Pulmonary Barotrauma and Scuba Diving

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Natalie Gibb owns a dive shop in Mexico and is a PADI-certified open water scuba instructor and TDI-certified full cave diving instructor.

One of the most important rules in scuba diving is to breathe continuously and never hold your breath.

In basic scuba training, you are taught that you must avoid holding your breath underwater and trapping air in your lungs. If you ascend while holding your breath, your lungs could expand (“explode”) as the air expands. This is known as a pulmonary barotrauma.

Just explaining this is often enough to frighten students into following the rule, but the details of what happens to a diver’s lungs when they over-expand are usually glossed over. For example, did you know that other conditions and actions besides holding your breath can cause lung over-expansion?


Barotrauma refers to a pressure-related injury. The word pulmonary refers to your lungs. A pulmonary barotrauma may also be called: lung over-expansion, burst lungs, or exploded lungs.

May Occur on a Small Scale

The term “exploded lungs” makes a pulmonary barotrauma sound like a very dramatic injury, but it isn’t very likely your lungs are actually going to explode. The alternate names for pulmonary barotraumas make the condition seem catastrophic, but pulmonary barotraumas more often occur on a nearly microscopic level.

At depth, air is caught in the tiny air sacs (called alveoli) where gas exchange takes place in a diver’s lungs. These air sacs are made of extremely thin and fragile tissue. If air is trapped in the sacs as a diver ascends, it will expand from the change in pressure and burst the sacs like many tiny balloons. This air escapes from the lungs and causes various types of damage depending upon where it travels.

Pressure Change

Very small changes in pressure can cause a pulmonary barotrauma. Because the lungs’ air sacs are so tiny and thin, even the pressure that occurs over a few feet can cause injury if air is trapped in the lungs. Divers should remember that the greatest pressure change underwater is near the surface, so all divers, regardless of depth, are at risk. Pulmonary barotraumas have even been documented in swimming pools.

Who Is at Risk

All divers are at risk. Pulmonary barotraumas are caused by expanding air trapped in the lungs and are not related to depth, dive time, or the amount of nitrogen a diver has absorbed underwater.

Actions and Conditions That Cause a Pulmonary Barotrauma

There are three main causes of pulmonary barotrauma:

1. Breath Holding

If a diver holds his breath and ascends as little as 3-5 feet, he is at risk for a pulmonary barotrauma. While most divers know they the shouldn’t hold their breath underwater, panic, out-of-air situations, sneezing, and even coughing can cause a diver to inadvertently hold his breath underwater. Remember that underwater, the simple act of holding your breath will frequently cause you to become positively buoyant and ascend, so it is best to avoid breath-holding while scuba diving.

2. Rapid Ascents

The faster a diver ascends, the more rapidly the air in his lungs will expand. At a certain point, the air will expand rapidly enough that it can not efficiently exit a diver’s lungs, and some of the expanding air will become trapped in his lungs.

3. Pre-Existing Lung Conditions

Any condition that can block and trap air in the lungs can lead to pulmonary barotrauma. Even conditions such as asthma, which only partially obstructs air from exiting the lungs can prevent expanding air from exiting the lungs efficiently on ascent. This includes temporary conditions, such as bronchitis or a cold, and permanent conditions such as scars, fibrosis, and tuberculosis. Aspiring divers with a history of lung problems should undergo a full medical exam by a doctor knowledgeable in diving medicine before undertaking scuba diving.

Scroll down for a more complete list of medical conditions that predispose divers to pulmonary barotrauma.

Main Types

Pulmonary barotrauma can manifest in several different ways.

1. Arterial Gas Embolism (AGE)

If the thin wall of the lungs’ air sacs rupture, air can escape into the small blood vessels in the lungs’ tissues. From there, the tiny air bubble travels to the heart, where it is pumped to any of several places, such as the arteries of the heart and brain. As the diver continues to ascend, the tiny bubble of air will continue to expand until it becomes too big to fit through an artery and is trapped. An air bubble trapped in an artery blocks blood flow, cutting off the oxygen supply to organs and tissues. In extreme cases, an air bubble in the heart’s arteries can cause cardiac arrest, and an air bubble in the brain’s arteries can mimic the symptoms of a stroke.

2. Emphysema

A burst air sac can also force expanding air into the tissues surrounding the lungs. There are two main kinds of emphysema caused by pulmonary barotrauma:

  • Mediastinal emphysema – Air is forced into the tissues surrounding the heart and trachea. Characterized by pain under the sternum, in the chest, and shortness of breath.
  • Subcutaneous emphysema – Air is forced into the space under the skin around the neck and collarbone. There is a characterized “crunchiness” under the skin around the neck and collarbone.
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3. Pneumothorax

Pneumothorax is perhaps the most dramatic of all the manifestations of pulmonary barotrauma. In pneumothorax, air from the burst lung expands into the pleural cavity, or the area between the lungs and chest walls. As the expanding air pushes against the lungs’ thin tissues, it exerts pressure which collapses the ruptured lung. X-rays of pneumothorax show the area once occupied by the lung almost completely filled with air, with the deflated lung compressed to a fraction of its original size. In extreme cases, expanding air on one side of the lung cavity can exert pressure on the heart, trachea, and other lung, causing a tension pneumothorax. This pressure can be so extreme that it visibly distorts the trachea, stops the heart, or collapses the second lung.

Medical Conditions That Predispose a Diver

Both temporary and permanent conditions can predispose divers to pulmonary barotrauma by completely or partially obstructing expanding air from exiting the lungs. Here are some examples of conditions that can cause barotrauma.

  • Temporary conditions – Bronchitis, respiratory tract infections, congestion from allergies, active asthma
  • Permanent conditions – Scarred lung tissue, fibrosis, sarcoidosis, tuberculosis, lung abscesses, damage from severe pneumonia, chronic bronchitis, persistent asthma, tumors, calcified glands, mucous obstructions from heavy smoking
  • BLEBS – Research indicates that BLEBs, balloon-like extensions of the lungs air sacs, BLEBs are believed to reduce the lungs’ elasticity. They release air more slowly during exhalation than the lungs’ air sacs. As a diver with BLEBs ascends, expanding air may not be able to exit the BLEBs rapidly enough, and some expanding air may become trapped in the BLEB, causing it to burst. BLEBs are normally found in chronic smokers but have been observed in non-smokers as well. Divers may be tested for BLEBs using breathing tests, x-rays, and CT scans.

Can Be Distinguished From Other Decompression Illness

While many symptoms of pulmonary barotrauma are similar to those of decompression sickness, pulmonary barotrauma can be distinguished from other dive-related injuries because its effects are immediate, which is not the case with the majority of decompression sickness incidents. According to scuba-doc.com,

“Out of 24 cases of pulmonary barotrauma in United States Navy divers, symptoms of pulmonary barotrauma appeared in 9 cases while the diver was still ascending underwater, in 11 cases within one minute of the diver reaching the surface, and in 4 cases within 3-10 minutes of the diver reaching the surface.”

This seems to indicate that if a diver surfaces with chest pain, stroke-like symptoms, immediately falls unconscious, or manifests other symptoms within a minute or two of surfacing, pulmonary barotrauma should be suspected.

Why Is It Dangerous to Hold Your Breath While Scuba Diving?

buddy breathing bonaire

buddy breathing bonaire

I remember my very first experience with scuba diving, which was a try dive in an indoor pool. The instructor explained how to put on the jacket and breathe from the regulator, equalize our ears and then let us crawl around the swimming pool floor in water shallow enough to stand up in for a couple of minutes. Before the instructor let us vanish under the surface, he said one more thing: Never hold your breath!

You might think that this was not the greatest first dive experience, and in retrospect, I agree, but nevertheless I was instantly hooked! I found breathing under water exhilarating and immediately enrolled in the next Open Water Diver course. Check out the following Scuba Dive Schools worldwide for your next Scuba Dive training:

Where again, I encountered this most important rule when scuba diving, and it was thoroughly drummed into me to never, ever hold your breath!’ This does of course not mean, you have to pump air at an insane rate as some divers seem to think. It just means that you should always keep your airways open so that no air gets trapped in your lungs in case you have to do an emergency ascent.

In this article, we will help to explain the importance of breathing continually while under the water.

You need to understand the physics of diving

To explain and understand the importance of continually breathing underwater we need to look into the physics.

Pressure is everything in scuba diving and as you may know, the deeper you descend, the more the pressure increases. If you think of your lungs for instance, when you take a deep breath above water and then descend five meters, the pressure on your lungs increases and so the volume of your lungs decreases. Even though you haven’t breathed out any of the air, you took in on the surface.

When you breathe air at depth, this air is compressed. And as long as you keep breathing this air can escape. So far so good. If you would breath air at depth and the pressure surrounding you decreases the air will expand. When the air cannot escape in a natural way, it eventually will find a way.

Why is holding your breath while scuba diving so dangerous?

Looking back to the science described above, we can see that as we descend the pressure on our lungs increases and our lung volume decreases. So when we do the opposite and ascend the higher we ascend on one breath of air the more the pressure drops and the more our lungs expand. Overexpansion of the lung can lead to serious injuries.

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There are four categories of lung overexpansion injuries

1. Arterial Gas Embolism (AGE):

When a person suffers from AGE, air diffuses into the blood and makes its way up the minuscule capillaries of the brain, forming an air bubble and consequently blocking the blood carrying vessels.

This obstructs the flow of blood in the body and oxygen supply is cut off to vital body tissues. The consequences can be as deadly as paralysis, brain damage, heart stroke, and death. AGE is the most dangerous effect of a lung overexpansion injury and is potentially fatal.
AGE affects the body at a more rapid rate than any of the other manifestation of lung overexpansion injury.

2. Mediastinal Emphysema (ME):

ME is a condition in which air is trapped in the cavities that surround the delicate heart muscles. This air, in turn, places pressure on the heart muscles, which in turn stop functioning properly; as a result, blood supply to the body becomes erratic. This condition is not as severe as AGE, but extreme Mediastinal Emphysema can lead to heart failure.

3. Pneumothorax:

In this condition, the air is collected at the outer side of the lungs causing the lungs to cave in upon themselves. The victim may end up with partial or completely collapsed lungs. Since Pneumothorax involves injury to lungs, it causes acute pain in the chest which may be accompanied by coughing up blood. Pneumothorax worsens as a diver ascends because the pressure on the damaged lung increases with the ascent.

4. Subcutaneous Emphysema:

Probably the least damaging of all common lung overexpansion injuries, Subcutaneous Emphysema is a condition in which air pockets are formed near the collarbone and the neck. With Subcutaneous Emphysema, there is irritation and squishiness in the skin, which may even crack if it is touched.

Do you remember that dive master on your last dive trip?

When the first people start their ascent, he would inflate his SMB (surface marker buoy) by letting a little bit of air in at depth and then releases it. When it reached the surface, the air inside the buoy expanded and completely filled the SMB with air making the buoy stand up in the water so it can be seen by boat drivers and surface support.

If the dive master added to much air into the SMB at depth, it would have ruptured before it made it to the surface. Now imagine that bouy being your lungs. Therefore the simple rule “Never hold your breath while scuba diving

Better safe then sorry

If you want to get all technical about it, it is possible to hold your breath while scuba diving as long as you neither ascend or descend.

The reason why you are taught to never, ever hold your breath is because it is an easy bad habit to fall into and one that when done unknowingly can lead to severe illness or even death.

Even if you lose your regulator underwater or run out of air, you should breathe out as you ascend to the surface (don’t worry, this is easier than it sounds, since you are only releasing the excess air from your lungs as it expands!)

After all that is said and done, remember that there are other contributing factors that will make you more susceptible to a lung overexpansion injury.

You should avoid diving with a cold, chest infection (even minor) or any form of congestion (do not dive with a cough!). If you are a smoker, quit, or at least do not smoke two hours before the dive and in the case of a history of lung injury, get checked by a physician.

And always remember that diving is not a high-risk sport, and accidents are very rare. You probably are at higher risk of slipping by the pool or on the boat and hitting your head or breaking a leg! And then there are always the falling coconuts to watch out for!

Blog written by Rutger who is an avid scuba diver and loves to travel, dive and write about scuba diving. Based in Amsterdam, he at least twice a year plans a dive trip of the beaten track.

This article is published by The Scuba Page, the online magazine for Scuba Dive lovers around the world. The Scuba Page is part of RUSHKULT: the online booking platform for adventure sports. Visit the RUSHKULT platform to book your next Scuba Dive training, guided trip and accommodation.

Why is inhaling while ascending safe, if breathing holding will cause lung over expansion?

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So the reason we say never hold your breath on scuba is because it’s the easy way to prevent an issue.
Physiologically there is a HUGE difference between “holding your breath” and “not actively breathing”. That difference is whether or not the epiglottis is open or closed.
When you take a breath in and are asked to “hold your breath”, if you pay attention to your throat you can actually feel when you stop inhaling when the epiglottis closes. The reason this matters is that the epiglottis can hold back a higher pressure than the lungs can withstand. I.e. the lungs are the weak link in the chain and if you are “holding your breath” with the epiglottis closed the lungs will burst before the epiglottis lets go.
When you are actively inhaling or exhaling, the epiglottis is open and as long as it is open it is highly unlikely for you to be able to suffer a lung over expansion injury. I suppose it is possible but you would have to do something pretty egregious so it is highly implausible. The same applies to when you “pause breathing”, so long as the epiglottis is open, there won’t be a differential pressure between your lungs and your open air cavities *sinus, mouth, nose, etc. that can equalize with ambient pressure*.

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thank you that was very informative and helpful!

I just took a deep breath then stopped inhaling to feel the epiglottis close and I think I can feel it close. Its very cool you can actually feel if its opened or close and control it, I guess its one of those things you never think about that’s on auto pilot.

Maybe to some extent it takes a little practice to keeping the epiglottis open correctly, but I assume that comes with time and experience diving

Rollin Bonz

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Messages 700 Reaction score 675 Location Georgia, the state, not the country 😉 # of dives 500 – 999

thanks, and very interesting. so regardless if your lungs are full of air, the pressure will force the excess air out as long as your airway is open

@tbone1004 did a superb job of explaining it. The easiest way to ensure your away is open is to keep breathing (i.e. don’t hold your breath). You don’t HAVE to be actively breathing to maintain that open airway, but it’s the easiest way to know for sure, and it’s something you can actively “do” rather than “relax” your airway, which is hard to know if you’re doing.

What you know ’bout Rollin’ down in the deep?
When your brain goes numb, you can call that mental freeze
When these people talk too much, put that *stuff* in slow motion, yeah
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thank you that was very informative and helpful!

I just took a deep breath then stopped inhaling to feel the epiglottis close and I think I can feel it close. Its very cool you can actually feel if its opened or close and control it, I guess its one of those things you never think about that’s on auto pilot.

Maybe to some extent it takes a little practice to keeping the epiglottis open correctly, but I assume that comes with time and experience diving

I’m also a professional wind musician so I’ve always paid attention to breathing but you can definitely feel it when it closes because your diaphragm won’t really let you create a vacuum in your lungs and it feels weird. You can push against the epiglottis and build pressure from your diaphragm and then open it. With time you can mess around with it and really get a feel for what your body is doing.
As instructors though, the reason we ask for small bubbles whenever the regulator is out of your mouth is because it’s the only way we know that you don’t have it closed. There is a bit of fear mongering that happens from most instructors who don’t fully understand the physiology behind it and from the ones that do, they often don’t have the time or interest from the students in why so it is undoubtedly easier to just say “never hold your breath, exhale small stream of bubbles whenever the regulator is out of your mouth”.

In terms of diving though, the key is really to just keep a natural breathing pace. We talk about the “scuba breath” and breathing from the bottom of your lungs which is important to prevent a buildup of CO2, but that doesn’t mean that the rate of breathing both in terms of volume and respirations per minute should be anything you think about. If you’re just casually diving you should be breathing similarly to walking down the street and if you’re hovering over a coral head then it’s the same as sitting on the couch reading Scubaboard. Volume is not big, frequency is quite low. If you pay attention to your breathing you will find your natural pace of breathing and habits that make you feel comfortable.
Part of that comfort is how your breathing affects your buoyancy. I like to be slightly negative on an empty breath so my breathing pattern is a fairly rapid inhale, pause, slow exhale for about half of my breath, then a rapid exhale to purge everything out and then rapid inhale again. This keeps my position in the water quite stable and on a normal sized breath if I’m pausing at the end of the inhale I don’t rise in the water column. A slightly bigger breath and I’ll go up but normal is stable. Exhale is going down hence the rapid second half of exhale and immediate inhale again. This actually follows what I do playing instruments so it’s a natural breathing pattern for my body but some of my buddies who are athletes have completely different breathing patterns so it’s all unique to what your body is comfortable doing.

Source https://www.liveabout.com/pulmonary-barotrauma-and-scuba-diving-2963056

Source https://rushkult.com/eng/scubamagazine/never-hold-your-breath/

Source https://scubaboard.com/community/threads/why-is-inhaling-while-ascending-safe-if-breathing-holding-will-cause-lung-over-expansion.626608/page-2

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