Cave-diver Jared Hires, who died in Norway’s Plura cave system on a practice dive on 3 April, had suffered an unprovoked seizure last year, putting him at heightened risk of suffering another within the next 12 months – though he was probably unaware of the implications of that earlier medical event.
In an unusually rapid move designed to undermine social-media speculation, dive-safety organisation Divers Alert Network (DAN) has issued a preliminary accident analysis of Hires’ death within less than a week of the fatal incident, reported on Divernet on 5 April. It concludes that the pre-existing medical condition and not the diver’s equipment was to blame.
The analysis is based on an interview with one of the group of three divers who entered the system together and witnessed the event; input from Hires’ father Lamar, founder of specialist diving-equipment manufacturer Dive-Rite of which Jared was general manager; and downloads of all three divers’ closed-circuit rebreather controllers.
The divers were carrying out their first dive of a trip to Plura, Scandinavia’s most popular cave-diving destination. The hour-long gear-check dive was intended as preparation for a deeper descent the next day.
The three were said to be using familiar equipment with adequate thermal protection – Plura waters get no warmer than 7°C.
Sudden descent
Hires and the lead diver, who acted as DAN’s witness, had dived the system before, though it was new to diver 2. The three reached a maximum depth of 34m and surfaced at the halfway point, called the Wedding Chamber, after half an hour.
After two minutes of checks they headed back down, again with Hires bringing up the rear. The dive was uneventful until, 16 minutes in, Hires’ log revealed him making a sudden 4m descent from 25m in less than 20 seconds.
At this point the witness had turned to assist diver 2, whose primary light had failed and who was deploying a backup. As these two swapped places, they saw Hires’ light moving erratically and heard him screaming, “potentially trying to articulate a problem”.
The witness reached Hires to find him already in what were described as “full tonic-clonic convulsions”. ‘Tonic’ means stiffening, while ‘clonic’ means twitching or jerking phases of muscle activity.
Hires’ rebreather loop was out of his mouth but closed, suggesting that he had tried to bail out but had been unable to get the regulator into his mouth before the seizure occurred.
The witness tried unsuccessfully to secure Hires’ airway, then started to swim him, still convulsing, to the exit, a distance of about 250m that involved several depth changes.
The seizures stopped after about three minutes, but when the witness tried once more to get the regulator into Hires’ mouth his jaw could not be unclenched. Diver 2 swam ahead to call for help and a fourth diver met the others near the exit to provide assistance. The divers surfaced 17 minutes after the onset of the convulsions.
CPR was initiated immediately, and oxygen and a defibrillator within minutes of surfacing. Resuscitation efforts by the team and emergency services attending by ambulance and helicopter lasted almost two hours but were unsuccessful.
Viral infection
DAN learnt that Hires had suffered an unprovoked seizure for the first time the previous year, and that there was a family history of very rare, medically unexplained seizures connected with over-exertion, stress and dehydration.
Hires had reported sleeping well the night before the dive, and not feeling jet-lagged. However, the previous week he had displayed flu-like symptoms of a viral infection, including gastro-intestinal problems.
DAN conjectured that this might have added to potentially existing electrolyte imbalance and dehydration following Hires’ flights from the USA.
Though the symptoms are similar, DAN says that Hires’ dive-logs fail to support the theory that central nervous system (CNS) oxygen toxicity might have caused the seizure. “At no point before the event did oxygen levels or cell readings spike significantly,” it reports.
The partial pressure of oxygen did exceed the high setpoint of 1.2, but only briefly, moving to 1.3 for less than a minute. PO2 changes seen only after the event are easily explained by the solenoid still firing and the efforts of the witness to vent and inflate equipment to exit the cave, says DAN.
Hires is thought to have felt the onset of a seizure, making its cause more likely to be an underlying medical than an oxygen-induced condition.
Such seizures rarely present with warning signs or ‘aura’, says DAN, and a medical event would be more consistent with the duration and quality of the seizure which, as witnessed, “would best be described as a Grand Mal rather than oxygen toxicity”.
Unprovoked seizures can develop suddenly at any age. After someone has experienced one, recent research has put the likelihood of a recurrence within the first 6-12 months as 25-41%.
Tragic accident
“We conclude that this tragic accident was caused by a medical event and predisposition of the diver, and that neither equipment failure nor error in human-machine interaction is responsible for the outcome,” says DAN.
“The diver was likely not aware of the implications that a first-time unprovoked seizure could have. The dive-team did everything humanly possible in this challenging environment to rescue the diver.
“In summary, we feel that it is important to educate the diving community about medical and physiological issues that, while easily manageable at the surface, can prove fatal when experienced under water, especially in extreme environments.”
DAN says it is continuing to collect information to help understand the events that led up to and potentially caused the fatality.
Also on Divernet: Cave-diver Jared Hires dies in Norway’s Plura
