Help for "older divers"

[Steve_S]

Hi Dr. Deco:

What a delight to read your valuable posts and expert knowledge. I’m very gratefull that you have voluntered

I have a few questions which pertain to “older divers” like myself. I am a male age 49, average weight, good health, smoke, and live a relatively sedantary life as a full time Web “geek” I have been diving for over 20 years with advanced certifications from all the majors as well as years of divemaster experience. and instructor assistance. The time line is broken like this: for 10 years I dove at least twice per week, then a five year lay off. For the last 5 years I usually take one or two diving vacations per year to exotic spots around the word. Underwater photography is my passion.

My last dive trip was to the Turks/Caicos Islands for 2 weeks of splendid diving. All my questions pertain to Decompression/Embolisim issues. My “rule” for the last 5 years has always been to stricly adhere to the tables via a DC meter for bottom time but always hang off at 30 feet and then 15 feet for 10 minutes whenever I’m even close to the red. I always tell the skipper and my fellow divers that this is my procedure and try and be the first in the water so I don’t inconvenience them. I have a very very low air consumption and often “slip breeth” while taking pictures. Each vacation begins with a day of snorkeling and then 2 days of shallow diving (30 feet and under) to acclimate myself. I’ve always been very comfortable in the water and this procedure always produces a “renewed” comfort level.

I’m not a daredevel or bounce dive junky. In my younger years I’ve been involved in dead diver recovery and had a best friend bent and cripled for life. Rather, as I’m sure you are aware, tropical diving offers unique stuff below 60 feet as well as open water diving that I love. I would be gratefull for your comments and help for “older divers”

Thanks once more for your valuable and detailed posts.

 

[Dr Deco]

Hi Steve:
It sounds to me that you are already a conservative diver, e.g., understanding the importance of the in-water stops. I would add the following general comments that seem to apply to safe decompression based on some of my laboratory work over the past several years:

1. During the offgassing phase (in water and out), it is good to have some extremity movement. Do not go to sleep on the boat, but rather move the arms and legs (this is natural in water during the safety stops). Physical activity promotes blood flow by keeping up the heart rate but, more importantly, promotes flow by what is termed the "muscle pump." Blood is made to flow in a large part by the contraction of the muscles that force the blood through the capillaries. [If one has given blood, you know that they ask you to squeeze your fist every few seconds to promote blood flow - - this is the "muscle pump."]
2. Do not perform any straining maneuvers. One should not climb a ladder on to the boat with heavy gear on. Someone should give a hand if possible to get you easily on board. This prevents nucleation in the tissues of the legs and arms. [Naturally, keeping up the blood flow should not be done with strenuous exercises such as jumping jacks, either.]
3. The prime directive: During offgassing, promote blood flow and restrict tissue micronuclei formation. [I do not know if you will prosper, but it should help to live long - - -my apologies to Mr. Spock.]

 

[Steve_S]

Thank you very much Dr. Deco.

Some additional questions:

When I'm "hanging off" should I move/excercise my exstremtys? To a degree this mimics what I would do in my surface interval?

What "DC" meter is the most accurate? Price should not be a concern. I'm sensative to the fact that this involves talking about commercial products for recreational divers and I respectfully hope this does not place you in a difficult position.

Thanks again for your valuable posts.

 

[Dr Deco]

Yes, indeed, exercise during the safety stop is just the ticket. I suspect that most divers do this to some degree while hanging off simply to maintain some degree of depth control. The point here is that we wish to increase the local blood flow to the arms and legs to promote off gassing. We are attempting to elevate the tissue perfusion to muscle and the associated tendons and ligaments.

When one is on board, it is advisable to move your arms and legs but mot involve oneself in strenuous activities. Thus what was done during WW II to promote gas elimination, such as running in place, squats, jumping jacks, resulted in a very unfavorable outcome. The concept of exercise augmentation was lost. This concept of exercise was revived in the last decade by Dr. Andrew Pilmanis and his laboratory in the High Altitude Protection Function at the Brooks Air Force Base. The method has been of tremendous assistance to us in our NASA program.

As far as deco meters go, I quite honestly am not able to answer that question. I am not aware of any meter that is capable to tracking tissue gas for the type of procedures that I am speaking about in this forum. At NASA, we measure the oxygen consumption of all of the activities. This is then compared to the outcomes of decompressions and linked back to changes in tissue half times. This results in an algorithm capable of predicting DCS risk and Doppler bubbles for eventual purposes of mission planning, should that be desired.

 

[Stoo]

2. Do not perform any straining maneuvers. One should not climb a ladder on to the boat with heavy gear on. Someone should give a hand if possible to get you easily on board. This prevents nucleation in the tissues of the legs and arms. [Naturally, keeping up the blood flow should not be done with strenuous exercises such as jumping jacks, either.]

I had the pleasure of hearing Dr. Bruce Cameron of DCIEM (the quasi-military research end of all things above and below sea-level up here in Canada) speak last weekend. He had recordings of Doppler tests done on his test subjects (all Clearance Divers). The sound of bubbles went through the roof with just a simple deep knee bend. These tests were done in divers that had performed no-deco dives, but were close to the mark. His comment was that the worst thing a diver can do post dive is to start hauling the anchor...

For many years, my buddies and I have followed a simple post-dive custom. We dive primarily from RHIBS and most dives are cold and deep and require at least some mandatory deco. After we have surfaced, we clip off our doubles, climb into the boat, unzip our suits, then sit for 45 minutes to an hour and shoot the breeze, possibly while enjoying an icy cold beverage of the adult variety. We have always figured that that hour of sitting quietly (with some moving around the boat) is time well spent before having to "clean and jerk" our heaving lumps of metal out of the water...

So far so good, after about 8000 dives conducted together...