Question...

[The Iceni]

Dear Dr Deco,

Thanks for all those references. I must be obvious that I am not in practice as a hyperbaric physician or an up-to-date researcher in diving physiology (A little bit of knowledge. . . ?) so I greatly appreciate your tolerance in answering my naive questions.

A little reading is called for!

Thanks again,

 

[Mouth Breather old]

It's obvious to me that the most of the lay people that were participating in this thread, were scared off or intimidated by the "high brow" medical discourse. I for one am not intimidated and would like to add my insights relative to the following quotes:

"...the embolisation of a thrombus or a bubble in a coronary artery can cause myocardial ischaemia and irreversible infarction, which can both lead to fatal arrythmias...

"...that the myocardium is irreversibly damaged if revacularisation in acute myocardial infarction is delayed..."



So like...this is bad, right?


Mouth Breather

 

[Dr Deco]

Dear Mouth Breather:

Argot of the trade

It is a fact that not all readers are at the same level of science. Some will be scientists but this likewise can vary. Some will have a background in medicine but not physics or vice versa.

Biophysics is a combination of biology, chemistry, and physics. There is also an interleaving of medicine in diving physiology. I try to keep my answers on a readable plane, but this is not always desirable. Often I respond to a single writer, although I acknowledge that others will certainly look in and read the responses on occasion.

And “yep,” myocardial embolization and infarction is bad (= heart attack”).

Dr Deco :doctor:

 

[BradfordNC]

Dr Deco once bubbled...
Recreational divers can reduce the risk by refraining from heavy physical exercise on the surface, reducing the venous bubble loads (safety stops), and not sleeping during the surface interval on the boat.

Ok, I understand the chill out and don't overwork yourself part. But now I'm trying to chill between dives and I shouldn't sleep during the surface interval on the boat?

what's up there Doc??

first ya take away my hot tub, and now any thought of a nap between dives. Oh well, with the seas the way they are in Carolina, not like i'm gonna snooze anyway.

And what about sleeping after a dive?

Brad

 

[The Iceni]

Mouth Breather once bubbled...
It's obvious to me that the most of the lay people that were participating in this thread, were scared off or intimidated by the "high brow" medical discourse. I for one am not intimidated and would like to add my insights relative to the following quotes:

"...the embolisation of a thrombus or a bubble in a coronary artery can cause myocardial ischaemia and irreversible infarction, which can both lead to fatal arrythmias..."

"...that the myocardium is irreversibly damaged if revacularisation in acute myocardial infarction is delayed..."

Mouth Breather

I am sorry you feel intimidated by medical language, Mouthbreather ( and I am NOT being sarcastic) but as Dr Deco says, diving medicine and physology is a combination of biology, chemistry, and physics. Medicine contains a considerable amount of biology but little chemistry and even less physics and we most certainly do not know all there is to know about diving medicine and, as I have said many times, I post on this forum as much to learn as for any other reason. I most certainly do not allow my foolish pride to initimidate me so that I do not ask important questions. I for one would much rather be made to look foolish than leave a question unasked.

I also try to explain things as I see them in layman's terms so the non-medical reader can get a grasp of what I am asking the specialists such as Dr Deco but on such a public forum it is difficult to target for general consumption, what is specifically aimed at those experts.

Medical terminology is a sort of shorthand which actually helps doctors or scientists to understand the question being asked and, after all, on this occassion at least, I am asking for answers from the experts.

For example.

"...the embolisation of a thrombus or a bubble in a coronary artery can cause myocardial ischaemia and irreversible infarction, which can both lead to fatal arrythmias...

Let me translate.

If an inert gas bubble or blood clot finds its way into one of the arteries that supplies the heart with oxygen and nutrients, it will block that artery, causing the affected area of the heart to die from lack of oxygen. This has at least two possible consequences. Firstly it can cause the heart to beat irregularly and even to cease functioning as a pump altogether due to the disruption of normal electrical pacemaker activity. The second is the dead heart muscle is unable to contract even if the electrical rhythm is restored. Without a functioning heart muscle the patient will die.

103 words can be compressed into 26 words and yet provide the exactly the same meaning.

"...that the myocardium is irreversibly damaged if revacularisation in acute myocardial infarction is delayed..."

Which means

If a patient has suffered a heart attack, the muscle in the affected area of the heart will have no chance of recovery if the blood supply to that area is not restored by the rapid removal of whatever it is that has caused the obstruction of that artery.

Heart attacks are pretty bad news, even on the surface.

:boom: :upset:

 

[Dr Deco]

Dear Brad:

Perfusion: Exercise versus No Exercise

This is indeed a difficult part to understand and is the topic of many discussions. How can exercise be both good and bad at the same time? The “secret” is in the intensity. Most of us are accustomed to believing that the heart moves blood in muscles. Quite a natural thought, I would say. I mean, what else is the purpose of the heart - - aside from the seat of emotion?

While the heart is the main source of “motivation” for blood to flow through the brain, kidneys, liver and what not, it is not the only driving force for active muscles. This perfusion source is the so-called “muscle pump.” It functions not unlike squeezing toothpaste from a tube or ketchup from a squeeze bottle. Each contraction of the muscle will compress the capillaries and express the blood from them. Because of the pressure maintained by the heart, the flow will be towards the low-pressure side, the veins.

If one has donated blood, you know that they ask you to gently squeeze something with your hand. This causes the blood to flow faster in your arm. (Surprising to some, but the muscles for your hand are located in your arm and connected to the fingers by the tendons passing through the wrist.) If you were a diver, this gently squeezing would cause the perfusion of your arm to increase and aid naturally, in gas washout. The same would be true of your legs. Tendons and ligaments are probably the tissues involved in “the bends,” but the muscle pump likewise will activate blood flow in these when they are in proximity to muscles.

Thus activity that is not too strenuous is advised to keep this muscle pump mechanism active. In addition, there are also mechanisms involving the nerves that lead to precapillary sphincters (= little valves at the head-end of the capillary), and local modulators such as the concentration of lactic acid and adenosine diphosphate.

Sleep

We can glean from this that the low activity during sleeping would not be a big promoter of regional blood flow. In this case, the heart is the only source of perfusion pressure and its rate is low during this somnolent state. Thus sleeping in the interdive surface interval is not something that I promote. Following the last dive of the day, it is fine.

Nuclei Generation

Nuclei formation, to any significant degree, appears to be a function of intense exercise. Researchers during WWII missed the effects of exercise-washout of nitrogen for high altitude flight because the activities chosen were too physically intense. These included our big “DO NOTs” such as jumping jacks, stair stepping, jogging in place, and lifting weights. They found that it was necessary to wait so long after the exercise that any operational time gains from this type of denitrogenation were lost.

Dr Deco :doctor: