Nitrox question

[Superlyte27]

Call Bill Rennaker and ask him about his heart attack he suffered while underwater. His "theory" about the nitrox mix he was breathing during the event is why he lived to tell the story. At least that's how I remember him telling me it.

 

[PhatD1ver]

How does it affect your being a buddy? Is it only physical stress or can mental stress like during a rescue bring it on?

I don't think it does, I don't tend to get mentally stressed. Even when the #2 is hitting the fan, I tend to control my emotions pretty well. Now, afterward, I tend to cry like a baby. Overall, unless I really push too hard, I don't notice it.

Four years ago when this first showed up, I was running a 5k and and 2.75miles I felt like someone had hit me with a 2x4 across the chest (not a pain, but as if a physical force actually just slammed me lengthwise across the chest). It stunned me so bad I immediately stopped running and walked it in... next day I was at the doc for a full work up, and a couple days later my first holter test.... since, it's been learning to recognize the onset, and then take corrective action. In a current situation, the prescribed methodology is to swim out of it if possible, if not, surface and blow my little air horn for a pick up.

---------- Post added September 4th, 2014 at 11:26 PM ----------

I don't think this is a SB question, but is one that should be saved for a physician with a specialty in dive medicine and cardiology.

This guy is a cardiologist and a DM, I don't know if he's specifically studied dive medicine, but his interest seems to lean that way with these crazy experiments.

My interest in hearing from SB comes from seeing what people who have some interest in dive physiology and the benefits of nitrox. I'm not a doctor, but I do have a background in medical education, so the physiology isn't beyond me. And the discussion with my doc was a discussion. The science for this is sound, in any cardiac episode, the first thing done is oxygen to ensure SATS are maintained as high as possible. So it makes some sense based on the laws of physics that using nitrox in the targeted depth profile would be pushing more O2 to the lungs both as a result of the higher O2 % and increased partial pressure. Providing more O2 for the lungs to process and the alveoli to absorb versus N2 is the same principle used in hospitals, they provide O2 to increase the levels in the blood. More o2 in the blood means in theory that my heart won't auto accelerate so easily even under physical stress (oh, did I note that we tested this above ground with the little do-hickey that trickles O2 into your nose during a stress test? I lasted an extra 1:25 in that case - which is significant), so the experiment isn't a blind effort, and without some validity, we just want to see if it's beneficial, and useful for prevention in MY situation.


So it isn't really a blind experiment

 

[DaleC]

I wonder if supplementing O2 levels in the air we breath will help someone who is experiencing exercise induced decreases in saturation... perhaps the millions of people with COPD hauling O2 tanks and wearing nasal cannulas might comment. They seem to be breathing EAN for a reason.

Sometimes we need to think outside the box for a moment.

 

[PhatD1ver]

Btw is the Holter able to withstand pressures of up to 4 bar and if it dies, is it at your expense? Medical machines don't come cheap.

Good question, we discussed that, and the doc says their insurance would cover it, but the thought is that a holter device doesn't really have any trapped air, and any air inside wouldn't harm the device itself. The device is already semi-sealed against water vapor, that is actually the biggest worry since I tend to sweat in my dry suit, especially in warmer water. But it's up to him, I'm game to wear it, but I'm not going to pay if it breaks, that's on him and his clinic.

 

[iamrushman]

good luck ..i hope all works out for you...call the company that make the holter device (medronic ,metropolitan medical, etc.) and see if they pressure tests their equipment.

 

[TSandM]

I just want to clarify a few things: First, the increased respiratory rate during exercise is not due to increased oxygen requirements. It's due to increased CO2 production. Blood CO2 is inversely proportional to minute ventilation, or the amount of air passed through the lungs in a given minute, so when CO2 production increases, so does respiration. The body is very sensitive to this, whereas the increased breathing seen with hypoxia doesn't occur until the oxygen levels are very low.

Secondly, the drop in arterial oxygen with exercise is pretty minimal. Only in very conditioned athletes exerting to exhaustion does the drop become significant. (I wasn't entirely sure of this, so I actually did a literature search on it.). If you are desaturating with typical, mild aerobic exercise, your lungs aren't working properly.

Third, I would be willing to bet that exercise-induced arrhythmia is more due to increased catecholamines (adrenaline) than decreased oxygen, unless you are desaturating significantly, in which case someone ought to be looking for the reason why.

You don't state what the arrhythmia is that you have. If it's just an increased frequency of premature contractions, that's probably not of any significance. But your description of your symptoms doesn't sound like that . . . it sounds more like SVT or Afib, both of which could have MAJOR implications for your safety if they occurred underwater. Unlike exercise on land, exercise underwater has to cope with the centralization of blood volume that occurs with immersion. An arrhythmia that is tolerated well on land might not be tolerated well at all underwater, and in addition, on land, you can simply cease the exercise that is causing the problem, whereas that may not be possible on a dive (if you are fighting current to get back to the boat, for example, or you are in a spot where you can't easily surface).

This whole story makes me really nervous.

Oh, and there are studies showing that people breathing Nitrox tend to retain a bit more CO2, so your breathing rate may decrease with Nitrox, but the physiologic effects of it doing so are not salubrious for the heart (pH drops when CO2 rises).

 

[stuartv]

My only input is that I have been shopping for a PDC recently and I believe I had seen at least one that has a heart rate monitor option. Maybe that would give you and your doctor the data he wants without having to wear his halter.

 

[Tony387]

Sounds like a risky proposition, to say the least. Cardio/pulmonary issues and diving just don't mix. Speaking only as a layman, it seems fairly obvious.

Sent from my SCH-I545 using Tapatalk

 

[sphyrnidus]

My only input is that I have been shopping for a PDC recently and I believe I had seen at least one that has a heart rate monitor option. Maybe that would give you and your doctor the data he wants without having to wear his halter.

Those kind of PDC's only record frequency, that does not suffice for the kind of info a cardiologist needs. A Holter records an ECG (though not completely)

 

[DivemasterDennis]

Nitrox will increase your partial [pressure of oxygen over using compressed air. So does being at depth. The nitrox won't hurt you ( I assume you are nitrox certified) if you follow appropriate depth limits for the mix you use. Might it help? As with others I am not qualified to answer.
DivemasterDennis