Recipe for Trouble: Pressuring a Diver to Make a Dive

[DevonDiver]

hyperventilating by definition creates low levels of CO2.

Hyperventilating is typically associated with rapid breathing.

Whilst not definitively correct, the rapid, but shallow, breathing associated with diver stress is often misnamed 'hyperventilation'.

To avoid confusion, lets call rapid/shallow breathing 'respiratory stress', rather than hyperventilation.

Elevation In lung CO2 is (I believe?) the trigger for respiratory demand. The body/brain does not recognize O2 depletion whatsoever as a physiological demand.

CO2 elevation signals a need to respire more urgently. If that increased respiration doesn't lower CO2, then the urgency maintains... or raises. In scuba diving, there are factors that can impede more rapid breathing from lowering CO2.

Freedivers 'hyperventilate' before submerging....to lower CO2.

Panicked scuba divers suffer from 'respiratory stress.... raising CO2.

Applied to scuba diving, there's the issue of extended dead air spaces. To some extent, the diver can 'rebreathe' expired gas; causing hypercapnia (aka CO2 retention).

Deeper breathing can overcome dead air spaces, but if the respiratory demand sensation has stressed the diver, then their breathing may have become shallower.

This will be further exasperated by increased gas density impeding respiratory efficiency AND the elevation of inspired gas partial pressures (in this case, ppCO2) on descent/at pressure causing more stress response.

The purely medical definitions don't always neatly apply to HYPERBARIC circumstances.

Hypercapnia is a significant issue for divers. CO2 increases respiratory stress AND is a highly narcotic gas.

CO2 seems to present as a form of narcosis often termed 'dark narc'. It's associated with feelings of anxiety and panic. It often presents after a rapid descent (rapid dissolved ppCO2 rise) where the diver isn't respiring efficiently and/or subject to exertion.

Coupled with respiratory stress from dead air spaces and increased breathing gas density, this can lead even the most psychologically robust diver into anxiety and stress. For the novice diver, it hits like an invisible sledge hammer.... and an instinctive panic response is more than likely.

 

[fmerkel]

I don't disagree with your more extensive discussion and careful wording of hyperventilation vs "respiratory stress", the compromises in ventilation at depth, or increased dead space, though a regulator body doesn't have a whole lot of that....but it might make a difference in a borderline situation.
Trouble is, in real world dive situations we will never actually know which state a distressed diver is in. Both are quite temporary if the diver gets out of it, and leave no physiological marker that can be tested for. All we have is a diver reporting respiratory distress.

In my OPINION, I think hyperventilation happens in diving a whole lot more than people credit, especially in newer divers in stress situations, which aren't all that uncommon. In the dive community it is seldom recognized as hyperventilation, almost always as a CO2 hit. CO2 is the bane of divers so it's the 'boggy man' hiding in the deep.

 

[Basking Ridge Diver]

Freedivers 'hyperventilate' before submerging....to lower CO2.

Freedivers don't 'hyperventilate" - it can cause shallow water blackouts. They teach you not to hyperventilate... But I think we get your point.

 

[Adam Grose]

"Most dive accidents begin on the beach."
-- Some smart diver.

When my oldest was getting her cert card, I always stressed to her that she owned every aspect of her dive, and if she wasn't comfortable, not going was a perfectly acceptable thing to do. Being a teenage girl, she was susceptible to peer pressure, it took a bit for her to get that "I don't feel like diving" is the only excuse anyone needed to call a dive, and if anyone gave them grief over it, they weren't worth talking too, anyway.

So it's her final checkout dive prep. She's sitting on a bench in her wet suit, shivering cold, and obviously in some discomfort. I just watched to see what she was gonna do. She did the right thing. Called her own checkout dive!

I was very proud of her.

You have EVERY reason to be proud of her. She made the right call... and in the process showed that she has the maturity and judgement to make a fantastic diver.

Adam

 

[Bob DBF]

Freedivers don't 'hyperventilate" - it can cause shallow water blackouts. They teach you not to hyperventilate... But I think we get your point.

Competitive freedivers do, that is why they have a spotter(s) when they attempt deep freedives.

In the case of competitive freediving they teach how t hyperventilate and how to mitigate the issues it causes.


Bob

 

[Basking Ridge Diver]

Competitive freedivers do, that is why they have a spotter(s) when they attempt deep freedives.
In the case of competitive freediving they teach how t hyperventilate and how to mitigate the issues it causes.
Bob

The Breathe Up | William Trubridge

It may be the way we are describing it - when I think of Hyperventilation I think of large exchanges of air in the lungs trying to completely remove the CO2 and getting as much O2 in the lungs as you can. That is not what I understand freediver's do - not saying you don't - just saying it is not taught that way anymore...

 

[Bob DBF]

Good article, more like I work up to a freedive. I'm not a fan of lowering CO2 to dive longer, but have run into a number of divers that have found my notions quaint according to their training.


Bob

 

[FinnMom]

Regarding "hyperventilation" leading to CO2 buildup, I agree with DevonDiver.

That's what I was taught and what I recall reading in DAN articles.DAN did BTW write a very interesting article on how hyperventilation is a classic syptom of someone on the verge of panic but still capable of being calmed, therefore important to recognize etc. etc. Good article. Back to my original point =>

I was taught that rapid, shallow breathing i.e. hyperventilation in the manner of someone under stress, does tend to cause poor exchange of air, where you suck back in a fair part what you just exhaled (approx. 16% O2) instead of getting normal air exchange, where you breath in fresh (approx. 21% O2) air. This would cause CO2 buildup.

If you were indeed rapidly breathing in FRESH air, like some have written that freedivers do, then @fmerkel's arguement makes sense.

 

[Bob DBF]

I was taught that rapid, shallow breathing i.e. hyperventilation in the manner of someone under stress, does tend to cause poor exchange of air, where you suck back in a fair part what you just exhaled (approx. 16% O2) instead of getting normal air exchange, where you breath in fresh (approx. 21% O2) air. This would cause CO2 buildup.

It is a definitation of terms problem.

Tachypnea is the term that your health care provider uses to describe your breathing if it is too fast, especially if you have fast, shallow breathing from a lung disease or other medical cause. The term hyperventilation is usually used if you are taking rapid, deep breaths.


Bob

 

[DiverDownD3]

So I'm having trouble with a situation with my wife. We are going to Puerto Rico next week for her birthday. When I originally planned the trip, she expressed interest in a discover scuba class. I was very excited about the idea, because it's an activity that I would like us both to do. She said she wanted me to join her for this dive and I wanted to get some other dives in myself. After calling around to a few dive shops, I found one that would meet both of our needs. I will go out and do a shore dive while she is getting her classroom brief and shallow water exercises. I will then come back in and join her and the DM for her dive at a shallow site.

As I tell her I am getting ready to call the shop to book the dives, she begins to tell me she has some doubts and that she is nervous about it. She seriously is on the fence, she really wants to do it but she is afraid. I have explained to her that the last thing I want is for her to feel like I am pressuring her into this, because that's just a recipe for a bad time. I want her to make this decision. She keeps asking for more info and what to expect, but at this point I feel like I have told her about everything I can. I can't explain it anymore, outside of her actually diving.

I really don't know what to do here. Any advice is appreciated.