Interrupted decompression leads to decompression sickness


During the 3 meter (10 feet) decompression stop on 100% O2, two divers unexpectedly became separated. Despite the fact that they had just started the 3 meter stop, one aborted her decompression obligation to see what happened to her buddy. After realizing that her dive buddy was already returning to the boat, the diver decided to go back down to 6 meters (20 feet) to resume her decompression on oxygen, but a few minutes into it she started feeling nauseated and general malaise. She then decided to switch to EAN32 and go a little deeper, down to 7 meters (23 feet), where she reportedly felt better, with the nausea and general malaise disappearing. After a few minutes, she ascended to 4 meters (13 feet) where she completed her 100% oxygen decompression without any problems.

Some 12 hours after surfacing, the diver noticed discomfort on her right upper extremity with mild pain, which for the following two hours evolved into paresthesia and increased pain. About 6 hours after symptom onset, the pain in her arm got progressively worse. Not only did pain killers not seem to have any positive effect but her right arm became completely paralyzed. She was then routed to an emergency room. After contacting the DAN emergency hotline, the patient was referred to a recompression facility where she was prescribed a USN TT6, which required extensions. After the treatment, the patient reported significant improvement on her pain and motor deficit, but reported a persisting mild paresthesia. She continued improving gradually and after a week she had no motor deficit, only a mild intermittent paresthesia on the affected limb.


Any omission of a decompression obligation should be considered a significant risk for developing decompression sickness. A diver should consider every possible event that could compromise a planned decompression. This will minimize stressful surprises, consequently reducing the chances of something bad happening and severely jeopardizing the diver's safety. Buddy separation is something that can happen, and prevention and procedures should be discussed during the dive planning, before entering the water.

Divers should avoid, by any means, interrupting a mandatory decompression; even when a timely descent to resume decompression seems warranted. A significant barometric change during the decompression stage can lead to a significant bubble formation, which could result in decompression sickness. Even with the simplest dives, decompression obligations should be executed according to what was previously planned. When a decompression obligation is not completed as planned, and corrections prescribed by your training agencies could not be applied, it is wise to administer normobaric oxygen and keep the diver under observation for the following hours after surfacing. In case of gross omission of mandatory decompression stop time, chamber recompression may be considered, even in absence of clinical DCS. In any case, divers should feel free to contact DAN for advice.

~ Sergio Viegas
DAN Brasil