Advice from Dr please

[Hoppy]

Hi all,

Advice sought please regarding the following :-

Someone has the intention to "sit" in a swimming pool for 24 hours.

Aside from the obvious water protection, heat loss etc etc. What in your opinions would be the "profile" of this dive ?

Where would one go for advice regarding deco times, I ask this because I make the assumption that this would at some point become a "decompression" dive even though the depth is no greater than 4m. How would it be best to perform the necessary calculations ?

Would it be best to deco on 100% o2 in the pool , or better to get into a "pot" where suitably trained people are available ? One is available nearby.

Your thoughts would be much appreciated.

Hoppy

Disclaimer
I hasten to add that no-one should even think about doing something this silly without a lot of research and thought and back up.

 

[Dr Deco]

Hello Hoppy:

This is such a shallow dive that decompression is not needed. Studies have been performed involving divers (in a hyperbaric chamber), and these have indicated that DCS limits are at roughly seven meters for at least 24 hours. The tests were actually for exposures of more than two days. The references are below.

From a standpoint of DCS, swimming pools are benign if breath holding is not involved.

Dr Deco :doctor:



References

Eckenhoff RG, Olstad CS, Carrod G.Human dose-response relationship for decompression and endogenous bubble formation. Appl Physiol. 1990 Sep;69(3):914-8.

The dose-response relationship for decompression magnitude and venous gas emboli (VGE) formation in humans was examined. Pressure exposures of 138, 150, and 164 kPa (12, 16, and 20.5 ft of seawater gauge pressure) were conducted in an underwater habitat for 48 h. The 111 human male volunteer subjects then ascended directly to the surface in less than 5 min and were monitored for VGE with a continuous-wave Doppler ultrasound device over the precordium or the subclavian veins at regular intervals for a 24-h period. No signs or symptoms consistent with decompression sickness occurred. However, a large incidence of VGE detection was noted. These data were combined with those from our previously reported experiments at higher pressures, and the data were fit to a Hill dose-response equation with nonlinear least-squares or maximum likelihood routines. Highly significant fits of precordial VGE incidences were obtained with the Hill equation (saturation depth pressure at which there is a 50% probability of detectable VGE [D(VGE)50] = 150 +/- 1.2 kPa). Subclavian monitoring increased the sensitivity of VGE detection. We conclude that the reduction in pressure necessary to produce bubbles in humans is much less than was previously thought; 50% of humans can be expected to generate endogenous bubbles after decompression from a steady-state pressure exposure of only 135 kPa (11 ft of seawater). This may have significant implications for decompression schedule formulation and for altitude exposures that are currently considered benign. These results also imply that endogenous bubbles arise from preexisting gas collections.


Eckenhoff RG, Osborne SF, Parker JW, Bondi KR. Direct ascent from shallow air saturation exposures. Undersea Biomed Res. 1986 Sep;13(3):305-16.

Thirty-four healthy human subjects were exposed to shallow air saturation for 48 h [25.5 fsw n = 19, and 29.5 fsw, n = 15] ] and then decompressed to 1 ATA (0 fsw) in about 2 min. Symptoms included fatigue, limb and joint pain, headache, myalgias, and pruritus. No subject of 19 was diagnosed as having decompression sickness (DCS) after the shallower exposure [25 fsw], but 4 of 15 were diagnosed and treated for DCS subsequent to the deeper exposure. Almost all subjects in both groups had Doppler-detectable venous gas emboli (VGE) lasting up to 12 h postdecompression. Treated subjects had a recurrence of VGE several hours after the hyperbaric oxygen treatment. Only the duration of VGE, and not the VGE score, correlated with symptoms; and only the subjects body weight and age correlated with the VGE variables. This study indicates that hyperbaric air exposures of this magnitude are not as benign as previously thought.

 

[DepartureDiver]

I agree with Dr. Deco ... good thing since he's the doc. Putting aside the medical considerations of being in the water that long in a wet environment, among other issues, a 24 hour dive to 4 meters is very benign and even the utmost conservative profile would not require any decompression or any oxygen breathing. For grins, you could breathe 15 minutes of oxygen for an ultra conservative dive. I would definately make sure the ascent is nice and slow though and be aware of the significant nitrogen loading if another dive was going to be made in the next couple of days.

 

[do it easy]

I recall that someone tried something like this a few years ago - 24 hours or so on scuba at 10 ft. They used a conservative ascent schedule whether it was warranted or not. One of the side effects was that the diver's skin was waterlogged/prunish/macerated to the point that it was painful to walk for a while (days not hours). I think that they were going for a record dive, so maybe there might be more info at Guinness Book of World Records, etc.

 

[DepartureDiver]

Yes, some people have done something like this. I certainly would not want to.

 

[emtdan]

Ripleys did this for a show a while ago. They had some1 in a tank on a bilboard in LA for 24 hours. It was stupid, and they made some bad choices. The diver did fine during the night, then during the morning the sun started to heat the water, and they overcompensated, by putting in large ammounts of ice, and the diver had to come out because of hyperthermia.