LOW ALTITUDE Flying after diving

[boulderjohn]

I will eventually make my article public, with the untested issues and theories clearly labeled as such. With NOTHING in print now, people are making guesses with no guidance whatsoever, and I know many are making their decisions based on poor information. The big issue is not so much flying after diving as it is driving to altitude after diving. There is no authoritative information about this anywhere that I know (if I am wrong, please tell me), but every day around the world people are driving to higher elevations within 24 hours of diving. Are they safe in doing so? What should they know before deciding if the planned trip is safe? I hope to give them some information that will help them plan a trip without taking the risk of providing advice. I do it regularly myself, and I know what I have decided is safe for me, but I am not going to assume that what I believe is what everyone believes, because there simply isn't any research to support it.

Similarly, I have a strong opinion about the OP's question, and I know what I would do in his position; however, that is a decision he has to make himself, hopefully after getting a lot of good advice in this thread.

 

[Trace Wilson]

http://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/US DIVING MANUAL_REV7.pdf?ver=2017-01-11-102354-393

Thanks, got it!!

 

[Trace Wilson]

US Navy Diving Manual.

Here is the ascent to altitude table it contains--as DDM said, the pressure groups are from the Navy tables. Those can be VERY different from recreational diving tables.
View attachment 444245

Here is how you can get into group G after a single dive:

Group G: 50 feet/15 meters - 48 minutes; 80 feet/24 meters - 28 minutes; 100 feet/30 meters - 21 minutes

John,

I reran my worst case dive profiles using the Navy tables & the Navy EAD values for EAN32, and got the following:

Sat
Dive 1 - 60 min @ 50 ft (60 ft @ EAN32) (Navy-RDG:I) + 60 min SI (Navy-RDG:H)
Dive 2 - 50 min @ 40 ft (50 ft @ EAN32) + 74 min RNT (Navy-RDG:M) + 16:00 hr SI (RESET Navy-RDG)
Sun
Dive 1 - 60 min @ 50 ft (60 ft @ EAN32) (Navy-RDG:I) + 60 min SI (Navy-RDG:H)
Dive 2 - 50 min @ 40 ft (50 ft @ EAN32) + 74 min RNT (Navy-RDG:M) + 4:00 hr SI (Navy-RDG: I)

Using the Surface Interval before Ascent, RDG:M gives me a 4:28 SI before ascent to 2000 ft. So, IN THIS CASE it looks like the numbers are very close to the results using the SSI tables + the Navy Ascent table (4:37) (or did I make a mistake somewhere?).

It's interesting that if I take Navy-RDG:M, and apply a 4 hr SI the Navy Repetitive Group Table puts me in Navy-RDG: I, which the Navy Altitude table will allow immediate ascent to 2000 ft. whereas RDG:M would require an additional 28 mins. SI. Yet another potential gotcha here.

 

[shurite7]

I will eventually make my article public, with the untested issues and theories clearly labeled as such. With NOTHING in print now, people are making guesses with no guidance whatsoever, and I know many are making their decisions based on poor information. The big issue is not so much flying after diving as it is driving to altitude after diving. There is no authoritative information about this anywhere that I know (if I am wrong, please tell me), but every day around the world people are driving to higher elevations within 24 hours of diving. Are they safe in doing so? What should they know before deciding if the planned trip is safe? I hope to give them some information that will help them plan a trip without taking the risk of providing advice. I do it regularly myself, and I know what I have decided is safe for me, but I am not going to assume that what I believe is what everyone believes, because there simply isn't any research to support it.

Agreed. We came up with our own guidelines as to when to drive over a pass when diving in Glacier and Yellowstone. The guidelines are simply a decision based off of guestimating with what little information we can find. So far there have been no symptoms.

Years ago a skydive instructor offered to teach me if I would teach him scuba. He was willing to fly his plane to the coast, but wanted to fly back on the same day of the final dive. He kept asking for the magic number for altitude. I finally told him it wasn't worth the risk and walked away.

 

[boulderjohn]

So, IN THIS CASE it looks like the numbers are very close to the results using the SSI tables + the Navy Ascent table (4:37) (or did I make a mistake somewhere?).

When I posted before, I didn't know diddly squat about the SSI tables. I just checked and saw that they are based on the US Navy tables, so there should be no surprise that they are about the same.

The PADI tables are very different from the Navy tables. They added many more pressure groups in order to minimize rounding. Consequently, you have to go a lot further in the alphabet with them to get to where you are in the Navy tables. The research they conducted to make their tables also led them to conclude that they could base their surface intervals on the 60 minute compartment, whereas the Navy still uses the 120 minute compartment for that. That means the required surface intervals between dives will be MUCH shorter using the PADI tables.

 

[Altamira]

I think a major reason some divers want to, or have, pushed the dive/no fly envelope is that they have the idea in the back of their minds that "If I get bent, no big deal because the chamber will fix that." Unfortunately, it does not always work out that neatly. Over many years I have found the I gotta get home syndrome makes for poor judgment, and kills or injures a lot of people.

 

[Trace Wilson]

I think a major reason some divers want to, or have, pushed the dive/no fly envelope is that they have the idea in the back of their minds that "If I get bent, no big deal because the chamber will fix that." Unfortunately, it does not always work out that neatly. Over many years I have found the I gotta get home syndrome makes for poor judgment, and kills or injures a lot of people.

You could be right on that one. I'll bashfully admit that 'GetHomeitus' has bitten me a couple of times. In fact, part of the reason for this thread was to battle that very thing. If some good discussion on the topic from people much more 'in the know' than me can show the current state of the research, then others in my position are in a better place to make a more informed decision.

While I appreciate the decision to use the 24 hr restriction in all cases, I've found very few cases where the one-size-fits all answer is really accurate in all instances regardless of subject. While I absolutely agree that adhering to the 24 hr restriction also further reduces the odds of DCS, my quest is to try and objectively determine by how much. If a 24 hr SI vs. a 5 hr SI reduces my likelihood of a DCS event at 2000 ft by 0.05%, then that extra risk may be worth it to me to reduce my travel time over a weekend from 15 hrs to 5 hrs, round trip. That reduction suddenly makes 'better' dive trips more of a reality, which will hopefully get me in the water more.

Unfortunately, I can't reduce my DCS risk to 0% unless I simply give up diving. By the same token, I can't reduce my risk of a plane crash to 0% unless I give up flying. Both diving and flying, in my opinion, are a matter of managing risks as intelligently as I can. To that end I need the best information I can find, which may or may not be the one-size-fits-all answers. It just seems to me, right now, that the 24 hr rule doesn't really cover the situation I'm looking at well.

 

[Altamira]

I think you are looking for an answer that really is not quantifiable. Every one of us is different, and nitrogen is not stored or released uniformly from one person to the next, and most likely not consistent within the same person from day to day. We all look for the magic number that will keep us safe in all of our endeavors, but that is not how life works. For example, I could fly 20 missions in a row at 100 ft AGL going 600 knots, but that does not give me any assurance that I would not bust my ass on the 21st flight. All it would take is for one thing, perhaps one moment of inattention at the wrong time to have a significantly different outcome from the first 20 flights. Same applies to diving and every other activity.

 

[T.C.]

Hi Trace,
You will find many threads covering this topic on SB, and I have made numerous comments sopporting the current PADI and USAF guidelines pertaining to flying after diving. As a retired USAF and American Airlines pilot, my primary concern is that you cannot guarantee you will be able to stay at or below planned altitude,even if you are the pilot in command. As you know, there are many contingencis that may require a climb to a much higher altitude. You do not want to have to chose between flying safely and possibly getting bent. The risk is not worth it.

While I am not a pilot, this seems to make the most sense of any.

How can anyone guarantee that weather, traffic, or Air Traffic Control won't require a climb to high altitude?

Second, I fail to see the issue; NE Florida has great ocean diving within an hour or two.

And if you fly to WBP, does that total trip of checking out the plane, filing a flight plan, checking the weather, landing, securing, fueling post checks, and getting a car not take just as much time as the drive?

 

[Duke Dive Medicine]

@Duke Dive Medicine, I'm not seeing a Rev 7 of the Diving Manual. The only full document I see "US Navy Diving Manual Rev. 6 with Change A entered", and a couple of ACNs which seem to imply they are to R7, but I don't actually see R7 on the page. And, when I try to pull down R6, I get a page back each time that just says an error has occurred. I pulled down the ACNs, but they are only partial updates which look like they are designed to be printed and inserted into a hardcopy.

Would you happen to have another link to the document?

Sorry, I took a second look... they re-configured the website and I didn't notice. Glad you got the link.