my shallow water blackout nightmare

[anthropisces]

A friend of mine and I began working fairly earnestly on a free-dive vest that would potentially save the life of a black-out victim. It timed both the dive and the surface interval, and evaluated pressure profiles indicative of descent at an odd time.
We worked fairly diligently on it but in the end, we abandoned the device since it took excessively large cylinders to bring someone up if they had a problem at 100'. We felt that the design had to be flexible enough to address problems at all depths and that it was becoming cumbersome. Free divers already are shy of excessive gear.
Still, the potential for the device is there, especially if one wanted to inflate the vest from perhaps 30' or less.

[tylerz]

We worked fairly diligently on it but in the end, we abandoned the device since it took excessively large cylinders to bring someone up if they had a problem at 100'. We felt that the design had to be flexible enough to address problems at all depths and that it was becoming cumbersome.

Well you may have just expressed the perfect combination of safety gear and requirement for common-sense. It appears part of your philosophy for the vest may be the distraction from a product that really makes sense for freedivers. By the vest not functioning deeper than 10m, the freediver can not relax into a reliance and false security towards the vest as easily as if it worked at all depths. If it does work in the range 0-10m or something similar, then it provides its function in the most critical zone. BO at depth is a rare beast. Not having the safety for the shallows, being 99% of the problem, just because it doesn't work for the other 1%, seems a waste.

My recommendation is keep at it.

How did you guage that it functions at 10m? With what neutral point for the diver? How big was the cyclinder for that depth?

[Fondueset]

Awesome thread.

I generally dive quite shallow - 10m would be close to max in the areas I dive most - so I'm generally weighted for neutral at 5-7m. I do sometimes hang out down there for awhile. From the movies I'm probably in the 2 to 2 and 1/2 minute range on most dives. I've got alot to learn about all this but I have noticed relaxing on the surface really helps. I do a sort of 'whole body breathing' - just releasing along all the peripheries and slowing the breath. I also like to exert minimally all during the dive. On the breakwall I like to sit on the rocks now and again and take my mask off - fresh air in the sinuses is really nice.

[lungfish]

It sounds like you were in a laryngospasm and a rescue breath to equalize the pressure on both sides of your larnxy would have released your breathing.

We had a blackout at the PFD clinic in Kona last week, a spearo, it was a non-event because the rescue is simple and gentle. Get them on top by holding their head while keeping their chin tucked in and the nostrils pinched to protect their airway, remove the mask while supporting the head, gently pat the face while blowing on the eyes and TALK to the victim.... it is the sound of being slapped, not being slapped, and air on the face that brings them around. If they are locked up and not breathing, like you were, then do a rescue breath, mouth-to-mouth to release the laryngospasm.

A properly prepared safety diver who is watching you can make it all like a bad hair day...

As far as going back, our diver who blacked out was in the water the next day heading towards his PB.

Surface intervals are important, but they need to be focused on preparation, not just letting time pass. You can be distracted watching for targets...Proper outgassing at the end of the previous dive - hook breaths and proper ventilations immediately afterwards. Surface intervals above 80ft should be at least twice the duration of the previous dive, and below 80ft should be 8min between, to cope with Nitrogen buildup, etc.

Then do appropriate long breath ups until you are really ready, purge, peak inhale, pack and dive..... You can fool yourself into thinking you are saturating (1-2sec inhale, 2sec hold, 10sec exhale) when you are really distracted and doing a full short inhale, a hold and a short exhale - which is actually a purge. You can tell if you are hypocapnic by tingling in fingers but if the water is cold, you can again be fooled and not notice that you have pounded down your C02 to the point that when you dive you aren't feeling the need to breath though you have depleted your 02 levels....

Your blackout could have been a result of the vacuum effect, gases returning to the lungs on ascent and pulling 02 away from your brain. In otherwords, it might not have been gas related at all but PRESSURE related. OR it can occur in combination with hypoxic/hypocapnic condition I described above.

If you are having traumatic memories, dreams, etc., it might be best to take a course and tell them why you are there. Your confidence may shore up a little with some physiology and physics. Get retrained. Spearfisherman die in this endeavor far more often than trained freedivers.....it is because they are swimming to hunt, and not focused on swimming itself.

Thanks for sharing your story, glad you are here to tell it. You and your buddies could use a freediving course with some emphasis on safety support. The rescues are quite easy and gentle...

[tylerz]

Originally Posted by lungfish

It sounds like you were in a laryngospasm and a rescue breath to equalize the pressure on both sides of your larnxy would have released your breathing.

What do you mean by "a rescue breath to equalize the pressure on both sides"? I have not heard of there being a technique to release a laryngospasm other than assisting the body to recognize the presence of air. Shortly after unconsciousness relaxation of the larynx should occur. Supposedly, 10-15% of the time it does not relax until cardiac arrest. In medical practice to release a laryngospasm often requires intubation.

them around. If they are locked up and not breathing, like you were, then do a rescue breath, mouth-to-mouth to release the laryngospasm.

Is there a reference that mouth-to-mouth assists with laryngospasm?

ventilations immediately afterwards. Surface intervals above 80ft should be at least twice the duration of the previous dive, and below 80ft should be 8min between, to cope with Nitrogen buildup, etc.

This is a very new and unexplored topic and specifying generalized times as short as 8min for anything greater than 80feet is not recommended. Recently Eric did some dives where he demonstrated that 8min intervals were not sufficient. If I recall he was doing 11min intervals and it still was not enough.

Then do appropriate long breath ups until you are really ready, purge, peak inhale, pack and dive...

This sequence is also controversial and not recommended by many. Purging wastes energy, increasing metabolism, and reduces CO2 to low levels. Packing you can find all sorts of threads and posts referring to the dangers involved and how it should not be employed for recreational diving, especially by those without considerable experience and understanding of their body.

You can tell if you are hypocapnic by tingling in fingers...

IF, you have tingling in your fingers, it is a good sign that you are hypocapnic, however if you don't have tingling in your fingers, it does not mean you are not hypocapnic. Too low of CO2 for a specific person, has nothing to do with the point that one has tingling in their fingers. It is just a generalization of an obvious sign that one is too low. They could have been too low half way to that point as well.

Your blackout could have been a result of the vacuum effect, gases returning to the lungs on ascent and pulling 02 away from your brain. In otherwords, it might not have been gas related at all but PRESSURE related. OR it can occur in combination with hypoxic/hypocapnic condition I described above.

Why would you distinguish between pressure related and gas related? Gas exchange only occurs due to pressure and related to pressure of the surrounding environment. When diving you are not static, and as long as you are ascending or descending you are being affected by changes in pressure. Considering we were told that the BO was during the ascent, we know that depleting oxygen and pressure were the cause, correct?

Cheers,

Tyler

[jimqpublic]

Tyler,

Viewed through the prism of PFI's training Lungfish's statement is completely consistent. They teach that if breathing does not spontaneously begin after appropriate stimuli (air, mask off, calling, tapping three times) to use mouth-to-mouth pressure to attempt to release the spasm. I may be reading too much into a possible typo when you say "Shortly after unconsciousness relaxation of the larynx should occur..." I think you mean when the body thinks it's in air, not water. With the mask still on and the face/airway possibly being slapped by waves it makes sense as a self-protective device that the larynx was still closed.

The 8 minute surface interval for depths greater than 80 feet, 2x dive time for shallower does seem a bit odd- isn't there a difference between 81' and 181'? It may also be tied with their suggestion to keep a maximum of 10 minutes surface interval to keep all facets of the mammillian dive reflex fully engaged.

Note that on super deep dives (in the 100 meter range) after completing surface protocol Martin of PFI will drop down to 15' and breathe 02 off a regulator similar to the safety stop scuba divers use.

Vacuum effect is described as the point where the partial pressure of O2 within the lungs becomes lower than that within the blood and O2 starts to migrate backward from blood to lungs.

[efattah]

Originally Posted by jimqpublic

Vacuum effect is described as the point where the partial pressure of O2 within the lungs becomes lower than that within the blood and O2 starts to migrate backward from blood to lungs.

To be even more accurate, in order for a vacuum effect to occur, the pressure of O2 in the lungs must drop below the O2 pressure in the VENOUS blood, not the arterial blood, since it is the venous blood which passes across the lungs.

Venous blood is far less saturated with oxygen than arterial blood. Yet, near a blackout, it has been shown repeatedly that even ARTERIAL O2 is extremely low. It can therefore be concluded that venous O2 is almost impossibly low as the blackout approaches. For a vacuum effect to occur, the lung O2 would have to drop below this almost impossibly low venous O2 pressure.

[laminar]

Hi Lungfish,

PFI has contributed a great deal to discussions and awareness of safety protocols. Having Kirk Krack spot you on a line dive is an awesome feeling.

However, please remember that much of what they teach is up for discussion, some of it controversial, and that as a student of any teacher, we all benefit from constant questioning of what we hear conveyed as fact or "the way you should do it." You seem excited by what you've learned in the clinic, and that's great. Remember that even PFI is constantly reviewing and revised their teaching material and some of their methods are different or even contrary to other instructors like Apnea Academy, Solomons, FREE, etc...

One small point: I remember Kirk speculating that slapping a blacked out diver was counter productive because it is a stress to be slapped and/or shouted at. Gently talking, blowing on the face, removing the mask is an invitation to regain conscious, and not remain in the oxygen conserving blacked out state (if that's really what it is).

Pete

[tylerz]

Originally Posted by jimqpublic

Viewed through the prism of PFI's training Lungfish's statement is completely consistent. They teach that if breathing does not spontaneously begin after appropriate stimuli (air, mask off, calling, tapping three times) to use mouth-to-mouth pressure to attempt to release the spasm.

Yes, I understood that. That made it even more important to point out what I did. My response was not meant to say the information was not an accurate and precise copy of what he had been taught, but instead, to present information for assessing the quality of the information presented, in and of its own. There are many variances in thoughts out there, and if all we do is take the most massively passed around ideas, without a check into the quality of those ideas, we will not progress or be very accurate in comprehending what we are dealing with. So, either there is information that stands to correct my response, that the PFI information is founded upon, or it is unnecessary to practice mouth-to-mouth on a laryngospasm. Either way, a bunch of us will learn something by uncovering which it is, as opposed to just taking a routine as a suggestion of accuracy.

I may be reading too much into a possible typo when you say "Shortly after unconsciousness relaxation of the larynx should occur..." I think you mean when the body thinks it's in air, not water. With the mask still on and the face/airway possibly being slapped by waves it makes sense as a self-protective device that the larynx was still closed.

It is not a typo. We tend to take it for granted that often we hypothesize on how the body operates in our community, and eventually many people begin referring to the details of the hypothesis as being fact. It is generally agreed that "when the body thinks it is in air, not water", consciousness returns. Therefore, what you say holds for the return of consciousness but it does not have any basis in reference to laryngospasm. The idea that laryngospasm releases as a result of reaching air or the discontinued sense of external water, is a conceptual idea but one not necessarily based in fact. See the section on "Water entering the upper airways" at: http://en.wikipedia.org/wiki/Drowning

Vacuum effect is described as the point where the partial pressure of O2 within the lungs becomes lower than that within the blood and O2 starts to migrate backward from blood to lungs.

So, the real significance involved here is the idea that blood will have a smaller amount of oxygenated cells travelling onward from the lungs. Without any other variables, during an ascent this is occurring throughout the complete surfacing. As you surface pressures are changing, therefore there is a decrease in O2 exchange from the lungs to the blood. The vacuum effect is simply when it decreases beyond zero and becomes a negative value. Nothing changed. The blood going to the brain still contains O2, just less than the previous less.

[lungfish]

I know there are a different aproaches to diving but only a few have enough experience and academic support behind them to warrant investigation. Sure, you can argue about negative pressure diving, etc but Purging and Packing as part of the breathup is not controversial unless you haven't been taught how.

I have been exposed to other techniques besides PFD, gang. Theirs is one of the most newbie/spearo friendly I have found.

Reference for surface intervals:

The Attitude A Breath Hold Diver Should Take To Avoid Arterial Gas Embolism
Battle, John M. MD, PhD Chairman MEDISUB Hyperbaric Institute.

The safety rescue I described is effective and simple. No slapping, just work with keeping the airway closed to the surface, get the mask off, gently pat them while talking loud enough to be heard and breathing on their eyes. One or two cycles of rescue breathing can release a laryngospasm. Otherwise, it releases with the terminal breath at the onset of anoxia.

I stand by my entire post.

[efattah]

Originally Posted by lungfish

Purging and Packing as part of the breathup is not controversial unless you haven't been taught how.

Both purging and packing are controversial.

From personal experience I can say that packing
1. Increases CO2 narcosis dramatically
2. Increases the risk of deep water blackout (by means of #1)
3. Increases the risk of lung squeeze
4. Increases the need for longer intervals between dives due to higher metabolic waste products
5. Increases the risk of DCS for various reasons
6. Creates a risk of damaging the intercostal muscles from overpacking
7. Creates a risk of vagal blackout during packing

Purging right before the dive isn't necessary at all. Purging, if done, should be done very early in the breathe-up, long before the dive, so that the energy expended from purging can be regained. Purging burns stored energy in the abdominal muscles & diaphragm, an energy debt which is repaid during the dive by draining the critical oxygen supply.

When I stopped purging and instead switched to sub-neutral breathing, all my apneas of all types increased significantly.

For these reasons I would still say that purging/packing are both controversial.

[lungfish]

Sure Eric,
I suppose you could say its controversial in that there are differences of opinion about when to do it. Sure there are other techniques and advanced practices that engage different perspectives however, for the trained, average freediver, it isn't risky. There are benefits to the practice and it can be undertaken safely, I think that was my point... Overpacking is due to poor training practices as are several other of your points.

I think that it is also important to point out the differences in this discussion between performance, one time dives, and repeated dives. Eric is probably talking about prep for a performance dive to extreme depths and I am talking about spearos, repeat dives and folks who operate up to 40meters.... There are definite differences between the two types of diving and the origin of this thread involved a spearo blacking out.

The surface interval addresses Nitrogen and DCS and the C02 narcosis question. Further, I think you are describing a performance problem rather than a spearo problem. Purging should be done carefully and in conjunction with a careful breathup if you are going to do it. Sure, you can dive negatively, or with other types of breathing patterns but for the average diver at base depths up to 40meters, and the spearo who is operating under 100ft, like most of them, then there is nothing at all negative about the breathup, purge, peak inhale and pack method as long as it is done correctly.

Sure you can overpressurize with packing and cause a vaso constriction lmoc or blackout, it can happen when you are doing dryland statics and tolerance tables too.

I do agree that for average divers who aren't going below 40meters, carefully purging early as part of the breath up is correct because of the rise in heartrate that accompanies purging. If bradycardia is a goal, then purging early and following up with another minute or two of basic breathup to continue lowering heartrate before peak inhale is appropriate instead of purging just before the peak inhale and pack. If you are trained to do it, and you are operating at depths more consistent with most of our skill levels than at extreme depths, it makes sense and is easy to do. You aren't risking anything extreme by the practice and it does help with C02 build.

On the other hand, if you are diving to the levels that you, and the more advanced divers go, then there are probably considerations that most of us don't face. That isn't controversy, that is modification to accomodate deeper and longer performance dives. Like Martin hitting the regulator at 5meters after a 100meter dive.

Lets talk about what works for spearos to 100ft. They are doing it repeatedly in the course of the hunt and its killing them. What is an appropriate pattern for them?



There are probably several good patterns for them.

Lungfish.

[efattah]

All this discussion is based on repeated 10-40m dives.

In my opinion, the only time packing is justified is for 'one max' dives such as what Martin does. I rarely if ever do 'one max' dives anymore.

Packing will always increase DCS risk, CO2 narcosis, deep water blackout risk, lung squeeze risk and surface interval times, when done with repeated dives such as a spearo does. There is no way to get around those effects, regardless of surface interval times. In my experience, packing increases the total dive time, but has a minimal effect on the actual bottom time, due to the increased descent time required from the extra buoyancy. Adding weight to compensate just increase the load when coming up. In my experience, I require 2 extra minutes to recover between packing dives, vs. between non-packing dives of similar intensity. Any extra bottom time from packing is quickly lost when you consider the longer surface interval required. Surface intervals are also critical in cold water diving when the total time in the water is limited.

I also think that purging late in the breathe-up is non-beneficial, regardless of the style of diving.

[lungfish]

Again, I can agree with you on some points regarding packing. It can cause problems, some of which can be mitigated by longer surface intervals, which is not a negative in my book. Improper application can cause problems also, and sometimes you squeeze no matter what you do...

I think a primary value of packing is that it allows for equalizing at average depths if we aren't wearing fluid goggles and are trying to operate at reasonable depths while we practice pursuit diving.

The values of packing for a performance dive are limited given that there are other practices involved. You can choose to do it or not, but it isn't necessarily a negative if you are trained to do it. Many, many freedivers use packing without incident. There are risks to every aproach, negative pressure diving has its drawbacks as well.

Surface intervals aren't a drawback for pursuit divers, it is another aproach to addressing issues when you choose a particular breathup pattern. If you are diving deep and long, longer surface intervals are a given. It is also a given that surface intervals must have a minimum and maximum duration for him to continue to be effective. So what is that minimum and maximum?

So lets get back to our Spearo friend here. What is appropriate for spearos, if you were going to give a class to any number of spearos on this site, what would you teach them to do to avoid SWB, DCS, CO2 Narc., etc. We aren't talking about prime atheletes, we are talking about Joe Spearo who isn't experienced beyond 100ft, probably hasn't taken a course, and is trying to survive his hunt with his buddies. What is the overall breathup cycle, safety profile and correct aproach to his twice monthly, Sat afternoon hunt? What does this guy and his friends need to know and do to survive their activities?

Lungfish

[tylerz]

Originally Posted by lungfish

I know there are a different aproaches to diving but only a few have enough experience and academic support behind them to warrant investigation.

Just to clarify, did you really mean to say by these words, that there are only a few people with enough experience and academic background who should be investigating what we are told by the few others? Isn't the only way to become experienced and academically supported, to investigate? How are you determining who has "enough" experience and academic support?

I do not think PFI would suggest that they are in the business of research. They do take a handful of information from other sources of research and incorporate what is reasonable into their courses and philosophy; mostly, as I understand it, in the interest of giving students a "good enough" background to reach some objectives of relatively comfortable and safe dives. But definately "not enough" to be experts or have precisely detailed comprehensions of the topic. I think it would be safe to say that the Italians have been involved, and employed, much more research when it comes to these topics, and noteably Apnea Academy has strong differences in philosophy, interpretation, and approach to PFI. If these two respected bodies have such differences, don't you think that exploring the nature of the differences becomes important to having a more accurate and precise comprehension of the topic? The value of this forum comes from exploring the suggestions as opposed to discounting them based on prejudice. Especially when there are more researchers and scientists in these forums than any freediving school.

It would be reasonable to say "according to PFI courses, they suggest...", and then newcomers would understand it is an opinion by one school. But stating things, that one has not looked into, as fact does not do justice to newcomers. Especially when conveying information to newcomers, if one has not looked into safety concepts themself, repeating what one thinks somebody else said, and assuming it to be accurate, is very dangerous. Therefore in the case of newcomers, I believe one should go to great lengths in the attempt to make a clear distinction between what is "known" and what is "opinion".

Your statement:
"Then do appropriate long breath ups until you are really ready, purge, peak inhale, pack and dive..." is comprised of only opinion of what is a good approach to a dive, yet with very little detail. It was presented originally amidst other technical details. As presented, it is extremely open to interpretation, therefore without further elaboration a newcomer can not get an accurate and precise impression of what is safe from that explanation. It has been presentedas though they are supposed to do what is stated. Now they go and try it, as described and I don't think many people would argue that, in its form, it presents a clear and safe practice. But how is a newcomer supposed to know that.

But even so, the fact that on these forums newcomers only have words as the medium to interpret what exactly is trying to be conveyed, wouldn't the safest approach be to only put emphasis on those elements that are minimally required practices and have the greatest degree of safety? Let's look at the recommendation from that light:
1. It is known that purging reduces CO2, which for safety reasons, whether you are trained or not, reduces your safety element. I have never heard an argument that suggests it is safer to recreationally dive with less CO2. The last thing required in teaching somebody to dive is generally purging or special ventilations. It is probably the most dangerous element to introduce to a newcomer. It is not about arguing whether it "can" be learned in a safe manner, but whether it will be.

2. Every doctor I have spoke to, or have heard that others have spoken to, has recommended not practicing packing. Experienced freedivers in the community are also suspecting physiological trouble from packing whether doing shallow or deep dives. I have first hand met 3 divers that have suffered from severe cases of blood in the lungs during shallow dives involving packing. Once again, without first hand working with another person, learning packing is not necessary and definately is a danger to newcomers.

Sure, you can argue about negative pressure diving, etc

Nobody was arguing about or suggesting negative pressure diving. To suggest not packing, is not the same as suggesting negative pressure diving. Packing can be considered as an artificial enhancement of our phsyique for diving. Diving on simply a peak inhale is not negative pressure diving and is more natural than packing.

but Purging and Packing as part of the breathup is not controversial unless you haven't been taught how.

That appears backwards. It is only controversial once one has comprehended the different sides of the argument. The controversy is in the experienced reasonsings and/or opinions.

I have been exposed to other techniques besides PFD, gang. Theirs is one of the most newbie/spearo friendly I have found.

Which other courses did you take?

... for the average diver at base depths up to 40meters ... like most of them, then there is nothing at all negative about the breathup, purge, peak inhale and pack method as long as it is done correctly.

Well, maybe you hit the nail on the head here, if you define "correctly" as when nothing goes astray from what we expected. But that is the problem, we can not control exactly when something goes astray. Therefore, if there is a known danger from some practice, then you can not say that there is "nothing at all negative" about that practice. You seem to be under the impression that there is no doubt if divers do as they are told, nothing will go wrong. Well, we have had plenty of experiences that tell us otherwise. At a PFI clinic this past weekend a participant came up spitting blood. They did not suggest she had done anything incorrectly.

Reference for surface intervals:
The Attitude A Breath Hold Diver Should Take To Avoid Arterial Gas Embolism
Battle, John M. MD, PhD Chairman MEDISUB Hyperbaric Institute.

From that reference comes your interpretation through the statement:

Surface intervals above 80ft should be at least twice the duration of the previous dive, and below 80ft should be 8min between, to cope with Nitrogen buildup, etc.

Whereas, Kirk quotes it as:

A dive to 69m for 2:20 which is typical of an expert competitive freediver the surface interval before any other freedive is 9:13.
He developed a simple rule of thumb; If the depth of your freedive was < 25 meters then your SI should be twice your total dive time.
If your depth was > 25 meters then your SI should be a minimum 8 minutes.

, which one can see has a much different meaning.

One or two cycles of rescue breathing can release a laryngospasm.

You state this as fact. Where do you see a reference to this? We have had a couple cases of laryngospasms here in Vancouver with Kirk present, and there was no such results. Saying that rescue breathing "can" release a laryngospasm, suggests that we know that sometimes it assists. But if it only happens sometimes, how did we determine that it was the mouth-to-mouth as opposed to simply the delay before it release? I do not believe you or anybody else in the freediving community has a reference that shows mouth-to-mouth assists. Please show otherwise and then we can safely conclude it to be fact.

Otherwise, it releases with the terminal breath at the onset of anoxia.

I interpret this as "a laryngospasm releases with one's last breath at the point that oxygen has been completely depleted from the blood stream." Is that intended? Where did you come across this idea?

I stand by my entire post.

Ok, but do you have any answers and reasonings towards the questions that were in response to your post. If I understand your response, I can summarize it as:

"Those, here in the forums, do not have the experience or academic background to assert opinions differing or going beyond those of PFI's course material. If you have been taught how to purge and pack you will not find any controversy in the topics or disapprove of such practices. There exists a study that recommends what it considers is possibly a safe interval practice under similar conditions as they describe. None of the responses and questions to my post are worth considering further."

I sure hope that is a misinterpretation, hopefully for obvious reasons.