Surface Intervals affect chance of BO?

[FreeRestriction]

I know SI increase with depth to reduce the chance of DCS but does it have anything to do with reducing the chance of BO? id assume 2-3 mins to recover from a 3 min dive at 10m and a 2-3 mins to recover from a 3 min dive at 50m would still be sufficient for recovery as far as reoxygenating the body and getting rid of CO2 right? of course the DCS factor should majorlly increase the SI times though.

Im asking because on another forum they showed this video:

[ame="http://vimeo.com/7575835"]Blackout!!! Never Dive Alone! on Vimeo[/ame]

and are claiming he needs to increase his surface time between dives to reduce the chances of BO. is this true? Assuming hes spending enough time at the surface to be completely reoxygenated which as i understand happens quite fast, and clear out all the CO2 (not so fast) then his SI time has nothing to do with him BO right?

 

[trux]

The main problem is the build up of lactic acid. It needs to be burn aerobically, which means the body will consume oxygen in accelerated rate, and you will blackout quicker than you would normally do, if you do not get rid of the excess lactates before your new dive.

 

[FreeRestriction]

The main problem is the build up of lactic acid. It needs to be burn aerobically, which means the body will consume oxygen in accelerated rate, and you will blackout quicker than you would normally do, if you do not get rid of the excess lactates before your new dive.

Oh i didnt even consider lactic acid build up. Now how does the time to clear the LA build up compare to the required time to reduce the chance of DCS? is LA the main cause for a long SI on deep dives or is DCS the thing that pushes SI so long? of course if a diver dove 5m and sat on the bottom for 3 minutes there will be a greatly decreased amount of LA versus a diver who was kicking the whole 3min. the question is will lactic acid build up EVER exceed the time required to safely avoid DCS?

Thanks for your responses Trux this is such valuable info im very grateful for.

 

[Simos]

Oh i didnt even consider lactic acid build up. Now how does the time to clear the LA build up compare to the required time to reduce the chance of DCS? is LA the main cause for a long SI on deep dives or is DCS the thing that pushes SI so long? of course if a diver dove 5m and sat on the bottom for 3 minutes there will be a greatly decreased amount of LA versus a diver who was kicking the whole 3min. the question is will lactic acid build up EVER exceed the time required to safely avoid DCS?

Thanks for your responses Trux this is such valuable info im very grateful for.

I am no expert but I don't see how the two are related - if you do a long DYN at 1m you might be full of LA whereas you are not running any risk of DCS so don't need any surface interval for the avoidance of DCS but still needed to get rid of the LA. So I guess the answer to your question would be yes.

 

[FreeRestriction]

I am no expert but I don't see how the two are related - if you do a long DYN at 1m you might be full of LA whereas you are not running any risk of DCS so don't need any surface interval for the avoidance of DCS but still needed to get rid of the LA. So I guess the answer to your question would be yes.

good point i didnt consider pool training so clearly there must be a depth threshold where DCS is more of a factor somewhere between 0-100m i suppose. not that its so cut and dry to depth but generally speaking. the pool dynamic i think is a great place to determine the required time to totally recover from LA. so lets give a 1:30 min dive at 1m while constantly swimming as a starting point. what kind of recovery could be required? im assuming depth has no factor on LA build up?

 

[Erki]

Accumulation of lactic acid depends on several factors like speed of the swimming, dive reflex, type of muscule, predive metabolic rate etc. Also the removal rate of lactic acid depends on number of things so its difficult to establish general formula that gives ideal surface intervals. You should test it by yourself, but even then the days are different and its better to listen carefully signals from your body and not trust to much all kind of mechanic formulas.

 

[cdavis]

Without commenting on the video or getting deep into the physiology, surface intervals for either of the two dives you listed is way too short. Short surface intervals in recreational diving definitely leads to increased B0s, personal experience(I got to do the rescues) and has been much commented on on these forums.

Longer surface intervals, double your dive time is one rule that works most of the time in mid depths, also lead to longer, easier dives.

Connor

 

[Simos]

The main problem is the build up of lactic acid. It needs to be burn aerobically, which means the body will consume oxygen in accelerated rate, and you will blackout quicker than you would normally do, if you do not get rid of the excess lactates before your new dive.

The one thing I (stupidly) never considered before is lactic acid buildup before even diving, because of swimming. Not sure how big a factor it is.

Occasionally when in the sea (especially in a new location) I just swim (front crawl) until I see something interesting and have a short pause, then I dive, come up, short pause and carry on swimming.

I don't use a snorkel when swimming and usually I can breathe as much as I want but when it's choppy sometimes I have to time my breathing and take smaller or less frequent breaths at times.

I wonder if this builds up significant lactic - is there a way of knowing? I never feel lactic in my legs (don't tend to kick much during crawl)...

Also I wonder if swimming before the next time actually clears any lactic from the previous - I was always considering the fact that I am working aerobically (in theory?) to be a good thing before the next dive but I am now having doubts...

 

[trux]

Light aerobic effort burns lactic acid, but on the other hand it depletes the oxygen stores much faster.

 

[efattah]

As I wrote in many other threads, the main factor in blackout is the surface interval, especially if you had acid from the previous dive. If you had acid, and you have a strong vasoconstriction, it can take up to 40 minutes (!!!) for the acid to go away and there is almost nothing you can do to speed that up. If you have a severely acid dive where your legs are actually in pain near the end, it can take 24 hours or even more to clear the acid.

If you start the next dive with any acid in you, the acid will burn oxygen during your dive, above any O2 you burn yourself, and will increase the chance of a blackout.

Increasing the surface interval is good, but if you increase your interval to over 5 minutes, then you cannot do deep breathing during your interval, and/or you need to do a static apnea to recharge your CO2 stores. If you take, for example, an 8 minute interval to clear acid, and you breathe deeply the whole time, now you start the next dive with too little CO2, and greatly increase your BO chance due to low CO2. You need to start your dive with medium CO2 and zero acid. Get this wrong and you have a big risk of BO.

I guess my point is that clearing acid takes time, not breathing. If you are resting to clear acid, don't breathe barely at all.

 

[FreeRestriction]

Wow great info! this is why i love this forum. Thanks efattah.