Equalize air space in our body

Our middle ears are dead air space, connected to the outer world only by the Eustachian tubes running to the back of our throat. On dive, the underwater pressure will squeeze our eardrums and causes painful middle-ear, this is the most common pressure-related ears injury. Therefore, we need to equalize so the pressure in our outer and inner ears match.

This is one of the basic skill that every diver need to practice, so we can dive safely. Another part that will needed to be equalized is our mask, because it contain air. The deeper we go, we will feel our mask squeeze and even cause pain. To equalize it we can blow a little air from our nose, enough to reduce the pressure.

If you dive without equalizing your middle ears, you can experience painful and damaging middle-ear barotrauma. Step by step here is what happened :
1. At one foot below the surface, you feel pressure on your ears.
2. At four feet, your ear drums bulge into your middle ears. Mucus begin to fill your Eustachian tubes, making it deficult to equalize your ears if you try. You start to feel pain.
3. At six feet, ear drums continue to bulge even further and tissue begin to tear causing inflammation that will last for 1 week. If small blood vessels in your eardrums breaks, this will last for up to 3 weeks. Your Eustachian tube are now locked shut by pressure, making equalization is imposibble.
4. At eight feet, if you are lucky, blood and mucus is sucked from surrounding tissues and begin to fill you middle ears. This is called middle-ears barotrauma. Fluid, not air, is now equalizes pressure on your eardrums.
5. At 10 feet, Eardrums may break. Water will flood your middle ear. The suddent sensation against your balance mechanism, your vestibular canals, may cause vertigo, especially if only one eardrum is breaks. Temporary or permanent hearing lost may result.

There is several ways to equalize, all methods for equalizing your ears are simply ways to open the lower ends of your Eustachian tubes, so air can enter.
-> Valsalva Maneuver, this method is the most common method. Pinch your nostrils and blow through your nose. The resulting overpressure in your throat usually force air up to Eustachian tube. But this methods do not activate muscles which open the Eustachian tubes, so it may not work if the tubes are already locked by a pressure differential.
-> Toynbee Technique, with your nostrils pinched or blocked against your mask skirt, swallow. Swallowing pulls open your Eustachian tubes while the movement of your tongue, with your nose closed compressed air against them.
-> Lowry Technique, this is a combination of Vasalva and Toynbee. While closing your nostrils, blow and swallow at the same time.
-> Edmonds Technique, while tensing the soft palate and throat muscles and pushing the jaw forward and down, do a Valsalva maneuver.
-> Frenzel Maneuver, close your nostrils and close the back of your throat as if straining to lift a weight, then make the sound of “K”. This will force the back of your tongue upward, compressing air against the openings of your Eustachian tubes.
-> Voluntary Tubal Opening, tens the muscles of the soft palate and the throat while pushing the jaw forward and down as if starting to yawn. These muscles pull the Eustachian tubes open.

When to equalize? Sooner and more often then you think.