Why does it feel like it's harder for me to empty my lungs at depth?

[Ayisha]

I find the work of breathing increases as you go deeper in extremely cold water, like 38 - 40F/3 - 4 C at 130'/40m+.

I don't really notice it in warm or moderately cold water at all.

 

[eckoback]

No, it works both ways. In fact it should affect your exhalation more because the reg is blowing compressed air into you -- personally I find it harder to breathe on the surface, for the first few breaths off the reg when I have to actively suck air in after an hour or so of not having to do that.

Out of curiosity, what's your respiratory stats/background? I don't feel any extra breathing effort at 60-70' but I've swimmer's lungs that even allergies and a couple of decades of smoking couldn't break. :fingers crossed:

Non-smoker, fairly active, no history of respiratory issues.

 

[dmaziuk]

Non-smoker, fairly active, no history of respiratory issues.

Maybe you're more sensitive to it and feel it at 20-something metres already, rather than 30-40 as per @Dr Simon Mitchell et al.: Density Discords: Understanding and Applying Gas Density Research

 

[adrian_diving]

First, I should say I am not experienced, but I read a few things.

There are two effects you may notice at that depth, due to breathing gas density:

• Increased work of breathing. Simply put, it is harder to inhale, and harder to exhale denser air.
• Decreased breathing efficiency -- ability to remove CO2 from your body. According to GUE manuals, at 100ft breathing efficiency is 50%. I don't know what it would be at 70ft. Elevated CO2 triggers the breathing reflex, can result in faster and shallower breathing, and even anxiety and panic.

People more experienced than me on this thread point out that while work of breathing is harder at 70ft, it is not really that noticeable. So I suspect what you experienced is elevated CO2 levels, which made it harder for you to wait 10 seconds before catching your breath again.

Interestingly, GUE recommends that to dive safely beyond 100ft, "using helium‐based breathing mixtures is clearly the favorable procedure with respect to diving safety", as helium is much less dense than nitrogen.

 

[AJ]

People more experienced than me on this thread point out that while work of breathing is harder at 70ft, it is not really that noticeable.

To them it may be not, but that does'nt mean for everybody. I'am quite sensitive when it comes to pressure and breathing. I too notice difference in breathing when I go deeper. Still, I consider myself quite advanced (almost 700 dives, also done a lot of deeper dives (max. 40+ metres on air)).

So I suspect what you experienced is elevated CO2 levels, which made it harder for you to wait 10 seconds before catching your breath again.

More pressure means thicker air, therefore it's harder to get rid of CO2. It may play a part but it's certainly not the whole story. I guess the OP is more sensitive to ambient pressure (= thicker air) than average. It's mostly a physical thing, maybe somewhat mental for inexperienced divers and certainly related to gas used (helium helps to overcome this effect).

The good news is: you will get used to it and it is'nt a hinderance, especially after you gain more experience.

 

[seeker242]

I recently started to pay more attention to my breathing pattern because you can never stop learning to improve different aspects of your diving, right?

IMO, you don't improve aspects of your diving by manipulating your breathing patterns or employing some special breathing technique. If you want to improve your breathing and air consumption, etc, all you have to do is just relax, physically and mentally, and the breathing will naturally follow.

 

[MaxTorque]

modern 2nd stages typically use a reasonably large amount of venturi effect, and so when you inhale, the reg is (to some degree) actually blowing air into your lungs, ie it is supplying air at a total (static + dynamic) pressure above ambient water pressure. When you exhale however, there is no such effect, and your body has to do the full amount of breathing work, and in fact, because you are exhaling through the exhaust flapper valve, there is an additional loss not present during inhalation.

Look at a typical work of breathing graph:

and notice how skewed towards exhalation it is, and how during inhalation the venturi effect actually crosses the zero line

 

[Matt2401]

modern 2nd stages typically use a reasonably large amount of venturi effect, and so when you inhale, the reg is (to some degree) actually blowing air into your lungs, ie it is supplying air at a total (static + dynamic) pressure above ambient water pressure. When you exhale however, there is no such effect, and your body has to do the full amount of breathing work, and in fact, because you are exhaling through the exhaust flapper valve, there is an additional loss not present during inhalation.

Look at a typical work of breathing graph:

and notice how skewed towards exhalation it is, and how during inhalation the venturi effect actually crosses the zero line

This is an excellent point and I would like to add one additional point: exhalation is primarily a passive action on land due to relaxation in the diaphragm. When we inhale the diaphragm contracts and pulls downward opening up space in the thoracic cavity, decreasing pressure in the lungs and causing air to rush in through our trachea. When we exhale the diaphragm relaxes causing the lungs to get a smidge positive pressure and air escapes if everything is working right. When people have asthma attacks, or COPD exacerbation, etc its the exhalation that is the first part of breathing that gets really, really tough. We have intercostal muscles that run in between the ribs that assist in inhalation/exhalation but they are comparatively weak and really are there to assist, not be the primary "air movers".

If someone had the beginnings of a restrictive airway disease like COPD or asthma, I could see physiologically how it would first present as increased difficulty exhaling at depth.

If this were occurring to me I think I would probably make an appointment with a pulmonologist just to make sure everything is ok, and possibly to see if there are any treatment options. A chest xray and pulmonary function test (you breath in and out in a specialized box a bunch of times and the rates are all measured precisely) are cheap and easy tests that can help guide your docs.

Honestly, its probably nothing and you're fine but it possibly isn't and finding out you can't exhale at depth would be a pretty lousy dive! On the other hand maybe a couple of toots of a proper metered dose inhaler on dive days will make it much more enjoyable.

I hope you feel better!

 

[Gone for diving]

I find the work of breathing increases as you go deeper in extremely cold water, like 38 - 40F/3 - 4 C at 130'/40m+.

I don't really notice it in warm or moderately cold water at all.

I think there is something....
I find that when it's cold, that the reg doesn't feed air as long as in warmer water..... so the trigger time is less.
But I wonder if its because the air is, cold, dense, and more molecules fit through the demand valve quicker because of the freezing action though the oriface... it can be very cold and build ice crystals...

I have see a similar problem with a dive buddy..at 48f 110ft. she is very small and at depth I think she was sipping her breaths. She was getting enough air, but the action makes ice and it froze up....
Bailed out to my long hose, shut hers down, 3 mins later it thaws... reg is good to go again... I am convinced it's how it gets breathed on. A more forceful initial inhale solves this problem... and blows out the build up of ice.

At depth and cold the diver doesn't need or feel they need as much air and breathe differently...