Ascent To Altitude From Santa Rosa

[boulderjohn]

Divers traveling north to Colorado from Santa Rosa, which is a high percentage of the people who dive there, know they have to ascend to altitude, and they have to make a decision about how and when to do that. I think everyone knows that if we go by the rules about flying after diving, we can't leave until the next day, so everyone who knows only that rule leaves Santa Rosa knowing a risk is being taken.

The truth is, though, that flying after diving assumes a rapid ascent to altitude--a gradual climb while driving a car has not been studied. Logically, a lot would depend upon the nature of the drive. Ascending a thousand feet, say, then driving for several hours at that elevation before ascending again would be like a decompression stop and should have a positive effect--but we have no guidelines on which to make that judgment.

In this thread I will make several posts in which I hope to provide helpful information for people making that trip north. I will provide information about using the NOAA ascent to altitude guidelines as well as a description of the elevations encountered on the route--some of which will be a surprise to many people. As a hint, I know that some instructors leave Santa Rosa quickly and then meet students in Las Vegas so they have a surface interval before the climb to Raton Pass; this thread may cause some people to rethink that strategy.

Please note that I am not advising anyone on what to do in this thread--I am just providing information so that others can make those decisions for themselves.

EDIT: See Post #32 for updated information.

 

[boulderjohn]

NOAA Guidelines

The National Oceanic and Atmospheric Administration has guidelines for ascending to altitude after diving. These guidelines identify divers in different pressure groups and tells how long in hours they should weight before ascending a certain number of feet. The pressure groups are from their tables rather than any of the tables used by any of the agencies. Use their tables to identify pressure groups--they are very different from the PADI tables, so the pressure groups of the two will not be nearly alike.

EDIT: NOAA has reorganized its site, and the ascent to altitude tables do not appear to be there. I will upload a copy. See below.

Of course, every diver will be a little different, but to give people a rough idea, I would guess that OW students doing two OW certification dives would usually be at most in the I pressure group as they leave the water on that second dive. According to the NOAA tables, an I diver must wait 1:32 before ascending to 2,000 feet and 3:20 before ascending 3,000 feet. An H diver can ascend 2,000 feet immediately and 3,000 feet in 1:31--about as long as it would take to do the paperwork and pack up. A G diver can ascend 3,000 feet immediately.

It is thus possible that divers doing shorter, shallower dives can leave as soon as they are ready, according to the NOAA guidelines.

 

[boulderjohn]

The Route North
Here is what you will encounter in terms of elevation changes as you leave Santa Rosa.

1. As you head west on I-40, you will begin your trip at about 4,600 feet. You will climb rapidly as soon as you start, reaching 5,145 by the first exit to the west.

2. By the time you reach Route #84 to head north (about 15 minutes), you will be at nearly 5,400 feet--an 800 foot gain in elevation.

3. You will stay at nearly that elevation for about 20 minutes or so, but you will then climb to 6,000 feet by Apache Springs.

4. You will continue to climb to 6,400 feet at the intersection with I-25, a few miles from Las Vegas. This will have taken you a little over an hour.

5. A few miles north of Las Vegas, you will reach nearly 6,800 feet.This is about the same elevation as Raton, NM, and it is the highest point on your drive until you climb Raton Pass.

Comment: When you leave Santa Rosa, you will ascend about 2,000 feet in an hour.This will be your most rapid ascent until you reach Raton Pass.

6. After that peak elevation just north of Las Vegas, you will descend to about 6,200 and stay near that level for most of New Mexico. Wagon Mound is at 6,200 feet, and Springer is at 5,800 feet. The stretch from north of Las Vegas to a bit south of Raton should take about 1.5 hours.

7. The elevation climbs rapidly starting just south of Raton, and you are back to about 6,700 feet when you reach that city.

8. The top of Raton Pass is at about 7,800 feet. This is the highest elevation you will reach. You will not surpass 7,000 feet again unless you travel north of of Colorado Springs.

Summary: The trip from Santa Rosa to Raton Pass will take about 3 hours and will have en elevation gain of a bit over 3,000 feet. Most of that gain will come in the first hour of travel.

 

[shurite7]

Based off of my experience of driving over passes after diving I have no reason to disagree with the above.

I've played around with this chart (see link above) on an excel sheet using nitrox. After a fair amount of research and experience with diving at high elevation I've come believe divers who are diving at higher elevations should be diving with nitrox. Another factor that I've learned during my research is acclimation. The Indian and Bolivian Navies reported that acclimation was an important factor for high elevation diving.

 

[boulderjohn]

Other Comments

1. According to information I got from DAN, not all ascents to altitude are the same. The impact of an ascent of a certain number of feet is greater the closer you are to sea level.

2. Breathing pure oxygen before setting out can have a dramatic effect. According to a NOAA statement provided by Dr. William Clem, a hyperbaric medicine specialist in Denver, divers wishing to ascend 8,000 feet can do so more rapidly if they breathe oxygen for a specified period of time. What follows are ranges of pressure groups from the tables above followed by the amount of time a diver in that range of pressure groups would need to breathe oxygen in order to be safe to ascend 8,000 feet. This will not help the average recreational diver, but technical divers at nearby Rock lake should find this useful.

M-Z 1:30 hour
H-L 1:00 hour
E-G 0:30 hour
A-D 0:00 hour​

 

[boulderjohn]

The Indian and Bolivian Navies reported that acclimation was an important factor for high elevation diving.

I would love to see that report.

 

[shurite7]

I'll dig around and see if I can find them. The files were on my old laptop that crashed, but I think I have them on a backup drive.

I do find the driving after diving over passes interesting. I've done it many times and have never had a problem. It would be nice if someone conducted a study on it.

 

[The Chairman]

Quite interesting. We don't have that issue down in Florida where our highest 'mountain' is Britton Hill at 345 ft.

 

[boulderjohn]

A number of years ago, my dive buddy and I did three days of decompression diving in Rock Lake in Santa Rosa, and we were together on every dive. On the last day, we hurried out to beat a coming snow storm. We breathed from our oxygen bottles for a while as we drove, getting to Boulder (5400 feet) around 10:00 PM. I went to my home in Boulder for the night, while he ascended to his home above Jamestown (over 8,000 feet). I awoke the next day feeling great. After a rough night, he spent the next three days getting chamber treatments for DCS. The hyperbaric doctor laid the blame squarely on our drive home and his late ascent to altitude. He gave my friend Bruce Weinke's book about diving at altitude to read during his Navy 6 treatment.. I'm not so sure the doctor was right, but, as i suggest above, we don't have much information to go on. Each time we drive home from diving it is part of a grand experiment.

 

[BigBubbaJ]

boulderjohn, your point is well made. It's not an insignificant change in elevation.I know that in a long ago post, rookers actually posted a graph about this very thing. I wonder if we could dig that up also as it had a lot of data points.

My personal opinion: I've done the drive home after both repetitive recreational and technical dives many times. I'm still a firm believer that if you come out of the water clean, your deco is over. But that's just me. I also tend to clean up on O2 longer than most in the water. Again, exit the water clean and who cares about a drive. YMMV.

Good to have data points on what works for you.