Alternobaric Vertigo & Diving

Text by Dr Frans J Cronjé

ALTERNOBARIC VERTIGO AND THE DYNAMIC MIDDLE EAR: INSIGHTS FROM A DIVER SURVEY

Underwater, the human body faces a complex interplay of physics and physiology. Nowhere is this more evident than in the middle ear — a small, air-filled chamber that can become a diver’s weakest link if equalisation fails. Among the lesserunderstood consequences of pressure imbalance is alternobaric vertigo (ABV), a disorienting condition that can surprise even experienced divers during descent, ascent, or shortly after surfacing.

To better understand how this phenomenon affects the diving community, we conducted a targeted survey on alternobaric vertigo and dynamic middle ear response (DRE), gathering insights from 92 divers across varying experience levels. This article explores the underlying mechanisms of ABV, shares findings from our survey, and offers practical guidance to reduce risk and enhance diver safety.

UNDERSTANDING ALTERNOBARIC VERTIGO (ABV)

Alternobaric vertigo occurs when pressure between the middle ears becomes unequal, often during ascent when gas trapped in the middle ear expands and exits at different rates between the ears. This pressure asymmetry can stimulate the vestibular apparatus disproportionately on one side, resulting in a transient but often intense sensation of spinning or tumbling — a classic vertigo.

Unlike inner ear decompression sickness or barotrauma, ABV usually does not involve actual structural damage. The vertigo typically lasts seconds to minutes, and may resolve spontaneously — but its impact in an underwater setting can be serious. Disorientation, loss of buoyancy control, and panic responses can lead to unsafe ascents or environmental injury.

Triggers for ABV include:

• Unequal middle ear compliance or Eustachian tube function.

• Congestion from colds, allergies, or sinus inflammation.

• Forceful or asymmetrical equalisation.

• Rapid ascents with poor ear clearing.

  In some cases, divers experiencing ABV may misinterpret it as nitrogen narcosis, panic, or even stroke. This makes awareness and prevention essential for diver safety.

DYNAMIC MIDDLE EAR RESPONSE (DRE): A NEW LENS

While ABV describes the symptoms, Dynamic Middle Ear Response (DRE) is a term we’ve begun to use to describe the underlying physiological variability in how each middle ear responds to pressure changes. Through survey responses and clinical otoscopy reviews, we’ve observed that some divers experience inconsistent, delayed, or hyperactive responses in one ear compared to the other, even when using correct equalisation techniques.

This asymmetry can be transient or persistent — due to anatomy, inflammation, or even learned behaviours such as favouring one side during equalisation. DRE may help explain why ABV recurs in certain individuals even after apparent recovery and offers a framework for divers and clinicians to discuss ear symptoms that go beyond simple “blocked ears.”

SURVEY FINDINGS: DIVER VOICES AND DATA

Our Divers Alert Network Southern Africa survey gathered 92 responses from recreational and professional divers. Participants ranged from recent open water divers to instructors and technical divers with thousands of logged dives.

Key findings included:

• 36% of respondents reported experiencing at least one episode of vertigo underwater they believed to be related to ear pressure.

• Among these, 71% described the onset during ascent, typically within 10 meters of the surface.

• 42% of vertigo episodes occurred while divers were ascending independently, away from a buoy line or reference structure.

• 58% of those who experienced vertigo acknowledged diving with nasal or sinus congestion, often from allergies or a lingering cold.

• 14% reported temporary ringing in the ears (tinnitus) or hearing loss, though most symptoms resolved within hours. A small subset experienced persistent auditory disturbances, later diagnosed as mild barotrauma.

• Divers who equalised forcefully or asymmetrically — such as using the Valsalva manoeuvre with one nostril partially blocked — were more likely to report recurring ABV symptoms.

Perhaps most striking, 19% of those who had experienced ABV had not initially recognised it as an ear-related problem until it was explained post-dive. This lack of awareness suggests a need for better education during training and post-dive debriefs.

LESSONS FROM THE FIELD: DIVERS REFLECT

We invited divers to share their personal experiences. One technical diver wrote:

“I thought I had a panic attack during a deco stop at 6 meters — everything started spinning. I almost bolted. Later, my ENT told me one ear hadn’t cleared during the dive. I never realised equalisation could still be a problem on the way up.”

Another diver reported:

“It felt like my mask was twisting around my face. I instinctively reached for the buoy line and waited it out. It passed, but I’ve never forgotten it.”

Such accounts point to a clear truth: even when the physiology is transient, the psychological imprint of ABV can be profound. Many respondents described increased anxiety on future dives and a greater focus on their ears during ascent with some adopting new dive practices to stay safe.

BEST PRACTICES AND DIVER RECOMMENDATIONS

Based on our data and clinical review, we propose the following practical recommendations for divers, instructors, and dive medics:

• Do not dive with congestion: Whether from a cold, sinus inflammation, or seasonal allergies, diving with impaired Eustachian tube function increases the risk of unequal middle ear pressures. Divers should treat symptoms or wait until fully recovered before resuming dives.

• Never force your ears: Aggressive or repeated Valsalva manoeuvres can cause barotrauma or provoke asymmetrical clearing. Instead, divers should learn and practice gentler techniques like the Toynbee or Frenzel manoeuvres, and equalise early and often.

• If you are prone to ABV, ascend using a buoy line or structure: Having a visual and tactile reference reduces disorientation and offers a physical anchor if vertigo strikes. It also slows ascent, supporting safer ear equilibration.

• Pause if you feel dizzy or disoriented: Stop, signal your buddy, and stabilise. Avoid sudden movements or rapid ascent. Most cases of ABV resolve within seconds to a minute. Breathe slowly and focus your vision on a fixed point if possible.

• If vertigo is persistent or accompanied by tinnitus or hearing loss, seek medical advice: These symptoms may signal inner ear barotrauma or other serious conditions. A dive-savvy ENT can perform tympanometry and vestibular tests to assess residual damage or risk of recurrence.

• Instructors should actively teach descent and ascent equalisation: Too often, equalisation is framed as a descent-only task. In reality, middle ear pressure management during ascent — especially in the final 10 meters — is equally critical.

• Keep a dive diary for recurring symptoms: Track dive conditions, health status, and symptoms to look for patterns. This can help divers and doctors identify contributing factors and implement personalised prevention strategies.

• Pre-dive ear warm-ups may help: Several divers reported fewer symptoms when performing gentle jaw stretches, yawning, and pressure manoeuvres on land before entering the water. While not formally studied, these techniques may help “prime” the Eustachian tubes for function.

A CALL FOR AWARENESS AND RESEARCH

Alternobaric vertigo may be brief and benign — but it is also insidious. Its unpredictability, psychological impact, and potential to cause uncontrolled ascent make it a genuine safety concern. Our survey confirms that ABV is more common than many divers realise, especially among those with subtle middle ear asymmetries or inadequate ascent practices.

The concept of Dynamic Middle Ear Response (DRE) provides a valuable new lens to understand individual variability and tailor prevention. We encourage dive instructors to include DRE concepts in training and for clinicians to consider it when evaluating recurrent ear symptoms in divers.

As divers, we often focus on depth, gas, and equipment — but perhaps it’s time to listen to the quietest spaces: the delicate balance of air and motion in our middle ears.

REFERENCES

Bove, A. A. (1996). Diving Medicine (3rd ed.). W.B. Saunders Company.

Campbell, J. T., & Rudge, P. (1984). Alternobaric vertigo: a review. Aviation, Space, and Environmental Medicine, 55(8), 707–710.

DAN (Divers Alert Network). (2021). Middle Ear Barotrauma and Vertigo. Retrieved from https://www.diversalertnetwork.org

Edmonds, C., Lowry, C., Pennefather, J., & Walker, R. (2016). Diving and Subaquatic Medicine (5th ed.). CRC Press.

Norton, S. J., & Allen, G. D. (1982). Alternobaric vertigo and Eustachian tube function in divers. The Laryngoscope, 92(1), 76–80.

Tysome, J. R., & Hamilton, S. (2014). Clinical assessment and management of diving-related ear injuries. BMJ Case Reports, 2014, bcr2013202906