Underwater Equalization
Equalization
The term equalization can have many meanings. We often use it in scuba to be synonymous with the Valsalva Maneuver or in freediving to be synonymous with the Frenzel Maneuver. These are not all-encompassing terms and can lead to confusion if we are not careful. The techniques we use to equalize airspaces when we are experiencing changing pressures while diving are not unique just to our sport. For example, the Valsalva Maneuver is used to treat and diagnose different cardiac anomalies as well as being a technique to equalize airspaces in the body. We need to ensure that when we are using these terminologies, we understand the difference between the true meaning of these words and the vernacular. In the world of diving many people have started using the term equalization to mean the performance of the act of mechanically influencing the movement of gas in our airspaces.
Equalization is purely the balancing of something between two areas. It’s critical to understand that in our sport we were dealing with and referencing pressure inside of different airspaces. Equalization in this specific instance means movement of gasses from higher pressure to lower pressure in our bodies. During diving when we equalize airspaces, we are taking taking high pressure gas and moving it to the lower pressure area via some type of connection between those spaces. When we talk about complications in equalization of our airspaces we are talking about some sort of blockage or prevention for that gas to flow freely.
Although there are many airspaces in our bodies, let’s focus on the equalization of the pressure in our ears. In this specific case there are tubes that connect are middle ear to our throat, these are called Eustachian tubes. At rest these tubes stay closed. However, when we chew, swallow, or move our jaw we often open these tubes. These tubes function to equalize the pressure of the middle ear with the outside air pressure. This equalization of pressure happens when the middle ear has a higher pressure, or lower pressure, then the surrounding air pressure. We equalize our middle ear often throughout our everyday lives.
What’s Happening During Equalization?
Let’s dive into what happens with changing pressure underwater. First, we will address the situation where the middle ear has a higher pressure than the surrounding pressure. This situation in diving would happen upon ascent. As we ascend the surrounding water pressure decreases as we get shallower in the water column. Equalization must happen because we have a pressure difference between the middle ear (higher pressure) and the surrounding air pressure (lower pressure). Luckily this equalization tends to happen by what’s called passive equalization. The higher pressure of the middle ear easily opens the Eustachian tube and equalizes the pressure between the middle ear and the surrounding air pressure in the throat. If this equalization doesn’t happen easily is what it’s called a reverse block. In this situation you would not want to add extra pressure to the middle ear so a technique like the Valsalva would be undesirable. We would however want to aid in the equalization of the pressures between the middle ear and the surrounding air pressure. We will shortly discuss other types of equalization methods that open Eustachian tubes without adding pressure to the middle ear. Techniques that involve pushing your jaw forward and / or swallowing are what we would use if we felt discomfort or needed to help equalize our airspaces on ascent where the pressure of the middle ear is greater than the surrounding air pressure.
The more common situation and the more noticeable equalization you see in diving involves the opposite situation. While descending the pressure outside the body, and in the airway, exceeds the pressure of the middle ear. Let’s revisit the fact that the eustachian tubes remain closed at rest and this makes it harder to have passive equalization with this pressure differential. The gas you are breathing, or in the case of freediving that is in your airway, needs help to find its way into that Eustachian tube. Physiologically this could be by encouraging gas into that tube and thus opening it or utilizing the movements of our jaw and throat to open this tube and allowing for equalization to occur. The following techniques and methods are ways that we can equalize our airspaces. Remember we are trying to get high pressure gas to flow towards lower pressure and create an isobaric (equal pressure) situation.
Equalization Techniques
Passive equalization
Passive equalization requires no action or effort from the diver. The passage between the high pressure and low-pressure gas is already open or is opened by the high-pressure gas and we reach an isobaric situation with no involvement of the diver.
Valsalva Maneuver
This maneuver requires a delicate touch and is highly effective but caution must be used. This is the most commonly taught maneuver to equalize in scuba diving. To execute this maneuver, the diver pinches their nostrils while gently blowing through their nose utilizing their diaphragm and intercostal (chest) muscles. The higher-pressure gas is forced through the Eustachian tubes into the middle ear thus equalizing or creating a slightly higher pressure inside the middle ear. It is easy to over pressurize these spaces and cause a barotrauma (injury from excessive pressure).
Frenzel Maneuver
This maneuver may appear very similar to the Valsalva maneuver however it utilizes the muscles of the neck, jaw, and tongue to open their Eustachian tubes which is much safer than the Valsalva. This technique increases the pressure of the middle ear and it’s used to equalize on descent. To perform this maneuver, the diver first must have a marshmallow size bubble of air in their mouth, then pinches their nostrils, shuts their throat like they are about to take a drink of water. The diver then presses their tongue toward the roof of their mouth, while the forward edge of the tongue is sealing against the roof just behind their teeth, raising their voice box upward also helps with compressing the tongue against the roof, while holding open the soft pallet, allowing the compressed air to pass into the sinuses and Eustachian Tubes. The easiest way to fill the mouth with air prior to conducting the Frenzel maneuver, is to make a “guh” sound, also known as a grouper call.
Other methods
Other methods involve pinching your nose, blowing, swallowing, and pushing your jaw forward. These different methods are described as the Voluntary Tubal Opening, Toynbee Maneuver, Lowry Technique, and the Edmonds Technique. Here is a general overview of what each of these is:
- Voluntary Tubal Opening – Push your Jaw forward.
- Toynbee Maneuver – Swallow while pinching your nose.
- Lowry Technique – Swallow while performing a Valsalva.
- Edmonds Technique – Push your jaw forward while performing a Valsalva.
Different combinations of these work better in some situations over others and there is a large amount of personal preference. On ascent equalization is better done by using a combination of these techniques that involve swallowing and pushing your jaw forward and avoiding techniques that would increase your middle ear pressure. If you are having trouble equalizing your air spaces during ascent or descent please reach out to your SDI Scuba Instructor or your PFI Freediving instructor for more help.
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