Lung Squeeze in Freediving: Symptoms, Causes and Recovery

Lung squeeze is a pressure injury to the lungs or airways that happens when a freediver goes deeper than their chest can comfortably cope with. Small blood vessels in the lungs or windpipe break, and the diver typically surfaces coughing, with a tight chest and sometimes blood-streaked saliva. Any suspected lung squeeze means you stop diving and get a medical assessment. Most cases come from depth jumps, tension or sudden movements at depth, and most can be prevented with patient progression.

What lung squeeze actually is

As you descend, water pressure compresses the air in your lungs. At 10 metres that air occupies roughly half its surface volume, at 30 metres roughly a quarter. Our guide to Boyle’s law has the full table. Your body adapts: the chest wall and diaphragm flex inward, and blood shifts into the vessels in and around the lungs to fill the space. This blood shift is one of the reasons freedivers can go as deep as they do, and our post on blood shift and bradycardia explains how it works.

A lung squeeze happens when that adaptation isn’t enough, or when the tissues are strained too quickly. Tiny blood vessels rupture and blood and fluid leak into the airways or air sacs. Doctors call it pulmonary barotrauma of descent. When the injury is higher up, in the windpipe or throat, freedivers often call it a tracheal squeeze; the typical signs are a hoarse voice and blood without much chest discomfort.

It is a different injury from the lung over-expansion that scuba divers can suffer on ascent, which happens when someone breathes compressed air at depth and holds it on the way up. A freediver can get that injury too, by taking a breath from a scuba diver’s regulator underwater. Never do it.

Symptoms of lung squeeze

Symptoms usually show up at the surface or within minutes:

• coughing, sometimes persistent
• pink, red or blood-streaked saliva or phlegm
• a metallic taste in the mouth
• a tight chest, chest pain or pain on a deep breath
• shortness of breath, wheezing, or a crackling or bubbling feeling when breathing
• a hoarse or weak voice, more typical of tracheal squeeze
• unusual tiredness or breathlessness over the following hours

Blood near the face doesn’t always mean lung squeeze. Mask squeeze and sinus squeeze can cause nosebleeds, or blood that runs down into the throat from the sinuses. If you are coughing blood up from your chest, assume it’s your lungs until a doctor says otherwise.

What causes lung squeeze in freediving

• Depth jumps. Going several metres deeper than your recent comfortable depth in one session.
• Tension. A tight chest, shoulders or throat at depth stops the chest adapting.
• Poor thoracic and diaphragm flexibility. A stiff ribcage has less room to compress safely. Regular, gentle stretching for freediving helps.
• Contractions at depth. Strong diaphragm contractions near the bottom put sudden strain on the lungs.
• Sudden movements at depth. Looking up sharply, twisting during the turn or yanking hard on the line.
• Exhale dives. Starting on partly empty lungs means reaching very small lung volumes at much shallower depths. Only do these under an instructor’s supervision.
• Skipping the warm-up. Starting the day with your deepest dive, especially in cooler water.

A smooth bottom turn with the head kept neutral removes one of these triggers. Some divers also seem more prone to squeezes than others, for reasons that aren’t fully understood.

What to do if you think you have a lung squeeze

1. Stop diving immediately. No “one last easy dive”. Your day is over.
2. Get out of the water and sit upright somewhere comfortable and shaded. Avoid any effort.
3. Breathe slowly and stay calm, and have someone stay with you.
4. Use first aid oxygen if it’s available and someone is trained to give it. Many dive boats and centres carry it for diving injuries.
5. Don’t take medicines on guesswork. Ask a doctor first.
6. Get medical help. Call emergency services straight away if there’s difficulty breathing, ongoing bleeding, chest pain, confusion or blue-tinged lips. For milder symptoms, see a doctor the same day.

Tell the doctor you were freediving and how deep. Similar symptoms can come from other conditions, such as immersion pulmonary oedema, which affects some swimmers and divers and needs proper assessment. Symptoms can also worsen over the first few hours, so a mild cough at the boat doesn’t guarantee a mild injury.

Resist the urge to play it down. Divers often feel embarrassed after a squeeze and insist they’re fine. A buddy who saw you surface coughing should end the day for both of you and make sure you get checked.

Safety: Coughing up blood, chest pain or difficulty breathing after a dive always needs a doctor. Don’t dive again until a doctor has cleared you, even if you feel fine the next morning.

How long does lung squeeze recovery take?

There’s no reliable number to give you. A minor squeeze may settle within days; a more significant one can take weeks. A doctor may want to listen to your chest, check your oxygen levels or arrange imaging before advising you. If you have a flight coming up soon after the injury, ask about that too.

Once you’re cleared, go back gradually. Start with pool sessions and shallow, relaxed dives, and rebuild depth over several sessions. Work out what caused the squeeze first, with your instructor if possible, or you’re likely to repeat it.

How to prevent lung squeeze

• Increase depth in small steps, a metre or two at a time, and only once your current depth feels easy. Our post on how deep a beginner can freedive covers realistic progress.
• Warm up with a few progressively deeper dives before any deep one.
• Stretch your chest and diaphragm regularly on land, gently and never to the point of pain.
• Stay relaxed at depth. If your chest feels tight or contractions start hard at the bottom, turn.
• Keep your head neutral and your movements slow near the bottom.
• Leave exhale dives and personal-best depths for sessions with an instructor.
• Don’t chase a new depth on the last, tired day of a trip.

Before your next depth trip

Write down the deepest dive you’ve done comfortably in the last few months, and plan your trip around small steps from there, not around the number you’d like to post. Add a few weeks of thoracic stretching beforehand. And agree with your buddy now that any blood coughed up ends the day, without debate.

If you’re travelling for a training block, schedule your deepest dives for the middle of the trip rather than the last day or two. That way a bad day, a cold or a minor squeeze doesn’t push you into a rushed decision before the flight home.

Stay tuned for the freediving.in community, launching soon.