I think the micronuclei are ALWAYS there (except some theories hold
>that 
>deep dives might crush a few into oblivion). The differences is in how 
>big the gas-phase bubbles are.  That's why when I do multiple deep
>dives, 
>I'm more "bubble conscious" than "tissue compartment conscious" in my 
>decompression planning.
>
>Aloha,
>Rich
>
>Richard Pyle
>deepreef@bi*.bi*.ha*.or*
>*******************************************************************
>"WHATEVER happens to you when you willingly go underwater is
>COMPLETELY and ENTIRELY your own responsibility! If you cannot
>accept this responsibility, stay out of the water!"
>*******************************************************************
>
>--
>Send mail for the `techdiver' mailing list to `techdiver@terra.net'.
>Send subscription/archive requests to `techdiver-request@terra.net'.
>

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]