Panic/Hyperventilation during wreck dive (~80 ft)

[fmerkel]

CO2 is an effective vasodilator. That's very good in hard working muscles to increase blood flow, get O2 and nutrients in, CO2 out. In normal aerobic work the CO2 level is still maintained at normal.
IF for some reason the CO2 does go up and stay up the vasodilation becomes systemic (body wide) including the brain. The vasodilation in the brain has no where to expand due to the skull so the brain gets squeezed. This happens sometimes in high altitude climbing causing altitude sickness. (Note - at high altitude you can't 'just surface' and resume normal breathing. It takes a good while to get down to lower altitudes so you are kind of stuck with your situation for awhile.) Headaches are a common symptom which is the same headache a diver might get that sustained too high a CO2 level for too long.

If it gets sustained much too long and becomes out of control the brain gets too squeezed, critical autonomic control centers start sending out improper signals, and you can go into a downward spiral with high altitude pulmonary edema, even worse breathing patterns, and possibly death. Not good. A normal dive does not have enough time for this degree of pathology to set up.

 

[Kevrumbo]

HYPERventilation (excessive breathing causing a drop in CO2 levels) vs. HYPOventilation (inadequate breathing causing a rise in CO2 leves) is frequently debated on this forum. Unfortunately some divers don't understand the terminology correctly.

IMO a fair number of cases that are discussed as a CO2 'hit', or hypoventilation are likely in fact hyperventilation. It's impossible to tell since there are no trace signs left in the diver and the symptoms to the diver are very similar. The state of mind that either condition cause while diving does not encourage cool and dispassionate reflection.

In this case I'd say it was pretty clear a case of hypoventilation caused by exercise at depth, compounded by increased gas density and possibly marginal equipment.

A subtle semantic distinction: With regards to exercise at depth, it is not hypoventilation per se in this case --but the increased CO2 production upon exertion along with increased Work of Breathing as the precipitating pathway into the prompt & vicious cycle of Hypercapnia. It's all clearly explained in the following video:

 

[fmerkel]

It can be a subtle semantic distinction. I come at it as a Respiratory Therapist. If the CO2 level (measurable in the blood stream) goes up, it's hypoventilation, however it got that way. You can breathe a lot, deeply and fast, but if you can't keep up, it's hypoventilation.

Likely the OP went into anaerobic metabolism in the chase. When those metabolites had to be paid back he was over the line for easy breathing to simply catch up. You can run a 100 yard dash without breathing much but when you finish you will pay for it dearly, and that's without a regulator and depth to compromise the situation.

 

[Kevrumbo]

It can be a subtle semantic distinction. I come at it as a Respiratory Therapist. If the CO2 level (measurable in the blood stream) goes up, it's hypoventilation, however it got that way. You can breathe a lot, deeply and fast, but if you can't keep up, it's hypoventilation.

Likely the OP went into anaerobic metabolism in the chase. When those metabolites had to be paid back he was over the line for easy breathing to simply catch up. You can run a 100 yard dash without breathing much but when you finish you will pay for it dearly, and that's without a regulator and depth to compromise the situation.

Yes but in this case, the proper terminology (or differential diagnosis) is more definitive as R/O Exertion Hypercapnia, secondary to high Work of Breathing resistance in Scuba Diving.

 

[Duke Dive Medicine]

The hypercapnia is a result of hypoventilation. Also, not to be pedantic, but hypercapnia is not involved in the increase in cerebral blood flow that precedes HACE or the pulmonary hypertension that precedes HAPE.

Best regards,
DDM

 

[Kevrumbo]

The hypercapnia is a result of hypoventilation. . .
Best regards,
DDM

DDM,

There is however a distinction of precipitating etiology of malignant Hypercapnia in Scuba, for example, between conscious deliberate depressed "hypoventilation" of skip breathing -which is not indicated in the OP below- versus "inadequate ventilation of CO2" in physical exercise despite active voluntary maximal exhalations due primarily to an increased Work of Breathing (WoB) resistance at depth. Hypoventilation can refer to either the latter -a pathophysiological state, or the former -a chosen tactical behavior of depressed respiration to conserve Air, and therein lies the confusion of non-specified use of this terminology.

And in the video above @Duke Dive Medicine , I don't recall in the lecture where "hypoventilation" is ever used by Simon Mitchell to describe this hypercapnic inducing high WoB resistance, or differing tolerances of rising arterial CO2 levels, or even mentioned in limitations of ventilation during diving. So in my opinion, hypoventilation is not entirely synonymous with WoB resistance, just as hypoventilation is obviously not at all synonymous with "respiratory arrest".

I am new to the forum and wanted to share my story, as I feel that experience is the best teacher.

I was doing a wreck dive in Cancun last week when I experienced this. It was a wreck dive with a depth of around 80ft. The group consisted of myself, 3 other divers and the DM. We descended to the wreck and everything was going fine. As we descended, a school of beautiful eagle rays were drifting by the wreck site. We reached the bottom and started to swim towards the wreck. The current was rough, and made swimming difficult. As we went around the wreck, I spotted to eagle rays near me and swam up to get a closer look and some footage. The current picked up, and I had to swim hard to keep up with them. After getting a good look, I slowed up......and that's when it hit me. I started breathing heavily and couldn't catch my breather. I suddenly felt like I was breathing through a straw. I looked up and saw how far the surface was and I started to panic. I was breathing hard but felt like I could not get enough air. I tried to slow myself and focus on my breathing, but continued to breath hard. I stopped swimming and grabbed the side of the wreck. I closed my eyes and focused on my breathing, and it started to subside. I found the anchor line, and held steady until I was semi under control of my breathing. My group noticed I was gone, so I kept an eye on them until they looked up and gave them the sign that I was going to surface. I slid up the line slowly, taking my safety stop and finally surfacing.

I wanted to share this story so that everyone can learn from it. I can assume I experienced overexertion and started to hyperventilate. I did not think how hard I was swimming to see the marine life, and I almost paid a heavy price for it. But takeways from this experience were to stay calm and try to control your breathing when something like this happens. Literally one of the scariest experiences of my life.

 

[Flutter]

@p0werline , thanks for sharing. In our OW we are told to Stop, Think, Act! None of us really knows if we'll do it until something happens - and then, we'd better or the consequences might be grim. I had a similar episode a few years back diving w a group in a fair current. I was caught in a small down draft along a wall & suddenly my group/buddy was above me 10' or so. I swam my way towards them against the current & all was good. But immediately afterward, I noticed my heart beating like crazy & I soon felt that shortness of breath of overbreathing my regulator. As with you, I looked up & remember thinking "Air!" but the surface was far away (plus that wasn't the answer). The choice to Stop, Think, Act was the clear alternative. In the current, I couldn't Stop, but I could slow down my breathing & so I went to deep, slow "yoga" calming/exhaling breaths & told myself , "You are fine, you just need to calm down & get a grip". I distracted myself with the view, also reminding myself, "you paid good money to see the fish - now LOOK at them!" (Lol - of which I don't even remember now), but it worked. The entire episode probably only lasted a matter of minutes but certainly seemed longer at the time. Afterward, my husband asked, what I was thinking, "leaving the group like that". He had no idea. But I knew then, & I certainly know now, that panic could have been a diaster. It actually feels encouraging knowing that I did as I was trained. Lesson learned - I am rather conscious of sticking pretty close to my buddy now, since no one else got caught in that draft. Again, thanks for sharing.

 

[gfaith]

Best explanation I have found on the rapid shallow breathing issue:

Hypercapnia/Hypocapnia???

The confusion often arises when people say "hyperventilation" when they really mean "tachypnea."

Hyperventilation occurs when the gases in the alveoli (tiny lung sacs) are exchanged more rapidly than normal. The most common cause of hyperventilation is tachypnea, which is the technical term for an increased rate of breathing.

Since tachypnea usually leads to hyperventilation, the two are often used synonymously.

But it is possible to have tachypnea with hypoventilation. This occurs in certain disease processes, such as emphysema, where there is increased "dead space." It can also occur in scuba if a diver takes rapid, shallow breaths which only move the air back-and-forth within the major airways, not getting the air all the way down into the alveoli where actual gas exchange occurs.

When there is too much gas exchange (hyperventilation), CO2 levels decrease and you have hypocapnea. When there is inadequate gas exchange (hypoventilation), you get hypercapnea.

Note that oxygen levels are not influenced by breathing rates as much as CO2 levels are. Obviously, breathing too slow can cause hypoxia (too low oxygen). But breathing too fast will not improve your oxygen levels (unless you are on a ventilator where we can manipulate things a bit more).

Confusing? It can be. That's why doctors spend the first couple of years in medical school just learning all the darned terminology. So here is a summary of the terms:

Hyperventilation = too much gas exchange
Hypoventilation = not enough gas exchange

Hypercapnea = too much CO2
Hypocapnea = not enough CO2

Hypoxia = not enough oxygen

Tachypnea = breathing too fast

This all agrees with what TSandM said.

2009 with 2 doctors discussing the issue and words.

 

[Kevrumbo]

But simply said with regards to Scuba, hyperventilation, tachypnea, dyspnea -all are obviously non-intentional, involuntary and abnormal respiratory conditions that can be pathological signs & symptoms of Hypercapnia.

Hypoventilation can also be termed in describing either a consciously controlled voluntary slower breathing rate ("skip breathing") to conserve Air; OR the lack of adequate CO2 elimination during physical exertion despite active maximal lung expirations due primarily to increased Work of Breathing resistance at depth. The better more accurate etiological term in the latter case is just increased WoB resistance, rather than and differentiating it from hypoventilation.

The proper response to Hypercapnia at depth:

• Decrease exertion to reduce CO2 production;
• Increase lung ventilation to eliminate excess CO2;
• Switch to another breathing source (i.e. Buddy) and/or abort the dive if a malfunctioning regulator is the cause.

 

[Duke Dive Medicine]

And in the video above @Duke Dive Medicine , I don't recall in the lecture where "hypoventilation" is ever used by Simon Mitchell to describe this hypercapnic inducing high WoB resistance, or differing tolerances of rising arterial CO2 levels, or even mentioned in limitations of ventilation during diving. So in my opinion, hypoventilation is not entirely synonymous with WoB resistance, just as hypoventilation is obviously not at all synonymous with "respiratory arrest".

You're absolutely correct, hypercapnia and hypoventilation are not synonymous. The former is precipitated by the latter. It's a nitpicky point, but since you're clearly a detail-oriented guy I'm sure you'll understand. You can voluntarily hypoventilate by skip breathing, or there can be a state of hypoventilation like fmerkel described in which gas density, inspiratory and expiratory breathing resistance, hypercapnic ventilatory response and VO2 max all contribute (to one degree or another) to CO2 buildup in divers and the diver cannot ventilate enough to eliminate the CO2. Simon Mitchell's a great guy and a fine physician, but just because he didn't mention hypoventilation in his video doesn't mean it's not (technically speaking) a factor in hypercapnia in diving. Circling back to the original post, it sounds like that's exactly what happened.