Diving decompression is a fundamental procedure to ensure the safety of every dive.
When a diver ascends to the surface after spending time at depth, the elimination of dissolved respiratory gases from the tissues occurs gradually.
Improper ascent can lead to serious health risks, such as decompression sickness (DCS).
In this article, we’ll explore every aspect of diving decompression: what it means, how to plan for it, and which tools to use to protect your body during dives.
Ready to learn everything you need to know to fully enjoy the underwater world? Keep reading!
Index:
- What is diving decompression?
- How is diving decompression done?
- How long does diving decompression take?
- What happens if you skip diving decompression?
- Recognizing decompression sickness
- Preventing decompression sickness
- How does cold affect decompression sickness?
What is diving decompression?
Diving decompression is the process that allows the body to safely eliminate inert gases (mainly nitrogen) absorbed during a dive.
When breathing compressed gas at depth, increased pressure results in higher solubility of gases in tissues.
Errors during ascent, such as ascending too quickly, can lead to the formation of gas bubbles in tissues and blood, causing symptoms ranging from joint pain to severe complications like gas embolisms.
How is diving decompression done?
Diving decompression involves following specific ascent stages and stops, known as “decompression stops,” dictated by decompression algorithms or dive tables.
Here are the main steps:
- Pre-dive planning: Set the desired depth and time for the dive.
- Monitoring during the dive: Check data from the dive computer.
- Safety stops: Pause at predetermined depths during ascent to allow for gradual elimination of dissolved gases.
- Gas mixture management: Using enriched gases like Nitrox, oxygen, or Trimix can reduce decompression times.
How long does diving decompression take?
The duration of diving decompression depends on:
- Depth and bottom time: Deeper and longer dives require extended ascent times.
- Respiratory mixture: Specific gases like Nitrox, oxygen, or Trimix can shorten decompression times.
- Diver physiology: Personal characteristics like age, fitness level, hydration, and thermal state can influence the timing.
There’s no strict limit for diving decompression. It can range from 3–5 minutes for recreational dives to several hours for technical dives and even days for professional saturation dives.
What happens if you skip diving decompression?
Skipping or improperly performing diving decompression can lead to decompression sickness (DCS). This condition occurs when gas bubbles form in tissues or blood, causing:
- Joint and muscle pain.
- Itching, rashes, or swelling.
- Dizziness and mental confusion.
- Respiratory and cardiovascular issues.
- Severe cases can result in gas embolisms and paralysis.
Immediate treatment is crucial, including oxygen therapy, hydration, and, in some cases, recompression in a hyperbaric chamber.
Recognizing decompression sickness
DCS symptoms vary in severity. Common signs include:
- Mild symptoms: Fatigue, itching, joint pain, and skin rashes.
- Severe symptoms: Breathing difficulties, dizziness, loss of balance, muscle weakness, and unconsciousness.
If DCS is suspected:
- Administer 100% pure oxygen.
- Contact a diving emergency service (e.g., DAN or hyperbaric centers).
- Hydrate by drinking water.
Preventing decompression sickness
Good news: Diving, according to many doctors, is beneficial to health. Studies show regular diving reduces oxidative stress, lowering the risk of many common diseases. However, diving incidents have multifactorial causes. These depend not only on dive parameters but also significantly on a diver’s physical fitness and how their body responds to inflammation caused by diving.
Non-Modifiable Causes
- Age: Advanced age can bring reduced physical ability and higher inflammation response, increasing susceptibility to DCS.
- Genetics: Individual differences in gas elimination efficiency and other genetic factors can influence DCS risk.
Modifiable Causes
- Health and fitness: Address factors like high blood pressure, cholesterol, smoking, and body mass index (BMI).
- Good practices: Regular physical activity (at least 90 minutes/week), a diet rich in fruits, vegetables, and hydration are key.
- Diving techniques: Adhere to safety protocols, manage gas mixtures, and avoid exceeding safe oxygen and nitrogen partial pressures.
Diving Best Practices
Certain rules specifically apply to diving:
- Gas partial pressures: Oxygen and nitrogen partial pressures should not exceed 1.4 and 3.2 bar, respectively, to minimize inflammatory responses and other negative effects. Helium in the breathing mixture can have a protective effect.
- Depth management: As some training agencies recommend, avoid exceeding depths where air is safe (“No deep air”). Beyond 30–40 meters, using Trimix (oxygen, helium, nitrogen) is strongly advised.
- Repetitive dives: Allow at least two hours between successive dives. Frequent diving (more than 30 hours annually) is beneficial.
Physical Activity and Effort
- Avoid intense physical activity (e.g., running, cycling) within 24 hours before and two hours after diving, as well as for the rest of the day.
- Minimize exertion underwater, especially during descent and the deep phase of challenging dives.
- Gentle finning during ascent and decompression is helpful.
- Avoid overloading joints; consider using an underwater scooter for assistance.
By following these practices, divers can reduce the risk of DCS and enjoy the full benefits and pleasures of diving.
How does cold affect decompression sickness?
Thermal protection deserves special attention. Best practices suggest avoiding diving when overheated (wait to reach a balanced thermal state), performing descents and bottom phases in a “cool” condition, and ascending and decompressing in a warm state. To achieve this, using a dry suit and an electric heating vest activated during ascent can be highly beneficial.
This guidance stems from a well-known study published in November 2007 by the NEDU (Navy Experimental Diving Unit): The Influence of Thermal Exposure on Diver Susceptibility to Decompression Sickness.
The study involved experiments conducted within the hyperbaric facility at the U.S. Navy’s Underwater Research Center in Panama City.
The research aimed to determine whether and how a diver’s thermal status during the dive influenced the likelihood and severity of decompression sickness (DCS).
To investigate, a series of dives were performed within the hyperbaric facility under controlled thermal conditions, testing various combinations of COLD/WARM exposure during both the deep phase and decompression.
Divers performed exercises on a cycle ergometer during the deep phase, wearing swimsuits, shirts, booties, and gloves. During decompression, they rested, followed by four hours of controlled rest, during which they were monitored with echocardiographic studies.
Although no physiological measurements were taken to assess the divers’ thermal state, self-assessment scores indicated that divers felt cold at 26.7°C and warm at 36.1°C.
While the study did not aim to uncover the physiological mechanisms behind the effects of thermal exposure on DCS risk, the results reinforced the idea that gas exchange dynamics in tissues affected by DCS are slowed by vasoconstriction during cold exposure and accelerated by vasodilation during warm exposure.
During the 400 dives conducted to a maximum depth of 37 meters, divided into seven series to test different thermal condition combinations, 21 cases of DCS were diagnosed. Below is a summary of the test results.
Key findings include:
- At the same depth, the high incidence of DCS (22.2%) during dives with perceived cold conditions both at depth and during decompression (C/C) contrasts sharply with the low incidence during dives where cold was perceived only during the deep phase (C/W), indicating that warmth during decompression helps prevent DCS. The incidence of DCS remained low (1.3%) even for tests at the same depth but with an additional 10 minutes of bottom time.
- The benefits of warmth during decompression were more pronounced than the adverse effects of warmth during the bottom time (BT). Furthermore, a 10°C increase during the decompression phase had effects comparable to halving the bottom time.
- The similar DCS incidence between dives of 37m/30min (W/C) and 37m/60min (C/C) suggests that warmth during BT is detrimental.
- Temperature changes of 10°C appear to have effects comparable to doubling or halving the bottom time.
- Warmth during the deep phase may accelerate gas absorption and increase the risk of DCS, while the same conditions during decompression accelerate gas elimination and reduce the risk of DCS.
Given these findings, it is clear that these effects should be incorporated as independent variables in decompression models. Improving these models, along with further research, is necessary to quantify the relationships between perceived temperature effects and to establish optimal thermal conditions to realize the benefits of warmth during decompression.
Diving decompression is essential for enjoying the diving experience safely.
By following proper procedures, using the right equipment, and planning dives carefully, you can minimize risks and fully appreciate the underwater world.
If you want to deepen your knowledge of diving decompression techniques or improve your diving skills, Argentario Divers is here to help! With years of experience and a team of qualified instructors, we can guide you to explore the sea safely.
Contact us for details on our courses, guided dives, and personalized consultations. Your next underwater adventure awaits!
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