Air Breaks: When & How Long do You do Them?

[Rick Inman]

Presumably y'all are only doing air breaks if doing deco at 1.6?

For me, yes, only air breaks on O2. And I have no problem gong back to high HE backgas, like 18/45 (another topic ).

Do you switch your computer when you switch back to your travel or back gas? Otherwise your computer would be thinking that you are still on O2 and give you undeserved credit, correct?

My longest deco ever was about 25 minutes including the safety stop, so this is an interesting discussion. I have never switched back to another mix after I switched to O2.

Dive Safe!

Some people add time for the air break. Some do not (ratio deco). Some software (like VPM on Liquidvision) can calculate the air breaks into the plan.

I do not dive a computer. I dive a plan (or variation of ).

 

[nadwidny]

I do air breaks on the surface between dives.

During the dive I do backgas breaks.

 

[do it easy]

I read somewhere that 3 mins is not enough time for the lungs to recover - that if you need at least 5 mins. Don't remember where I read it or if it's true.

It works for me and the people I dive with wouldn't care if we did 20 minutes straight through. If I was doing more than one air break, than I would probably use 5 or 6 minutes.

 

[Rick Inman]

Tomorrow's dive, I have 25 mins on O2. Would you all do an air (ok... backgas) break? Would you do the break on the 18/45, or the 50%? I know what we do... Interested in what you guys do.

 

[Meng_Tze]

Presumably y'all are only doing air breaks if doing deco at 1.6?

Using 80% the PO2 on the second stop at 20 feet is only 1.3,would you do air breaks here?

(Just asking,please dont get into the 80% thing )

Depends on my total exposure, at 1.3 I would probably just suck it up.

 

[Meng_Tze]

Do you switch your computer when you switch back to your travel or back gas? Otherwise your computer would be thinking that you are still on O2 and give you undeserved credit, correct?

My longest deco ever was about 25 minutes including the safety stop, so this is an interesting discussion. I have never switched back to another mix after I switched to O2.

Dive Safe!

I don't think the 'undeserved credit' would hurt you if you got out according to a full 100% schedule. If your conservatism is appropriate, you have a buffer on the up side. I have done long deco's (40+ mins on O2) without accounting for airbreaks. Just followed the schedule and came out fine. Then again, my conservatism for those dives is +3-4 on VPM.

If you are cutting things close, work on high PO2's and cut times off/very close; resetting your comp to BG during air breaks is not going to make a difference in your potential to get a hit on anything.

 

[rjack321]

Tomorrow's dive, I have 25 mins on O2. Would you all do an air (ok... backgas) break? Would you do the break on the 18/45, or the 50%? I know what we do... Interested in what you guys do.

I would do 10-5-10, but could also skip it. Its borderline.

If you chose to break definately do it onto 18/45. 1) the He is easier on the lungs (you want a break right, not just a reduction) and 2) the backgas regs are right there. Switching from your O2 reg to your 50% reg is convoluted.

 

[JeffG]

Tomorrow's dive, I have 25 mins on O2. Would you all do an air (ok... backgas) break? Would you do the break on the 18/45, or the 50%? I know what we do... Interested in what you guys do.

Since I am a bit of a deco weenie, I would add a little time, but I would use it as a backgas break.

So I would probably do: 12 on, 6 off, 6 on, 6up

 

[nadwidny]

Tomorrow's dive, I have 25 mins on O2. Would you all do an air (ok... backgas) break? Would you do the break on the 18/45, or the 50%? I know what we do... Interested in what you guys do.

Backgas at the 30' stop.

For the O2 12 on, 6 off, 7 on with the breaks on backgas.

 

[Gene_Hobbs]

The data on when and why is interesting...

I'd start here when deciding what to do:

Extension of oxygen tolerance by interrupted exposure.
Clark. Undersea Hyperb Med. 2004 Summer;31(2):195-8.
RRR ID: 4009

Most of the work started with Lambertsen and Clark in the Predictive Studies Series:

Pulmonary Oxygen Tolerance in Man and Derivation of Pulmonary Oxygen Tolerance Curves.
Clark and Lambertsen. 1970 PhD Thesis
RRR ID: 3863

with a better summary of the whole series here:

The Predictive Studies Series: Correlation of physiologic responses to extreme environmental stresses.
Clark. Undersea Hyperb Med. 2004 Spring;31(1):33-51.
RRR ID: 3988

There has been a strong interest in this area for US Navy for some time but lots of new data coming out recently:

Pulmonary effects of submerged oxygen breathing: 4-, 6-, and 8-hour dives at 140 kPa.
Shykoff Undersea Hyperb Med. 2005 Sep-Oct;32(5):351-61.
RRR ID: 4031

Pulmonary Function After Oxygen-Accelerated Decompressions from Repetitive Sub-Saturation Air Dives.
Shykoff. 2005 NEDU Report.
RRR ID: 3484

Pulmonary Effects of Six-Hour Dives: In-Water or Dry Chamber Exposure to an Oxygen Partial Pressure of 1.6 ATM
Shykoff. 2005 NEDU Report.
RRR ID: 3471

Two Consecutive Five-Day Weeks of Daily Four-Hour Dives with Oxygen Partial Pressure 1.4 ATM
Shykoff. 2006 NEDU Report.
RRR ID: 3493

Performance of Various Models in Predicting Vital Capacity Changes Caused by Breathing High Oxygen Partial Pressures.
Shykoff. 2007 NEDU Report.
RRR ID: 6867

I am tired of pulling my favorite Shykoff work of late so check here

and if all that was too "heavy" start here:

Tolerating oxygen exposure.
Hamilton Jr, RW. SPUMS 1997 Volume 27 Number 1.
RRR ID: 6038

and... my ratio changes by the deco time involved...