What Happens if You Ascend Too Fast While Diving

Yikes. Just the thought sends shivers down my spine. “Slowly ascend from every dive”, cleverly remembered by the acronym SAFED, is the second most important rule in scuba diving, the first being “never hold your breath”.

To violate these two cardinal rules is to endanger yourself, and your buddy while scuba diving.

Before understanding the effects of compressed air on the body, we have to understand how depth affects pressure.

🌊 1. How Does Depth Cause Pressure Changes

You have probably been taught this in your open water course. Very quickly, divers breathe compressed air. Pressure is measured in atmospheres (also called bar), or pressure per square inch (also called PSI).

When you are on the surface, the pressure is at 1 bar. Every 10 meters you descend, the pressure increases by a bar. This means at 10 meters, the pressure is at 2 bar, and at 20 meters, the pressure is at 3, and so on, you get the idea.

When you breathe compressed air at the surface, you are breathing 21% oxygen and 79% nitrogen at 1 bar. When you do that at 20 meters, that figure is tripled.

Checking the dive computer

🌀 2. Effects of Pressure Changes On The Scuba Diver

Where’s that excess air going? Well, we metabolize oxygen, but the nitrogen has to be dissolved in our blood. Ordinarily, this isn’t a problem, as the nitrogen swishes around our bloodstream and gets dissolved.

The problem happens when you are breathing 3, 4, or 5 times the compressed amount of nitrogen.

▶️ 3. What Is Barotrauma

Broadly speaking, “baro”, meaning pressure, and “trauma”, well you know, is physical damage to body tissues caused by pressure differences between air filled spaces within your body and the ambient pressure.

It covers all kinds of pressure injuries including:


When a dead space from a filling is full of air and you start to ascend, and the air is unable to get out.

Sinus Pain

Once of the most common pressure injuries, this is when you have air stuck in your sinuses and try ascending. That’s why you never dive with a cold.

Barotrauma injuries

Joint Pain

When air bubbles are hiding in your joints and start to expand as you ascend, pushing into your bones and tissues and causing pain.

Air Embolism

This is the real bad one we’re covering next.

▶️ 4. What Is An Arterial Gas Embolism

Arterial gas embolism, or AGE, is also known as pulmonary barotrauma and is the most common form of air embolism. A few things can cause AGE, the most common two being holding your breath, and ascending too fast.

Picture this. Your lungs are full of air and you are holding your breath, and suddenly, a current sweeps you up a few meters, or you ascend too quickly and the bubbles in your little microscopic structures in your lungs known as the alveoli start to expand. Quickly.

The expanding air has nowhere to go, so the bubbles enter the arterial circulation and eventually settle in an artery that’s supplying blood to your spine, brain, or vital organs, causing a blockage and depriving your brain of life-giving oxygen. Yikes!

AGE is an extremely serious illness that requires immediate medical attention at the nearest hyperbaric chamber.

Diver ascending fast

▶️ 5. What Is Decompression Sickness

Decompression sickness (abbreviated DCS), is often used interchangeably with DCI (decompression illness).

Both refer to a diving injury caused by dissolved nitrogen building bubbles inside your body’s tissues, joints, and bloodstream, and being unable to get off-gassed.

Also known colloquially as “the bends”, decompression sickness is a common diving injury, especially among scuba diving instructors and other professionals who do multiple deep dives a day over long periods without having a “dry day”.

It is caused by ascending too quickly, especially if you have loads of nitrogen still in your bloodstream (otherwise called Residual Nitrogen).

Since we cannot metabolize nitrogen, it lies dormant in our bodies as we go about our dive. Because the ambient pressure is keeping the nitrogen compressed, that’s not a problem.

The problem happens when we start ascending and the nitrogen has nowhere to go. With slow ascents, nitrogen has the chance to leave the body through the lungs as the water pressure decreases.

However, during a rapid ascent, the nitrogen has no chance to off-gas, and now form gas bubbles that stay in your body tissues, potentially causing massive problems.

Decompression illness treatment
Petty Officer 2nd Class Chelsy Alamina / U.S. Navy, Public domain, via Wikimedia Commons

▶️ 6. Type I and Type II Decompression Sickness

There are two types of DCS – Type I and Type II.

Type I DCS can range from mildly painful joints (also called the niggles) to a skin rash. While many Type I DCS symptoms are less severe and at times can go away on their own, it is always better to seek treatment and stay out of the water for several days.

Type II DCS is more serious and requires immediate medical attention. This kind of DCS can affect the lungs, pulmonary system, spinal cord, and other vital organs.

❗ 7. Symptoms Of Decompression Sickness

While not exhaustive, symptoms of decompression sickness tend to be telltale. However, some muscle soreness and joint pain might also be due to the physical exertion of diving, so it can be difficult to tell the difference.

Chest Pain

After a dive, divers who feel chest pain or difficulty swallowing may have developed pulmonary barotrauma. In addition, a pneumothorax, also known as a collapsed lung, is characterized by sharp discomfort on one side of the chest and a tightness in the chest.

Shortness of breath, trouble breathing, quick heart rate, rapid breathing, cough, weariness, and blueish skin are other symptoms.

Paralysis, Partial Paralysis or Weakness

Type II DCS can cause paralysis in one or more areas of the body, and air embolism can cause weakness or paralysis in the extremities.

Other signs of AGE include bloody froth from the mouth or nose, as well as spasms, however, loss of consciousness is the most prevalent symptom.

AGE is regarded as exceedingly dangerous, and any indication of AGE signs necessitates prompt medical attention.

Joint Pain

This Type I or II DCS can cause steady or throbbing pain, especially in bigger joints like the shoulders and elbows.

The discomfort may seem like a muscle strain, but it’s crucial to be proactive and get any symptoms assessed by a skilled specialist.

Skin Rash

A rash, uncomfortable sensation, or skin marbling might be signs of a skin bend, a kind of Type I DCS. This kind of DCS has been connected to more significant neurological DCS symptoms, and it should be treated just like any other diving-related injury.

Dizziness, Confusion, and Nausea

These are severe symptoms that need to be looked at by a medical professional. It could indicate an air embolism or other serious barotrauma.

Weakness and Fatigue

Although difficult to tell since you might be tired after a long dive, excessive weakness and extreme fatigue is also an indicator of decompression sickness.

⚕️ 8. What Is Nitrogen Narcosis

On the flip side, you can get nitrogen narcosis, or “narc’d”, if you descend too quickly. It is the increasing air pressure raising the nitrogen gas levels too rapidly, especially on deep dives.

You can feel somewhat intoxicated, or woozy, potentially causing you to do silly things. We once had a student pretend he was running underwater!

Narcosis happens only at depths of about 30 meters (100 feet) and below. You can easily avoid it by descending slowly to let your body get used to the increasing pressure of the nitrogen gas.

🚫 9. How Can You Prevent Scuba Diving Injuries

Here are some rules you should observe to prevent scuba injuries and keep yourself out of trouble.

  1. Never hold your breath. Always, and non-negotiable.
  2. Slowly ascend from every dive (SAFED). Unless you have some kind of emergency, ascend at a rate of 10 meters (30 feet) a minute.
  3. Don’t cut it too close, leave lots of time as you get closer to your no decompression limits (NDL).
  4. On a repetitive dive day, try staying shallower or increasing the surface interval time, allowing your body to dissolve the leftover nitrogen gas.
  5. If you dive several days in a row, think about skipping a day.
  6. Keep healthy. Tobacco, alcohol, dehydration, and obesity all contribute to increasing the risk of decompression sickness.
  7. Stay away from airplanes for 18, if not 24 hours after your last dive. Air is thinner at altitude and whatever leftover nitrogen gas bubbles you have will expand yet even more.
Pool training with an instructor

⚕️ 10. How Are Injured Scuba Divers Treated?

First things first, administer 100% oxygen to reduce the amount of nitrogen in the blood. Then depending on the severity, off to the “chamber” you go!

At the center of dive medicine is the hyperbaric chamber. It recompressed the nitrogen bubbles back into your bloodstream and then, with slowly decreasing pressure, allows your body to dissolve the nitrogen.

🔚 11. Final Thoughts

While all this might sound really scary, keep in mind that scuba diving is a relatively safe sport. After all, the minimum age to dive is 8 years old!

Just stick to nice, cautious calculations and obey scuba diving rules and you’ll be just fine.

Dive safe and happy bubbles!

Scroll to Top