My husband was scuba diving a week ago in Mexico. After he dove the first time, his ear was blocked but got better within 24 hours. The second day he dove, his ear felt blocked again afterward, and it has not gone away. He has seen his primary care physician, who told him he may have "baro syndrome," and he will see an ear, nose and throat specialist. I have been unable to find information on this disorder. Can you give me some information on this syndrome and how long it takes to get better?

B.J.

If you did a web search for "baro syndrome," I'm not surprised that you came up with goose eggs. This is an odd way to refer to "barotrauma" or "barotitis." (I suspect that these are better search terms.)

Baro means pressure (as in barometer), so these terms mean a pressure-related injury of the ear (barotrauma) or pressure-induced inflammation of the ear (barotitis). Scuba diving is probably the most common circumstance for such an injury, but plane flight and skydiving can also generate the rapid pressure changes that lead to barotrauma.

To understand barotrauma, you will have to sit through a little lecture on middle-ear anatomy and physiology. Here goes:

The middle ear is an air-filled space located behind the eardrum. On most of its sides, it is bounded by bone. There are three thin membranes within the walls of the middle ear: the eardrum and two membranes (each much smaller than the eardrum) that separate the middle ear from the inner ear. The two small membranes are known as the oval and round windows. The only other relevant feature of the middle ear is the opening to the eustachian tube. The eustachian tube is a tube of muscle and cartilage that opens into the middle ear and also the upper throat, effectively connecting the middle-ear space to the outside world. This tube is usually closed, but it opens occasionally to allow air-pressure differences between the middle-ear space and outside to equalize.

If the air pressure in the "outside world" changes very suddenly, as it might for a deep-sea diver, sky diver or passenger in a rapidly depressurizing airplane, the eustachian tube may not be able to do its job of equalizing the pressure between the middle ear and outside. If the pressure differences are severe enough, a number of different barotraumatic injuries may occur. From least serious to most serious, they are:

• Symptoms related to the pressure difference: pain, fullness, dizziness or ringing in the ear.
  
• A build-up of middle-ear fluid (this is known as an "effusion"), resulting in a sense of fullness and hearing loss.
  
• Bleeding into the middle ear (known as "hemotympanum"), also resulting in fullness and hearing loss.
  
• Bursting of the eardrum, just as a balloon could pop under similar circumstances. This would result in a hole in the eardrum, some hearing loss and possibly drainage from the ear canal.
  
• Rupture of the round window or oval window, causing damage to the inner ear. This is the most serious injury because it is the one most likely to be irreversible.
  

I cannot tell you how long it will take for your husband to recover, because I do not know the severity of his injury. By examining your husband's ear and by obtaining a hearing test, the ear, nose and throat specialist (ENT) will be able to differentiate among the above possibilities and advise you about the time course of his recovery and the possible need for further treatment.