Decompression sickness and freediving: myths vs reality

Freediving is a unique form of underwater diving in which divers plunge without the use of breathing apparatus, relying solely on their ability to hold their breath. This sport is gaining increasing popularity, but with this, there are also growing questions about the associated risks, particularly the likelihood of developing decompression sickness (DCS).

Decompression sickness (DCS), also known as "diver's disease," occurs due to the formation of gas bubbles in the blood and tissues of a person, which can happen when the pressure around the body decreases rapidly. This is most commonly associated with diving using compressed air. The nitrogen inhaled underwater under pressure dissolves in the blood and tissues, and if the ascent is too rapid and the pressure decreases sharply, nitrogen does not have time to exit the body naturally and forms bubbles.

In our previous article, we discussed how the risk of decompression sickness (DCS) can arise as a result of breath-hold dives following scuba diving. This time, we will examine the likelihood of DCS occurring solely after freediving.

It was long believed that the risk of developing decompression sickness (DCS) in freedivers was non-existent, since they do not use pressurized air like scuba divers. The main reason for this assumption was that freedivers do not inhale additional nitrogen under pressure from compressed air tanks, which can dissolve in the body's tissues and lead to DCS upon surfacing.

The atmospheric air we breathe is composed of 78% nitrogen and 21% oxygen. Nitrogen does not participate in cellular respiration but is important for the cycle in nature. Oxygen is vitally necessary for the respiration of living organisms, as it supports the processes of energy production in cells. These gas proportions are important for understanding physiological processes during diving, as changes in pressure underwater affect the solubility of gases in the blood, which can cause decompression sickness without taking certain precautions.

The key aspect is understanding how exactly and in what amount nitrogen accumulates in the body during freediving. When freedivers hold their breath and dive, the water pressure increases the partial pressure of gases in their lungs and blood. This leads to an increase in the dissolution of nitrogen in the blood and other tissues, which is usually safe during short dives.

However, modern research indicates that with multiple consecutive dives, and especially with deep dives, even without using compressed air, nitrogen can also accumulate in a freediver's body. This accumulation of nitrogen can become sufficient for conditions where, in the case of a rapid return to the surface, nitrogen does not have time to leave the tissues normally, leading to the possibility of developing DCS.

Therefore, freedivers, like divers, must consider the time and depth of dives, as well as provide adequate surface intervals for the safe elimination of nitrogen from the body. It is important to remember that even with natural breathing, the body is saturated with nitrogen, which, although an inert gas and does not participate in metabolic processes, under certain conditions can cause serious illnesses.

Symptoms of DCS can vary, but the main ones include:

• Prolonged feeling of fatigue after dives
• Pain in the limbs, torso
• Dizziness, disorientation
• Breathing problems
• Numbness, tingling, paralysis in different parts of the body

The International Association for the Development of Apnea (AIDA) urges those practicing freediving to observe surface intervals between dives. This is an important safety measure aimed at minimizing the risk of decompression sickness (DCS). Surface intervals allow the body to recover and eliminate excess dissolved gases, including nitrogen, which may have accumulated during the dive.

Surface intervals are time periods between dives that are necessary to allow the body to expel excess nitrogen from the tissues.

For dives up to a depth of 30 meters, a simple formula is recommended:

Surface time = dive time x 2;

That is, the surface time should be twice the time underwater. For example, if you dived for 2 minutes, you should rest on the surface for at least 4 minutes.

For deeper dives, the rules become more stringent. In AIDA4 courses, the following rules are discussed:

• For dives from 30 to 55 meters deep: surface interval = dive depth (m) / 5.
• For dives deeper than 55 meters, it is recommended to perform only one dive within 24 hours.

These recommendations help to create a significant safety margin and reduce the risk of DCS, but it is important to remember that individual susceptibility to DCS can vary greatly depending on physical condition, level of training, and other factors.

Although the common recommendation for dives deeper than 55 meters is to perform only one dive within 24 hours to minimize the risk of decompression sickness, in the practice of competitive freediving, this precaution is often ignored. Athletes, during intense training sessions, may perform several dives to depths exceeding 60, and sometimes up to 70 meters in one day. This significantly exceeds standard safe practices and requires additional precautions.

To reduce the risk of potential health problems after such extreme dives, athletes increase their surface interval times. For example, after a dive to 70 meters, a surface interval of at least 15 minutes should be observed, during which the freediver recovers and monitors their condition. Such measures do not guarantee complete safety, but they can help reduce the strain on the body and prevent some of the complications associated with multiple deep dives.

It is important to emphasize that such training should remain an exception and be conducted under the strict supervision of experienced professionals, with a full understanding of all associated risks.

Before starting freediving, it is crucial to assess your physical condition. If there are any doubts about your health, it is mandatory to seek medical consultation. Since certain health conditions can increase the risk of decompression sickness (DCS), it is vital to rule out any medical contraindications to diving.

Research indicates a low frequency of DCS cases among freedivers; however, the risk still exists, especially when surface intervals are not observed or due to physical overexertion. This highlights the importance of adhering to rest times between dives.

To prevent DCS, it is important to carefully plan dives, taking into account personal physical characteristics and health. Factors such as alcohol consumption, hydration, and physical condition must be carefully monitored. Avoiding dives when feeling unwell also reduces the risk of DCS.

Adhering to rules and recommendations is the foundation of safe freediving. A conscientious attitude toward one's own health and safety, as well as understanding the risks, are key to preventing DCS. It is not only necessary to plan each dive carefully but also to assess your strength, avoid overexertion, and ensure proper hydration levels.

Be prepared to forgo a dive if you feel discomfort or fatigue, and remember that safety always takes precedence over any record or achievement. Exchanging experiences with other divers and continuous learning enhance personal safety levels and contribute to the development of freediving as a safe sport.

14.12.2023