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SCUBA in Kona then Mauna Kea/Volcanoes Natl Park in Hilo?

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From what I've been reading, going to the top of Mauna Kea is enough altitude that it's considered as if you are flying from the perspective of getting rid of nitrogen in the blood after diving. We have Kona on day 6 and Hilo on Day 7 of my upcoming Hawaii cruise.


Is there a way to be able to do both? Is the diving good enough in Kona that I should skip Volcanoes National Park, or if I have other dive opportunities (Oahu, Kawaii, Maui) should I skip diving the big island?

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From what I've been reading, going to the top of Mauna Kea is enough altitude that it's considered as if you are flying from the perspective of getting rid of nitrogen in the blood after diving. We have Kona on day 6 and Hilo on Day 7 of my upcoming Hawaii cruise.



You are correct that ascending to altitude after diving is a concern. However, given the time lapse between diving on one day and ascending to elevation the next, you likely have little to worry about.


Specifically the concern is decompression sickness (DCS) brought on by nitrogen in the blood or tissues expanding due to the reduction of ambient air pressure. Ambient air pressure drops as altitude increases.


Without using a dive computer, the recommendation from most SCUBA training agencies is to wait at least 18 hours after a single dive, and 24 hours after repetitive dives before flying (your case is a little different than flying, but you’ll see where I’m going here). The reason for the 24-hour recommendation is that it’s presumed at all residual nitrogen will be purged after a 24-hour surface interval. Since 24 hours is presumed to rid the body of all excess nitrogen, then after that interval you would be presumed back to your baseline, and thus not affected by altitude for DCS.


Assuming you’d be diving in the morning of day one, and doing the standard two-tank dive, you’d likely be completing your second dive by noon of day one. On day two, given the ship’s arrival time in Hilo, and the travel time to the top of Mauna Kea, if you didn’t have a 24-hour surface interval, you would be extremely close to it. Therefore, I wouldn’t hesitate to dive then go the next day. Adding to the safety factor is that Kona isn’t known for particularly deep dives.


You can stop reading here if you just want to know the answer to the question; because now I’m going into boring detail.


First, for flying after diving, the assumption is made that we’re talking about pressurized aircraft (e.g. commercial airliners). Regardless of the altitude the flight reaches, the plane’s normal pressurization is considered to be the equivalent of 8000 ft. The altitude of Mauna Kea is 13,803 feet.


Nominal air pressure at sea level is 14.7 psi. At 8,000 feet it’s 10.9 psi, and at 14,000 feet it’s 8.6 psi. This is important because it is that ambient pressure that is serving to keep nitrogen in solution, in your blood, and thus preventing decompression sickness. You may also notice that the pressure decrease slows as altitude increases; in other words the difference in pressure between sea level and 1,000 feet is greater than the difference between 10,000 and 11,000 feet. Most research in ascending after diving has focused on flying after diving, and thus tends to look at the 8,000 foot pressure. However, as the pressure drop that occurs lessens as you go higher, it’s likely safe to use the same limits for ascending to greater altitude. This is especially true considering that by the time you’re at altitude, you’ll be very near, if not past 24 hours from the end of your dive (again since, all excess nitrogen is presumed gone after 24 hours, additional altitude is not considered a factor).


All that being said, some people have issues at altitude anyway. I’ve lived in Colorado my entire life, and everyone here has some story of people from lower elevations not doing well at extremes. It’s popular here for tourists to drive to the high mountains (elevations similar to Mauna Kea) and experience mild symptoms of altitude sickness (headache, nausea, generally not feeling well). My concern is that given your planned itinerary, if you had issues with the altitude, you may think it’s DCS when in fact it’s just the altitude anyway. Some symptoms would overlap, but DCS would manifest some specific symptoms of it’s own presumably.


So, to wrap up (finally):


Given the surface interval between your dive and your arrival at altitude, you will be presumed to have ridded all nitrogen for your body.


You can ensure this is the case by limiting your depth to a moderate point, and thus reducing your nitrogen uptake.


If you want to add another layer of safety, and you’re trained to do so, pay the extra to dive on nitrox. Nitrox 32 has 14% less nitrogen than air. The less you have in you, the less time it takes to leave.



Denver, CO

Edited by omeinv

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Thank you for your thorough and informative answer! I appreciate the detail, since I've seen notes for at least one tour of Mauna Kea that state they won't accept anyone who has been SCUBA diving within 24 hours of tour start. Sounds like they are erring on the side of much more caution than the SCUBA Agencies recommend. I always dive with a computer, which will also help me monitor the situation.


Thank you also for the information re: altitude sickness vs DCS. I did experience some issues with headaches during a visit to Colorado Springs a few years ago, so it's good to have that information.


I learned a lot from your post, and am glad I have time to check into NITROX certification. Most of all I'm glad that I'll get to do both items I really want to during my visit to the big island, as long as I'm planful and safety conscious.

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Nitrox is usually an easy specialty course to schedule, since it's all class room. Since nitrox doesn't change anything about the physical act of diving, you don't learn anything additional by diving on it. Therefore you get fully certified with approximately a 3-hour class. If your local dive shop can't get you scheduled, email me at the link below, and we'll get it worked out.


Your dive computer almost certainly has a "time to fly" function. That will give you a specific number of hours after your dive - based on the particulars of your exact dives - that it is safe to go to 8,000 ft. Adding 5 hours to that figure (to a max of 24 hours) would be another way to make sure.


I know you didn't ask but... For Kona I highly recommend Big Island Divers. We spent a week there and dove with them several times each day. They were 100% great. The only thing is I don't know that they offer any transportation from the pier to the marina, and it's a bit of a trek, so a cab gets pricey. Definitely check that issue regardless of who you book with.



Denver, CO

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