Depth, pressure and squeeze

[cebaztian]

Let´s talk about squeeze.

When I started freediving equalization set the depth limit. After some training it was oxygen consumption. Then again equalization and after learning frenzel it was lack of oxygen again e t c.

Last week I did my longest selfpropelled dive ever and it was also my deepest dive. FIM 72 meter in 2.48 minutes. A clear surfacing and happy ears at the bottom - but within seconds I started coughing. Soon I saw traces of blood. I have seen worse, but nevertheless I have decided not to go deeper if I cannot solve the issue of squeeze (lung/trachea).

I have 6 litres of VC and an RV of 1.9. I packed maybe a litre at the surface. My descent time was 1.30 - 1.35.

I have tried to gather some facts/suggestions about squeeze:

Definition of squeeze:
Diving below RV
(RV as the volume AFTER bloodshift has reduced it)
This causes bloodvesel bursting in throat and/or lungs.

Scenarios where squeeze can appear:
Realy at any depth. A negative or FRC dive can get you squeezed at very shallow depths as 10 meters.
Squeeze can only occur when you have mastered frenzel equalization fully and the mouthfill effeciently.

Description of symptomps:
Couching, higher breathrate, soarness in throat, traces of blood in the saliva.
A continious state where you breath at a higher rate (A high shallow breathing, being tired for hours, maybe even days. Fever might occur.
Similar symptoms as secondary drowning due to the blood and/or bloodplasma covering alveolis in the lung.

Treatment of squeeze:
Stop diving. Rest. Lean forward and spit out as much salivablood as possible.
Drink. In severe cases breath at least 5 minutes of oxygen (on land). Eat
vitamins, get extra hours of sleep. Drink more.
In severe cases you might need many days of rest, even weeks.

How to avoid squeeze:
- Slow descent.
- Do not stretch out at depth.
- If possible; turn before contractions.
- Breath out well before the surface
- Do not pack air
- Warm up with (at first) gentle FRC or negative dives
- Drink less before diving deep (statement by S.Murat)

I have disovered that starting breathing out 4-5 from surface will avoid finding yourself back on sealevel with fully packed lungs and a bloodshift that in some cases amount to at least a litre. Maybe the blood is not the result of squeeze in all cases but rather of lung overaexpansion.
Deep BO cases (that might hold their breath even after surfacing) sometimes show foaming mouths of saliva and bloodplasma.

Where does the blood come from:
This has not been proven scientificly. Lungs or throat or both. Fact is that the lungs are very flexible and prone to bloodshift while the throat is made out of cartilage. Under pressure the throat folds into itself. I think it is
likely that it is here that the bloodvessels break. A so called trachea squeeze. I also believe that it doesnt take that many to procuce enough blood to scare a freediver. All in all I dont think it will be more than 50ml in a very severe case, but this is a guess.

It could in some cases come from the sinusarea. An area that can be overpressurized due to blockage or equalizing techniques.

Note that different types of blood can appear. Small specks of blood in saliva or small quantities of what looks like only blood. These usually has different shades, the later probably from arteries (more pressure=more blood) and also a different more sharp red color (due to being recently oxygenated in the lungs).

Do you have any personal experience/conclusions?
Do you find and faults in my presentation?

Sebastian
Sweden

[cebaztian]

More on squeeze here:
http://forums.deeperblue.net/showthr...hlight=squeeze

[fpernett]

Hi Sebastian
I believe is important to define what really is "lung squeeze". The proper term should be something like pulmonary edema of immersion. And pulmonary edema means that some fluid is going away from blood vessels into pulmonary interstitium an even to alveolar space. The main factor for this fluid to move are hydrostatic pressures gradient, the higher the pressure gradient more fluid will move away from vessels. The pulmonary vessels can withstand a lot of blood volume without significant increase in pressure, and that's why I don't believe that over-hydration (in fact, is quite difficult to be over-hydrated during immersion) is a factor in pulmonary edema (if your heart is working fine).
How can we increase the hydrostatic pressure gradient?
-Increasing intra-arterial hydrostatic pressure: This is affected by several things
1) Lung Volume: At Total pulmonary Capacity (TPC) there is High resistance in pulmonary vasculature, and the same is for Residual Volume (RV). The Lowest resistance is at Functional Residual Capacity (and advantage of FRC diving). After a full pack you are over your TPC and the resistance of the vessels is higher than normal, and the flow is minimal. When the dive start lung volume decrease rapidly and resistance goes down, with increasing flow that can produce shear stress on endothelial cells. So, I think rapid changes in lung volumes is a main factor
2) Interstitial pressure: Contractions produce high negative pressures in pleural space, that is transmitted to interstitial tissue, increasing the hydrostatic pressure. This is also an explanation for contraction of intercostal muscles (due to stress or fear) this reduces flexibility of the chest and increase the negative pressure in pleural space.
3) Exercise: This is not a problem only for freedivers, SCUBA and swimmers also are affected by pulmonary edema. The exercise induces high flow in pulmonary vessels and increase pulmonary pressure with increasing work for the right side of the heart. In the last part of a deep and long dive you are probably very hypoxic and due to the pulmonary hypoxic vasoconstriction the resistance is very high, and with higher flow than usual make the apneist prone to the pulmonary edema.
Also, with all of this conditions it's possible a rupture (microscopic) of pulmonary vessels that affect the permeability and produce more edema.

That's why I believe that training in a conservative way is the best way to avoid it. And agree with your statements, and will include Confidence, that make you go more relaxed and without fear.

It's quite difficult to know where the blood comes from, but with X-ray and Thoracic CT of the few reported events in medical literature the more severe forms are from alveolar damage. Spitting blood is not always the same as pulmonary edema, you can spit blood from sinuses if equalization was too hard, or even throat specially with heavy contractions. Shortness of breath and rapid and shallow breathing indicate a more serious conditions.
My brother had in 2004 a severe pulmonary edema, with fluid in his pleural and pericardic space, high fever and low levels of Oxygen in blood, he took oxygen for 12 hours.
There is a lot of room for investigation to make things clear

[Bill]

Sebastion
First, congratulations on the dive and second, thanks for collecting all the data into one place for us.
My spear fishing buddy for 20 years used to cough up specks of blood once in a while. This would occur on long diving days (5-6 hours in the water) and maximum depths of 20 meters. It wasn't possible to tell if he was hurt or just very concerned about the possibility.
Aloha
Bill

[cebaztian]

I have a feeling that our main problem is:

1) Tracheasqueeze and that the bloodspecks mainly comes from the throat and bloodvessel inbetween (?) the cartilage. The throat I believe goes deeper down into the lungs than we generally percieve as "the throat".

I do not believe that the small increase of pressure from let say 60-70 causes bloodvessels to break in the alveolis.

I also believe that a significant factor for producing squeeze symptoms are strong contractions at depth. But I also believe that high CO2 is very beneficial for extreeme dives.

This is just a theory on what happens in most cases of blood spitting.

2) It might just be that the PACKING is the main culprit, actually inhibiting bloodshift and therefore the blood comes from the lung as FERNET implies.

Originally Posted by fpernett

After a full pack you are over your TPC and the resistance of the vessels is higher than normal, and the flow is minimal. When the dive start lung volume decrease rapidly and resistance goes down, with increasing flow that can produce shear stress on endothelial cells.

But packing is what takes me from 60-70 meters.

3) Or can ALL symptoms of squeeze (during a dive with packing) be avoid if you descent slow from 0-15. The question is how slow would this be? 2 m/s ?

Originally Posted by fpernett

...due to the pulmonary hypoxic vasoconstriction the resistance is very high, and with higher flow than usual make the apneist prone to the pulmonary edema.

But the chest area is not exposed to vasoconstriction, is it?

And yes - we must not forget that the blood in some cases can come from the SINUS area. Maybe caused by ruptured bloodvessels due to blockage and overpressure.

Sebastian

[DeepThought]

A great thread you started here Sebastian.

Originally Posted by cebaztian

I do not believe that the small increase of pressure from let say 60-70 causes bloodvessels to break in the alveolis.

Could be the straw that broke the camel's back.

Originally Posted by cebaztian

I also believe that a significant factor for producing squeeze symptoms are strong contractions at depth. But I also believe that high CO2 is very beneficial for extreeme dives.

I agree with you about CO2 being beneficial. Question is, does it always has to be accompanied by contractions at depth? I often wondered if really deep divers get contractions before getting back around to residual volume area. Assumed they don't. Can anyone comment?

Originally Posted by cebaztian

2) It might just be that the PACKING is the main culprit, actually inhibiting bloodshift and therefore the blood comes from the lung as FERNET implies.
But packing is what takes me from 60-70 meters.

You can try finding something else to take you there. Much much easier said than done, ofcourse. For example: Eric F's calculations on his own mouthfill gets him much deeper equalization-wise, and hypoxic limits can be changed.

Originally Posted by cebaztian

3) Or can ALL symptoms of squeeze (during a dive with packing) be avoid if you descent slow from 0-15. The question is how slow would this be? 2 m/s ?

I remember there were some graphed dives of Martin/Herbert/Carlos somewhere over the net. Might be a valueable reference, though they might have a different level of adaptation than "shallower" divers.

Originally Posted by cebaztian

But the chest area is not exposed to vasoconstriction, is it?

http://en.wikipedia.org/wiki/Hypoxic...soconstriction

[naiad]

Originally Posted by cebaztian

And yes - we must not forget that the blood in some cases can come from the SINUS area. Maybe caused by ruptured bloodvessels due to blockage and overpressure.

I once got a sinus squeeze in a pool 2m deep! I had blocked sinuses and kept on doing dynamic for over an hour. It was extremely painful, but I ignored it and kept going. Afterwards I was spitting blood.

Probably a record for depth-related injury?

[fpernett]

Originally Posted by cebaztian

I have a feeling that our main problem is:

1) Tracheasqueeze and that the bloodspecks mainly comes from the throat and bloodvessel inbetween (?) the cartilage. The throat I believe goes deeper down into the lungs than we generally percieve as "the throat".

Yes, Sebastian that is possible, and can be one of the sources of blood spiting, but if diver suffer shortness of breath and his/her pulse oximetry is lower than normal, the problem has to be in other place. The trachea goes a little deeper in the thorax and subdivide in the two main bronchi, the intrathoracic trachea is more affected by pleural pressure, and extra-thoracic trachea by atmospheric pressure. And as You and I said before contractions can reduce dramatically the pressure in the airway, making a big gradient pressure when comparing it with the atmospheric.

Originally Posted by cebaztian

I do not believe that the small increase of pressure from let say 60-70 causes bloodvessels to break in the alveolis.

Nobody knows exactly what is the pressure breaking point for stress failure in pulmonary vessels

Originally Posted by cebaztian

But the chest area is not exposed to vasoconstriction, is it?

Yes it happens, hypoxic pulmonary vasoconstriction is a reflex mediated by Oxygen reactive species and it produces vasoconstriction in the blood vessels of low oxygen alveoli, when all or most of the alveoli are low in oxygen the reflex can led you to extremely high resistance. Some persons develop extreme vasoconstriction with little exposure to alveolar hypoxia.

About slow descent, it's quite difficult to know the depth where the descent has to be the slowest, the first part where biggest changes in pulmonary volume take place, or the deepest part where the vessels can be reaching the breaking point.
By looking the descent profiles of deep divers like Coste, Stepanek, Nitsch, Nery, Molchanova, the slowest part is the deepest one. And the profile of deep diving mammals like weddell seal, the profile is the same.
That´s why I think that a personalized approach is the rule.

[laminar]

Thanks for sharing your experience and ideas, Sebastien.

Thanks Frank for your excellent comments.

A couple of questions, though, Sebastien:

1. What was your progression to 72m like? What dives preceeded it in terms of depth and difficulty? Did you jump 5-10 metres or was it incremental? How long you've been diving to these depths in this particular session?

2. Barotrauma can happen at any depth (I believe) given specific conditions. So an increase from 60m-70m is fair game for it because there are so many variables.

3. Diving below RV is not "squeeze" as Frank has pointed out. I dive below RV most of the time with the exhale/FRC method. I believe that this approach when done "properly/cautiously" (not referring to any standard or rule here, just my own judgement), squeeze risk is minimized.

4. Packing: Interestingly, it seems that studies are being considered to see how much regular packing practice increases RV (see PFI's Dr. Ralph Potkin...others too are looking into this, I believe). So by saying that packing is the only way you can get to 70m, it may also be the cause of increased RV and thus make it more likely for you to get squeezed, especially given the pressure effect of packing that fpernett descibed so well and I have theorized about in laymans terms on other threads. Ideally, your RV would be as small as possible to begin with and the dive response would activate quickly and be strong enough to protect your lungs. Harder to do with packing, I think. Much easier with FRC/exhale style diving.

5. A proper mouthfill will likely get you deeper than 72m (depending on your physiology). Are you using a mouthfill from a depth shallower than 30m for all your remaining equalizations or are you drawing air from your diaphragm for repeated frenzels?

It's frustrating to think that you're being careful and have a "squeeze" incident. That's why I've cut back progressions and line diving considerably and only venture into it with a commitment to a very slow progression, while recognizing that it's not failsafe. FRC diving has also eliminated squeeze incidents when I've been careful, also you can easily overdo it, too.

Pete

[Mullins]

Can you elaborate on why long-term packing might increase RV? I understand you're only citing somebody else's study, but do you have any more details on what their hypotheses might be?

I may be off-track here, but my understanding is that RV is determined by the limit to which the ribcage/diaphragm can be compressed by ambient pressure before resistance increases to the point where the pressure differential between the space in the lungs and the ambient pressure has to be equalised in another way - by liquid first filling the alveoli forming the walls of the lung cavity and then forcing its way through them (causing damage) into the space itself.

I don't understand RV to be an attribute of the lung tissue itself (please correct me if this is wrong). The term 'RV' as it is commonly used seems to me to mean "lung volume following forceful exhale without other mechanical aid" and as such is reliant on the force supplied by the breathing muscles as well as the flexibility of the diaphragm/ribcage. Given adequate mechanical force (over and above that supplied solely by the breathing muscles) RV for everybody would be zero. Given sufficient bloodshift even in a thoracically inflexible person, RV would also be zero. Obviously this would mean a nasty injury in both cases because nobody is that flexible/nobody's alveolic can take that much engorgement, it's just my way of suggesting RV is not an absolute value unless you add the above condition.

If this is the case I would have thought that long-term packing would decrease RV, as it presumably makes the diaphragm and ribcage (intercostals, other connective tissue, whatever) more flexible. If they can flex further outwards, surely they would also be able to flex further inwards - particularly in the case of the diaphragm?

What in my account is missing/inaccurate? There must be something awry if there is an assumption (prior to actually testing it, granted) amongst medical professionals that packing increases RV...

[efattah]

Definition of squeeze:
Diving below RV
(RV as the volume AFTER bloodshift has reduced it)
This causes bloodvesel bursting in throat and/or lungs.

Scenarios where squeeze can appear:
Realy at any depth. A negative or FRC dive can get you squeezed at very shallow depths as 10 meters.
Squeeze can only occur when you have mastered frenzel equalization fully and the mouthfill effeciently.

There are numerous cases where people have gotten squeezed way above RV; for example Perry Gladstone of Canada and Stig of Denmark.

Mastering frenzel or mouthfill is definitely not required to get squeezed -- in fact some of the worst squeezes have happened to valsalva divers (i.e. Dieter Baumann).

In terms of equalizing, it is definitely possible to equalize to at least 100m with air, on an FRC dive, with a good mouthfill, so it should be definitely possible to reach 70m without packing....

[jome]

Just my small input to this complicated topic.

Just to clear the air that people don't get the misconception that there is no such thing as "lung squeeze", but it only affects the tretchea etc...(I'm not saying this has been implied, but someone reading this thread might get that idea)

There are documented cases of severe edema in the lungs after getting squeezed, visible still days later after the dive and severly impairing the persons physical abilities (shortness of breath, feeling weak) for days.

But there are other cases, where there's just a little blood from "somewhere" and it doesn't seem to have any effect...Problem is, it's really hard to tell which is which, but I would not like to flirt with the former kind...But I think there might be 2 kinds of squeeze we're dealing with.

[naiad]

Would reverse packing reduce the risk of squeeze? If packing increases RV, then reverse packing would surely reduce it?

Just an idea...

(I meant as a training method... not diving with reverse-packed lungs to 70m! )

[cebaztian]

This is getting complicated :-)

Please note: My try to define Squeeze was not: "diving under RV", but "diving under RV AND taking the bloodshift reduction of volume into account".

Can you elaborate on why long-term packing might increase RV? I understand you're only citing somebody else's study, but do you have any more details on what their hypotheses might be?

A rumour that T.Sietas had mentioned this.

but if diver suffer shortness of breath and his/her pulse oximetry is lower than normal, the problem has to be in other place than The trachea

My hypothesis is that things break around the trachea area and that fluids goes down into lung and causes near drowning symptoms (described).

Mastering frenzel or mouthfill is definitely not required to get squeezed -- in fact some of the worst squeezes have happened to valsalva divers (i.e. Dieter Baumann).

Hmm, I am getting confused. These examples above RV must be untrained freedivers progressing too fast to depth. I thought that EARDRUMS would fail long before a squeeze if you only have VALSALVA.

Originally Posted by laminar

1. What was your progression to 72m like? What dives preceeded it in terms of depth and difficulty?

To short warm-up period (I must confess). It was a 14 day trip to Dahab. Last deep dive four month earlier. Some negatives to 4 meters three week before. Some negatives on land (reverese packing).
In Dahab: 35x10 (some FRC),46,58,60,66,72.

So by saying that packing is the only way you can get to 70m, it may also be the cause of increased RV and thus make it more likely for you to get squeezed,

Exactly.

5. A proper mouthfill will likely get you deeper than 72m (depending on your physiology).

Ears is not the problem.
I hope I am not totally wrong when I say that mouthfill technique takes care of equalizing, BUT makes you more prone to squeeze, since your ears are not stoping you.

Are you using a mouthfill from a depth shallower than 30m

Once at about 30.

It's frustrating to think that you're being careful and have a "squeeze"

I wasnt careful. I should have had two week more warm-up dives.

Sebastian
Thanks for all input.