Spitting blood after freediving: squeezes and squeeze-like symptoms

Spitting blood after freediving: squeezes and squeeze-like symptoms

You might have come up from a dive and coughed up some foamy pink mucus, or some phlegm with blotches of blood in it. Chances are that you experienced a squeeze. We will discuss the causes for squeezes and squeeze like symptoms in this article. If at some point you were spitting blood after freediving and wondered what was going in, keep on reading.

As usual, remember that I am not a doctor. The symptom of spitting or coughing up blood is called hemoptysis and can have numerous (potentially life-threatening causes). If in doubt, see a doctor.

True squeezes

Squeezes happen when the negative pressure on the lungs or trachea is too much for the tissue to handle. Squeezes commonly do not occur unless you reach residual lung volume. Residual lung volume is reached between 25 and 45 meters for most divers, depending on how big the inhalation was and if the diver packed or not. A squeeze may occur at shallower depth if you have bad posture, or if you have heavy contractions.

Trachea squeeze

The trachea squeeze might be the most common squeeze type. The trachea is the least compliant to pressure changes. It is essentially a tube reinforced with cartilage rings. These cartilage rings don’t stretch very well and keep the trachea open, even if you would rather have it collapse. Blood vessels along the wall of the trachea can rupture if the negative pressure becomes too high.

Phlegm from the trachea looks white, transparent colourless, or transparent yellowish (opaque yellow or green if you have an infection), and will contain blotches or strings of blood if you have a squeezed trachea.

spitting blood after freediving
Find the trachea, lungs and alveoli here.

Lung squeeze

The lungs are soft spongy organs that stretch and compress better than the trachea, but unfortunately they can still get squeezed. If the lungs are subject to negative pressure, yellow fluid can start to leak into the lungs from the alveolar capillaries. Although this is not diagnostic of a squeeze, it does mean that you are descending to depths at which you may be at risk.

If the negative pressure increases, capillaries in the lungs may start to rupture, causing blood to fill the alveoli. This is called a lung squeeze.  If you have suffered a lung squeeze you will cough up pink foamy mucus.

What do you do after a squeeze?

There are no set guidelines for how to deal with squeezes. Most teaching organizations will state you need to be medically cleared for diving by a specialized doctor. Although I agree, my guess is that most divers do not follow this mandate.

Another recommendation that I have seen is as follows:

If your sputum (sputum = what you cough up) contains less than 50% blood, take one week off diving. If your sputum contains more than 50% blood, take two weeks off diving. If you only cough up blood, seek medical attention as soon as possible.

This is a more conservative approach:

If you see less than 25% of blood in your sputum, take one week off diving. If you see 25 – 50% of blood in your sputum, take two weeks off diving. Seek medical attention if:

  • You see more than 50% blood in the sputum
  • You cough up fresh blood more than 12 hours after the dive
  • Other symptoms such as pain or tightness in the chest are severe
  • Any symptoms persist for more than 5 days
  • SaO2 is <95% more than 15 minutes after the dive

Note that the symptoms will probably be gone within a day or two. This does not mean you can go back to diving again. The damaged tissue will likely still be weak and you should give it ample time to heal.

Protecting yourself against squeezes

  • Technique

To avoid getting squeezed, practice your technique at maximum 20 meters depth. Until you can do a dive with perfect posture (including the turn), do not dive deeper.

  • Stretching

Intercostal and diaphragm stretches will help increase the flexibility of the ribcage, and protect yourself against squeezes. In Pre-Dive Preparation, Sara Campbell teaches excellent stretching routines.

  • Gradual adaptation

Your body protects the trachea and lungs by blood shift, an effect of the diving reflex. Your adaptation to depth should be gradual to allow your body to get used to the depth and the required blood shift. In Holistic Freediving, Eric Fattah shares methods of training the dive reflex.

Not all squeezes are squeezes?

From April 2016 onwards, I started getting squeeze like symptoms on dives shallower than 25 m. These dives were well in my comfort zone, my average leisure dive was about 20 – 30 m. I would come up and cough up bloody sputum, indicative of a trachea squeeze. One time, the issue seemed to start 5 minutes after my last dive.

I took a week rest every time it happened and started more serious stretching of the lungs and trachea, to no avail. After I got back to diving, it was only a matter of time before the next ‘squeeze’.

It took me a while to figure out what was going on.

The ‘squeezes’ started after I moved to a busy intersection, with poor air quality. During that time, I had more colds, and often had an aggravated throat. I was more ‘phlegmy’ to start with. After I realized that the ‘squeezes’ started after I moved places, I bought a HEPA (high efficiency particulate absolute) filter and put it in the bedroom.

End of story.

Since I have started using a HEPA filter I have not once had squeeze like symptoms despite diving deeper, I’ve had better sleeps, and less colds. Starting your dive with an aggravated throat greatly increases the chances that you burst a blood vessel in the throat. Poor equalization technique probably increases the risk. Although the symptoms are the same as those of a trachea squeeze, these are not squeezes. They may occur simply when you clear your throat at the surface after a dive.

Immersion pulmonary edema

A phenomenon that results in similar symptoms (to those after squeezes) is called immersion pulmonary edema (IPE). This is a leakage of fluid from the bloodstream into the lungs. It has been reported in triathletes, swimmers, U.S. navy SEALs and scuba divers. You can read more about IPE on the website of DAN (Divers Alert Network). Although IPE may be somehow related to squeezes, the cause is likely different from negative pressure induced edemas.

Please share your experience in the comments.


Jaap is a geologist by trade and a freediver by passion. Jaap wrote the book Longer and Deeper in 2018. His book teaches how to train for freediving and spearfishing on land.

This Post Has 8 Comments

  1. Connor Davis

    Nice job! The “Not all squeezes are squeezes” was especially interesting.

    One aspect not covered and I’m wondering how well (or not) it has be researched. With repeated exposure to negative pressure, the walls of the alveoli seem to get more resistant to seepage into the air sacs as negative pressure increases, ie more resistant to squeeze. Both Murat and E Fattah remarked on this and I’ve certainly experianced it. Other than this kind of personal experiance, what else is out there?

    A bit more discussion of stretching, particularly intercostal and diaphragm, would have been nice. At least for me, it makes a huge difference. I haven’t seen much research on this aspect and would love to know what works for others.


  2. Jaap

    Thanks Connor, Kurt.

    @Connor, as far as I know stretching has not been researched much. But from what I have in my notes, your equalization limit goes from 45 feet to 90 feet just by stretching… If we quantify that you are able to sustain an addtional 15% (40% @ 45 ft to 25% of 90 ft) of chest compression, if you stretch.

  3. Connor Davis

    Thats a little too much stretch. More accurate would be 65 to 90 and that appears to be a combination of better flexibility and increasing resistance to negative pressure in the alveoli. Whatever, 25 ft is a lot. I’m diving 1/2 lung and a very rough equivalent for a full lung diver should be something like 40-50 ft.

  4. Jaap

    In that case the difference turns into about 8%. Definitely still a large difference.

  5. Pete

    It would be interesting to discuss symptoms after a squeeze. I’ve experienced squeezes with the less than 25% of blood in sputum and after the last, I waited a week before diving although I stopped coughing blood the next day. I resumed diving with full lungs to 10m for a week, 20m the week after, 30m 5 days later and am now back to RV depths of 40m. Peers remark how conservative I am proceding. I sensed a slight taste of blood after dives on occasion during these weeks but do not spit blood. I have sensitivity in my chest and throat which is gradually diminishing. I wonder – if lung tissue has no nerve endings – why I would feel chest sensitivity (like a stretched intercostal muscle)? Throat I can understand with the cartilage.
    Nevertheless, I will proceed with patience and caution before getting back to sub-60m dives.

    Thanks for your website.

    1. Jaap

      Hi Pete, there is one thing that comes to mind. If you breathe, the lungs slide past the pleura. In between the lungs and pleura is the pleural cavity, which contains a sort of lubricant. Although neither the lungs nor pleura contains nerve endings that can detect pain, if either of them is inflamed the two don’t slide well against each other. This can be a cause of pain. Try googling ‘pleuritic’ pain. I’m not sure if that is truly the case but I have heard other divers complain of ‘tightness’ or pain in the chest and I think this might explain it. I also think your conservative approach is very sensible. The last thing you want to do is damage the same area multiple times, or you risk it being a weakness for the rest of your diving career. Thanks for my website? Thanks for reading! I’m glad you find it useful.

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