Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:
You can gain access to all this absolutely free when you register for an account, so sign up today!
in your extreme example of (permanent) reduced lung volume at depth (lung volume -0.5 l, the shifted blood), the freediver would have a total lung volume of 5.5 litres (5 l gas and 0.5 l blood) when surfacing
Thanks for your analysis and the corrections. Unfortunately you focused on unimportant or deliberately simplified details, but do not seem to be willing to accept the fact that volume and pressure are very much bind together. Although lungs (+the surrounding body) are flexible, there are limits on both extremities of the volume, resulting so in overpressure or underpressure in the lungs, and leading hence possibly to an injury or embolism.bubestube said:VOLUME damages the lung,
PRESSURE influences haemodynamics (bad enough, I guess packing is responsible for many surface black outs).
Hey, basically you accuse me of denying Boyle's law? I am sorry iftrux said:Thanks for your analysis ..., but do not seem to be willing to accept the fact that volume and pressure are very much bind together. Although lungs (+the surrounding body) ...to an injury or embolism.
I agree with most of it but still have to stick to my VOLUME claim. Here is why (although I think we more or less mean the same thing and that this is only about some sort of misunderstanding):In the moment the ambient pressure is higher than the pressure inside lungs (descent), the lungs (volume) are being compressed to equalize the pressures, ... if there were no pressure gradient.
Let’s leave packing out for the moment (will discuss it later). In my previous post I gave you the reference of the N2 net uptake (700 ml) at a dive to 90 m. This would already be substantial to answer your question of importance. Further, assuming you don’t have a respiratory quotient (RQ, volume of carbon dioxide released divided by volume of oxygen consumed) of 1 (which would mean you only utilize glucose for energy generation) but rather a normal 0.8, you would loose some more gas during the dive because you extract more O2 and return less CO2. Resting O2 consumption is about 3.5 ml/min/kg (245 ml in a 70 kg person). So having a RQ of 0.9 would mean 24.5 ml of net gas absorption per minute. Even though I don’t know what the O2 demand during a free dive is, it seems to me that this consumption mechanism further reduces the gas volume. Finally, gas will be taken up and stored in the blood/tissues. This applies to all 3 gases (N2, CO2 and even O2 to a small extend). Having said all this I must conclude (and agree with the doctors of Mullins) that you definitely won’t surface with the original amount of gas you inhaled at your last breath. Also, the difference may also be quite substantial. In other words, you’ll “loose” gas on your dive which protects you against ascending barotrauma.In the discussed case though the situation is more complex, because we have several additional factors changing both the volume and the pressure: the initial packing increases the inner pressure, the blood shift reduces the volume, and there may be also some differences due to a different level of gas dissolving in the blood. Especially nitrogen, as you wrote too. Unlike the doctors of Mullins, I do not think that "fair proportion of the gas taken down is used for respiration and not exchanged back into the lungs" - oxygen may be transformed into CO2, and the volume of gas dissolved in blood may vary in different moments of the dive, but I wonder whether the difference is really important.
OK…, I agree…, like you said, depending on the several factors (worst case scenario: maximum pack and a blood volume that refuses to leave the thorax on ascent) there definitely is a chance of barotrauma during ascent. The key factor here is the reduction of intrathoracic blood (the shifted blood) on ascent (gas is not the problem, rather protective as explained above). And like I mentioned in my previous post, I don’t think that this will be a big problem unless you ascend with your heart beating only a few times. It has been shown (same book page 560) that cardiac output increases during the ascent, especially due to increased stroke volume (the chest trying to get rid of the shifted blood).So depending on several factors, specifically the speed of the ascent, the speed of the reverse blood shift, and the speed of nitrogen and CO2 releasing, the resulting overpressure in the lungs may be higher than the initial one caused by the packing. This is just a speculation - I do not know the specific speeds, so am unable to tell when (or whether at all) it happens, but think that such possibility is rather realistic and should be taken into consideration.
Well… why do I get the impression that you are putting words into my mouth?Unlike bube, I am with wolleneugebauer and others in this thread who expressed their worries that extreme packing can lead to problems other than just a BO. Sorry, bube, but by claiming that packing (pressure) cannot damage lungs or cause embolism, you are virtually telling that you can attach compressor to your mouth and put as much pressure into your lungs as you want, without causing any damage. You certainly realize that it is nonsense, and I hope that you realize that by extreme packing (or the consequent overpressure at surfacing as described here), the overpressure inside lungs can indeed reach dangerous levels.
Well… I hope from what I have explained above you will now understand what I mean with VOLUME trauma. But just for the fun of it I’ll take up your compressor example. Let’s say your compressor is capable of generating 6 atm. Then I will be delighted to put the compressor tube into my mouth after having descended to 50 meters. Get my point?Sorry, bube, but by claiming that packing (pressure) cannot damage lungs or cause embolism, you are virtually telling that you can attach compressor to your mouth and put as much pressure into your lungs as you want, without causing any damage. You certainly realize that it is nonsense, and I hope that you realize that by extreme packing (or the consequent overpressure at surfacing as described here), the overpressure inside lungs can indeed reach dangerous levels.
Well… the book I am referring from (The Lung at Depth, Ed. C.E.G Lundgren and J.N. Miller, Volume 132) talks about intrathoracic blood pooling. I understand that as blood inside the thoracic cavity (the blood vessels there should also be much more compliant to taking up extra blood due to negative pressures). In theory, whether the blood pools inside the thoracic cavity (increasing the volume of the lung tissue, heart… = what I think) or outside the visceral pleura (resulting in a sort of “bulging in” of the latter into the thoracic cavity reducing the volume) does not matter at all in terms of truxe’s dilemma of no or only little reverse blood shift. As soon as the ambient pressure falls below the gas pressure inside the lung, the lung will expand until pressure equalizes no matter what (this leading to ruptures). This is because neither the rib cage nor the abdominal contents can restrict the volume expansion of the lung before it reaches the point of stress failure.Mullins said:Can anybody out there give a good mechanical account of how and where bloodshift occurs?
bubestube said:... so, in my opinion, the answer is NO, no high pressure lung damage due to a too fast ascent. even if it takes the shifted blood longer to leave the chest cage again refusing the air in the lung to "claim" its appropriate volume (according to the ambient pressure), the remaining blood still restricts the available volume in chest cage. so ,YES, the gas pressure in the lung may be a bit higher than expected (according to the ambient pressure) because of the "slow returning blood", but this will cause no damage since the higher pressure cannot be translated into a greater VOLUME.
Yes, it was wrong info (like I have indicated (italic = wrong) I was thinking of deleting them first but thought this is a better way of correcting myself).trux said:Though, if I interpreted well your later posts, with your current analysis, you actually withdrew your original claim, or didn't you?
You keep repeating yourself here and I am not sure of how to interpret this since I thought I had elaborated on all the factors that are involved in your scenario. If I left one out, please tell me so...However, again, you just concentrate on unimportant and well known facts that no one argues about.
I have already answered that, so I am just going to quote myself:So let's clear your original claim, now, without lengthy details - do you agree that such injury can indeed happen in extreme cases, or do you still deny such possibility even remotely?
bube said:OK…, I agree…, like you said, depending on the several factors (worst case scenario: maximum pack and a blood volume that refuses to leave the thorax on ascent) there definitely is a chance of barotrauma during ascent. The key factor here is the reduction of intrathoracic blood (the shifted blood) on ascent (gas is not the problem, rather protective as explained above). And like I mentioned in my previous post, I don’t think that this will be a big problem unless you ascend with your heart beating only a few times. It has been shown (same book page 560) that cardiac output increases during the ascent, especially due to increased stroke volume (the chest trying to get rid of the shifted blood).
So… to summarize, Yes, in theory, there may be a risk of barotrauma on ascent IF you go up super fast (with only a few heart beats, but at the same time super fast would mean a higher workload (if you don’t use an air balloon for ascent) with consequently higher heart rate and higher cardiac output) not allowing the heart to pump the shifted blood out of the thorax. But I honestly don’t think that this is a realistic scenario. But to be on the absolute safe side, maybe take at least 10 seconds for the last ten meters.
I find it difficult to argue against something that is refered to as being "extreme" although it is actual numbers we are talking about. What is extreme pressure, what is extreme volume? I gave you references of lung pressures (trumpet player, stress failure pressures etc.) and volumes (39% increase during packing, also Mullin confirmed this number from personal experience). So maybe we should stick more to the actual numbers and figures than to personal feelings and impressions.On my mind, extreme packing, hence extreme PRESSURE (and consequently extreme VOLUME - if you prefer) either before the dive, or upon a fast resurfacing with a delayed reverse blood shift can cause lung damage or micro embolism.
Who would not like to see real-time live measurements? Although I got the impression that a lot has already been measured in simulated chamber deep dives and apparently your scenario has not yet been identified as a possible problem.I do not think that it can happen easily - we would see it much more often among freedivers, but I would much more prefer seeing serious scientific real-life measurements, than excluding such possibility just because it does not look probable in theory. I'd like to see some more specific numbers based on reality, than just excluding such possibility theoretically.
First, I am always only expressing my oppinion. I never claim anything. As you may have noticed, I am rather careful with absolutes and tend more to talk about probabilities. I also have corrected myself (earlier posts of mine).I think that claiming that packing cannot cause any embolism or lung damage, like you did, only based on a theoretical analysis, is very dangerous. And it is the more dangerous because you accompanied your claims with a lot of "scientific speech" creating the impression to an average reader that you are very well familiar with the topic, and that your facts are perfectly correct and safe.
Although I have no proof that the embolism or lung damage can actually happen, or that it ever happened, if people follow your claim instead of being more vigilant with packing until the issue is seriously researched, it may lead to some ugly accidents.
So let me say it clearly - I am not trying to attack your knowledge (you apparently know much more than average freediver about the physiology and the physics of freediving). I am just trying to make clear that your claims are not necessarily compatible with the more complex reality, and that people should do better to be really careful with packing until more research is done.
Rather, these symptoms sound very much like the ones of people suffering from TIA's (Transient Ischemic Attack) which is caused by local hypoxic episodes in the brain (symptoms depend on where the hypoxia occurs). wolle has described that these severe symptoms were reversible. The fast recovery (20 min) on the other hand argues against air embolism as being the cause. To suffer from such severe symptoms (hemiplegia) large areas of the brain must have been affected. Hence, it must have been a rather large embolus (air) that has plugged brain vessels. If this was the case I seriously doubt that these symptomes could wear of in such a short amount of time with no further lasting effects.wolle said:furthermore I know 3 examples that freedivers had symptoms like dsc without deepdives. the symptoms are coming directly after or while performances with over-packing!
fortunately all symptoms (blindness, hemiplegia, syncope, kaleidoscope viewing, tachycardia etc.) wear gon after 20 minutes...
bubestube said:After having re-read my long post I think I have elaborated on all the important factors concerning your inhibited reverse blood shift scenario.
Based on scientific facts I came to the conclusion that under normal circumstances your scenario does not seem very propable, that as long as you ascent with your heart beating, it does not make sense why the shifted blood should not leave the thorax. But as I have already mentioned in one of my previous posts, I always refer to healthy lung conditions.
good to hear that you are all right (you are aren't you?OceanMan said:I think I may have had an inhibited blood shift scenario this week end. I have healthy lungs and my heart was hopefully beating during the ascent.
One hour after the dive, I felt like mucus was coming up from my lungs/throat (like it happens when you are ill from lungs or nose), I cleared my throat hard to make it come into my mouth, and I spit blood. I don't know if the over-pressure was the cause or the consequence of bleeding (other things went wrong during this dive).
http://mattcl.free.fr/commun/squeeze_small.jpg
was this with or without packing?OceanMan said:I know very little about my Spiro-Data. I just made an experiment similar to this one http://forums.deeperblue.net/showthread.php?t=66480 so I know I can breath out 6.2L-6.8L of air.
I agree with that.In your case I'd rather go for some sort of airway squeeze...
Fitz-Clarke said:OceanMan:
Interesting case. Would you mind answering the following questions about your dive with spitting of blood:
(1) Did you make prior dives that day?
Fitz-Clarke said:(2) Did you have contractions during the dive? If so, please describe.
Immediately after the dive, or maybe one minute. It was a light congestion. I could breathe normally. I could hear the congestion when breathing strongly.Fitz-Clarke said:(3) How many minutes post-dive until your bronchial congestion started?
Completely resolved after the spit, I would say approximately one hour after the dive. It had already decreased a lot 30 minutes after the dive.Fitz-Clarke said:(4) How long until your symptoms resolved completely?
No.Fitz-Clarke said:(5) Have you had this happen before?
good point, I indeed negleted this factor in my calculation. I reckon the mask can be a serious "air eater" (I estimate the volume of the middle ear to be 2-4 ml including the eustachian tube - I could unfortunately find nothing in the medical literature concerning the volume of human middle ear).OceanMan said:I think your calculation of bloodshift volume is quite good although you neglect all the air that one have to put in the mask/nasal cavity/middle ear.