Charlie99
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NOAA dive planning tables including time to ascend; and the air, EAN32, and EAN36 NDL tables.
Driving up the Mountain?
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SeaJay
Contributor
DISCLAIMER: I am not a doctor, and have not been trained to do specific decompression diving yet. I have no advice to offer, and am not offering that one should or shouldn't do anything regarding diving and soon before or after ascending to altitude.
All I have to offer is an observation of the facts relevant to this subject.
This weekend I participated in DAN/Duke University's "Flying After Diving" study. Here's the facts as I know them:
The term "flying" or "altitude" is based on the concept of 8,000 feet above sea level. This is due to the fact that most commercial aircraft function on a partially pressurized cabin; that is, even if they're flying at 35,000 feet, the interior pressure of the aircraft generally doesn't fall below the 8,000 foot limit. In fact, most of them only go to 5,000. Also, many Navy divers who take transport planes or helicopters to/from a dive site generally stay below 8,000 feet of altitude in an unpressurized cabin, or fly in planes with cabin pressures similar to that of commercial airliners.
Other factors that come into play when talking about altitude come into play, such as repetitive dive profiles, time of surface interval, tissue loading (those that are slow or fast to ongas/offgas), etc. Also, some people seem to be more prone to "bending" or not bending, which can be independent of whether or not bubbles are formed in the bloodstream. For example, a particular individual may be prone to "bubbling" rather easily, but not exhibit DCS symptoms, while another may not "bubble" easily, but exhibit DCS symptoms quite readily. As far as I know, there has not been a definite correlation found by the observers of the data; that is, people who "bubble" do not necessarily bend easily, or vice-versa. Also, smokers, people with high body fat content, out-of-shape divers and the like are not necessarily at higher risk, contrary to common sense.
PADI teaches the age-old axiom that if you dive, you must wait at least 12 hours to fly. This idea, I found out this weekend, does not have data to support the notion.
There is a study going on right now to see if there is a correlation between flying, diving, time spent between, and the correlation of DCS. After about 1500 participants, there does not seem to be a statistical correlation between any of it.
My profile this weekend was the following: 60 fsw dive for 40 minutes; 30 fpm ascent and descent at the beginning and end of the dive. We had a 1 hour surface interval, and then were taken to an altitude of 8,000 feet in two minutes and left there for four hours. We were observed using complex medical instruments, including an ultrasound machine on our hearts to observe bubble formation every 20 minutes during the dive and for four hours after the dive. We were also observed for the following two days for DCS symptoms.
None of us exhibited any DCS symptoms, and one of us actually developed bubbles. There were nine subjects in the study. These results seemed to be consistent with the rest of the data collected at other studies.
The next study, which I will also be participating in, will be the same profile but with no surface interval at all.
Lastly, I thought it was also an interesting discovery that people who have experienced a DCS hit in the past show no evidence of being any more or less susceptible to DCS in the future; that is, if you do get bent, it does not necessarily make you more or less susceptible to getting bent in the future, despite what many agencies believe.
Further questions should be forwarded to the DAN/Duke University Hyperbaric Chamber facility. Speak to Eric... He seemed very knowlegable on the data collected.
All I have to offer is an observation of the facts relevant to this subject.
This weekend I participated in DAN/Duke University's "Flying After Diving" study. Here's the facts as I know them:
The term "flying" or "altitude" is based on the concept of 8,000 feet above sea level. This is due to the fact that most commercial aircraft function on a partially pressurized cabin; that is, even if they're flying at 35,000 feet, the interior pressure of the aircraft generally doesn't fall below the 8,000 foot limit. In fact, most of them only go to 5,000. Also, many Navy divers who take transport planes or helicopters to/from a dive site generally stay below 8,000 feet of altitude in an unpressurized cabin, or fly in planes with cabin pressures similar to that of commercial airliners.
Other factors that come into play when talking about altitude come into play, such as repetitive dive profiles, time of surface interval, tissue loading (those that are slow or fast to ongas/offgas), etc. Also, some people seem to be more prone to "bending" or not bending, which can be independent of whether or not bubbles are formed in the bloodstream. For example, a particular individual may be prone to "bubbling" rather easily, but not exhibit DCS symptoms, while another may not "bubble" easily, but exhibit DCS symptoms quite readily. As far as I know, there has not been a definite correlation found by the observers of the data; that is, people who "bubble" do not necessarily bend easily, or vice-versa. Also, smokers, people with high body fat content, out-of-shape divers and the like are not necessarily at higher risk, contrary to common sense.
PADI teaches the age-old axiom that if you dive, you must wait at least 12 hours to fly. This idea, I found out this weekend, does not have data to support the notion.
There is a study going on right now to see if there is a correlation between flying, diving, time spent between, and the correlation of DCS. After about 1500 participants, there does not seem to be a statistical correlation between any of it.
My profile this weekend was the following: 60 fsw dive for 40 minutes; 30 fpm ascent and descent at the beginning and end of the dive. We had a 1 hour surface interval, and then were taken to an altitude of 8,000 feet in two minutes and left there for four hours. We were observed using complex medical instruments, including an ultrasound machine on our hearts to observe bubble formation every 20 minutes during the dive and for four hours after the dive. We were also observed for the following two days for DCS symptoms.
None of us exhibited any DCS symptoms, and one of us actually developed bubbles. There were nine subjects in the study. These results seemed to be consistent with the rest of the data collected at other studies.
The next study, which I will also be participating in, will be the same profile but with no surface interval at all.
Lastly, I thought it was also an interesting discovery that people who have experienced a DCS hit in the past show no evidence of being any more or less susceptible to DCS in the future; that is, if you do get bent, it does not necessarily make you more or less susceptible to getting bent in the future, despite what many agencies believe.
Further questions should be forwarded to the DAN/Duke University Hyperbaric Chamber facility. Speak to Eric... He seemed very knowlegable on the data collected.
That's impressive SeaJay. I don't know if I'd volunteer for that kind of thing. A little scary even if they have a chamber warmed up waiting for you.
SeaJay
Contributor
It seems like a risky maneuver, but when I found out that there was no evidence to suggest that getting bent increases your propensity for getting bent in the future, I actually looked forward to the study.
Let me make sure that I communicate that right: If you have two subjects with equal propensity for DCS, and one gets bent, data suggests that there is no reason to believe one of them is somehow less or more likely to get bent in the future.
I found that rather interesting... And because of it, I actually asked if they would cause me to get a mild DCS hit.
Obviously, there is no better place for it in the world... And I wouldn't mind finding out what it feels like so that I can better understand my own personal limitations, and better recognize the symptoms when they occur.
Now, obviously, there is a point in DCS where permanent paralysis can occur... They called it "Stage Four" DCS, or the "dangerous" type... And there have been a few cases of it over the decades of recording the data. Obviously, I would not want to go there... Or even into Stage Three. However, I wouldn't have minded seeing what it was like to experience tingling or pain in the joints so that I understood better my exact limitations.
With these guys literally able to "dial in" whatever they wanted... And then dial it back out again... Well... I would like to know.
Obviously, they weren't willing to do something like this, because it would have nullified their test data for the study.
Maybe one day...
How awesome would it be to understand your own limits on this stuff?
Another thing I found out which was interesting... A PFO is something that every human fetus has. When you are born, the heart is supposed to "heal" the perforation over, but it happens only partially or not at all in some people. Data suggests that something like 20% of the population has some sort of PFO. 20%!!
I was thrilled to find that I have no perforation between the atriums of my heart (which is what a PFO is, effectively).
I'll do a full writeup of the chamber experience... It was truly amazing. But first I'm waiting for my pictures to arrive, as well as some of the sounds recorded from people's hearts... Including mine... And including the one guy's who bubbled. Yes, you can actually hear the bubbles being passed...
Let me make sure that I communicate that right: If you have two subjects with equal propensity for DCS, and one gets bent, data suggests that there is no reason to believe one of them is somehow less or more likely to get bent in the future.
I found that rather interesting... And because of it, I actually asked if they would cause me to get a mild DCS hit.
Obviously, there is no better place for it in the world... And I wouldn't mind finding out what it feels like so that I can better understand my own personal limitations, and better recognize the symptoms when they occur.
Now, obviously, there is a point in DCS where permanent paralysis can occur... They called it "Stage Four" DCS, or the "dangerous" type... And there have been a few cases of it over the decades of recording the data. Obviously, I would not want to go there... Or even into Stage Three. However, I wouldn't have minded seeing what it was like to experience tingling or pain in the joints so that I understood better my exact limitations.
With these guys literally able to "dial in" whatever they wanted... And then dial it back out again... Well... I would like to know.
Obviously, they weren't willing to do something like this, because it would have nullified their test data for the study.
Maybe one day...
How awesome would it be to understand your own limits on this stuff?
Another thing I found out which was interesting... A PFO is something that every human fetus has. When you are born, the heart is supposed to "heal" the perforation over, but it happens only partially or not at all in some people. Data suggests that something like 20% of the population has some sort of PFO. 20%!!
I was thrilled to find that I have no perforation between the atriums of my heart (which is what a PFO is, effectively).
I'll do a full writeup of the chamber experience... It was truly amazing. But first I'm waiting for my pictures to arrive, as well as some of the sounds recorded from people's hearts... Including mine... And including the one guy's who bubbled. Yes, you can actually hear the bubbles being passed...
Seajay,
I'd like to congratulate you for volunteering for the study! You are definitely helping us all by doing so!
I've had several discussions with Eric about the program. He is an extremely knowlegeable fellow! I specifically discussed joining the tests myself, but found out later that I am expressly prohibited from doing so by certain clauses in my contract.
Again, thank you for volunteering and participating. I look forward to more of your reports from the "tank"!
SeaJay
Contributor
...To tell y'all all about it. As soon as I get these files in, I'll do a writeup...
I'm just thrilled to be able to participate in the study. There's a bit of compensation, but I'll be honest... I didn't care about it at all. I just wanted to be a part of the study.
So what do you do that requires a contract which prevents you from participating?
I can't wait to tell y'all about how the room instantly got hot (weird... Like the whole room raised in temp about 15*) and how we were all a little "narced" (like one or two beers narced) for about five or ten minutes after the descent to 60'. Apparently, it pretty much happens to everyone, even at only 60'... But I'm usually too focused on the dive to notice! What surprised me was how fast it left, too... With no lasting effect whatsoever. We did not have to "raise" ourselves in the "water column" to get rid of the narcosis... We just sat there, and suddently, it was gone. Strange.
...Another amazing thing was watching fog suddenly appear inside the chamber when we ascended... That is, it condensed out of thin air... It didn't blow in from a vent or something. Suddenly, there was fog. Unmoving, stationary fog... When we ascended from 60' to 0'. How amazing... Oh, and the temperature dropped 15*. I mean, you want to talk about cooling efficiency? In a matter of two minutes, this entire room dropped by 15*, without "blowing," like you'd normally see with an air conditioner. It was seriously weird... Went from basically room temperature to the temperature inside a walk-in fridge in two minutes, with no apparent external influence. Very odd...
I highly recommend the study. I learned amazing things about pressure and how my body reacts to it, all while safe in a controlled environment. ...And every bit of it I can use in my daily diving...
I'm just thrilled to be able to participate in the study. There's a bit of compensation, but I'll be honest... I didn't care about it at all. I just wanted to be a part of the study.
So what do you do that requires a contract which prevents you from participating?
I can't wait to tell y'all about how the room instantly got hot (weird... Like the whole room raised in temp about 15*) and how we were all a little "narced" (like one or two beers narced) for about five or ten minutes after the descent to 60'. Apparently, it pretty much happens to everyone, even at only 60'... But I'm usually too focused on the dive to notice! What surprised me was how fast it left, too... With no lasting effect whatsoever. We did not have to "raise" ourselves in the "water column" to get rid of the narcosis... We just sat there, and suddently, it was gone. Strange.
...Another amazing thing was watching fog suddenly appear inside the chamber when we ascended... That is, it condensed out of thin air... It didn't blow in from a vent or something. Suddenly, there was fog. Unmoving, stationary fog... When we ascended from 60' to 0'. How amazing... Oh, and the temperature dropped 15*. I mean, you want to talk about cooling efficiency? In a matter of two minutes, this entire room dropped by 15*, without "blowing," like you'd normally see with an air conditioner. It was seriously weird... Went from basically room temperature to the temperature inside a walk-in fridge in two minutes, with no apparent external influence. Very odd...
I highly recommend the study. I learned amazing things about pressure and how my body reacts to it, all while safe in a controlled environment. ...And every bit of it I can use in my daily diving...
TheAvatar
Contributor
Disclaimer: I'm obviously no doc, even if dr dad writes stuff for aerospace phsyiology textbooks. I am a new member of the local volunteer dive rescue team. We are covering this topic presently at trainings.
We deal with funky high altitude diving for portions of the charts that were never tested and even off the charts (above 10,000). Duke is using some of the divers on the team for case studies.
Sometimes the divers have to stay in another town before they can drive home. We use SSI tables with navy numbers and use the dopplar limits and the the NOAA alt charts to determine the time required before the diver can ascend a 12,000ft pass.
We also have to deal with the fact that many of the divers maybe ascending thousands of feet before making their dive. One of our divers always starts himself as a B or C repet group and another would start at D or E even though he hadn't dove in days because he might be ascending 5000-6000 ft from Denver. We have a chart for that too! It shows the starting repet group for the first dive of a diver based on his altitude change (ex 2000ft-B, 10,000ft H). Lovely!
That's all I can say from the highcountry... I'm gonna go find some air to breath... I though I saw some hiding under the chair yesterday. Current ppO2 in the room right now: 2.1PSI w00t!
We deal with funky high altitude diving for portions of the charts that were never tested and even off the charts (above 10,000). Duke is using some of the divers on the team for case studies.
Sometimes the divers have to stay in another town before they can drive home. We use SSI tables with navy numbers and use the dopplar limits and the the NOAA alt charts to determine the time required before the diver can ascend a 12,000ft pass.
We also have to deal with the fact that many of the divers maybe ascending thousands of feet before making their dive. One of our divers always starts himself as a B or C repet group and another would start at D or E even though he hadn't dove in days because he might be ascending 5000-6000 ft from Denver. We have a chart for that too! It shows the starting repet group for the first dive of a diver based on his altitude change (ex 2000ft-B, 10,000ft H). Lovely!
That's all I can say from the highcountry... I'm gonna go find some air to breath... I though I saw some hiding under the chair yesterday. Current ppO2 in the room right now: 2.1PSI w00t!
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