Equalization & Eustachian tube function. DocV's Fri AM Medical Minute.+

[DocVikingo]

Interesting study on Eustachian tube function in a scuba-related barotrauma.

Appears to be a bit of a rough translation from the Japanese, but I believe that one take-away for board members is to use a non-pressurized equalization technique (e.g., Toynbee, Rodyhouse, Beance Tubaire Volontaire (BTV)) rather than a pressurized maneuver (e.g., Valsalva) if you can.

"Nihon Jibiinkoka Gakkai Kaiho. 2012 Dec;115(12):1029-36.
[A study of the Eustachian tube function in patients with a scuba diving accident].
[Article in Japanese]
Kitajima N, Sugita-Kitajima A, Kitajima S.
SourceKitajima ENT Clinic

Abstract
The scuba diving population has increased very much recently, bringing with it a rise in barotrauma. Ninety-seven patients with scuba diving-related accidents (34 males and 63 females; mean +/- SD: 36.6 +/- 10.3 years) and 39 healthy volunteers (9 males and 30 females; mean +/- SD: 41.1 +/- 16.9 years) without a history of Eustachian tube dysfunction participated in this study. All patients underwent audiometric measurements, including hearing testing, tympanometry, and Eustachian tube function testing (sonotubometry and impedance test). The tympanometry results of the majority of the patients were normal (Jerger A type), however, 83 of 97 patients (85.6%) were diagnosed as having Eustachian tube dysfunction: all patients had tubal stenosis. Compared with healthy volunteers, the Eustachian tube function in scuba diving patients was significantly lower. According to whether the affected parts were one ear or both ears, we classified these patients into 2 types, that is, the unilateral group and the bilateral group. The symptoms in the unilateral group were more serious than those in the bilateral group. In the unilateral group, the Eustachian tube functions of the affected ear did not always show lower than those of the healthy ear, so we thought that excessive positive pressure at the mesotympanum caused by the Valsalva maneuver might have affected not only the affected ear but also the healthy ear and have resulted in healthy ears being severely impaired by excessive positive pressure. To prevent scuba divers from pressure injury, we think that divers should have their Eustachian tube dysfunction accurately evaluated and any problems should be treated well."

Cheers,

DocVikingo

 

[doctormike]

Interesting study...! A few quick thoughts.

1) "Tubal Stenosis" is not a real diagnosis for most divers. It's more of a functional problem with the ET. True stenosis of the ET generally results from radiation therapy for skull base tumors. More to the point, it's very difficult to diagnose this in a living person - one way to do it is to inject radioopaque contrast up the ET (believe me, you don't want to know!). Some docs are starting to experiment with ET endoscopy, but this is still pretty early in development.

2) Divers should know all of the different maneuvers to open their ET's, including valsalva (which pressurizes the middle ear via positive pressure from the airway) as well as Toynbee (which results in a negative pressure gradient by dropping the nasopharyngeal air pressure) and the other ones as well.

3) The best advice is to avoid doing something that hurts, which is the only way that you would know about the efficacy of your equalization during the dive. While it is true that a valsalva which is forced to open a blocked ET on the left could overpressurize the middle ear on the right, if done gently and repeatedly, it may actually be more helpful than a negative pressure technique during descent. The reason for this is that unless you are in the relatively rare reverse-squeeze scenario, pressure in the middle ear will be lower than airway pressure (ambient pressure), so you do need to push air into your ear along a gradient.

4) ET function at sea level in adults is not much of a predictor of of the ability to equalize during diving. If a tympanogram is abnormal, yes, that person might have troubles equalizing. But a normal (Type A) tympanogram just means that your middle ear is at ambient pressure in the doctor's office. It doesn't mean that you will be able to equalize when ambient pressure changes rapidly. The best way to test that is in a swimming pool!

5) Not sure why divers would have more ETD than non-divers, but I guess the devil is in the details. Hard to tell from just the abstract.

 

[Saturation]

Some questions I'd raise, I did not read the whole paper:

Divers selected had prior diving accident history. Did this select population have some form of ETD before their accidents that contributed to their risk of a diving accident or did an accident lead secondarily to ETD in previously normal divers?

It would help to compare against a group of accident free divers.

Accidents are a fairly heterogenous group of disorders, what is the definition?

Is the ETD related to number of dives? Over what time frame? Length of each dive?

I'm not sure I can draw specific conclusions about this study to apply to divers.

 

[doctormike]

Yup!

Having spent many years on the editorial board of the Archives of Oto-HNS, I am continually amazed by what makes it through to publication. There is a lot of pressure (here anyway, don't know about Japan) to publish things, and despite the best efforts of peer reviewers, not everything that appears in print is clinically applicable or even based on sound methodology.

Of course, you really can't assess a study from the abstract only. Often the lay press will take a study with an interesting grain of truth in the abstract and trumpet it as a cure for cancer, because that makes for more clicks, etc...

But still, always happy to see SCUBA research making it into the medical literature... Thanks for finding this, Doc!



M