Unconsciousness/Blocked Airway/Embolism

[Rick Murchison]

In a recent accident discussion a great deal of speculation and disagreement over the possibility of an embolism occuring from surfacing an unconscious diver has erupted. If I understand the two sides of the argument correctly, one is that an unconscious (passed out, as from CO2 retention for example) diver can't embolize from an ascent because the airway will naturally relax and allow the lungs to vent. The other position is that this isn't necessarily so, that an unconscious diver can in fact get a blocked airway and embolize during an ascent.
We'd sure like the docs to weigh in with medical explanations as to the possibilities and probablilities.
Thanks,
Rick

 

[Ontario Diver]

May I expand the question please?

Can alveoli or bronchail tubes become blocked and lead to embolism or pneumothorax without the entire airway/lung system being blocked?

 

[vlada]

In a recent accident discussion a great deal of speculation and disagreement over the possibility of an embolism occuring from surfacing an unconscious diver has erupted. If I understand the two sides of the argument correctly, one is that an unconscious (passed out, as from CO2 retention for example) diver can't embolize from an ascent because the airway will naturally relax and allow the lungs to vent. The other position is that this isn't necessarily so, that an unconscious diver can in fact get a blocked airway and embolize during an ascent.
We'd sure like the docs to weigh in with medical explanations as to the possibilities and probablilities.
Thanks,
Rick

THis is from
DAN's website - stroll a bit down to Getting the Diver to the Surface part - italics highlights are mine
"Time is a definite concern in a rescue like this. The panicked diver?s tissues will consume oxygen, even while he is not breathing. This means that during the ascent, as oxygen concentrations in the lung decrease and gas expands, the diver is at risk of losing consciousness (called shallow-water blackout) and perhaps in danger of an arterial gas embolism from lung overexpansion.

On the other hand, if the diver is unconscious, he may relax the pharynx and allow passive exhalation. This will allow air to vent out of the lungs without over-pressurization and barotrauma.

The diver, whether conscious or not, may also experience laryngospasm, a reflex spasm that occurs when water enters the throat. Because the spasm may completely or partially close the airway, an ascending diver experiencing this reflex risks arterial gas embolism."

 

[Warren_L]

I'm not a doctor (nor do I play one on TV), but is an air embolism not just an air bubble or nitrogen bubble in the blood stream? If so, is it not possible for one to form in the brain (or blood vessels in and around the brain) from too rapid an ascent? If so, this would point to possible embolism formation even in the event of an open airway to allow the lungs to vent. However, one pehaps should also consider that even if the airway is open, is it still possible that a rapid enough ascent may be sufficient to still cause a lung over expansion injury (perhaps even just a minor injury) enough to cause mediastinal emphysema which might lead to an embolism?

 

[Doc Intrepid]

I'm not a (medical) Doc either, nor did I stay at a Holiday Inn Express last night, but currently GUE suggests that, when surfacing with a diver suffering convulsions from Oxygen Toxicity, the ascent be halted during the convulsive spasms (until the convulsions cease) because during the convulsive spasms the glottis closes and air cannot vent from the lungs.


Short of a convulsive spasm, shutting the glottis, (and assuming the diver didn't aspirate something solid,) what else would block the bronchial tubes in an unconscious diver?

 

[MikeFerrara]

I think we had a thread like this once and the docs did weigh in if I remember right.

Also I wonder if a really rapid ascent can cause an empolism even if the airway sn't completely closed. Kind of like when a few too many drops of oil in a gun barrel cause it to peel the barrel leven though it wasn't completely blocked. All you need is for the pressure to get "high enough".

I raise this issue because wasn't there talk of dumping weights and a really fast ascent in the thread in question. There is going to the surface and there's GOING to the surface. Maybe?

 

[wolf eel]

I think a doctors thougts would be nice. As we know all of the others. Heres mine there is all kinds of reason how it may cause an embolism. But that changes the game. Also if you are convulsing that is not the same as a limp diver. We all know not too take a convulsing diver on up as he may hold his breath as he is convulsing.
Derek

 

[lamont]

In a recent accident discussion a great deal of speculation and disagreement over the possibility of an embolism occuring from surfacing an unconscious diver has erupted. If I understand the two sides of the argument correctly, one is that an unconscious (passed out, as from CO2 retention for example) diver can't embolize from an ascent because the airway will naturally relax and allow the lungs to vent. The other position is that this isn't necessarily so, that an unconscious diver can in fact get a blocked airway and embolize during an ascent.
We'd sure like the docs to weigh in with medical explanations as to the possibilities and probablilities.
Thanks,
Rick

imo, in the absence of convulsions the best you can say is:

1. the diver isn't breathing and will be dead soon
2. their airway /might/ be closed and you really can't tell

because of the risk of a closed airway, dropping their weights and letting them shoot to the surface probably isn't the best care you can give them -- but would be preferable to leaving them there on the bottom. the best care would be to ascend normally with them -- although if doing that put you at risk at some point or if they were getting away from you, dropping their weights so that they would float on the surface would seem like an acceptable last resort.

 

[Doppler]

Just want to bring to your attention that AGE is a complex series of events...

FYI

 

[divemed06]

A diver's airway can be obstructued if he becomes unconscious. The obstruction can be caused either by the epiglottis or surrounding tissues (this can also occur if very cold water is swallowed by the uncon. diver). That being said....in a rescue situtation, you don't have the luxury to make an educated guess in this regard. Basic first aid and CPR principles will tell you that you'll have to deal with the obstruction first anyways...only way to do that is to get the person out of the water (ie. ascend).

And yes, I am an MD (curently a resident in Emergency Medicine) and former paramedic.