The diverThe diver was a healthy female in her 20s who was diving as part of her job. She was a scientific diver participating in training exercises with her team.
The divesSeveral divers were in the water practicing survey techniques and learning to use new equipment in depths between 20 and 30 feet. Most dives lasted less than 20 minutes, and divers were in communication with topside support staff at all times. After each training scenario they would surface for a debriefing and learn about the next scenario. The group had some newer members, so divers switched buddies regularly to allow everyone to interact with each other. It was summer, and temperatures were in the 90s (°F).
Most of the divers were wearing drysuits, their normal diving attire, so the group took precautions to limit overheating during surface intervals. Conditions were calm, and the water temperature was 84°F on the surface. Due to significant thermoclines, the temperature was 72°F at 15 feet and 64°F at 30 feet. All divers carried lights and used full-face masks. As part of the training, each diver took a turn using a new surface-supplied-air helmet to get used to working with an umbilical line and to learn to operate the helmet's emergency bailout system.
The IncidentAll participants admitted to being hot and tired toward the end of the sessions. This diver was the second-to-last member of the group to use the surface-supplied-air system. She had some trouble adjusting to the umbilical line and seemed to get frustrated on several occasions when the line became entangled in features on the bottom. Halfway through her 10-minute dive, she complained to the topside tender of feeling strange and overheated. She called off the dive, asked the tender to begin taking up slack in the umbilical line and started to ascend.
At 8 feet, a safety diver who was watching her stated that the diver's eyes rolled back and her head fell forward. She stopped ascending and quickly sank to 20 feet, where the umbilical line stopped her descent.
The safety diver initiated emergency procedures, and other divers in the water came to assist. During the ascent, the rescuers noted that the diver was breathing and described her as being stiff and sometimes twitching. On the surface she was immediately towed ashore, and her gear was removed. A certified diver medical technician (DMT) was on scene, and he quickly cut the diver out of her drysuit. Another member of the team contacted emergency medical services (EMS) and was told response time might be as long as 15 minutes due to the location of the training. When the paramedics arrived, the DMT provided them with his assessment, the diver's vital signs and interventions made.
Assessment and EvacuationThe DMT reported that the diver appeared to lose consciousness in the water during ascent, and, based on rescuer reports of twitching and muscular rigidity, there was concern of possible seizure activity as the diver was being brought to the surface. She was responsive to verbal stimuli by that time and would open her eyes for a few seconds when spoken to but was unable to follow commands. Her vital signs (including blood glucose) were checked and found to be normal except for a slightly elevated blood pressure and heart rate.
The diver's mental status precluded detailed neurological evaluation, but potential concerns included arterial gas embolism (AGE), hyperthermia and postictal state following a seizure. The gas supply was thought to be safe; none of the other divers who had used it that day reported any problems. Rather than route the patient to the local hospital, the emergency personnel decided to have her flown to a larger facility 45 miles away due to the severity of the symptoms. A helicopter had been placed on standby at the time of the initial call, and it was ordered to launch within a few minutes of the paramedic's arrival at the scene of the accident.
During the flight the diver was sleepy but able to answer some questions. The paramedics noted weakness on her left side, and she experienced a seizure that lasted about 45 seconds. Due to the possibility of that being her second seizure, she was given medication to prevent additional seizures, and the medication made her very drowsy.
Diagnosis and TreatmentIn the emergency department, the doctor diagnosed the diver with AGE. This diagnosis was based on the fact that symptoms began during ascent from a dive, the symptoms noted during the ascent may have been associated with impaired breathing (or even breath holding), there was persistent unilateral (one-sided) paralysis, and the diver had no known history of seizures. A CT scan of the diver's head showed no evidence of bleeding, and the risk of stroke was minimal because of her health status and age.
She was transferred to the hyperbaric unit and treated in a chamber. Her drowsiness made it challenging for the staff to assess her response to treatment, and they reported that during treatment she seemed to experience three periods of "spacing out" that lasted 15 to 30 seconds each. After treatment she was admitted to the hospital's neurological floor. She received an additional chamber treatment the following morning due to persistent neurological deficits on her left side.
The HistoryBy the next day the patient's family had arrived. After discussing the incident with family members, she admitted to the doctors that she had a history of complex partial seizures and that she had discontinued her medications so she could be a part of the dive team. She had not had a seizure in years and had done many recreational dives without incident. Of the two seizures she had experienced in the past, both had occurred during periods of extreme stress.
Despite this revelation about the patient's medical history, the diagnosis was left as AGE. However, the hyperbaric physicians and neurologists who treated this diver wondered if her symptoms were actually the result of a seizure complicated by a condition called Todd's paralysis (a type of paralysis that can follow seizures and usually occurs on one side only). Todd's paralysis resolves spontaneously within hours or a couple of days; the average time to resolution is about 15 hours.
Lending support to the suspicion of Todd's paralysis is the fact that hyperbaric treatment had no effect. The physicians stated they probably would still have done the initial chamber treatment even if they had known about the diver's medical history, but they probably would not have treated her a second time because there was no improvement after the first treatment and there was a plausible alternative explanation for her state.
Fortunately for this diver, her underlying condition did not warrant any medical treatment she did not receive. However, her case serves as a compelling advisory to make sure your dive medical officer — or dive buddy — is aware of any medical conditions that could affect your diagnosis or treatment if you are injured while diving.
© Alert Diver —Winter 2013