Blood shift and Exhale(FRC) diving, musings

[cdavis]

During pool practice, I noticed something that nobody seemed to have commented on, blood shift appeared to be cumulative, increasing through the dive session. I had previously thought that blood shift mostly dissipated during the recovery phase. I went back to Seb Murats posts in 2004-2005, where he explained in detail how frc diving works, and, sure enough, its there. Blood shift is cumulative.

This has a whole bunch of ramifications, some of which I can see and probably some hidden. I'd appreciate some comment on these from knowledgeable divers.

First: Sebs observation that breathing style affects blood shift. You can help the process by taking small breaths and don't force exhale thereby avoiding putting positive pressure on the lungs that works to dissipate blood shift.

Second, it explains why I can dive so much deeper at the end of the diving day.

Third: as blood shift increases, a larger and larger quantity of oxygenated, low co2 blood is building up in the lungs, increasing total 02 available and decreasing total co2 load. Effectively this is replacing some of the air you don't take with you by a less than full inhale. Does anybody know how significant this factor might be??? It might go a long way toward explaining why practiced exhale divers can do longer dives on exhale than on inhale and why hyperventilation is so negative to exhale diving.

Forth: it might be useful to reevaluate how to train . Blood shift promotes thickening of the alveolar corpuscles, allowing more blood shift, promoting more thickening, and so forth. A virtuous circle for exhale divers, which may explain why frequent exhale diving to modest depth dramatically improves the ability to dive deep. If you are training in a pool for exhale diving or just better dive response during full lung diving, it seems like the best strategy would be frequent relatively long sessions with lots of full exhales and shallow breathing during recovery to maximize total cumulative blood shift. Can we use this idea to train exhale without getting wet? A tantalizing thought.

Finally and on a more personal note: after getting well blood shifted, If I switch over to high aerobic exercise(swimming laps) my heart does some really screwy things, beating at double speed for 2 or 3 beats, skipping beats. It acts exactly like a mechanical pump that is being overloaded by too much head pressure(excess pulmonary pressure maybe?). It also takes 3 or 4 times longer than normal to get up to a steady 75-80 % of max heart rate. In the mean time it is very hard to push hard. I feel extremely lethargic. Once up to speed, heart beat issues disappear. No issues during dry land exercise up to max or swimming laps when no apnea precedes it.

Ideas and comments are appreciated.

Connor

 

[efattah]

The biggest blood shift I ever can get is by starting with some FRC warm ups, then switching to full exhale to 15m, 20m, 22m, 24m, 26m, 28m, 30m. After full exhale to 30m (which is my chest limit), I feel like my chest is SUPERBLOATED with blood and every inhale/exhale feels way different at the surface.

And also my diving ability becomes superhuman. The problem? I'm usually cold by then since it takes so many dives to reach 30m. Plus I need to be super flexible already from previous days' diving to even do it. But yes, I do feel it is cumulative, accumulating each day of consecutive diving, though it can be 'undone' by aerobic exercise.

Warning: do not try full exhale dives to these depths without an experienced guide !!

 

[azapa]

..... after getting well blood shifted, If I switch over to high aerobic exercise(swimming laps) my heart does some really screwy things, beating at double speed for 2 or 3 beats, skipping beats.
Connor

Connor, I have been doing full exhale DNF pool training, short swims, short recovery, but lots of them, like a series of 500m to 700m. On friday afternoon after doing this workout I cycled home (25 mins in 33Celcius) and that whole evening had heart arrhythmia as well, I have never really noticed it before, but it was not too nice.

 

[Mullins]

After full exhale to 30m (which is my chest limit), I feel like my chest is SUPERBLOATED with blood and every inhale/exhale feels way different at the surface.

You don't think this might be oedema, Eric? I usually get a bit of a rattle after doing exhale dives.

 

[cdavis]

"not too nice"

Know what you mean. The first time it happened to me, I had not connected it to apnea and went to a heart doc. He hung a (not water proof) heart monitor on me for several days, which included lots of running, no problems. He thought I was a hypochondriac.

Ever have anything similar before?

Connor

 

[Fondueset]

subscribing

 

[azapa]

"not too nice"


Ever have anything similar before?

Connor

nope. I am (now) quite bad at aerobic sports, and I'll assume that the combination of extreme anaerobic activity (the empty lung reps) and the killer bike ride home did it.

The extreme temp difference (vasoconstricted body 1:30 in the pool to 33C in the sun) was probably equally to blame in my case. There are quite a few threads mentioning this here on DB, must dig them up..

 

[Simos]

Subscribing too. Not too sure on the point that blood replaces the volume of air not taken in because of frc, I thought the blood plasma was not actually inside the alveoli but in the surrounding tissue... I do however think that taking too much air in and thus having the chest muscles not fully relaxed is really counter productive when it comes to blood shift.

For sure it feels that blood shift can be cumulative through a diving session as long as you are maintaining activities that contribute to it eg fast swimming i think would not help etc

Interesting about the irregular heart beating. Theoretically I guess if your extremities are vasoconstricted and your lung area full of blood the heart would start to work differently ie one side of the heart (the weaker) pumping harder and the stronger side pumping less...
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[Mullins]

Well there should be more blood filling up the chest cavity on FRC because although it doesn't make it into the alveoli, that airspace is still smaller and taking up less room in the thorax.

I'm not too sure about blood shift being cumulative though. I don't know how you would 'feel' like bloodshift is increasing over the course of a session because you'd have to exclude other factors like lactic accumulation (making your muscles feel progressively tighter) and pulmonary oedema (which I guess is similar to bloodshift, but not the same and not beneficial). Oedema definitely gives my chest a full/stiff feeling. Similarly, if I get into the water the day after a hard exhale session my legs are stiff and it feels like I'm already bloodshifted - but that's probably just leftover lactic acid.

I get heart arrythmias during inhale training sessions in the pool (usually a few seconds after surfacing as my HR quickly peaks and then drops right back below normal resting), but they are more frequent when doing (CWT) exhale dives. In that case I often get them on the way down or at the bottom.

 

[Fondueset]

Just a thought: Electrolytes - and acidity.

 

[efattah]

I had heart arrythmias at around 85-90m during the descent to 100m last April at Vertical Blue.

I have also, at times, had heart palpitations (technically premature ventricular contractions), throughout the day. During times of stress, at one point I was getting more than 1,000 palpitations during a normal working day! Not healthy! Reducing stress makes them go away, though intensive exercise makes them reappear during the exercise and sometimes afterwards.

Personally I have not correlated heart palpitations with diving, unless we are talking about stressful dive training activities (for me the 'stress' that produces the palpitations can be any combination of work/life stress and training stress).

At one point a doctor was doing an ultrasound on my chest looking for DCS bubbles, and he "couldn't believe" how many PVC's I was showing (palpitations), since these are "normally only seen in old people." !!

Anyway since reducing all types of stress I only get about one palpitation per week.

 

[Bill]

'.............It also takes 3 or 4 times longer than normal to get up to a steady 75-80 % of max heart rate. In the mean time it is very hard to push hard. I feel extremely lethargic. Once up to speed, heart beat issues disappear.'
This is a new experience for me. I thought that it had more to do with giving up my long aerobic training (2 hours above 70%) than my diving but since starting the one minute static, max exhale and one minute dynamic series, it is much more noticeable. I never could go from 40-90% in 10 seconds like the sprinters can but now my heart won't do 70% in less than 2 minutes no matter what. I thought it might be old age, heaven forbid.

 

[Simos]

Ok I can see why there will be more bloodshift needed for FRC but that's not necessarily a good thing right? The crucial thing is oxygenated blood to the brain and the more blood 'stuck' in the lungs for the purposes of keeping the lungs from collapsing should mean that the blood supply to brain is less? Also it will mean I guess that there might be more lactic produced...
Above might be wrong but my rationale is that for depth there needs to be enough bloodshift to support the lungs but more is not necessarily beneficial. This might be different in a pool say, where if bloodshift is triggered then it does mean that extremities have less blood and the vital organs and brain have more, but I would have thought for depth it might not exactly work like this.

I guess it depends on how much the blood plasma that fills the lungs is free to circulate...
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[Andrew the fish]

Interesting topic. Very recently noticed that I cough when exhale fully, but only after I had done a few FRC dives just minutes before. I couldn't understand why, I thought maye I just learned how to exhale past my usual FRC volume or something. Aftr reading about cumulative effect I think maybe thats what it is. Bloodshift, lungs filled with more blood and full exhale makes it irritating to lungs, almost as if something got inhaled and I am trying to cough it out. Don't know is it good or bad, apparently doesn't hurt me.

Apart from depth dives I wonder if bloodshift is beneficial to dynamic disciplines?

 

[Mullins]

Still sounds more like oedema...

 

[Andrew the fish]

Still sounds more like oedema...

if you are talking pulmonary edema then I disagree. just quick google search brings simptoms and them do not match - no sputum production, blood coughing or whatever. Edema is serious condition, nothing like this temporary fluid accumulation.

 

[Mullins]

Pulmonary oedema is really common in deep inhale divers and I expect more common in even moderately deep FRC divers. I was among those studied at Sharm in 2007 and had plenty of 'interstitial lung comets' showing up on ultrasound. The info you'll find on the net likely relates to serious cases with other causes, most of which are pretty nasty. That's the net for you I guess. The oedema you get freediving is pretty transient and doesn't cause many symptoms - but you can feel it, and the feeling you describe sounds right.

It's not that dissimilar from bloodshift, but it is different and it isn't helpful. Problem is the fluid is outside the blood vessels, not in circulation.

 

[fflupo]

over the years i experienced most of what you describe,connor

here are my first thoughts after looking a seb's lecture notes from 2006 again

increased pulmonary bloodvolume improves gas exchange which results in accelerated recovery rate for freq. divers, isn t a oedema an increased bloodvolume?

pulmonary capillary engorgement stiffens the lung reducing their compliance to expansion.

does this feels like bloodshift ?

 

[cdavis]

Great discussion guys. Thanks

fluppo: "increased pulmonary blood volume improves gas exchange which results in accelerated recovery rate" I'd wondered about that. The fast recovery is something that has always been undeniable, but very puzzling. Great that Seb thinks so.
"pulmonary capillary engorgement stiffens the lung reducing their compliance to expansion." Sebspeak that goes over my head.
"does this feels like bloodshift ?" not sure what you mean.

Simos: oedema and bloodshift are different. Laymans explanation: Blood shift makes the lung blood vessels swell, blood stays inside the vessels, no problems. Oedema occurs when plasma and sometimes blood cells escape the blood vessels into the tissue and air spaces, problem.
Blood shift is caused by the skeletal muscles arteries constricting, doesn't restrict the brain arteries.

Bill: Absolutely could not be age. I don't believe in that stuff, myths designed by young farts.


The idea that cumulative blood shift might create a reserve source of 02 is fascinating and depends a lot on where the blood is in the lungs. If it is in the blood vessels leading to the alveoli, no extra benefit. If it is in the alveolar corpuscles or lung blood vessels after that point, there should be a big benefit. I did some modest searching through scientific literature (not my strong suit) and I think I discovered that the amount of blood in the alveoli capillaries is pretty small, so it must be somewhere else. Also that the amt of blood in the lungs is highly variable and can increase by 50 % from hard exercise alone. Lots of room for increased storage somewhere. Does anybody know what volume of blood is normally in the lungs and/or how much might be accumulated through blood shift in the area in or after the alveolar capillaries? Trux or efattah especially, help?

Connor

 

[Mullins]

increased pulmonary bloodvolume improves gas exchange which results in accelerated recovery rate for freq. divers, isn t a oedema an increased bloodvolume?

Kind of, but 1. it's mostly plasma and 2. it isn't in blood vessels, so it wouldn't improve the rate of gas exchange. If anything it would hinder gas exchange by reducing gas volume and coating the alveolar wall.