CPR in rescues

[Zine Parker]

Having been part of an unsucessful resuscitation attempt on someone who had arrested as a result of hypoxia and thinking about the relative resistance to ischaemia of brain cells and the heart muscle; in what diving situations would CPR be of use?

Zine

[Philip Smith]

Having been part of an unsucessful resuscitation attempt on someone who had arrested as a result of hypoxia and thinking about the relative resistance to ischaemia of brain cells and the heart muscle; in what diving situations would CPR be of use?

Zine, please accept my sincere condolences that your resuscitation attempt was not successful. You have my respect for making the attempt. I can understand your disillusionment, but it is recognised that CPR is not guaranteed to lead to a successful outcome. Your comment about relative resistance to ischaemia is not clear to me; more medically qualified people can comment on that. To answer your question, as far as amateur divers are concerned, CPR would be of use in any situation of cardiac arrest, prior to the arrival of advanced life support. Defibrillators are becoming more readily available, but there are important safety concerns about using them in a wet, salty environment.

Philip Smith

[iainmsmith]

> Your comment about relative resistance to ischaemia is not
> clear to me; more medically qualified people can comment on
> that.

The brain is far less resilient to hypoxia than is heart muscle. We teach students about irreversible brain damage after 3 minutes of anoxia. I have seen a patient with a gunshot head with a detectable heartbeat some 20 minutes after he stopped breathing. (Due to the injuries sustained, the decision was made not to ventilate the patient, as he was not going to survive whatever we did).

In other words, I think Zine is asking, "Given that the heart will carry on beating long after someone becomes brain-dead due to lack of oxygen, hence by the time CPR is necessary in a diver who has suffered a purely hypoxic insult, the casualty will be brain dead, what diving situations exist where CPR might achieve anything?"

Unfortunately, I haven't got time to read through the last several years worth of incident reports, however, I'm fairly certain that I remember reading of successful resuscitation attempts.

If you do a Google Search for "Paul Thomas Stoney Cove" you will find reports of the incident involving a former contributor to this forum who spent 10 minutes at the bottom of Stoney, who received "resuscitation techniques" all the way to hospital, spent 3 weeks in ITU and who has made (as I understand it) a complete recovery.

Let us, however, consider a possible situation. As a result of an incident, a diver aspirates water, causing laryngeospasm. This causes a respiratory arrest. Remembering that laypersons are no longer taught to check for a pulse (and even if they were, finding one in a casualty who has suffered a respiratory arrest with hands as cold as most British divers' typically are is going to be a fluke), a respiratory arrest is going to present in a similar fashion to a cardiac arrest (cyanosis, no respiratory effort, no movement)

One could therefore make an argument for teaching AV only, but this is less of a "life skill" (indeed, chest-compressions only are almost as effective as unenhanced BLS, whereas AV only will only ever work with a beating-heart casualty)

Additionally, since the resus guidelines changed to say, "If in doubt, give CPR" it appears that the concern about the dangers of CPR on a beating heart casualty has been laid to rest. Indeed, I have a feeling that CPR would increase cardiac output, but please don't ask me to justify that or cite sources (although you might start with the resus journals)

Finally, if you were the casualty and had suffered a cardiac arrest, query cause, would you want me to attempt CPR or not?

Iain

Iain

[Steve Walker]

Having been part of an unsucessful resuscitation attempt on someone who had arrested as a result of hypoxia and thinking about the relative resistance to ischaemia of brain cells and the heart muscle; in what diving situations would CPR be of use?

Zine


My condolences, it must be quite traumatic to be involved in such an event. However, even if the chance of a succesful outcome is minute I think it is worth the effort regardless.

For instance, current knowledge tells us that after 5 minutes without oxygen circulating in our system we should suffer massive neuronal loss, such that we are left "brain dead". Yet it is reasonably well known that (Dr.) Paul Thomas survived around ten minutes of this and is well on the way to a full recovery. This is undoubtedly due to the protective effects of cold water, so I think CPR is quite useful in terms of cold-water diving.

I am intrigued as to your statement of 'ischemia resistance' in neurones and cardiac muscle (for non-medical folk that is blockage or restriction of the oxygenating blood supply).
As someone involved in redox research, my current understanding is that reperfusion (ie reoxygenation) following short-term ischaemia results in a damaging burst of oxygen free-radicals (e.g. see Halliwell & Gutteridge, Free-Radicals in Biology and Medicine, 3rd Ed., chapter 9.5.2, pg 646.) This becomes less relevant with increased duratation of ischaemia as the overall damage done to the tissues by hypoxia is so muh greater than the 'reperfusion insult'.

Although there is some evidence for cardiac muscle resistance up to 60 or 90 minutes (depending upon which species model is considered) I would have to consult the source literature to determine what is defined as 'resistance', this may not mean a return to normal functioning.

Additionally, in a whole organism, hypoxia levels in cardiac muscle ischaemia can vary considerably as collateral blood vessels may contribute some O2 and remove metabolic products (e.g. protons) leading to reduced acidosis. Consequently, CPR could very well be beneficial under these circumstances.

As for neuronal resistance to hypoxia/ischaemia, considering "Global" brain ischaemia (as opposed to local ischaemia), relatively short-term ischaemia leads to damage in selected groups of neurones , particularly parts of the hippocampus( the site of learning) other brain tissues are intermediately sensitive to ischaemia (parts of cerebral cortex, striatum, hypothalamus and cerebellum).

Don't forget that much of our 'understanding' comes from "Other Animal" studies, which give rise to suggestions that the majority of other neurones can tolerate up to 30 minutes of ischaemia. At 60 mins or more, one can expect all fully ischaemic cerebral tissues to die.

But given that it is our perception of our own cerebral functioning which leads us to seperate ourselves from all other animal groups, who would be so bold as to make recommendations for medical treatment on these findings?

From a professional point of view, if you have other corroborated information contradictory to the above, I'd be interested to hear more about it.
Regards

[angiemac]

Having been part of an unsucessful resuscitation attempt on someone who had arrested as a result of hypoxia and thinking about the relative resistance to ischaemia of brain cells and the heart muscle; in what diving situations would CPR be of use?

Zine

Many condolences, but much respect.
My simple answer is that applying CPR is as much for you as for them. Whilst they need it to continue living (even if the chances are slim) you need to do it for you own peace of mind - at least you gave them all the chances possible. For your sake try CPR if the situation even occurs again and hold your head up high for doing so.

Angiemac

[John Bantin]

I think Angiemac has hit the nail on the head, so to speak.
I have recently returned from an on-going Coroner?s Court Hearing abroad regarding the (high-profile) death of a diver that happened last summer. Those of us who were actively engaged in the recovery and (sadly failed) resucitatation of the casualty went into court and calmly gave a similar account of what happened.
However, that small number of people involved who ran round like chickens-without-heads at the time, but then continued on with their ?holiday? (it was a press trip) obviously have been suffering some sort of reaction, possibly a feeling of guilt, in the intervening period. They went into court with an obvious agenda - and with the intention of attributing blame for the accident to a third party where in my opinion absolutely none was due. They seemed very angry but naturally their evidence was demolished by an interrogating lawyer. It seemed to me they needed to blame someone.
So, if the worst happens, you do what you can at the time and if you are not successful, you can at least take comfort from that.