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We report on a Japanese male professional breath-hold diver (Ama) who developed neurological disorders during repetitive dives to 22 meters of sea water. Each diving duration and surface interval were 40-80 seconds and 20-30 seconds, respectively. He suffe... (Source: SafetyLit: All (Unduplicated))

Decompression sickness in breath-hold divers: A review.
J Sports Sci. 2009 Dec 3;:1-16
Authors: Lemaitre F, Fahlman A, Gardette B, Kohshi K
Although it has been generally assumed that the risk of decompression sickness is virtually zero during a single breath-hold dive in humans, repeated dives may result in a cumulative increase in the tissue and blood nitrogen tension. Many species of marine mammals perform extensive foraging bouts with deep and long dives interspersed by a short surface interval, and some human divers regularly perform repeated dives to 30-40 m or a single dive to more than 200 m, all of which may result in nitrogen concentrations that elicit symptoms of decompression sickness. Neurological problems have been reported in humans after single or repeated dives and recent necropsy reports in stranded marine mammals were suggestive of decompression sickness-like symptoms. Modelling attempts have suggested that marine mammals may live permanently with elevated nitrogen concentrations …

The formation of bubbles is the basis for injury to divers after decompression, a condition known as decompression illness. In the present study we investigated the effect of endurance training in the rat on decompression-induced bubble formation.

[Central nervous system involvement in patients with decompression illness] Sangyo Eiseigaku Zasshi. 2003 May;45(3):97-104 Authors: Kohshi K, Katoh T, Abe H, Wong RM Dysbarism or decompression illness (DCI), a general term applied to all pathological changes secondary to altered environmental pressure, has two forms decompression sickness (DCS) and arterial gas embolism (AGE) after pulmonary barotrauma. Cerebral and spinal disorders have been symptomatically categorized as AGE and DCS, respectively. Magnetic resonance images (MRIs) of divers with DCI showed multiple cerebral infarction in the terminal and border zones of the brain arteries. In addition, there were no differences between MRI findings for compressed air and breath-hold divers. Although the pathogenesis of the bra...

Since the 1960s there have been several reports of divers suffering from decompression sickness (DCS) after repetitive breath-hold (BH) diving. In the period from 1995 to 2000 John Batle observed apparent DCS in 30 free divers competing with underwater scooters in the sea around Mallorca. The cases were treated successfully with recompression therapy. Two of the typical diving profiles, described by Batle, have been submitted to calculations with a modified Haldane model: a perfusion limited, symmetrical multitissue/multilevel model. The model predicts that the two dive profiles will lead to DCS as recorded. A third profile, confirmed by reports to avoid DCS, also were accurately predicted. In order to protect free divers, John Batle developed a dive table for repeated BH diving. According to our calculations the Batle table does not prevent DCS during prolonged exposures. A alternative range of tables is developed and presented.
PMID: 17987510 [PubMed - indexed for MEDLINE]

Dysbarism or decompression illness (DCI), a general term applied to all pathological changes secondary to altered environmental pressure, has two forms decompression sickness (DCS) and arterial gas embolism (AGE) after pulmonary barotrauma. Cerebral and spinal disorders have been symptomatically categorized as AGE and DCS, respectively. Magnetic resonance images (MRIs) of divers with DCI showed multiple cerebral infarction in the terminal and border zones of the brain arteries. In addition, there were no differences between MRI findings for compressed air and breath-hold divers. Although the pathogenesis of the brain is not well understood, we propose that arterialized bubbles passing through the lungs and heart involved the brain. From the mechanisms of bubble formation, however, this disorder has been classified as DCS. We propose that there is a difference between clinical and mechanical diagnoses in the criteria of brain DCI. In contrast to brain injury, the spinal cord is involved only in compressed air divers, and is caused by disturbed venous circulation due to bubbles in the epidural space. The best approach to prevent diving accidents is to make known the problems for professional and amateur divers.

A report is given of a case of apparent decompression sickness after repetitive breath-hold dives to depths of 50–66 ft (15–20 m). Three similar cases in Norwegian Navy escape-training-tank instructors are also discussed. A parallel is drawn between the Scandinavian cases and the 'pearl diver disease' (taravana), found in the Tuamotu Archipelago in the South Pacific. Symptoms and signs in these conditions are consistent with the diagnosis of decompression sickness. It is emphasized that in such cases immediate recompression is the treatment of choice. Consideration of various depths and patterns of breath-hold diving in terms of nitrogen uptake and elimination permits the relative risk of decompression sickness to be predicted with the help of decompression tables

A question is often posed on whether a free diver could develop decompression sickness. The question has been studied in several countries, but the best information comes from the natives of the Tuamotu Archipelago in Polynesia where free divers in the past made 40-60 dives a day to depths of 100 to 140 feet to retrieve pearls. Their descent was assisted by a lead weight , and they ascend by pulling themselves up a rope tethered to their collection basket. An assistant then raised the basket to retrieve the shells gathered on the bottom. Descent times were 30-50 seconds, total dive time about 100 seconds, and surface interval between dives was 4-6 minutes. Many of these divers developed severe illness which was called Taravana to describe the abnormal behavior associated with falling that the divers manifest when they are affected. The symptoms of Taravana are similar to those of decompression sickness. After ascent, divers would develop paralysis, visual changes, hearing loss, dizziness, and some divers died. Many divers who survived had permanent brain and spinal cord injuries. Although Taravana is likely to be decompression sickness, there are some features which do not fit the picture of decompression sickness and other causes such as hypoxia have been proposed.

Intravascular bubble formation and symptoms of decompression sickness have been reported during repetitive deep breath-hold diving. Therefore we examined the pattern of blood N2 kinetics during and after repetitive breath-hold diving. To study muscle N2 uptake and release, we measured brachial venous N2 partial pressure (PN2) in nine professional Korean breath-hold divers (ama) during a 3-h diving shift at approximately 4 m seawater depth and up to 4 h after diving. PN2 was determined with the manometric Van Slyke method. Diving time and depth were recorded using a backpack computer-assisted dive longer that allowed calculating the surface-to-depth time ratio to derive the effective depth. With the assumption that forearm muscle N2 kinetics follow the general Haldanian principles of compression and decompression, i.e., forearm muscle is a single compartment with a uniform tissue PN2 equal to venous PN2, PN2 data were fitted to monoexponential functions of time. In the early phase of the diving shift, PN2 rapidly increased to 640 Torr (half time = 6 min) and then slowly declined to baseline levels (half time = 36 min) after the work shift. Peak PN2 levels approximated the alveolar PN2 derived from the effective depth. We conclude that forearm muscle N2 kinetics are well described by a Haldanian single-compartment model. Decompression sickness is theoretically possible in the ama; it did not occur because the absolute PN2 remained low due to the shallow working depth of the ama we studied.

Introduction

The first well-documented case of decompression sickness was that of a snake, described by Boyle in 1670 (Phil Trans R Soc 1670;5:2011-58). Based on the observation of a gaseous bubble formed in the intraocular fluid, Boyle concluded that bubbles could form in tissues undergoing rapid decompression. More than three centuries later, the formation of tear film bubbles, after both dry-chamber simulated compressed air dives (Mekjavic et al., Undersea Hyperb Med 1998;25:201-10) and in-water recreational compressed air dives (Bennett et al., Undersea Hyperb Med 2001;28:1-7), has been indicated as a sign of decompression stress in humans. Based on the these observations, and evidence that a breath-hold diver could undertake profiles sufficient to elicit decompression illness (Paulev, J Appl Physiol 1965;20:1028-31), the aim of the present study was to investigate tear film bubble formation in breath-hold divers.

Methodology

The surface of the right eye of 17 breath-hold divers was examined and digitally recorded before and after repeated breath-hold excursions to a maximum depth of -28.5m in the Submarine Escape Training Tank (SETT, Gosport, UK). Dive profiles were recorded with wrist mounted personal dive computers (Stinger, Suunto, Vantaa, Finland) and downloaded to PC via commercially available dive software (Dive Manager, v.1.3, Suunto, Vantaa, Finland). Data was manually transferred from Dive Manager to a spreadsheet (MicroSoft Excel) and analysed as maximum percent nitrogen saturation via calculations derived from Buhlmann’s ZH-L16c algorithm (Tauchmedizin, 1995, 4th ed. Springer- Verlag: Berlin). Grubb’s test was used to identify significant differences in dive profile parameters and theoretical nitrogen loads between individuals with and without bubbles present. A stepwise multiple linear regression model was used to determine the relative contribution of number of dives, depth, time at depth, ascent and descent rates to bubble formation.

Results

Tear film bubbles (n = 5) were presented by only one diver, post-dive. The total and average times below -15m for this diver were significantly longer (both P = 0.025) than for the non-presenting divers. An analysis of peak nitrogen saturation indicated that the presenting diver had significantly higher saturations in ’tissue’ compartments 14-16 of the Buhlmann ZH-L16c model (P = 0.046 to 0.048). Multiple regression modeling suggested that of all parameters considered, only total time below -15m and average time below -15m had significant predictive power (both P < 0.001; 97.1% and 2.7%) for bubble formation.

Conclusions

It is believed that this is the first time that ocular tear film bubble formation has been reported in breath-hold divers.

There have been no reports of diving accidents involving Korean or Japanese professional breath-hold (ama) divers except for our 2 recent cases. We investigated a direct interview survey on their village to determine whether other ama divers had experienced any accidents during or after dives. Interview responses were retrospectively obtained from 16 partially assisted male ama divers belonging to the Utsu Union on Mishima Island, Yamaguchi Prefecture in Japan. We questioned the divers about diving history (diving depth, length of the diving shift, number of dives and diving accidents), medical history (hypertension, cardiac arrhythmia, diabetes mellitus, and cerebrovascular diseases) and health habits (smoking and alcohol consumption). Nine of 16 ama divers previously had stroke-like neurological accidents, in which the most common symptom were unilateral motor weakness [7 cases] and sensory abnormalities [4 cases]. All of these neurological problems had manifested transiently. In addition, 13 of 16 divers had occasional episodes of dizziness, nausea and/or euphoria during such dives. Repeated deep breathhold dives may be harmful to the divers and cause brain involvement.

If you're interested in how the body reacts to severe stress, whether it be encountered at great depths, high altitude or heavy exercise, researcher Claes Lundgren says, "It is useful to push the body to its limits. These conditions allow you to look at how the body reacts as if it were under a magnifying glass." Lundgren is Director of the Center for Research and Education in Special Environments (CRESE) at SUNY Buffalo, which is set up to determine how humans cope with extreme conditions.

Under the magnifying glass in Lundgren's studies is "the diving response," a universal reaction shared by all mammals, including humans, seals, dolphins and whales, to going underwater. And Lundgren's studies - including seven New York Sea Grant-funded projects since the mid-1980s - provide new data to better understand how humans and other mammals sharing this deep diving mechanism cope with underwater conditions.

Description from www.ncbi.nlm.nih.gov:

Since the 1960s there have been several reports of divers suffering from decompression sickness (DCS) after repetitive breath-hold (BH) diving. In the period from 1995 to 2000 John Batle observed apparent DCS in 30 free divers competing with underwater scooters in the sea around Mallorca. The cases were treated successfully with recompression therapy. Two of the typical diving profiles, described by Batle, have been submitted to calculations with a modified Haldane model: a perfusion limited, symmetrical multitissue/multilevel model. The model predicts that the two dive profiles will lead to DCS as recorded. A third profile, confirmed by reports to avoid DCS, also were accurately predicted. In order to protect free divers, John Batle developed a dive table for repeated BH diving. According to our calculations the Batle table does not prevent DCS during prolonged exposures. A alternative range of tables is developed and presented.

Description from www.informaworld.com:

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.

Description from www.emedicine.com:

Although decompression sickness (DCS), a complex resulting from changed barometric pressure, includes high-altitude–related and aerospace-related events, this article focuses on decompression associated with the sudden decrease in pressures during underwater ascent, usually occurring during free or assisted dives. People involved with tunneling projects, in submarines during emergencies, and in breath-hold free diving may also experience the physiologic effects of decreased pressure brought on by such ascents.

Since 4500 BCE, humans have engaged in free (breath-hold) diving to obtain food and substances from shallow ocean floors at depths of 100 ft or more. The 2007 record-setting breath-hold unlimited dive of Herbert Nitsch to 702 ft (214 m) attests to this human feat. Humans began experimenting with crude diving bells as early as 330 BCE. These bells were submerged containing only air. In 1690, the first diving bell with a replenishing air supply was tested. The first crude underwater suit dates back to 1837, and helium was first used in place of nitrogen in 1939.

All these early diving methods required a physical connection to a support platform or boat. The Aqua-Lung, developed by Cousteau and Gagnon, and the submarine escape appliances, developed by Momsen and Davis in the 1930s, were forerunners of the self-contained underwater breathing apparatus (SCUBA), which frees divers from the limitations of tethering.

The increasing popularity of scuba diving and the growth of commercial diving have increased the frequency of deep-pressure injuries. Even in regions far from coasts, individuals are diving in quarries, lakes, rivers, and caves. In addition, the ability to travel rapidly between areas of disparate altitudes in a matter of hours (including the exacerbation caused by decreased pressures in flight) increases the chance of experiencing decompression injuries. Emergency physicians worldwide should know the physiologic effects and management of decompression sickness.

Decompression illness(DCI) may theoretically be possible which is following after breath-hold dives because the nitrogen gas is accumulated in blood and tissues. Since the 1960s, when Cross reported Taravana diving syndrome in Polynesian pearl divers, the occurrence of diving accidents has been widely debated. However, such incidents have not been reported for more than 3 decades. Recently, we have encountered 2 Japanese professional breath-hold (ama) divers with a history of diving accidents. Our interview survey showed in their island that many ama divers had previously experienced transient stroke-like neurological accidents, in which the most common symptoms were unilateral motor weakness and sensory abnormalities. In addition, we have treated another 2 ama divers who suffered visual disturbance or motor weakness in one side during deep repetitive breath-hold dives. Brain magnetic resonance imagings of above 4 ama divers showed multiple cerebral infarction in the terminal and border zones of the brain arteries. Although the pathogenesis of the brain lesions is not well understood, we propose that arterialized bubbles passing through the lungs or heart involved the brain. In breath-hold divers, DCI involved the brain looks like clinical signs as arterial gas embolism following pulmonary barotrauma. From the mechanisms of bubble formation, however, this disorder has been classified as decompression sickness. We propose that there is a difference between clinical and mechanical diagnoses in a criteria of brain DC. (author abst.)

We report a case of transient neurological disorder compatible with cerebral decompression illness in a breath-hold diver. A large right-to-left shunt was later detected with contrast transcranial Doppler ultrasound. While the mechanism of brain damage is unclear, this observation highlights the need for breath-hold divers to avoid excessive nitrogen loading and to refrain from forceful Valsalva maneuvers that may contribute to the opening of a patent foramen ovale and lead to paradoxical cerebral embolism. Because decompression illness is a possibility, anyone who experiences unusual symptoms after breath-hold diving should seek immediate medical attention.

A reader recently asked me if freedivers ever developed decompression sickness. This has been studied in several countries but the best information comes from the natives of the Tuamotu Archipelago in Polynesia, where freedivers in the past made 40 to 60 dives a day to depths of 100 to 140 feet to gather pearls. Their descents were assisted by a lead weight and they ascended by pulling themselves up a rope tethered to a collection basket. An assistant then raised the basket to retrieve the shells gathered on the bottom. Descent times were 30 to 50 seconds, total dive time, about 100 seconds and the surface interval between dives was four to six minutes. Many of the divers developed a severe illness called Taravana, the symptoms of which are similar to those of decompression sickness-paralysis, visual changes, hearing loss and dizziness. Some divers died. Many who survived had permanent brain and spinal cord injuries. Although Taravana is most likely decompression sickness, some symptoms do not fit the picture of decompression sickness and other causes, such as hypoxia, have been proposed.

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Description from forums.deeperblue.net:

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Something is better than nothing. This "modo" drives the decision to post these tables in this forum.

This table covers depths of 10 to 40 meters and bottom times between 1 and 5 minutes.

Allways use your judgment and knowledge that you acquired on your proper training.

Allthough, I have put some effort to make the tables as conservative as possible, there are considerable areas of uncertainty, hence do not use this table to plan your dives as they can not guarantee DCS free diving!!!

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Description from forums.deeperblue.net:

... Having read your post I am attaching this file for information purposes. This work is only an excercise and as such shall not be used in any way as a means to prevent or predict DCS. ...