Here's a shot Pat took of one of the white tip reef sharks that occasionally hangs out in the mouth of "suck 'em up", a lava tube we have here in Kona.
I thought I'd write a post about something that comes up for divers on the Big Island from time to time.... Driving to altitude after diving. Many visiting divers, and some that live here, don't give it a second thought, they seem to forget that not only is the Island of Hawaii BIG... it's TALL too.
For the non-divers reading this, when you go through scuba certification classes one of the things taught is the use of dive tables to track your nitrogen loading, or computer use that will do the tables for you on the dive, and the time to fly rules. I'll give a brief over-simplified version of what it's all about... Nitrogen comprises the bulk of the air we breathe, and normally it's inert and our bodies do not absorb it, but when we breathe compressed air at depth our bodies absorb nitrogen. Sudden loss of pressure, such as flying in an airplane or driving to altitude, can cause that nitrogen to fizz out of solution and cause all sorts of problems with your body. In essence what happens is similar to opening a pop bottle, the dissolved gas fizzes out of solution, but when the dissolved gas is in your blood and it fizzes out of solution into your joints and such, you're in trouble. Anyway, the easy to use guidelines you are taught in your Open Water course are to avoid this.
Most visiting divers do think about the time to fly rules... no flights within 18-24 hours of diving is common... but some think inter-island flights don't qualify as "flying" for some reason and I get the question asked of me several times a year. It's all airplanes, they fly well above the altitudes they're pressured to (generally airplanes are pressurized to an equivalent of 7000-8000 feet altitudes), so yes, inter-island flying has the same recommendations. Lots of people though tend to forget that you can drive to altitude here on the island, often times to altitudes well higher than what you'd find an airplane pressurized to. It's important to be aware of elevation changes while driving too.
Currently, I'm thinking DAN and PADI are typically suggesting you should be safely able to drive to somewhere between 1000 and 2000 foot elevations after diving without worry... don't quote me on that as I'd have to look it up to be certain. Above that elevation they're very vague. I've heard recommendations for driving to altitudes over that which are all over the board.
You can NOT drive between the Kona side of the island and the Hilo side of the island without going well above 2000 feet in elevation. The southern route will put you well over 4000 feet in the volcano area. The northern route runs through Waimea, which is at 2500 feet, and you're heading uphill when leaving Waimea, so you need to consider it to be at least 3000 feet - I don't know what the altitude peaks at on that highway. Over the top via Saddle Road, you might as well consider it to be a flight, as it approaches 7000 feet at the summit of the road. The observatories should be considered extreme altitudes, and I personally wouldn't visit them for at least a couple days after diving.
So, what do you do? The only guide I've seen on this is by NOAA.
Here are the NOAA dive tables. Dive tables are only a guide, and even their no-decompression tables carry this warning: "WARNING: EVEN STRICT COMPLIANCE WITH THESE CHARTS
WILL NOT GUARANTEE AVOIDANCE OF DECOMPRESSION
SICKNESS. CONSERVATIVE USAGE IS STRONGLY
RECOMMENDED."
Anyways, to give you an idea of the time you need before heading to the other side of the island you can use their no-decompression tables and then follow up with their driving to altitude table. I'll run a relatively common, and non-aggressive dive profile run on their tables just to give you an idea.... 1st dive - 50 feet for 50 minutes, an hour and a quarter surface interval, 2nd dive - 40 feet for 50 minutes. Running that you you'll end up with a K group letter. Going to their altitude after diving chart, as a K diver you are recommended to spend at least 6 hours and 25 minutes out of the water before driving to 3000 feet, say Waimea. If the dives were any deeper or any longer, and those dives I just ran were very conservative, we often do dive days that would put you in a much higher group letter, the time you'd need to spend at sea level would be even greater.
Now in real life, there are people diving here and driving back to the other side on occasion without problems. I did hear a rumor that someone took a DCS hit driving to Waimea in the last year or two, but I can't substantiate it though. So what happens if you take a DCS hit? You're looking at a private helicopter flight over to Oahu and then a few days in the chamber is my best guess. Last numbers I heard bantied around for the cost of this (not sure if they were accurate numbers though) were fairly similar to the numbers I heard for a week's stay at the Presidential Suite at the Four Seasons... Not cheap! For me it's not worth trying to go to the other side of the island after diving. I personally won't go to Hilo after I dive 'til the next day, and if I was diving Hilo side, I'd probably rent a hotel room for the night before coming back.
Just some food for thought... before you dive and drive, you might want to pay attention to the elevation here. For most of Kona you're in pretty good shape to drive after diving if you stay below the upper highway. Above that you maybe should think about elevations and maybe spending some extra time at sea level.
later,
Steve
