The Editor says: Scuba diving is an extremely safe water activity. As long as you follow the guidelines and SOPs of your training agency, you can glide through the ocean and enjoy the breathtaking underwater scenery. That said, the underwater environment is fundamentally different from dry land, and the physiological changes triggered by shifts in the physical laws of nature can cause discomfort — and even real risk — during a dive. Let's take a look at what Dr. Tsai Kai-Yu, ENT and Head & Neck Surgery Specialist, has to share about common causes of diving-related physical discomfort and how to address them!
More and more friends have recently been asking Dr. Tsai Kai-Yu about physical discomfort experienced after diving, as well as general diving precautions. Dr. Tsai has compiled a list of the most frequently asked questions from the diving community and provided possible explanations for your reference!
What Are the 3 Types of Diving?
For those unfamiliar with diving, it actually encompasses three common forms:
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Snorkeling
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Scuba diving (with a tank)
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Freediving (without a tank)
Before Reading On, Here Are a Few Physics Principles You Should Know:
1. Changes in Water Pressure
As a general rule, pressure increases by one atmosphere for every 10 metres of depth — a fairly dramatic change in pressure.
2. Boyle's Law
At a constant temperature, the volume of a gas is inversely proportional to the pressure applied to it. This means that the air-filled cavities in the body are prone to squeeze injuries (barotrauma) during descent. Which cavities are we talking about? The middle ear, inner ear, sinuses, teeth/periodontal spaces, throat and trachea, lungs, and gastrointestinal tract, among others.
3. Henry's Law
The solubility of a gas in a liquid is directly proportional to the pressure of that gas above the liquid. This means that the deeper a scuba diver goes, the more gases — including oxygen, nitrogen, and helium — dissolve into the body. This can lead to oxygen toxicity, nitrogen narcosis, and decompression sickness (DCS) caused by ascending too quickly without proper decompression stops.
Common Questions — Answered
Ear Pain After Diving:
This is probably the most common issue beginners encounter, and even seasoned divers may run into it from time to time. The air-filled space behind the eardrum is called the middle ear. Its pressure is regulated through the Eustachian tube, which connects to the nasopharynx at the back of the nasal cavity. Chronic nasal allergies, a deviated nasal septum, colds, sinusitis, nasal polyps, or adenoid hypertrophy can all impair Eustachian tube function. When ambient pressure rises during descent, the tube may fail to open properly and allow air into the middle ear for equalization — resulting in a middle ear squeeze.
Middle ear squeezes range in severity from mild eardrum redness and swelling, to fluid accumulation, bleeding, middle ear infection (otitis media), and even eardrum rupture. This can also occur when a diver hasn't mastered equalization techniques — for example, the Valsalva maneuver commonly used in scuba diving, or the Frenzel Maneuver used in freediving. If you experience a middle ear squeeze or difficulty with ear equalization, it is recommended that you see an ENT specialist for an endoscopic evaluation of the nasal cavity and Eustachian tube, along with tympanometry to assess the severity.
Unlike a middle ear squeeze, a more serious inner ear squeeze can result in hearing loss, tinnitus, and vertigo — this is a medical emergency and requires prompt attention from an ENT specialist. A similar condition, inner ear decompression sickness (DCS), has a very different treatment protocol and must be distinguished by an experienced physician.
Nosebleed After Diving:
This is another frequently encountered issue. Some instructors tell their students it's caused by pinching the nose too hard — but that's not usually the case, unless the mucous membrane or blood vessels at the front of your nasal septum are particularly fragile. In most cases, the bleeding originates from a sinus squeeze, or from blood that has traveled from the middle ear through the Eustachian tube into the nasal cavity following a middle ear squeeze.
Headache After Diving:
There are several common causes:
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Sinus squeeze headache — the location varies depending on which sinus is affected; for example, frontal sinus pain presents in the forehead, maxillary sinus pain in the cheeks, ethmoid sinus pain around the eye sockets, and sphenoid sinus pain at the back of the head.
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Tension headache: a muscle-origin pain, often caused by excessive tension in the water or clenching the mouthpiece too hard.
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Elevated carbon dioxide levels in the blood, causing cerebral vasodilation and resulting in a headache similar to a migraine.
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Decompression sickness (DCS)-related headache, which usually occurs alongside other DCS symptoms.
Dizziness After Diving:
Common causes include the caloric response triggered by cold water in the inner ear, pressure imbalance between the two ears, inner ear squeeze or perilymph fistula, oxygen toxicity (which can occur with pure oxygen at pressures of 1.5–2 atmospheres or above), and nitrogen narcosis (at 30 metres underwater, the level of nitrogen narcosis is roughly equivalent to drinking one martini — and increases by one martini equivalent for every additional 10 metres of depth).
Coughing Up Blood After Diving:
Possible causes include a throat or tracheal squeeze, or a pulmonary squeeze resulting in hemothorax. It is recommended to seek evaluation from both an ENT specialist and a pulmonologist.
Chest Pain and Difficulty Breathing After Diving:
This is typically caused by a pulmonary squeeze leading to pneumothorax, or alveolar rupture causing hemothorax. This is a medical emergency — seek immediate emergency treatment.
Decompression Sickness (DCS):
According to Henry's Law, when the pressure of a gas above a liquid decreases, the amount of that gas dissolved in the liquid also decreases. Nitrogen is a gas that dissolves in body tissues and fluids. When the body is exposed to a sudden reduction in ambient pressure, nitrogen is released from the blood into the tissues. If nitrogen escapes from the body's fluids too rapidly, bubbles form inside the body, causing DCS symptoms such as skin itching and rashes, joint pain, sensory impairment, paralysis, and even death. It is therefore essential to observe proper decompression stops and to avoid flying on the same day as a dive (as this effectively subjects the body to a second round of decompression). Treatment involves recompression in a hyperbaric chamber with breathing of pure oxygen — known as hyperbaric oxygen therapy.
Shallow Water Blackout:
This occurs during freediving. On descent, the rising partial pressure of oxygen leads to unconscious overconsumption of oxygen. During rapid ascent, the partial pressure of oxygen drops suddenly, causing cerebral hypoxia and temporary loss of consciousness — a form of blackout.
Dr. Tsai Kai-Yu ENT and Head & Neck Surgery Specialist Hyperbaric Oxygen and Undersea Medicine Specialist
Cover image source: Image by David Mark from Pixabay
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