Do we need O'Dive? - Personalized decompression and myths in tech diving

The article “Of Bubbles and Dive Profiles - One Diver's Journey into Personalized Decompression” in InDEPTH Magazine describes the experiences of a diving instructor with the Doppler-based O'Dive from Azoth Systems, which is designed to personalize dive profiles and make them safer. The article offers interesting insights - not only into the technology itself, but also into the mindset of many tech divers and especially their instructors.

Walensee. Foto: Karin Aggeler

A new gadget

Azoth Systems is promoting O'Dive as a tool for personalized decompression. It is an ultrasound device that measures the amount of venous gas bubbles (VGE) after a dive. The device is held on the vein under the collarbone (subclavian vein) for around 20 seconds. The data is sent to an app via Bluetooth and then analyzed in the cloud. The analysis is not carried out transparently, but using a proprietary algorithm. The user does not receive a direct bubble count result, but only an evaluation of the “profile quality” and suggestions for optimizing the next dive - for example by extending shallow stops. O'Dive is therefore a proven but old technology that has been “modernized” by a black box analysis. What exactly it calculates is not discloses.

The great bubble confusion

By measuring the amount of VGE after the dive and deriving recommendations for future dive profiles, O'Dive is supposed to make dives safer. But this is where the problem begins: there is no reliable evidence that these bubble measurements actually help to improve diving safety.

As David Doolette impressively demonstrated in his study “Within-diver variability in venous gas emboli (VGE) following repeated dives”, the intra-individual variance in bubble formation is enormous. The same diver can show many VGE after identical dives on one day and hardly any on the next - without a clear explanation.

But that's not all: even the most severe VGEs, as discussed in this article, do not lead to decompression illness (DCI) in 90% to 95% of cases. DCI did tend to occur with higher VGE exposure, but only in isolated cases.

It is still unclear why these bubbles form in the first place, why they fluctuate so much and what influence they really have on the development of decompression sickness. The fact that reducing them automatically makes you a safer diver is at best an unproven hypothesis. (Click here for the blog post about the study on dekoblog.ch).

The following quote sums up the value of the device:

"For an individual, measuring VGE ist not a useful tool."- David Doolette, Rebreather Forum 4

The mindset of the tech community

The article is also enlightening because it provides a deep insight into the thinking of many tech divers and instructors - and this is precisely where a crucial problem lies: the adherence to outdated concepts such as the so-called “deep stops”. These have long been scientifically refuted. Numerous studies, including one by Doolette, show that such stops additionally saturate the slow tissues without having a positive effect on decompression. Bühlmann explained in his models decades ago that a rapid ascent to shallower depths with sufficient decompression time is much more effective. Unfortunately, these myths persist in the tech diving scene, not least because they are still taught by instructors.

Extended range with compressed air - please don't!

Another questionable aspect: The article refers to the extended range course of TDI, which involves diving to depths of up to 45 m with compressed air. This is another practice that should be abandoned as a matter of urgency. Nitrogen narcosis at this depth is not only noticeable, but potentially dangerous. There is also the problem of gas density, which was mentioned in this article. Dives with compressed air at depths of over 40 m are simply obsolete. Such courses give the false impression that this practice is recognized. It is not. You don't need an O'Dive to come to realize this either, but simply a serious understanding of diving physiology.

Conclusion

If Azoth Systems helps to rectify outdated and misguided diving practices, that would be welcome. But you don't need expensive equipment for that. If you stick to modern, evidence-based decompression strategies with shallower stops and more decompression gas, you will dive more safely without an O'Dive. The idea that measuring VGE is of individual benefit must be completely dispelled, as Doolette has impressively demonstrated. This has nothing to do with personalization. You can spare the money for O'Dive. It's better to invest it in more gas to ensure longer and safer decompression - and in proper diving training.