Tropic/Maya Air and DCS

[Downing]

I'm in the early planning stages for my return to Belize next summer. I'm thinking the trip will be the usual two and a half weeks, flying in on a Wednesday or Thursday and back out on a Saturday or Sunday. One item very high on my list is to attend Mass at the Church of the Nazareth just outside of PG. Obviously, this would be on a Sunday.

So I'm trying to plan my trip around this event.

One possibility is to spend a week plus based in Placencia and dive with Splash again before heading to the Toledo District for the weekend. Then return to Placencia and dive through Thursday. Fly up to BZ City on Friday and catch the Saturday boat to Turneffe Island Resort for another week of diving there before returning home.

Which leads me to my question: what are the DCS risks involved in flying to BZ City a day after diving in Placencia? Splash does two tanks a day, one in the morning followed by another one after lunch. I most likely would have done four consecutive two tank dive days at around 60 to 70 feet before getting on the plane to BZ the next day.

I'm not sure of the altitude of the flight, maybe 3,000 feet? Total flight time is something like 30 minutes. Last time, we landed briefly in Dangriga on our way to BZ City, if that makes any difference.

Typically I just don't dive the day before I fly but in this case it just seems like the risk would be minimal. I'd like to squeeze in an extra dive day if possible, but I don't want to spend the rest of my vacation in a hyperbaric chamber, either.

 

[peterbj7]

Official advice has to be to leave at least 12 hours and maybe 18 hours before flying. Normally no need for more. I'm not sure what height planes from Placencia reach, but between San Pedro and Belize City and between Belize City and Dangriga they rarely exceed 1500ft, and will fly lower if you tell them you've been diving and ask them to. But if you're out of the water by say 4pm at the latest you'll have 17 hours clear before you fly (assuming it's not before 9am). I'd say your risk is minimal. Not zero, and undeserved hits do happen, but pretty low. If you're nitrox certified (?) I'd suggest using it for the final day's diving before flying, just to reduce the odds even more. If you're not then I suggest you add it to your arsenal asap - Patty will be able to do it in a few hours if you don't do it before.

 

[Ralph Capeling]

Peter's comments are well founded. The dive medical community says that for single dives a minimum preflight surface interval of 12 hours is suggested and for repetitive dives and/or ultiday dives, a minimum preflight surface interval of 18 hours is suggested. This does not guarnatee that decompression sickenss will never occur but is cosidered to be conservative.
I checked with one of the local airlines and they say the normal flight from Placencia to the International airport does't go higher than 2000 feet and as Peter says, if you tell them you have been diving, they try to fly lower.
Regards
Ralph

 

[Hank49]

On the short jumps between BZ City, Dangriga and Placencia the planes don't usually go above 1000 feet. I watch pretty close

My son had done a dive in San Pedro a few years back and had to run to catch the plane back to the city where I picked him up. He told the pilot who flew only at 500 feet all the way.

If it was me, I wouldn't dive. For a couple dives you may risk the best part of your vacation. TURNEFFE !!! What? are you nuts?

 

[Downing]

Thanks for all the advice. Good stuff. There's surprisingly little info on the risk of DCS and relatively quick, low altitude flying out there--at least that I could find.

I'm nitrox certified, but I don't believe Splash offers nitrox (Ralph?). Otherwise, I would definitely use it.

Diving with Splash last summer, we were usually done with the second dive around 2:30 in the afternoon. I'm thinking I would fly up to BZ City around noon, so my SI would be about 20 hours. I suppose I could even add on another few hours by skipping the afternoon dive and just snorkel or even stay out of the water altogether, take a nap on a caye and wait for the boat to pick me up when they're through.

Hank, yes, I am. Maybe this time we can finally hook up--unless, of course, you flee the country when I arrive as per usual, lol.

 

[Hostage]

I took a look into this, as I am going to be in Belize next week and will be diving and taking a plane to go tubing most likely.

The average pressurized airplane has a pressure of 75kpa, which is equivalent to the air pressure at about 8000ft in altitude.

I haven't been to Belize in many years, but I remember the 15min flight from Belize City to San Pedro was very close to the ground, I would estimate no higher than 1000ft. Which would be about ~97kph.

I don't think I would worry about it, especially after you spent more than a few hours out of the water. Then again I am not a doctor or an expert.


Sources:
Atmospheric pressure - Wikipedia, the free encyclopedia
Aerospaceweb.org | Ask Us - Airline Cabin Pressure

 

[peterbj7]

The rate of change of pressure as you go up is greatest close to the ground - it drops FAR more in the first 500ft than it does in the 2nd. It is a risk I am personally prepared to take, and indeed I have done many times, but there is no way I can recommend it to anyone else. Undeserved hits do happen, and I know of one person who had a DCS hit in a car driving over a pass just a few hundred feet high in the evening after diving that morning. It is NOT guaranteed safe.

 

[Downing]

Well, based on all of the above it appears the risk is so minimal that it appears to me to be one well worth taking.

Isn't it likely that the guidelines of 1 dive/12 hours and 2+ dives/18 hours were contemplating the more typical flights at 30,000 feet? If so, surely if my SI is around 20 hours the risk must be really, really small on a puddle jump back to BZ City.

 

[peterbj7]

The guidelines aren't "one dive - 12 hours, 2 dives - 18 hours". The 18 hours kicks in after several days of recreational diving well within "no stop" limits. More extensive diving requires 24+ hours. But remember that these are averages based on average people in good health who haven't done anything to increase their exposure (like drinking alcohol). It is a very good idea to be more prudent if at all possible.

And bear in mind that the effect of alcohol on the body is greater and longer-lasting than most people realise. After a single beer the alcohol can be detected in your body more than 24 hours later.

 

[Ralph Capeling]

Hi Downing. Yes we offer nitrox at Splash Dive Center.
The other thing to keep in mind is that there are lots of inland adventures you can do from Placencia on the last day of a vacation here.
Regards
Ralph

Thanks for all the advice. Good stuff. There's surprisingly little info on the risk of DCS and relatively quick, low altitude flying out there--at least that I could find.

I'm nitrox certified, but I don't believe Splash offers nitrox (Ralph?). Otherwise, I would definitely use it.

Diving with Splash last summer, we were usually done with the second dive around 2:30 in the afternoon. I'm thinking I would fly up to BZ City around noon, so my SI would be about 20 hours. I suppose I could even add on another few hours by skipping the afternoon dive and just snorkel or even stay out of the water altogether, take a nap on a caye and wait for the boat to pick me up when they're through.

Hank, yes, I am. Maybe this time we can finally hook up--unless, of course, you flee the country when I arrive as per usual, lol.