djhall
Guest
First... before everyone jumps in to point out the obvious, let me say it for you. No, I am in no way qualified, experienced, or equipped to attempt in water recompression, decompression diving, or any similar situations. That said, I have seen the debates regarding prophylactic administration of surface O2 for asymptomatic diverts at increased risk of DCS, pros and cons of IWR, various IWR treatment methods, and so forth, and I had a couple of purely theoretical questions.
It seems that the "Australian Method" of 30-90 minutes of oxygen at 30 feet followed by a 1ft/4min ascent is the most practically feasible method for most divers. The procedure is easy to understand, and the shallower depths should be easier on tender divers, especially in case emergency complications arise. It seems unlikely that enough O2 would be available for the US Navy method, and the Pyle method sounds far to complicated. I just don't know enough to be able formulate an opinion on whether the Hawaiian "bounce" on air first is a good idea or not. Therefore, I will assume the Australian method from here out.
1) I assume no form of IWR is possible without pure O2? Could the procedure be carried out using standard air if that was all that was avaliable?
2) Could this method be used as a preventative measure for someone at increased risk of DCS, but who was sign/symptom free? If someone were to, say, miss a required deco stop, could they immediately switch to O2, select a tender diver, and re-descend to 30 feet to start the procedure in an attempt to prevent the onset of DCS?
3) 1ft/4min is an EXTREMELY slow ascent rate! 30ft * 4min/ft = 120 minutes to surface. That's 2 hours! In cold water where an additional 2 1/2 to 3 1/2 hours under water may not be possible, what happens if a 1ft/min or 1ft/2min ascent is used? Would that substantially negate any benefits gained from the 30-90 min at 30 feet?
4) What minimum equipment would be necessary to make this option possible? At the very least, I assume some method of anchoring at 30 ft and ascending slowly, sufficient avaliable O2, a knowledgeable tender diver, and environmental protection adequate for the additional period of immersion would be required.
For a rough calculation of what constitutes sufficient O2, how does this look? Assume a SAC of 1cf/min? 30 feet = 2 cf/min O2 consumption. 30 min = 60cf, 60 min = 120cf, 90 min = 180cf. Ascent is 120 min at an average consumtion rate of 1.5cf/min = 180cf. For the maximum treatment of 90 min + ascent, 360cf minimum would be necessary? For the minimum treatment of 30min + ascent, 240cf would be needed? That could be done with a set of double 120's of pure O2.
5) Twin 120's of pure O2 plus 2 1/2 hours water immersion is not looking very practical. Can anything be done to acheive a benefit from a singe 120/130cf of pure O2? Say 30 min at 30 feet + a faster ascent? Perhaps 1ft/min or 1ft/2min for the first 15 feet and 1ft/min for the last 30 ft?
I know this is long, and perhaps, unanswerable, but I hear of people attempting IWR, and I am fairly certain they did not just happen to have a spare 360cf of pure oxygen lying around. I've been curious about how this is done by people who actually attempt it, and how it could be done in a practical and informed manner, if there is such a combination.
It seems that the "Australian Method" of 30-90 minutes of oxygen at 30 feet followed by a 1ft/4min ascent is the most practically feasible method for most divers. The procedure is easy to understand, and the shallower depths should be easier on tender divers, especially in case emergency complications arise. It seems unlikely that enough O2 would be available for the US Navy method, and the Pyle method sounds far to complicated. I just don't know enough to be able formulate an opinion on whether the Hawaiian "bounce" on air first is a good idea or not. Therefore, I will assume the Australian method from here out.
1) I assume no form of IWR is possible without pure O2? Could the procedure be carried out using standard air if that was all that was avaliable?
2) Could this method be used as a preventative measure for someone at increased risk of DCS, but who was sign/symptom free? If someone were to, say, miss a required deco stop, could they immediately switch to O2, select a tender diver, and re-descend to 30 feet to start the procedure in an attempt to prevent the onset of DCS?
3) 1ft/4min is an EXTREMELY slow ascent rate! 30ft * 4min/ft = 120 minutes to surface. That's 2 hours! In cold water where an additional 2 1/2 to 3 1/2 hours under water may not be possible, what happens if a 1ft/min or 1ft/2min ascent is used? Would that substantially negate any benefits gained from the 30-90 min at 30 feet?
4) What minimum equipment would be necessary to make this option possible? At the very least, I assume some method of anchoring at 30 ft and ascending slowly, sufficient avaliable O2, a knowledgeable tender diver, and environmental protection adequate for the additional period of immersion would be required.
For a rough calculation of what constitutes sufficient O2, how does this look? Assume a SAC of 1cf/min? 30 feet = 2 cf/min O2 consumption. 30 min = 60cf, 60 min = 120cf, 90 min = 180cf. Ascent is 120 min at an average consumtion rate of 1.5cf/min = 180cf. For the maximum treatment of 90 min + ascent, 360cf minimum would be necessary? For the minimum treatment of 30min + ascent, 240cf would be needed? That could be done with a set of double 120's of pure O2.
5) Twin 120's of pure O2 plus 2 1/2 hours water immersion is not looking very practical. Can anything be done to acheive a benefit from a singe 120/130cf of pure O2? Say 30 min at 30 feet + a faster ascent? Perhaps 1ft/min or 1ft/2min for the first 15 feet and 1ft/min for the last 30 ft?
I know this is long, and perhaps, unanswerable, but I hear of people attempting IWR, and I am fairly certain they did not just happen to have a spare 360cf of pure oxygen lying around. I've been curious about how this is done by people who actually attempt it, and how it could be done in a practical and informed manner, if there is such a combination.
!!
