Accident Assessment: A 38-year-old male diver was participating in a recreational dive. The profile was 58 fsw(approx 27m) for 40 minutes. This individual experienced transient problems with equalization of his middle ear during descent. During his ascent he developed acute vertigo, sense of fullness in one ear, nausea and slight disorientation at around 20 fsw (7m). He managed to reach a buoy line at 15 fsw(5m) and hold on. Within the 3 minute safety stop all symptoms completely resolved and he returned safely to the surface. What do you suspect and why?
Response: This was most likely alternobaric vertigo related to a reverse block. Typically equalization during ascent is passive with the air venting from the middle ear easily. If for some reason the expanding air vents more easily or quickly from one ear than the other, the difference in pressure between the two middle ears can cause the symptoms. It is possible that the transient difficulty with equalization during descent may have contributed to the reverse block. If you experience a reverse block, especially if the more serious symptoms manifest, stop your ascent, descend a few feet and move the jaw to help facilitate equalization.