First of all, lung overexpansion (LO) injury is very rarely in Freediving. So, don’t be scared. But since it can be a serious trauma better to have a solid understanding of what it is and how to avoid it.
First, let’s have a talk about the structure of the lungs.
Our lungs are sponge-like air-filled organs that transfer air molecules to and from blood
cells. The trachea (windpipe) conducts inhaled air into the lungs through bronchi, which then dived into smaller branches (bronchioles), finally becoming microscopic.
The bronchioles eventually end in clusters of very small air sacs called alveoli. In the alveoli, O2 from the air is absorbed into the blood and CO2 (a waste product of metabolism) moves from the blood to the alveoli (and eventually exhaled). This process in the alveoli calls gas exchange.
Lungs are major airspace in our body. We have actually two lungs – a right and left lungs. They are situated within the thoracic cavity of the chest. The right lung is bigger than the left, which shares space in the chest with the heart.
Lungs are delicate tissues, and can easily be ruptured. If the air flow inside our lungs becomes restricted as you ascend, the expanding air can rapture the delicate alveoli inside the lungs. This can happen without any warning sensations (since the lungs do not sense pain). Chest congestion, scar tissue, lung disease, and damage from smoking can also create air flow restriction and contribute to LO.
When you do a scuba course, your instructor going to repeat many times that the main rule of Scuba Diving – never to hold your breath. Why?
When you do scuba diving you breathe compressed air from scuba tanks and your lungs have the same volume at any given depth. This is why if you are even 10 meters deep and make a rapid ascent with breath hold (due to a panic let’s say) your lungs will expand twice from the normal size! Lung tissue can stretch out a little bit, but not twice from its normal size. Which is easy can bring a scuba diver to the risk of lungs barotrauma.
Lungs barotrauma (LB) can be in a few basic forms
- Arterial gas embolism – gas from the lungs escapes into the bloodstream (which can
form bubbles and block blood circulation) - Pneumothorax – air enters the space between the lungs, expands and cause lungs to collapse
- Mediastinal emphysema – air enters the space between the chest and the lungs, expands and put the pressure on the lung, heart, or blood vessels.
- Subcutaneous emphysema – air escapes from the lungs and travels underneath of the skin (most often around the neck), which can result in voice changing, difficulties swallowing
Common symptoms of LB are
- Paralyze, especially on one side of the body
- Unconsciousness
- Dizziness and confusion
- Coughing up blood
- Loss of vision
- Change in voice
- Heavy chest pain and difficulties in breathing
Is lung overexpansion can be a problem for Freedivers? Normally it is not. When you freedive, lungs compressed on your way down and re-expand on your way up to the original volume. So, there is no overexpansion.
But let’s have a look at two situations which can have a potential risk of lungs overexpansion injury
- BREATHING FROM SCUBA TANK UNDERWATER. Imagine, a Freediver makes a dive to 10 meters. His lungs compressed at this depth almost twice. When he ascends, lungs come back to their normal shape. But what happened if Freediver takes a breath from scuba tank underwater and then ascent? After inhale from scuba tank lungs will expand to its normal size (sea level), but then, on the way up the lungs will expand twice. What about exhaling on the way up? It will defiantly reduce the risk, but not illuminate it (you also have to keep the ascend speed as slow as you can). But to remove the risk – DON’T TAKE AIR FROM SCUBA DIVER UNDERWATER!
- By doing packing Freediver will over expand the lungs on the surface (lungs volume is going to be higher than Total Lungs Capacity). Then Freediver dive to the planned depth. During the dive he is going to have MDR (blood shift in particular) which moves a certain amount of blood into the lungs (causing blood vessels around alveoli to expand in size), preventing from crushing. On the way up air starts to expand, and blood vessels still bigger in size. This theoretically can increase the risk of lung overexpansion. The risk is not huge, but do exist. To minimize it, Freedivers who are packing exhale before they reach the surface (which also decrease the risk of BO). So, before you start practicing packing, please ask your self – DO YOU REALLY NEED TO DO IT? Please, keep in mind that packing is a highly advanced technique and should be practiced only by experienced athletes. Are you high experienced Freediver?
Treating lung overexpansion injury.
Symptoms of LO occur immediately and can include difficulty breathing, chest pain, crackling under the skin, unconsciousness or death. First aid must begin immediately while transportation to a medical facility is arranged. 100% O2 should be provided as soon as possible and CPR started if necessary. Ask yourself, do you have CPR skills?
The victim will need treatment in a hyperbaric (pressurized) chamber as soon as possible to shrink the air bubbles, and then slowly decompressed to allow the air to pass out of the body before it expands and interferes with respiration and circulation.
Suspected tension pneumothorax is treated with needle decompression followed by tube 
thoracostomy (at the hospital of course). If a smaller pneumothorax is present and there is no sign of hemodynamic or respiratory instability, the pneumothorax may resolve when high-flow 100% O2 is given for 24-48 hrs. If this treatment is ineffective or if a large pneumothorax is present, tube thoracostomy is done.
Computed tomography of the chest is recommending in any case of suspected pulmonary barotrauma in order predicting future fitness to dive