Your lungs shrink to a certain degree when you dive due to the relocation of blood to the center of your body and the increasing pressure of water. This affects how your lungs operate while diving and requires special consideration when ascending.
A lot happens to your lungs while diving, and understanding these changes keeps you informed on what to expect when scuba diving. Keep reading to learn about how lungs shrink and expand, as well as some of the lung-related risks while scuba diving.
What Happens to Your Lungs When You Dive?
Your lungs change due to the decreasing volume of air, reflexive responses, and the increase in pressure while diving.
Boyle’s law explains that any given gas will decrease in volume if the surrounding pressure increases. This means that as you descend, the volume of air in your body decreases, while ascent increases the volume of air increases.
Another major change to your lungs relates to your body’s natural response to relocate blood to your center. This adds up to about 700 ml of blood for the vessels of the heart and lungs to accommodate, and it makes your lungs stiffer.
Paired with the increasing outside pressure of the water, this makes your lungs stuffer and reduces your elastic recoil. The blood also takes up some of the volume of your lungs that could be used to accommodate air, and breathing takes more effort than normal.
Risks to Lungs and Breathing While Scuba Diving
Risks related to your lungs and breathing include:
- Rebreathing and hypercapnia (excessive carbon dioxide in the blood)
- Pulmonary barotrauma (thoracic squeeze or lung squeeze)
- Pneumothorax (collapsed lung)
- Running out of air
- Gas contamination
These can lead to greater issues, such as drowning, and are caused by human error or equipment failure.
Why Do Lungs Shrink Underwater?
Your lungs shrink underwater due to the increased pressure from blood pooling to the area and the external water pressure.
These factors may be compounded by your wetsuit, but the shrinking happens regardless of what you are wearing.
Your lungs won’t shrink by much, but you’ll notice the difference when you first start out. The smaller size and change in the density of your breathing gas makes it more difficult to breathe, but you can overcome this with breathing techniques and procedures you learned in your scuba diving course.
You may eventually get used to the changes in your lungs with practice.
Do Your Lungs Expand When You Dive?
Your lungs do expand when you dive, but only on the way up.
As you ascend, the volume of the air in your lungs increases and pushes outward on your lungs, but this alone is not enough to expand your lungs.
Water pressure decreases the higher up you go. You won’t completely reverse the diving response that relocates blood to the surrounding vessels, but you may notice changes as the temperature warms the closer you get to the surface.
Your lungs eventually return to their normal, expanded size, but you need to take care when ascending to not let the volume of air become too much for your lungs.
Why Don’t Scuba Divers’ Lungs Collapse as They Descend?
Scuba divers’ lungs can collapse underwater, but it’s more likely to happen on the ascent.
When you’re descending, the volume of air inside the lung decreases. This is more likely to result in an injury known as a lung squeeze (formally pulmonary barotrauma).
The increased environmental pressure and the decreasing volume compresses the lungs, and if they compress too small, it leads to tightness and pain. At a certain point, this may be enough to cause the lung to collapse, but you’re likely to turn back once you start to experience pain.
What Causes a Collapsed Lung?
A collapsed lung occurs most often during ascent, especially if they hold their breath. As water pressure decreases, the volume of the air in their lungs expands. This can reach a point where it tears the tissue of the lungs, letting air out into the intrapleural space.
When this happens, the air continues to leak out through the tear, and it eventually pushes in on the lung and causes collapse. At this point, the diver will take rapid, shallow breaths and start to turn blue on their lips, fingers, and skin.
This is more likely to happen if your lung tissue is weakened from:
- Disease
- Previous lung injuries
- Inflammation (usually due to smoking)
These lead to the formation of blisters (blebs) on the lung’s air sacs, and they can even rupture with normal pressure buildup.
Can You Dive After a Collapsed Lung?
In most instances, you will not be able to dive after suffering from a collapsed lung. The chances of recurrent pneumothorax are a major concern, and you would not be able to have a quality dive worrying about whether it would happen again.
There is a difference between suffering a spontaneous pneumothorax and knowing it’s likely to happen again. You not only put yourself at risk, but those diving with you. They can be injured or suffer their own accidents in their attempts to save you, and you rob them of a capable diving buddy.
You need medical clearance before diving again, but most professionals who understand the heightened risk of arterial gas embolism and tension pneumothorax are unlikely to clear you for diving at any depth.
How Deep Can You Dive Before Your Lungs Collapse?
Depth is not a major factor when it comes to lung collapse. In theory, your body could dive to any depth on earth without collapsing a lung as long as you could equalize your air spaces.
Most of your lung-related issues related to depth revolve around running out of air or the toxicity of certain elements at depth.
What Limits Your Depth While Scuba Diving?
Depth and pressure are not the limiting variables while scuba diving. Instead, you need to adhere to the limitations of:
- Nitrogen narcosis
- Oxygen toxicity
- Running out of air
- Increased cold
- High Pressure Nervous Syndrome (HPNS)
- Visibility
Divers are constantly testing their limits on how deep they can travel, but it’s a slow progression. Because diving is less risky and more enjoyable at shallower depths, there is little reason to try to travel deeper than we’ve been before.
References
https://dan.org/alert-diver/article/your-lungs-and-diving/
https://www.britannica.com/science/thoracic-squeeze
https://theknowledgeburrow.com/why-don-t-divers-lungs-collapse-when-they-descend/
https://www.medicaldaily.com/breaking-point-how-much-water-pressure-can-human-body-take-347570