A diver suffered acute vertigo and unstoppable vomiting during a dive in a lake. After emergency care and multiple hyperbaric chamber treatments, he recovered to a large extent. Was it a decompression incident?
Case vignette
The previously healthy man completed several dives as part of an "advanced" course accompanied by a diving instructor. After a dive to 40 m with compressed air, he was suddenly hit by acute nausea while surfacing at a depth of 15 m in poor visibility. He had to vomit once. The nausea disappeared as he continued to ascend. On reaching a depth of 5 m, he again experienced nausea accompanied by severe vertigo and insatiable vomiting. Although not mandatory due to the dive profile, the instructor ordered a "safety deco" for 10 minutes at this depth. During this time, the diver had great difficulty breathing through the regulator due to the ongoing vomiting. Finally, the dive was terminated. Due to severe vertigo, the diver was unable to walk out of the water. The diving instructor and others present initiated emergency treatment with oxygen administration and alerted the emergency center in case of suspected acute decompression illness. The diver was airlifted to a hyperbaric chamber for treatment.
The day before, he had already completed two dives with compressed air to a depth of 40 m with a 150-minute surface interval. During the second ascent, a sharp, one-sided earache occurred, which quickly disappeared. All dives were completed within the no-decompression limits.
The diver had obtained his diving certification 1 year previously during a vacation at sea. The pressure equalization in the middle ear had always been delayed on one side. This had not led to any further problems. The diver was in possession of a valid diving fitness certificate.
The first pressure chamber treatment was initiated approximately two and a half hours after the emergency call. A total of 5 treatments lasting several hours were carried out over the next few days. The symptoms of vertigo and nausea disappeared on the 2nd day of treatment. Additional investigations (CT of the brain, ENT examinations) were unremarkable. Tinnitus (ringing in the ears) had been persisting since the accident. A PFO (patent foramen ovale) was ruled out by TEE (transoesophageal echocardiography) on the recommendation of the hyperbaric physicians.
Was this a decompression accident?
The facts that the dives were completed within the no-decompression limit, that the symptoms occurred on the first dive on the second day of the course, that the surface interval (night) beforehand was quite long and that an acute onset of decompression sickness while still underwater is rather unlikely in this setting speak against decompression sickness. On the other hand, the question arises as to whether the dives were actually within no-decompression limit, as three dives with compressed air to 40 m were made within just under 24 hours.
Alternobaric vertigo
Overall, the picture is typical of another syndrome: alternobaric vertigo. In this disorder, pressure equalization in the middle ear is absent or delayed while ascending. Normally, the Eustachian tube opens passively from an overpressure in the middle ear of less than 50 cm water column, i.e. when the depth is reduced by less than half a meter. If it remains blocked, a reverse barotrauma of the middle ear occurs with pain on the affected side. Indirect irritation of the semicircular canals due to the excess pressure in the middle ear causes acute vertigo and nausea. Tinnitus often occurs. Mild symptoms can be relieved by further ascent if the blocked Eustachian tube opens after all due to the increasing pressure difference. If this does not happen, the symptoms worsen. If the round window ruptures, severe symptoms with acute loss of orientation occur. This and repeated vomiting lead to panic and an acute risk of drowning.
Alternobaric vertigo is a threat in all conditions associated with inflammation of the middle ear or swelling of the sinuses. For this reason, it is not advisable to dive if suffering from a cold. If the symptoms are mild, the diver should ascend very slowly and may need to descend a little to alleviate the symptoms. In this respect, the air supply is critical.
Lessons learned
The previous history of delayed pressure equalization during the beginners' course must already be interpreted as a risk of reverse barotrauma, which means that a certain degree of caution should have been exercised when completing deeper dives. The ear pain on the day before the accident should certainly have served as a warning not to make further dives without an ENT examination. After the first feeling of vertigo and vomiting, the dive should have been aborted as quickly as possible. However, the dive should have been terminated immediately at the latest when the most severe symptoms with repeated vomiting reappeared. Delaying the ascent was of no benefit and only entailed the risk of a fatal outcome due to panic. Underwater, it is not possible to assess severe symptoms correctly, let alone treat them. Therefore, the rule in such a situation is: get out of the water as quickly as possible.
Emergency care
Decompression illness can manifest itself with symptoms affecting any organ system. For this reason, oxygen should always be given in a diving accident if there is even a small chance of decompression illness. The first aid with oxygen was undoubtedly the right thing to do due to the unclear situation, even if it probably had little effect. The rescue chain was set in motion immediately by the rescuers. It should be emphasized here that in Switzerland REGA should be generously alerted under the keyword "diving accident", as they always have access to advice from a diving physician if required.
What about fitness to dive?
In the case of alternobaric vertigo, diving can be resumed after full recovery. However, fitness to dive is not given as long as symptoms persist. In this case, the persistent tinnitus prohibits any further diving. But even if it disappears one day, the person concerned should be advised to refrain from diving, as it is highly likely that there is an unsolvable pressure equalization problem in the middle ear and therefore the risk of future complications during diving is high.
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