How to get the Bends

[LavaSurfer]

I read somewhere that Dr. Deco created a thread or document called "How to get the bends" or something like that. I have searched until blind for the document and would like to see it.

Can anyone point me in the right direction?

Thanks
Scooter

 

[Louie]

I second Scooter on this. Sounds very interesting and would make a good educational tool.

 

[Dr Deco]

Hello Lava Surfer:

I can not find it either. I did piece together some replies from several years ago.

Why DCS?

I must add at the onset that the ideas concerning DCI are as extensive and varied as the researchers in the field. Since this disorder of DCS was first found around 1850, ideas have come in and out of vogue. These are some observations and ideas that have been developed at JSC/NASA, and some of these are applicable to recreational SCUBA divers. The observations that we make, however, apply to altitude DCI, although much of this information is applicable to divers.

In the past, the causes of DCI were difficult to elucidate, since the gas loads could be very different in each diver at the close of the bottom phase. In the case of altitude decompressions, all individuals initially have the same gas load (that is, they are all saturated at sea level pressure) and thus variations are caused either by the person’s physiology, or what they did before or during the depressurization phase.

We can separate factors into [1] individual characteristics, [2] activities before depress and [3] activities during depress. Let us look at each of these in turn:

1. INDIVIUAL CHARACTERISTICS

[a.] It is fairly clear from data that, in a controlled laboratory setting, all individuals do NOT demonstrate the same response to a given depressurization. The tendency to acquire JOINT-PAIN DCS definitely varies from person to person, and some are definitely more susceptible. (This has been known for decades in animal subjects also.) This applies likewise to bubble formation as measured with Doppler devices. {At NASA, we do not test individuals for sensitivity and segregate them out of a particular job (such as EVA, “space walks”). The current philosophy is to generate depressurization schedules that are applicable to all - but a selection could probably be made were the decision made by management to do so.}

[b.] If we accept that some people are more susceptible to JOINT-PAIN DCS, then we must also accept the possibility that, if you are once “bent,” you could be bent again (unless something changes your particular susceptibility).

[c.] An important question for us at NASA is the nature of that DCS-provoking characteristic(s). One determinant in DCS is the ability for gas bubbles to grow from preformed tissue micronuclei that are generated in the body (apparently) from musculoskeletal movement. Surface tension is a determinant in this nuclei “formation/growth/lifetime” process. {We are all aware that blowing bubbles with pure water is possible but difficult. The addition of a small amount of soap will greatly facilitate bubble formation; this is an everyday example of surface tension. The same bubble-formation process no doubt occurs in your body.} The QUANTITATIVE significance of this is not currently known, however. We are looking into this, but the jury is still out.

[d.] For NEUROLOGICAL DCS, the presence of a patent foramen ovale (PFO) is of importance, but this must be coupled with the generation of bubbles during decompression. Bubble formation is very common in altitude depressurizations but less so in diving situations. Thus the PFO question is very important to NASA but might be less so to SCUBA divers, unless they have a neurological hit. [Dr. Wilmshurst presented his views to a NASA workshop recently, and I share his viewpoints on the significance of this entity. This viewpoint is not equally shared by some of my NASA colleagues, however.]

2. ACTIVITIES BEFORE DEPRESSURIZATION

[a.] Because we are concerned with DCS in space, the activity level is very important. In a large series of laboratory tests, we found that walking (exercise of the lower extremities) BEFORE depressurization was capable of provoking bubble formation during to depress up to three hours later. Since astronauts do not actually walk during “spacewalks,” all of our decompression schedules are now developed with seated subjects. For a diver, strenuous activities, such as carrying one’s gear from the car to the boat and then lugging it around prior to a dive are probably nucleating events and likely to contribute to increased DCS risk. Some of this research actually dates back to the second World War when DCS in high altitude bomber crews was studied.

[b.] Very strenuous activities at depth are bad, e.g., tugging to free an anchor.

3. ACTIVITIES DURING DECOMPRESSION

[a.] Again, we do not have the test subjects walk during the decompressions in the altitude chamber. The resultant change in DCS risk between seated and walking individuals is between three and ten-fold (not 10% but 10 TIMES). We attribute this to tissue micronuclei formation, although we do not have direct evidence that this is indeed the mechanism. The message to SCUBA divers is not to climb ladders with full gear, do not strain the arms while boarding the dive boat, don’t lug heavy gear around on deck, etc.

[b.] Blood flow is important for the washout of dissolved gas following the dive. We modify the gas loads of the individuals with specific,graded (but mild) exercise (the oxygen consumption is measured). This greatly accelerates inert gas washout (in the altitude case, they are breathing oxygen by mask). The take-home lesson is maintain moderate physical activity post-dive, and don’t go to sleep following the dive. This exercise-augmented washout was known even during WW II, but they combined it with the wrong type of exercise (e.g., jumping jacks) and RENUCLEATED themselves. Naturally one should maintain a good fluid load so as not to compromise circulation and not to reduce surface tension by concentrating surfactants (e.g., proteins in the body’s fluids)

As you can see from this response, none of these risk-modifying factors are listed as increasing the possibility of DCS in classical, canonical teaching.

Differences in Table Tests and Actual Dives

While we do not have our test subjects walk, I do not see a good alternative for recreational divers under the usual circumstances. The reason for the proscription of walking for test subjects in altitude decompression studies at NASA is so we can mimic the decompression conditions in space as closely as possible. While we refer to “space walks,” the astronauts do not actually do weight-bearing activity in space.

Walking by the divers on the boat is fine since the tables were designed with that activity in mind. What they were not tested for was the vigorous activity that is somewhat common in the recreational scenario. In table testing protocols, here are the activities that are NOT performed. These are strong points of difference between the laboratory and the field:

[1.] Laboratory subjects never climb ladders – and never walk around, or climb, with diving gear. These activities produces nuclei because the equipment is heavy. This is DCS provoking and has been well documented for several decades:

Ferris, E.B.; J. P. Webb; H.W. Ryder; GL Engel; J. Romano; and M.A. Blankenhorn (1943). The importance in straining movements in electing the site of the bends. U. S. NRC C. A. M., Report no 121, 16 February.

Ferris, E.B., Jr. and GL Engel (1951). The Clinical Nature of High Altitude Decompression Sickness. In: Fulton, J. F., ed. Decompression Sickness. Saunders, Philadelphia.

Henry, F. M. (1945). The role of exercise in altitude pain. Amer. J. Physiol. 145, 279 – 284.


[2.] Laboratory subjects never lift diving gear such as scuba air tanks. They do not bend over at the waist thus exercising and stress the tissues of their spinal cord.

[3.] Laboratory subjects never engage in any strenuous activity that causes them to perform Valsalva-like maneuvers. These activities can result in arterialization of bubbles from the venous side to the arterial side.


Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology is September 10 – 11, 2005 :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[LavaSurfer]

Dr Deco,

Thanks a bunch. That answers some of my questions. The reason I am looking is my wife and I started diving just recently and we did our OW and AOW in Cayman last week.


The first day consisted of two checkout dives and we did these 3 hours after landing. All went well and most activity was sitting watching others perform skills. Light duty you might say.


Here is a chronology of dives from my computer.


Dive 1 - 40 ft 40 Min
SI = 00:25
Dive 2 - 36 ft 29 Min
No Safety Stop


The second day of diving consisted of two more dives at and no real SI between dives, just an ascent and back down basically.
Dive 3 - 45 ft 32 min
SI < 00:10
Dive 4 - 48 ft 25 min
No Safety Stop


We continued day 2 with a wreck dive and a night wreck dive
SI = 00:42
Dive 5 – 50 ft 40 min (5 Min SS) (Wreck Dive)
SI = 07:59
Dive 6 – 37 ft 50 min (5 min SS) (Night Dive)


Day three continued with more adventure dives
SI = 12:33
Dive 7 – 105 ft 24 min (6 min SS) 9 minutes below 80 feet (Deep Dive)
SI = 01:03
Dive 8 – 50 ft 46 min (5 min SS) (Boat Dive)
SI = 04:06
Dive 9 – 15 ft 57 min (No SS) (Navigation course)


Needless to say, it was a busy weekend. Every dive ended in climbing a ladder to get out with the equipment on our backs. I always floated for 5-10 minutes just relaxing before exiting the water but my wife always was the first out of the water. She wanted the gear off to relax.


After day two she was sore in her shoulders, arms and neck and was told that it was just all the excretion from learning, additional stress and normal. She did not think she felt right and that night she crashed and had a hard time waking up the next day. After some coffee she felt fine and we finished the dives. By the time we left she has resolved her aches and was fine with no recurring issues. There were several instances on her dive computer that shown ascents that were two rapid. Most were small and after she became more skilled she was able to control ascent better. Now she’s a pro at ascending but the first two days were rocky.


As for me, after day three we were at dinner and I was hit with a sudden wave of dizziness and nausea. It felt like sea legs had set in so I wasn’t all too concerned. After several days on a boat I usually start walking like an old drunk sailor. It did seem odd how quickly it hit me though. This was well after our dives and a good 10 hours after any dive of depth. I had no other symptoms and they passed later that night. I did have a few periods where I felt like the sea legs had come bak and I wrote it off as inner ear. Whether it was a hit or not, who knows. Too late now to know but in the future we both will be more aware and less in denial.


I nothing else, its lessons learned and I am arming myself with as much knowledge as possible. I have skin dived for years and always wanted to dive and not hold my breath. I plan on doing this for a very long time and want to protect that desire.

 

[cmalinowski]

Dr Deco,

Thanks a bunch. That answers some of my questions. The reason I am looking is my wife and I started diving just recently and we did our OW and AOW in Cayman last week.


The first day consisted of two checkout dives and we did these 3 hours after landing. All went well and most activity was sitting watching others perform skills. Light duty you might say.


Here is a chronology of dives from my computer.


Dive 1 - 40 ft 40 Min
SI = 00:25
Dive 2 - 36 ft 29 Min
No Safety Stop


The second day of diving consisted of two more dives at and no real SI between dives, just an ascent and back down basically.
Dive 3 - 45 ft 32 min
SI < 00:10
Dive 4 - 48 ft 25 min
No Safety Stop


We continued day 2 with a wreck dive and a night wreck dive
SI = 00:42
Dive 5 – 50 ft 40 min (5 Min SS) (Wreck Dive)
SI = 07:59
Dive 6 – 37 ft 50 min (5 min SS) (Night Dive)


Day three continued with more adventure dives
SI = 12:33
Dive 7 – 105 ft 24 min (6 min SS) 9 minutes below 80 feet (Deep Dive)
SI = 01:03
Dive 8 – 50 ft 46 min (5 min SS) (Boat Dive)
SI = 04:06
Dive 9 – 15 ft 57 min (No SS) (Navigation course)


Needless to say, it was a busy weekend. Every dive ended in climbing a ladder to get out with the equipment on our backs. I always floated for 5-10 minutes just relaxing before exiting the water but my wife always was the first out of the water. She wanted the gear off to relax.


After day two she was sore in her shoulders, arms and neck and was told that it was just all the excretion from learning, additional stress and normal. She did not think she felt right and that night she crashed and had a hard time waking up the next day. After some coffee she felt fine and we finished the dives. By the time we left she has resolved her aches and was fine with no recurring issues. There were several instances on her dive computer that shown ascents that were two rapid. Most were small and after she became more skilled she was able to control ascent better. Now she’s a pro at ascending but the first two days were rocky.


As for me, after day three we were at dinner and I was hit with a sudden wave of dizziness and nausea. It felt like sea legs had set in so I wasn’t all too concerned. After several days on a boat I usually start walking like an old drunk sailor. It did seem odd how quickly it hit me though. This was well after our dives and a good 10 hours after any dive of depth. I had no other symptoms and they passed later that night. I did have a few periods where I felt like the sea legs had come bak and I wrote it off as inner ear. Whether it was a hit or not, who knows. Too late now to know but in the future we both will be more aware and less in denial.


I nothing else, its lessons learned and I am arming myself with as much knowledge as possible. I have skin dived for years and always wanted to dive and not hold my breath. I plan on doing this for a very long time and want to protect that desire.

Next time, call DAN (Divers Alert Network). Waiting to see what the scubaboard people say may be too late. And, while everything seems to be fine, next time with similar simptoms, it may not be. DAN knows what questions to ask to help you determine whether possible DCS or not.

Diving Emergencies (Remember: Call local EMS first, then DAN!)
1-919-684-8111
1-919-684-4DAN (collect)
1-800-446-2671 (toll-free)
+1-919-684-9111 (Latin America Hotline)
International Emergency Hotlines
Travel Assistance for Non-Diving Emergencies
1-800-DAN-EVAC (1-800-326-3822)
If outside the USA, Canada, Puerto Rico, Bahamas, British or U.S. Virgin Islands, call +1-919-684-3483 (collect).
Non-Emergency Medical Questions
1-800-446-2671 or 1-919-684-2948, Mon-Fri, 9am-5pm (ET)
All Other Inquiries
1-800-446-2671 or 1-919-684-2948

 

[LavaSurfer]

Next time, call DAN (Divers Alert Network). Waiting to see what the scubaboard people say may be too late. And, while everything seems to be fine, next time with similar simptoms, it may not be. DAN knows what questions to ask to help you determine whether possible DCS or not.

I wasn't waiting for any response as far as medical advice goes.
That wasn't why I am asking or telling.

The issue I wanted to relate, I guess, was that I did not see this as an issue until it was way too late and I was reading some material. Its very easy to write it off as muscle aches, which it may have been, or sea legs which it may have been.

Trust me, If I felt this was an emergency I would never rely on the internet for a fast response or diagnosis. I am just relaying my story.

The issue with my wife does concern me and in the future both she and I will be more aware. As for me I still think that its just water in the ear or something else because I have had similar episodes freediving and there is no nitrogen involved in freediving. Maybe more frequesnt clearing are in order. I have always had ear problems anyway.

I see you are in columbia MD. Intersting, I am in Germantown.