Post by Argo on Nov 2, 2005 13:10:11 GMT -5
This ones a hot theme........... been digging around and found a very good article on this subject. Here are just short excerpts from the major article (17 pages). If anybody is interested check out the link at the bottom............
In-water Recompression as an Emergency Field Treatment of Decompression Illness
There are many controversial topics within the emerging field of "technical" diving. This is not surprising, considering that technical diving activities are often high-risk in nature and extend beyond widely accepted "recreational" diving guidelines. Furthermore, many aspects of technical diving involve systems and procedures which have not yet been entirely validated by controlled experimentation or by extensive quantitative data. Seldom disputed, however, is the fact that many technical divers are conducting dives to depths well in excess of 130 feet for bottom times which result in extensive decompression obligations, and that these more extreme dive profiles result in an increased potential for suffering from Decompression Sickness (DCS).
Although technical diving involves sophisticated equipment and procedures designed to reduce the risk of sustaining DCS from these more extreme exposures, the risk nevertheless remains significant. Along with this increased potential for DCS comes an increased need for many "technical" divers to be aware of, and be prepared for, the appropriate implementation of emergency procedures in response to DCS. In the words of Michael Menduno (1993), "The solution for the technical community is to expect and plan for DCS and be prepared to deal with it".
Case #1. Hawaii.
"Four fisherman divers were working in pairs at a site about 165 to 180 feet deep. Each pair alternated diving and made two dives at the site. Both divers of the second pair rapidly developed signs and symptoms of severe CNS decompression sickness upon surfacing from their second dive. The boat pilot and the other diver decided to take both victims to the U.S. Navy recompression chamber and headed for the dock some 30 minutes away [the recompression chamber was an additional hour away from the dock]. During transport, one victim refused to go and elected to undergo in-water recompression, breathing air. He took two full scuba tanks, told the boat driver to come back and pick him up after transporting the other bends victim to the chamber, and rolled over the side of the boat down to a depth of 30 to 40 feet. The boat crew returned after 2 hours to pick him up. He was asymptomatic and apparently cured of the disease. The other diver died of severe decompression sickness in the Med-Evac helicopter en route to the recompression chamber." (Hayashi, 1989, p. 157)
Case #2. Fiji.
Five minutes after surfacing from the fourth dive to moderate depth (75-120 feet) over a 24 hr period, a diver developed progressive arm and back weakness and pain. She returned to 60 feet for 3 min, then ascended (decompressed) over a 50-minute period (with stops at 30, 20, and 10 feet), breathing air. Tingling and pain resolved during the first 10 min of IWR. Three hours after completing IWR, she developed numbness in the right leg and foot, and reported "shocks" running down both legs, whereupon she was taken to a recompression chamber. After 3 successive U.S. Navy "Table 6" treatments, she still felt weakness and some decreased sensation.
The effect of IWR on the recovery of this diver is unclear. Although the pain and weakness were resolved during IWR, more serious symptoms developed hours afterward. Perhaps numbness would never have developed had the diver been taken directly to a recompression chamber instead of re-entering the water, in which case she may have responded to treatment without residuals. On the other hand, had she not returned to the water, the initial symptoms may have progressed into paralysis during her evacuation to the chamber, and she might have ultimately suffered far more serious and debilitating residuals. Cases such as this do not contribute much insight into the efficacy of IWR.
Other cases, however, provide stronger evidence suggesting that IWR has been of benefit. Consider the following case documented in Farm et al. (1986) and Hayashi (1989):
After spending 18 minutes at a depth of 220 feet, a diver experienced a serious malfunction of her Buoyancy Compensator inflation device which resulted in the rapid loss of her air supply and a sudden increase in her buoyancy. Additionally, she became momentarily entangled in a guide line, further delaying ascent, and was freed from the line with the assistance of her diving companion. As they ascended, they were met by a second team of divers just beginning their descent. Although one of the members of the second team was able to provide her with air to breathe, he was unable to deflate her over-expanded B.C., and both ascended rapidly to the surface. Within 4 minutes, she returned to a depth of 20 feet where she breathed 100% oxygen for 30 min. She then ascended to 10 feet where she completed an additional 30 min of breathing oxygen. Upon surfacing, she was taken to a nearby recompression chamber facility, breathing oxygen during the 30 min required for transport. Arriving at the facility, she noticed no obvious symptoms of DCS, but was diagnosed with mild "Type II" DCS and treated several times in the chamber. She suffered no apparent residual effects.
Although no DCS symptoms developed prior to recompression, serious symptoms undoubtedly would have ensued had recompression not been immediate, given the extent of the exposure and the explosive rate of ascent. It is interesting that a modified version of the Australian Method of IWR was employed, rather than the diver descending to greater depth on air to complete the omitted decompression. Recompression depth was limited to a maximum of 20 feet due to concerns of oxygen toxicity at greater depths. The victim was monitored continuously while breathing oxygen underwater by at least two tending divers.
It should be noted that successful attempts at IWR are not limited to cases which take advantage of the ability to immediately recompress the victim. Edmonds et al. (1981) report on a case where IWR yielded favorable results many hours after the initial onset of DCS:
Personaly myself I have done it. It worked for me at the time. I only considered it because I was 2 days away from a chamber, had a safety diver with me, 100% O2 and a full face mask.............. It could have easily gone the other way................. It didn't and Im alive to tell the story......
Argo
www.bishopmuseum.org/research/treks/palautz97/iwr.html
In-water Recompression as an Emergency Field Treatment of Decompression Illness
There are many controversial topics within the emerging field of "technical" diving. This is not surprising, considering that technical diving activities are often high-risk in nature and extend beyond widely accepted "recreational" diving guidelines. Furthermore, many aspects of technical diving involve systems and procedures which have not yet been entirely validated by controlled experimentation or by extensive quantitative data. Seldom disputed, however, is the fact that many technical divers are conducting dives to depths well in excess of 130 feet for bottom times which result in extensive decompression obligations, and that these more extreme dive profiles result in an increased potential for suffering from Decompression Sickness (DCS).
Although technical diving involves sophisticated equipment and procedures designed to reduce the risk of sustaining DCS from these more extreme exposures, the risk nevertheless remains significant. Along with this increased potential for DCS comes an increased need for many "technical" divers to be aware of, and be prepared for, the appropriate implementation of emergency procedures in response to DCS. In the words of Michael Menduno (1993), "The solution for the technical community is to expect and plan for DCS and be prepared to deal with it".
Case #1. Hawaii.
"Four fisherman divers were working in pairs at a site about 165 to 180 feet deep. Each pair alternated diving and made two dives at the site. Both divers of the second pair rapidly developed signs and symptoms of severe CNS decompression sickness upon surfacing from their second dive. The boat pilot and the other diver decided to take both victims to the U.S. Navy recompression chamber and headed for the dock some 30 minutes away [the recompression chamber was an additional hour away from the dock]. During transport, one victim refused to go and elected to undergo in-water recompression, breathing air. He took two full scuba tanks, told the boat driver to come back and pick him up after transporting the other bends victim to the chamber, and rolled over the side of the boat down to a depth of 30 to 40 feet. The boat crew returned after 2 hours to pick him up. He was asymptomatic and apparently cured of the disease. The other diver died of severe decompression sickness in the Med-Evac helicopter en route to the recompression chamber." (Hayashi, 1989, p. 157)
Case #2. Fiji.
Five minutes after surfacing from the fourth dive to moderate depth (75-120 feet) over a 24 hr period, a diver developed progressive arm and back weakness and pain. She returned to 60 feet for 3 min, then ascended (decompressed) over a 50-minute period (with stops at 30, 20, and 10 feet), breathing air. Tingling and pain resolved during the first 10 min of IWR. Three hours after completing IWR, she developed numbness in the right leg and foot, and reported "shocks" running down both legs, whereupon she was taken to a recompression chamber. After 3 successive U.S. Navy "Table 6" treatments, she still felt weakness and some decreased sensation.
The effect of IWR on the recovery of this diver is unclear. Although the pain and weakness were resolved during IWR, more serious symptoms developed hours afterward. Perhaps numbness would never have developed had the diver been taken directly to a recompression chamber instead of re-entering the water, in which case she may have responded to treatment without residuals. On the other hand, had she not returned to the water, the initial symptoms may have progressed into paralysis during her evacuation to the chamber, and she might have ultimately suffered far more serious and debilitating residuals. Cases such as this do not contribute much insight into the efficacy of IWR.
Other cases, however, provide stronger evidence suggesting that IWR has been of benefit. Consider the following case documented in Farm et al. (1986) and Hayashi (1989):
After spending 18 minutes at a depth of 220 feet, a diver experienced a serious malfunction of her Buoyancy Compensator inflation device which resulted in the rapid loss of her air supply and a sudden increase in her buoyancy. Additionally, she became momentarily entangled in a guide line, further delaying ascent, and was freed from the line with the assistance of her diving companion. As they ascended, they were met by a second team of divers just beginning their descent. Although one of the members of the second team was able to provide her with air to breathe, he was unable to deflate her over-expanded B.C., and both ascended rapidly to the surface. Within 4 minutes, she returned to a depth of 20 feet where she breathed 100% oxygen for 30 min. She then ascended to 10 feet where she completed an additional 30 min of breathing oxygen. Upon surfacing, she was taken to a nearby recompression chamber facility, breathing oxygen during the 30 min required for transport. Arriving at the facility, she noticed no obvious symptoms of DCS, but was diagnosed with mild "Type II" DCS and treated several times in the chamber. She suffered no apparent residual effects.
Although no DCS symptoms developed prior to recompression, serious symptoms undoubtedly would have ensued had recompression not been immediate, given the extent of the exposure and the explosive rate of ascent. It is interesting that a modified version of the Australian Method of IWR was employed, rather than the diver descending to greater depth on air to complete the omitted decompression. Recompression depth was limited to a maximum of 20 feet due to concerns of oxygen toxicity at greater depths. The victim was monitored continuously while breathing oxygen underwater by at least two tending divers.
It should be noted that successful attempts at IWR are not limited to cases which take advantage of the ability to immediately recompress the victim. Edmonds et al. (1981) report on a case where IWR yielded favorable results many hours after the initial onset of DCS:
Personaly myself I have done it. It worked for me at the time. I only considered it because I was 2 days away from a chamber, had a safety diver with me, 100% O2 and a full face mask.............. It could have easily gone the other way................. It didn't and Im alive to tell the story......
Argo
www.bishopmuseum.org/research/treks/palautz97/iwr.html
