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People with asthma have typically been prohibited from scuba diving due to the perceived risks associated with narrowed airways when you need to breathe underwater in a pressurized environment.

But there’s not enough scientific evidence to suggest that people with mild or controlled asthma are more likely to have severe symptoms or complications during scuba diving than people without asthma. Many experts agree that people with asthma can scuba dive safely if they have normal lung function.

Keep reading to learn about what the latest research has found about diving with asthma and what the potential risks are.

Asthma involves a chronic inflammation of the lungs that causes a narrowing and swelling of your airways, sometimes making it dangerously difficult to breathe. The Centers for Disease Control and Prevention (CDC) estimate that asthma affects about 25 million Americans.

Whether people with asthma can safely dive remains a controversial topic. Many experts now suggest that some people with asthma may be candidates for diving if they have normal lung function.

Many diving societies have often prohibited people with asthma from diving due to the risks of triggering airway inflammation. This is because diving exposes people with asthma to several possible triggers that can increase the chances of a potentially lethal asthma attack underwater, including:

These risks are largely theoretical. Little evidence is available to suggest that people with mild and controlled asthma are at more risk during scuba diving compared to people without asthma.

But it’s thought that current studies may underrepresent people with severe or uncontrolled asthma — who may be at a much higher risk of drowning or severe health complications than people with mild or controlled asthma.

Diving always comes with some risks, such as drowning or developing decompression sickness. But diving is also thought to expose people with asthma to several risk factors for developing bronchospasms and asthma attacks.

Bronchospasms are a tightening of the muscles that line the large airways in your lungs, called bronchi. They can lead to obstruction of your airways and air trapping.

When you ascend from diving, the air in your lungs expands due to changes in pressure before you breathe it out.

If you have a blockage from inflammation or tightening in your lungs or airways, trapped air can cause a rupture of your lungs that leads to potentially fatal conditions such as collapsed lungs or air embolism. This happens when air bubbles enter your blood.

If a diver has an asthma attack underwater, they may not have enough energy to come back to the surface and could drown.

Other respiratory conditions, such as chronic obstructive pulmonary disease and cystic lung disease, can also cause air trapping.

If you have asthma, get medical clearance from your doctor before diving. All people who want to scuba dive need to have some swimming ability and maintain a certain level of strength and cardiovascular fitness.

According to the Undersea & Hyperbaric Medical Society, doctors typically assess whether you can safely dive with asthma by determining:

  • how well your asthma is controlled
  • what your triggers are

While evaluating whether you can safely dive with asthma, your doctor will likely consider factors such as:

  • your asthma history
  • results of allergy tests
  • spirometry
  • result of bronchial challenge test

Asthma history

People with a history of sudden asthma attacks may not make good candidates for diving.

People with asthma induced by exercise, cold, or emotions such as stress may also not make good candidates.

Results of allergy tests

Contaminants in compressed air, such as pollen, can potentially trigger an asthma attack in some people.

People with allergic asthma may still be able to dive if their asthma is well controlled, and they have normal lung function.

Spirometry

Spirometry is a test that measures how well your lungs function.

This test involves breathing into a machine that measures the amount and rate you can inhale and exhale.

Bronchial challenge test

Some diving societies recommend that people with asthma pass a bronchial challenge test (sometimes called a methacholine challenge test or bronchoprovocation test) before diving.

This test involves inhaling the drug methacholine, which causes your airways to narrow. The goal of the test is to measure how reactive your lungs are and your level of airway irritability. It’s also conducted with supervision by a doctor, so there’s no need to be concerned that your reaction will be severe or dangerous.

Before diving with asthma, the United Kingdom Diving Medical Committee recommends the following:

  • Measure peak flow with a spirometry test twice per day for at least 3 days before diving, and avoid diving if your score drops 15 percent below normal.
  • Avoid diving until your peak flow is normal for at least 48 hours if you use a rescue inhaler.
  • Abandon your dive if you become wheezy or short of breath at any point.
  • Ascend slowly from your dive, particularly in the last 5 meters.
  • Take a rescue inhaler 30 minutes before diving to reduce risk of bronchospasm.
  • Seek medical advice before diving if there are any changes in your asthma control.

Other general ways to stay safe while diving include:

  • Avoid diving if your asthma is exacerbated by cold, exercise, or emotion.
  • Always discuss your asthma with your doctor before diving.
  • Avoid diving if you’re experiencing breathing problems or a flare-up of symptoms.
  • Never dive alone.
  • Do not dive if you have congestion in your nose or ears.
  • Follow all your diving instructor’s directions.

Many experts consider diving safe for some people with mild and well-controlled asthma if it isn’t induced by exercise, cold temperatures, or emotion.

If you have asthma and you’re interested in diving, it’s a good idea to talk with a doctor. They can help you determine if you’re a good candidate and help you make sure your asthma is under control.