Yes, freedivers can experience Decompression Sickness (DCS), often called “the bends,” though it is extremely rare compared to compressed gas diving. DCS is caused by inert gas, primarily nitrogen, dissolving into body tissues under pressure. Upon a rapid reduction in pressure, such as during ascent, this dissolved gas forms bubbles. Since freediving relies solely on a breath-hold, the duration of pressure exposure is typically too short for significant nitrogen saturation. The risk becomes relevant only under highly specific, prolonged, and repetitive deep-diving conditions.
Understanding Decompression Sickness
Decompression Sickness results from the physics governing gas solubility in liquids, described by Henry’s Law. This law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid. When a person descends underwater, the ambient pressure increases rapidly, which increases the partial pressure of nitrogen gas in the lungs.
As the partial pressure of nitrogen rises, a pressure gradient causes the inert gas to dissolve into the bloodstream and then into body tissues. The longer a person stays at depth, the more nitrogen dissolves, leading to saturation. If pressure is reduced too quickly during ascent, the dissolved nitrogen comes out of solution and forms bubbles, similar to opening a carbonated drink.
These gas bubbles can obstruct blood flow, irritate nerve endings, or damage tissue, causing the symptoms associated with DCS. SCUBA divers are the primary group affected because their continuous supply of compressed air allows them to remain at depth for extended periods, leading to high nitrogen saturation. Symptoms range from joint pain (Type I) to serious neurological issues like paralysis (Type II).
Physiological Reasons Freediving Minimizes Risk
The main factor minimizing DCS risk in freediving is the limited time spent under pressure. Nitrogen requires sustained exposure to high partial pressure to accumulate significantly in body tissues. A typical recreational freedive is often less than three minutes long, which is insufficient time to cause substantial nitrogen loading.
Tissues are categorized by how quickly they absorb and release nitrogen, known as their half-time. Fast tissues, such as blood, take up and release nitrogen quickly, while slow tissues, like fat and bone, take hours to fully saturate. The short duration of a breath-hold dive prevents nitrogen from fully loading the slower tissues, which are primary sites for bubble formation in compressed gas diving.
A freediver does not carry a compressed gas source, which limits the total nitrogen available for absorption. As the diver descends, the air volume in the lungs is compressed, reducing the total gas available at depth. This compression acts as a brake on the nitrogen loading process, making a single, moderate-depth freedive unlikely to cause DCS.
Specific Conditions That Lead to DCS in Freedivers
DCS in freedivers occurs almost exclusively under extreme conditions. The risk profile is defined by two main factors: depth and repetition. Cases have been documented in competitive deep freediving, where dives exceed 80 to 100 meters, and in professional harvesting, such as spearfishing or pearl diving.
The most common scenario involves highly repetitive deep dives with inadequate surface intervals. When a diver performs multiple deep descents in a short period, the body lacks sufficient time on the surface to offload accumulated nitrogen. This leads to a gradual, cumulative increase in nitrogen saturation over the diving session, sometimes called “saturation diving” in breath-hold activities.
Neurological symptoms are common in freediving DCS, historically described among Polynesian pearl divers as “Taravana,” meaning “to fall mad.” This neurological DCS is caused by nitrogen bubbles crossing into the arterial circulation and lodging in the brain. The risk is compounded by factors like dehydration, cold water exposure, and rapid ascent, all of which encourage bubble formation.