Middle-Ear Equalisation

Middle-ear equalisation is a basic, essential diver skill that equalises the pressure in the sinuses and middle-ear spaces with the ambient pressure. To be a safe diver and avoid middle-ear injuries, you must understand the effects of pressure changes and learn how to actively let air into your middle ears through your Eustachian tubes.

Mechanisms of Equalisation

Middle Ear

The middle-ear cavity is bounded by rigid structures except for the eardrum. When ambient pressure increases, the only way for the middle-ear volume to decrease is through the bowing of the eardrum into the middle-ear cavity. After the eardrum stretches to its limits, further reduction of the middle-ear cavity volume is not possible. If you continue descending, the pressure in the middle-ear cavity remains lower than its surroundings. The only way to change this pressure difference is to add gas to the middle-ear space.

In a typical middle ear, the Eustachian tube, which connects to the nasal cavity, is the only way to add gas. The Eustachian tubes are normally closed. Every time we swallow or yawn, the muscles in our throat allow for a small transient opening that is enough to ventilate our middle ear and compensate for pressure changes. Nothing challenges our ears and Eustachian tubes more than scuba and breath-hold diving.

Descent

As divers descend, the ambient pressure increases linearly at a rate of one-half pound per square inch (psi) for each foot (or 0.1 kg/cm² for each meter). This increase applies to body tissues and fluids. Boyle’s law describes how the volume of a gas decreases when pressure increases if the amount (mass) of gas and the temperature remain the same. A small pressure difference will cause leakage of fluid and bleeding from the eardrum and the mucosa lining the middle-ear cavity (ear barotrauma O’Neill Grade 1). When the pressure difference reaches 5 psi (0.35 bar), the eardrum may rupture in some divers. At a pressure difference greater than 10 psi (0.75 bar), a rupture will occur in most divers (ear barotrauma O’Neill Grade 2). Sudden and substantial pressure changes may also cause inner-ear injury.

Ascent

During ascent, the ambient pressure decreases, and if the gas has no way to leave the middle-ear cavity, the pressure in the middle ear remains elevated. When the pressure in the middle ear exceeds surrounding pressure by 15 to 80 centimetres of water (cm H₂O), which corresponds to an ascent in the water of 6 inches to 2.5 feet, the Eustachian tubes open, and surplus gas escapes. If your ears do not equalise at the same rate and the pressure difference reaches about 66 cm H₂O (equivalent to 2 feet of water), alternobaric vertigo may occur. Upper respiratory tract infections, hay fever, allergies, snorting drugs, cigarette smoking or a deviated nasal septum may compromise equalisation.

Techniques

When properly employed, the following equalisation techniques are effective in middle-ear and sinus equalisation in healthy divers.

• Passive: Requires no effort; occurs during ascent
• Voluntary Tubal Opening: Yawn or wiggle your jaw
• Valsalva Maneuver: Pinch your nostrils and gently exhale through your nose
• Toynbee Maneuver: Pinch your nostrils and swallow (useful for equalising during ascent)
• Frenzel Maneuver: Pinch your nostrils while contracting your throat muscles and make the sound of the letter K
• Lowry Technique: Pinch your nostrils and gently try to exhale through the nose while swallowing (a combination of the Valsalva and Toynbee maneuvers)
• Edmonds Technique: Push your jaw forward and do the Valsalva or Frenzel maneuver

Tips for Equalisation

• Before descent, while you are neutrally buoyant with no air in your BCD, gently employ one of the listed techniques to add air to your middle ears and sinuses as you descend.
• Descend vertically, feet first, to allow air to travel naturally upward into the Eustachian tube and middle ear. Use a descent line or the anchor line to control your speed.
• Gently inflate your ears every few feet for the first 10 to 15 feet.
• Pain is not acceptable. If you have pain, you have descended without adequately equalising. Ascend a few feet until the pain stops.
• If you do not feel your ears equalising, stop descending and try again. You may need to ascend a few feet to reduce the ambient pressure. Do not bounce up and down.
• It may be helpful to tilt your blocked ear toward the surface.
• If you are unable to equalise, abort the dive. The consequences of descending without equalising could ruin an entire dive trip or cause permanent damage or hearing loss.
• If at any time during the dive you experience pain, vertigo or sudden hearing loss, abort the dive. If these symptoms persist, do not dive again and consult your physician.

Medications

• Some divers use decongestants (oral medications or nasal sprays) before diving to reduce swelling in the Eustachian tubes and nasal passages. Talk to your doctor before using these medications prior to diving, and be aware that if they were to wear off during a dive, a reverse block may occur.
• Take caution when using over-the-counter nasal sprays. Repeated use can cause a rebound reaction resulting in increased congestion and a possible reverse block on the ascent.
• Decongestants may have side effects. Do not use them before a dive if you do not have previous experience with them and know how they will affect you.