Breathing O2 during surface interval

[lowwall]

Wouldn't you already be acclimatized?

It's a decompression issue, not an acclimatization one. They will have been at least overnight at the lower elevation, so most tissues will be saturated at the lower elevation.

Acclimatization refers to physiological changes when enough time is spent at higher altitudes such as increased red blood cell count.

 

[MaxTorque]

If Shearwater allowed us to tell our computers that we are breathing oxygen instead of air, everything would be hunky dory. We could check our tissue saturations as we drove, but it won't do it, obviously because there is no science behind it.

Pedantic point: There is plenty of "science" but little demonstrable real world data surely?

There is (i believe but correct me if i'm wrong) no difference between deco in water and deco in air so to speak, so all the same models and data points apply, so your dive computer could use all it's existing calcs. The issue is simply almost certainly that any change to their s/w must be fully validated, and the small number of users who require this capability make that non-viable?

 

[hsinhai]

I suggest to all divers to do a full five-minute deco stop and not just three. The difference I feel since I started this is amazing. Also, limit activity. You don't need to help haul tanks if you don't have to.

This.. I like to do a longer than required safety stop, and I will also take time to go from the safety stop to the surface (minutes not seconds).. I see many ppl complete the safety stop and then immediately bolt to the surface.. as I get older slowing down surfacing makes me feel less lethargic/achy at the end of a long multi-dive day..

I am not sure if there is any theory behind it but I feel if I keep the 'fizz' to a minimum surfacing (keep further away from the M-line?) it is putting less stress on the body. I guess in subsurface the fast tissues show as less red vs just 3min and straight to surface, so that has to be a good thing..

 

[kelemvor]

I have a Luna as well and have been using the PDIS function for several years. I let my DB know about the anticipated stop before we start the dive. This helps in eliminating confusion.

You may want to do some reading on deep stops. I believe they have been debunked as a useful tool these days.

 

[rick00001967]

Why? You're breathing 0% N2, what's driving the decompression is PPN2insp, not PPO2 -- depth or no depth.

yes you are correct. not sure why i was thinking this. we are talking about the high pressure gradient between o2 an N. so if you are breathing 100% o2 it should not matter what the ppo2 is. thank you for pointing out my mistake. i guess i was only thinking of accelerating a deco obligation.

 

[boulderjohn]

Wouldn't you already be acclimatized?

I am going to give a longer answer than you probably wanted because there is a point of common confusion here. I don't know if you personally were confused about it, so I am writing for any reader who might have been.

Acclimatization is an important factor to consider prior to a dive before which you ascended from a lower altitude. In that case, using dive tables, you need to act as if the ascent from lower altitude was the same as a prior dive. Many altitude diving instructional courses treat that as the primary factor to consider because they do not talk at all about what I was talking about in my post--ascending to altitude after a dive, which is a very different thing. It is possible that your "already acclimatized" comment comes from a common misconception because of an oft published quote from a famous dive leader who sais, in essence, that he never worries about altitude in diving because by the time he is ready to dive, he is already acclimatized. That led to the erroneous belief among his followers that altitude did not need to be considered in dive planning.

Ascending to altitude, on the other hand, is essentially the same as ascending during a dive. You are moving from greater pressure to lesser pressure, so you have to plan for decompression. That is why NASA and the Pentagon use decompression specialists in their planning--going from sea level to high altitude flight or into space creates a dramatically fast loss of pressure that can lead to DCS.

ScubaBoard has a forum called Ask Dr. Decompression, and for the first years of this forum, Dr, Decompression was Dr. Michael Powell, one of the scientists who did the research leading to the PADI dive tables. Powell's main job was as a decompression scientist at NASA.

Here is an article I wrote about ascents to altitude.

 

[boulderjohn]

Pedantic point: There is plenty of "science" but little demonstrable real world data surely?

There is (i believe but correct me if i'm wrong) no difference between deco in water and deco in air so to speak, so all the same models and data points apply, so your dive computer could use all it's existing calcs. The issue is simply almost certainly that any change to their s/w must be fully validated, and the small number of users who require this capability make that non-viable?

I may have misunderstood you, but I think we are essentially in agreement. Breathing oxygen during a surface interval rather than air will have a significant effect upon decompression, but Shearwater is understandably reluctant to build that capacity into their algorithm because of a lack of data. In a past thread someone said that the computers used by the military do have that ability, but I am jt repeating something I read on the Internet for that information.

You actually can use the existing Shearwater algorithm to guide such an ascent. The graph showing tissue loading and unloading continues to function during the surface interval, and I believe it reacts to changes in pressure. You should be able to follow it on a drive to altitude. I asked them about it, though, and they would provide no comment, and they told me to follow guidelines for flying after diving.

 

[boulderjohn]

Where are you getting supplemental oxygen to breathe on a surface interval or at the end of the dive day?

If you are a technical diver, you breathe high nitrox percentages and pure oxygen during the last decompression stops in order to lower the amount of nitrogen you are breathing and thereby increase the speed at which you decompress. The difference is huge. You carry additional tanks with these gases in them and switch from one to another.

At the end of the dive day, you should have oxygen left in that tank, and you can breathe as you would on a dive. (Not quite--I recommend inhaling from it, letting the O2 bathe your lungs, and then exhaling without the regulator in your mouth. Otherwise it slobbers up quickly.)

Technical divers have certifications that allow them to get oxygen fills at dive shops that offer that service.

 

[Scuba Client]

It's a decompression issue, not an acclimatization one. They will have been at least overnight at the lower elevation, so most tissues will be saturated at the lower elevation.

Acclimatization refers to physiological changes when enough time is spent at higher altitudes such as increased red blood cell count.

I was reading a quote: hike high, sleep low. But my main concern was why someone would want to breath O2 in their car on the drive home (supposedly at altitude) and during surface intervals. Expensive habit if you're not bent.

 

[Scuba Client]

I am going to give a longer answer than you probably wanted because there is a point of common confusion here. I don't know if you personally were confused about it, so I am writing for any reader who might have been.

Acclimatization is an important factor to consider prior to a dive before which you ascended from a lower altitude. In that case, using dive tables, you need to act as if the ascent from lower altitude was the same as a prior dive. Many altitude diving instructional courses treat that as the primary factor to consider because they do not talk at all about what I was talking about in my post--ascending to altitude after a dive, which is a very different thing. It is possible that your "already acclimatized" comment comes from a common misconception because of an oft published quote from a famous dive leader who sais, in essence, that he never worries about altitude in diving because by the time he is ready to dive, he is already acclimatized. That led to the erroneous belief among his followers that altitude did not need to be considered in dive planning.

Ascending to altitude, on the other hand, is essentially the same as ascending during a dive. You are moving from greater pressure to lesser pressure, so you have to plan for decompression. That is why NASA and the Pentagon use decompression specialists in their planning--going from sea level to high altitude flight or into space creates a dramatically fast loss of pressure that can lead to DCS.

ScubaBoard has a forum called Ask Dr. Decompression, and for the first years of this forum, Dr, Decompression was Dr. Michael Powell, one of the scientists who did the research leading to the PADI dive tables. Powell's main job was as a decompression scientist at NASA.

Here is an article I wrote about ascents to altitude.

Thanks for the article; will include it into my vast library of e-books.