Nordic Deep stories 2006

Safety & freediving

text on drowning

text on near drowning

Another blackout

A scientist remarks on how to handle a freediver in blackout:

By Johan Andersson (Lunds university Sweden).

1. Is there a laryngospasm? The evening at Nordic Deep when we were discussing this, I stated that laryngospasm would prevent you from blowing air into the lungs. However, not all people with blackout have laryngospasm. I only wanted to point out that you should not state that all people with BO have laryngospasm - that is not the case. You can have BO without laryngospasm. And obviously, you can have BO with laryngospasm.

2. Cause of laryngospasm: In the diving situation, the most obvious cause of laryngospasm is getting water into your throat. It is a protective reflex, preventing water from getting into the lungs.

3. When does laryngospasm go away? It ceases when hypoxia (low oxygen levels) and hypercapnia (high carbon dioxide levels) develop. It goes away before you get to the point when oxygen levels are so low that you start getting brain damage. Stig writes that the laryngeal
muscles can continue to function anaerobically for some time. However, from the clinical knowledge and scientific literature about laryngospasm, this does not seem to happen. My conclusion is that the larynx go far earlier than your brain...

4. "Dry drownings" - laryngospasm being continued util death without aspiration (inhaling) water. This is a "myth" dating back to a study from 1931, subsequently misquoted in later research. It doesn't matter what you read on the internet or in other sources. There are very good reasons to be more than sceptical to the literature on "dry drowning". In my opinion (and the opinion of experts in the area), "dry drownings" do not exist. My point is: laryngospasm will not be continued until death. This is not a matter of belief. Forget what you have read about 10-15% of drowning victims dying of "dry drownings". Even scientists arguing for the occurence of "dry drownings" some 20-30 years ago do not believe it exists any more.

5. Having a diver brought to the surface that has inhaled water, eliciting a full laryngospasm, I do not think that you will be able to blow air into the lungs of the victim until the laryngospasm ceases. Better protect those airways under water... If you are able to blow air into the lungs of this diver, there is no or only a partial laryngospasm.

6. If a diver is brought to the surface with protected airways (safety diver closing the mouth) and water is not allowed to enter the airways, laryngospasm is unlikely to have happened. From what we heard, this was the situation in Klara's case.

7. OK, now being on the surface, having had the airways protected and not having a laryngospasm, what is there to do with a person not breathing? Here are my thoughts:

Being in water it is very difficult to perform a proper mouth-to-mouth resuscitation. Wolle said it was impossible and you will only blow air into the stomach. I'm not convinced that it is impossible to do it in water, but remember that also during mouth-to-mouth resuscitation with the victim lying on land it is not unlikely that you will blow air into the stomach. If it is a problem on land, it is probably a greater problem in water. Anyway, you must take care not getting the stomach content coming up into the lungs by blowing before you have cleared the mouth, because that will for sure make the situation worse.

I think that in conditions involving blacked out divers that are not breathing at the surface you should do about the same thing as was done this time.
Step A. Blow-tap-talk. A well-known procedure for most if not all freedivers, and as far as I have understood from talking to extremely experienced freedivers, a very useful approach. It usually does the trick - getting the diver to breathe. And remember to "talk" - not scream. Say "breathe, you're safe, we've got you..." or something similar.
Step B. If the diver does not resume breathing, try blowing into the mouth (even when in water). You should possibly move to this step earlier if it has been a deep BO, because then you really need to get the oxygen into the body quickly (maybe skip step A).
Step C. Get the diver to a boat, platform, land or whatever as fast as possible as it will be easier to perform a proper mouth-to-mouth resuscitation. This step should of course also be taken even if the diver starts breathing after step A or B.

Finally, I think we all agree on the most important things; Do something. With a BO occurring after the diver has reached the surface, BTT usually (if not always) works. With a deep BO, you may need to speed things up and not continue with BTT as long as you would do with a diver blacking out at the surface.

Johan Andersson


The reaction to water inhalation
If water enters the airways of a conscious victim the victim will try to cough up the water or swallow it thus inhaling more water involuntarily. Upon water entering the airways, both conscious and unconscious victims experience laryngospasm, that is the Larynx or the vocal cords in the throat constrict and seal the air tube. This prevents water from entering the lungs. Due to this laryngospasm, water enters the stomach in the initial phase of drowning and very little water enters the lungs. Unfortunately, this can prevent air from entering the lungs, too. In most victims, the laryngospasm relaxes some time after unconsciousness and water can enter the lungs causing a wet drowning. However, about 10-15% of victims maintain this seal until cardiac arrest, this is called dry drowning as no water enters the lungs. In forensic pathology water in the lungs indicates that the victim was still alive at the point of submersion; the absence of water in the lungs may be either a dry drowning or indicates a death before submersion.