Decompression Sickness Following Breath-Hold Diving
Authors: J.D. Schipke, E. Gams, Oliver Kallweit
DOI / Source: 10.1080/15438620600854710
Date: 2006
Reading level: Intermediate
Why This Matters for Freedivers
A lot of freedivers still think “DCS is a scuba problem.” This paper pulls together many real cases showing that repetitive breath-hold diving can load nitrogen enough to cause serious neurological symptoms, especially with short surface intervals and long sessions. It’s a strong argument for smarter dive planning: manage depth + frequency + surface intervals, and treat post-dive neurological symptoms as an emergency that needs oxygen and proper evaluation.
Synopsis
This paper is a classic early-warning review that tried to shake the community out of a dangerous assumption: “breath-hold dives are too short for nitrogen to matter.” The authors argue that while a single breath-hold dive is usually not the issue, many breath-hold dives repeated over hours can slowly push nitrogen levels higher and higher—until symptoms appear.
They compare four groups where incidents were reported most often: 1) traditional “ama” divers (Japan/Korea and Pacific regions), 2) naval training instructors doing repeated dives, 3) spear fishers (including competition divers and scooter users), 4) freediving athletes pushing deep training and records.
A key theme is that many cases look neurological rather than “joint pain bends”: dizziness, vertigo, visual disturbances, confusion, poor coordination, numbness/tingling, weakness, hemiplegia-like symptoms, speech problems, even loss of consciousness. In several reports, symptoms improved rapidly with recompression / hyperbaric treatment—one of the strongest practical clues that decompression illness was involved.
The review also introduces a very useful way to think about “risk” without needing a complex decompression computer: the surface interval vs. dive time ratio. If your surface interval is short compared to your dive time, you’re essentially doing something closer to a “continuous exposure” at a meaningful depth. Over time, some tissues saturate quickly (brain/heart/viscera reach a plateau early), while slower tissues (like fat) can keep accumulating nitrogen during long sessions. That helps explain why people can feel fine for hours and then suddenly develop symptoms later in the day—or even after they’ve stopped diving.
The spear fishing section is especially relevant for modern freedivers because it describes the exact “high-risk recipe” many people still follow: lots of dives per hour, moderate-to-deep depths (often 25–45 m), short surface intervals, repeated for 5+ hours, sometimes with extra stress (competition pressure, heavy exertion, heat, dehydration), and sometimes with scooters that increase the number of deep dives possible. The review also notes that bubble detection and symptoms don’t always match perfectly—some divers can have bubbles without symptoms and vice versa—so relying on “I feel okay” or “I don’t see bubbles” is not a safety strategy.
Their conclusion is blunt: DCS after breath-hold diving is real, prevention guidance is underdeveloped, and we need simple, practical algorithms divers can actually use. Until that exists, the safest approach is conservative behaviour: longer surface intervals, fewer deep repeats, controlled ascents, and respecting cumulative exposure across the whole session (and across multiple days).
Abstract
Despite convincing evidence of a relationship between breath-hold diving and decompression sickness (DCS), the causal connection is only slowly being accepted. Only the more recent textbooks have acknowledged the risks of repetitive breath-hold diving. We compare four groups of breath-hold divers: (1) Japanese and Korean amas and other divers from the Pacific area, (2) instructors at naval training facilities, (3) spear fishers, and (4) free-dive athletes. While the number of amas is likely decreasing, and Scandinavian Navy training facilities recorded only a few accidents, the number of spear fishers suffering accidents is on the rise, in particular during championships or using scooters. Finally, national and international associations (e.g., International Association of Free Drives [IAFD] or Association Internationale pour Le Developpment De L’Apnee [AIDA]) promote free-diving championships including deep diving categories such as constant weight, variable weight, and no limit. A number of free-diving athletes, training for or participating in competitions, are increasingly accident prone as the world record is presently set at a depth of 171 m. This review presents data found after searching Medline and ISI Web of Science and using appropriate Internet search engines (e.g., Google). We report some 90 cases in which DCS occurred after repetitive breath-hold dives. Even today, the risk of suffering from DCS after repetitive breath-hold diving is often not acknowledged. We strongly suggest that breath-hold divers and their advisors and physicians be made aware of the possibility of DCS and of the appropriate therapeutic measures to be taken when DCS is suspected. Because the risk of suffering from DCS increases depending on depth, bottom time, rate of ascent, and duration of surface intervals, some approaches to assess the risks are presented. Regrettably, none of these approaches is widely accepted. We propose therefore the development of easily manageable algorithms for the prevention of those avoidable accidents.