Jan. 5th 2023

We usually think of DCI (Decompression Illness) or “the bends” as a condition that only scuba divers are susceptible to and not us freedivers.

But research shows that we can also get DCI or another condition known as Taravana (which can present “serious neurological disorders, including unconsciousness, convulsive seizures, and/or crossed sensory numbness” and can even be fatal).

More importantly, you don’t have to dive to the extreme depths that No Limits divers like Herbert Nitsch dive to (he famously had a severe case attempting to dive to -253m) to be at risk of DCI.

The authors of the paper linked below studied a male Ama diver who had a case of DCI (there are more cases studied in the referenced papers).

The Ama (海女, "sea women") are Japanese divers famous for collecting pearls, though traditionally their main catch is seafood. The vast majority of Ama are women. Their tradition holds that their practice may be 2000 years old but official records go back around 1000 years.

The subject of the paper was a 65 year old man with 30 years of experience in breath hold diving. He would typically work from 08:00 to 15:00 in two shifts and dive to depths of between 10 and 20m, descending using ballast and ascending without assistance.

"On the day of the accident, which was his fourth successive day of diving, the diver began diving at around 8:00 AM with the usual dive depth of 10-20 m. At the end of the morning diving shift, however, he experienced slurred speech and right-hand paresthesia. On the boat, he could rise without any assistance, but he was not able to walk steadily. He had no chest pain, bloody sputum, loss of consciousness, or motor weakness.”

An interesting observation from this paper is that DCI in freedivers presents similarly to a stroke with injury to brain regions and doesn’t seem to affect the spine as much as scuba related DCI does.

“Typically, cerebral DCI manifests with sensory numbness or motor weakness on one side, disturbed speech, and/or visual deficit after repetitive dives for several hours.”

It is imperative that if we spot these symptoms on a diver that we rush them to the hospital and that they have an MRI scan as soon as possible to “evaluate stages of brain ischemia”.

Immediate treatment (within 6 hours of symptom onset) is necessary! “A survey from Divers Alert Network described early NBO breathing improved or stabilized DCI symptoms in 95% of 1045 cases.” Treatment includes Normobaric Oxygen (NBO), which is a gas rich in oxygen at 1 ATM of pressure and Hyperbaric Oxygen (HBO), which is oxygen administered under higher pressure in a hyperbaric chamber.

In the paper it is not made clear how frequently the Ama was diving or what his surface intervals were. Importantly though, the reports “indicate that multiple breath-hold dives in succession are not benign and that neurological accidents following such diving require early diagnosis and treatment”.

In conclusion, you see how important it is to monitor our surface intervals and how easily and seemingly "out of the blue" something very bad can happen. Personally and from experience, I would say at least 3 times the dive time for dives that are comfortable to you and down to less than 30m. Ideally, the longer the surface interval, the better recovered you will be and the better the next dive will be. After a hard dive, I would wait as long as 10 minutes to do the next one and I felt completely fresh for it.

Remember that you can always dive another day and the point is to have nice enjoyable safe dives, not to dive for hours on end until you’re exhausted. I understand that you may either not have much access to water other than when you’re at your dive location and / or want to get the most out of each session. We have to take care of our safety first and make sure our sessions are nice and relaxed, not tiring and pushed.

And watch your buddies up close to make sure they don’t exhibit any worrying symptoms!

Thank you for reading and happy safe diving!

To read the full paper, please visit this link.