First Aid for DCS
Why Oxygen is so Important
“I don’t need oxygen, it just went away on its own last time.”
Someone said this to me a while ago, who at the time was showing slight circulatory problems and pronounced marbling of the skin. And he is not the only one who reacts like that. In a survey of Finnish Tek divers – i.e. experienced divers with a lot of knowledge and access to oxygen! – of 27 people who had experienced DCS symptoms, only 6 breathed oxygen. When asked why they didn’t breathe it, the others gave answers such as “I felt uncomfortable”, “there was so much else to do” – or even a clear “I don’t know, I don’t understand it myself.”
So, if divers don’t take oxygen when they start experiencing symptoms of DCS, it’s usually not because none is available or they don’t even know they should use it. The reasons lie elsewhere.
For one thing, giving oxygen means admitting that it could be a diving accident. And this realization is often avoided for as long as possible. Denial is one of the earliest and most common symptoms after an incident. It is closely linked to the stigma attached to diving accidents and the fear of having done something “wrong.”
Secondly, the importance of oxygen in acute care is still underestimated today. It is firmly anchored in many minds that the actual treatment only takes place in the recompression chamber. Oxygen then appears to be a temporary solution, at best supportive. In certain cases, early administration of oxygen can decisively influence the course of a decompression accident – and sometimes even prevent the need for recompression chamber treatment.
And then there is also a very crude misconception floating around in some people’s heads: oxygen is medicine, and you can’t just give it like that. That’s not true, on the contrary: not giving oxygen, even though you have it available, can certainly be failure to provide assistance. You can achieve a lot with oxygen, but you certainly can’t do anything wrong.
“My O2 saturation is ok”: It’s not about oxygen deficiency
Since every other person checks their vital signs, including blood oxygen saturation, via smartwatch, a widespread misunderstanding can occur even more often than before. The administration of oxygen in a diving accident, especially in DCS, is not about the body being undersupplied. In most cases of decompression sickness, this is not the case, the oxygen saturation in the blood is usually normal. The problem is not primarily a lack of oxygen, but an excess of inert gas, usually nitrogen, in the body.
Only in individual situations can there be a real local undersupply, for example when gas bubbles block small vessels and certain tissues are no longer adequately supplied. However, the central mechanism of action of oxygen lies elsewhere.
Oxygen changes the pressure gradient for nitrogen
The most important effect of oxygen administration in decompression accidents is physical in nature. If pure oxygen is breathed, the nitrogen content in the lungs drops to almost zero. This creates a significant diffusion gradient between the nitrogen dissolved in the body and the nitrogen partial pressure in the lungs.
This gradient accelerates the elimination of nitrogen from blood and tissues. Nitrogen is transported to the lungs more quickly and exhaled. The faster this process takes place, the lower the probability that new gas bubbles will form or existing bubbles will continue to grow.
In this sense, oxygen does not act symptomatically, but causally. It directly intervenes in the mechanism that underlies decompression sickness.
Oxygen can reduce and destabilize gas bubbles
Another important effect concerns existing gas bubbles. Gas bubbles in the blood or tissue consist predominantly of nitrogen. If an affected person breathes pure oxygen, the gas balance inside and outside the bubble changes.
The nitrogen partial pressure in the surrounding tissue decreases, while the oxygen partial pressure increases. Nitrogen diffuses out of the bubble, oxygen diffuses into it, but is simultaneously consumed in the tissue. The result is a gradual reduction in the size of the bubble. Its stability decreases, and it can partially or completely dissolve.
This process depends on time, gas composition and blood flow, but begins early – often with the first administration of oxygen.
Oxygen also has an anti-inflammatory effect
In addition to the physical effects, there is evidence that oxygen also influences secondary processes. Gas bubbles trigger inflammatory reactions in the body, activating endothelium, platelets and the immune system. These reactions contribute significantly to the symptoms and tissue damage.
A high availability of oxygen can weaken these processes. Oxygen thus acts not only on the cause of bubble formation, but also on its biological consequences.
Time is a crucial factor
There is a clear connection between the time of oxygen administration and the further course of a decompression accident. In an evaluation of cases known to DAN between 1998 and 2003, it was shown that in 14% of patients the symptoms disappeared completely with the administration of oxygen alone, and in a further 51% it became significantly better. And these are only the cases that have become known to DAN – if oxygen alone is sufficient, the insurance company is not always informed. The efficiency, especially with very mild symptoms, should be significantly higher.
The earlier oxygen is administered, the better the chances of a complete regression of symptoms and the lower the probability of permanent damage. Delays of several hours are associated with poorer results. Every hour without oxygen means that excess nitrogen remains in the body for longer and harmful processes can progress.
Better too early than too late
Oxygen is not a luxury, an overreaction or an admission of failure in diving accidents. It is an evidence-based, effective and comparatively simple measure that should be used early on, as soon as a decompression accident is even considered.
Better to give too much oxygen once than too little once. This attitude not only protects the person affected, but also ourselves from the consequences of hesitation, repression and false restraint.
