Ascending without BC's deflation / inflation

[Bubbletrubble]

Hmmm... interesting. I've never thought of that. But the idea to minimize the chance of uncontrolled ascent like that is quite unusual but worth attention. Most probably I was more on the weight side and exposure protection buoyancy I guess... You made a good point here though. Let alone it is much more work

To clarify, I am not advocating that a diver dump all of his air from the BCD and then ascend while being negatively buoyant. That's just what the novice divers explained as their reasoning behind initiating an ascent in that manner. It's poor practice in my opinion.

 

[Den7]

...Ascending on the lungs does not necessarily imply that the diver is ascending with a closed airway. Keep in mind that any residual gas inside your lungs (after exhalation) contributes to buoyancy. "Ascending on the lungs" means that the divers are simply varying the depth of their breathing. FYI, people with bigger lungs can compensate for a buoyancy swing as large as 10 lbs. of lift. For a recreational diver, that's almost certainly less than the buoyancy swing of a single tank (full vs. empty).

So theorethically is it possible to ascent just "on lungs" isn't it? And.. people with bigger lungs do not necessarily have to use BCDs do they?

 

[markmantei]

I try to kick as little as possible on most of my dives, so it's not surprising that I prefer to stay neutrally buoyant most of the time. On most dives, I'm super-relaxed and not exerting myself at all. If you're diving to get a good work-out, then I suppose you could kick all the time if you wanted to.

I agree and generally try to be as relaxed as possible through my dives as well, that is one of the things I like most about diving.

One disadvantage of doing this is that you'll run through your gas supply faster.

I wouldn't be incredibly worried about this as I am ascending at the end of the dive, at this point the additional gas requirements would be negligible.

Theoretically, it's beneficial to maintain a low level of activity during a safety stop. It's probably easier to do this while being neutrally buoyant, though.

I agree 100%. Just never really thought about it. Its not like I'm finning like crazy, just a single slight kick every few seconds to maintain approx depth.

Ascending on the lungs does not necessarily imply that the diver is ascending with a closed airway. Keep in mind that any residual gas inside your lungs (after exhalation) contributes to buoyancy.

I think I get what you are saying here. My thought was that if you have a full or relatively full lung, and then ascend, that it would be like taking a balloon that you have inflated and tied and ascending. I think that what you are getting at is that as long as you are not "forcefully and intentionally holding your breath" that your open airway will allow the increased volume of air to safely vent prior to an over-expansion injury. Am I on the right path here?

 

[Den7]

To clarify, I am not advocating that a diver dump all of his air from the BCD and then ascend while being negatively buoyant. That's just what the novice divers explained as their reasoning behind initiating an ascent in that manner. It's poor practice in my opinion.

No worries I hear you and see what you mean. My apologies I was not clear enough in my response. I meant to say it was interesting to find out and worth attention on what your "creative" students come up with to reason and justify their poor practice.

 

[TSandM]

"Ascending with your lungs" means varying the volume around which you are cycling your breathing. You can breathe "at the top of your lungs", which means with your lungs almost full, taking small breaths in and out, so the average volume in your lungs is very large. Or you can breathe from the "bottom of your lungs", with the lungs almost empty, cycling your breathing around a much smaller volume point. Neither is efficient breathing, and it's not what you want to do throughout your dive -- that's why you HAVE a buoyancy compensator. At the beginning of the dive, you adjust your BC to compensate for the gas you intend to use, and any compression of your exposure protection. Then, as the dive goes on and you work your way shallower, you slowly bleed gas out of the BC to retain neutral buoyancy. During this time, if you need to go up or down small amounts, you can do that with breath control -- but if you remain at a different depth, you adjust the BC, rather than continuing to breathe in an artificial manner.

For ascent, you inhale and begin to cycle around a large lung volume. As you begin to rise, you can exhale more, or exhale sharply to stop your ascent. If exhaling doesn't stop you, you vent your BC and bring your system back to neutral.

If you run out of air in the BC (and dry suit, if you are using one) before you get to your safety stop, you were underweighted. And some of us weight ourselves so that we will never have an empty BC until we get to the surface.

If, for some reason, you are unable to retain air in your BC, you should be able to swim your rig up. I don't like doing routine ascents that way, though, because if you get distracted during the ascent and forget to keep kicking, you will sink, and you must always be titrating the amount of kicking to keep your depth or your desired ascent rate. I find a neutral ascent is much more of a lazy man's ascent -- by being near neutral all the time, it's extremely easy to stop, either for decompression, or to deal with a problem or even just watch something interesting.

 

[Pliny]

I think I get what you are saying here. My thought was that if you have a full or relatively full lung, and then ascend, that it would be like taking a balloon that you have inflated and tied and ascending. I think that what you are getting at is that as long as you are not "forcefully and intentionally holding your breath" that your open airway will allow the increased volume of air to safely vent prior to an over-expansion injury. Am I on the right path here?

Yes, if airway is open gas will escape to equalize the pressure, thats just physical chemistry of gases. I suppose If you ascended really quickly you might have issues with the rate at which gas could escape the alveoli into the trachea even if the airway is open.

I recall one dive where I was ascending up a slope using lung control of bouyancy. Very slow inhale (meaning chest/diaphragm expanding) and gas was escaping the reg tee because the expansion of the gas in my lungs was faster than the inhalation rate. I didn't feel like I was in danger of embolizing but the experience definitely increased my respect for the power of gas under pressure.

 

[Bubbletrubble]

I wouldn't be incredibly worried about this as I am ascending at the end of the dive, at this point the additional gas requirements would be negligible.

You may want to reconsider this approach. Wasting your gas needlessly means that you'll have less gas to use in an emergency, e.g., equipment malfunction, entanglement, your buddy has a problem. Also, if you're kicking to stay at a certain depth, it will complicate your efforts to remain in a good position relative to your buddy.

I think that what you are getting at is that as long as you are not "forcefully and intentionally holding your breath" that your open airway will allow the increased volume of air to safely vent prior to an over-expansion injury. Am I on the right path here?

Yes. As long as the airway is open, it should allow venting of the expanding gas inside the lungs.

 

[markmantei]

I don't have my open water manual on me so I did a google search and found sites that advocated both starting negative and finning, and starting neutral and lung breathing up.

Slightly negative:
Safe and comfortable scuba diving ascent tutorials and tips
How To Complete A 5 Point Scuba Ascent

and Lung Breathing
Deep-Sea Sherpa » Scuba 101 – Controlled ascents

The diagram on the lung breathing perfectly illustrates what you are advocating.

I am going to try out the lung breathing ascent in the pool prior to my next trip.

How are the instructors teaching proper ascent procedure?

My general feeling is that the lung breathing method is definitely less work, but for new divers I think the finning ascent is safer. How many threads are on this board about uncontrolled ascents? I personally had to let go of a buddy that was so overly positive from not monitoring buoyancy on ascent that I could not hold him down without being dragged up myself at an unsafe speed (luckily there was no ill affects from the incident). Again, negative does not mean having an empty bc, just slightly negative. As I remember back to my earlier dives a couple of years ago, I think that this method also made managing the air bubble in both the BC and drysuit much easier on ascent.

TSandM, very good description of ascending with your lungs. As my previous posts indicate, the confusion was in regards to using that method to ascend and the risk of embolism, I routinely use the lungs for what I term micro adjustments, not only is it an important skill for diving in general, but without that fine control photography would be impossible, and doing cavern dives like the centoes in yucatan you would be bouncing off the bottom and ceiling. I guess I was more nervous about the full lung issue with ascent.

Pliny that would have made me nervous as hell. My understanding is that you cannot feel an embolism as you have no nerves in your lungs. I'm look forward to your response on this TSandM. Is there any way to tell if you are in danger of an embolism from feeling?

 

[fire_diver]

I use just enough weight so that I will be neutral when my tank is at 500psi. I have a very small amount of air when doing my 20 foot hang, then dump it all and make a very slow swimming ascent. I'm only a pound or so heavy at this point, since I usually have about 1000 psi left.

I can always add a shot of air if I need it. Otherwise I just wait until the surface to re-inflate.

 

[markmantei]

You may want to reconsider this approach. Wasting your gas needlessly means that you'll have less gas to use in an emergency, e.g., equipment malfunction, entanglement, your buddy has a problem. Also, if you're kicking to stay at a certain depth, it will complicate your efforts to remain in a good position relative to your buddy.

While I don't disagree with your comment on "wasting" gas, I do think that the difference is negligible. We are talking about much less work than getting around on your dive, and how low on gas are you at the end of your dive that you can't manage an emergency plus or minus what 20 or 30 psi difference max??? I don't even think the difference would be measurable on an ascent where you are "breathing normally". I also fail to see how finning would risk buddy separation. You have as much or more control of your position. You can kick harder or softer, more or less often to maintain buddy contact. Also, if you need to divert your attention and you sink a few feet it is no big deal, but if you are buoyant and you divert your attention you could find yourself in a uncontrolled ascent. The sinking may be easier to deal with than the ascent.

I don't dispute that the lung breathing ascent is easier, just don't agree with your conclusion that a finning ascent is necessarily undesirable.