Apnea Media Base

Linér MH, Andersson JPA. Hypoxic syncope in a competitive breath-hold diver with elevation of the brain damage marker S100B. Aviat Space Environ Med 2009; 80:1066-8.
Introduction: Competitive breath-hold divers can accomplish previously unbelievable performances; e.g., the current world record for apnea during rest (“static apnea”) is 11 min 35 s. However, whether such performances are associated with a risk for hypoxic brain damage has not been established. Case Report: A breath-hold diver's competitive performance resulted in a loss of consciousness, after which he was subjected to a medical examination by the event physician. Blood samples were collected for analysis of the brain damage marker S100B in serum. The S100B in serum was 0.100 μg · L−1 in the blood sample collected 15 min after the loss of consciousness. At 1 and 5 d after the incident it was 0.097 μg · L−1 and 0.045 μg · L−1, respectively. Discussion: The elevated level of S10…

We report a case with a breath-hold diver who inadvertently experienced a packing blackout. During the incident, an electrocardiogram (ECG) and blood pressure were recorded, and blood samples for determinations of biomarkers of cardiac muscle perturbation (creatine kinase-MB isoenzyme (CK-MB), cardiac troponin-T (TnT), and myoglobin) were collected. The ECG revealed short periods of asystole during the period of 'packing blackout', simultaneous with pronounced reductions in systolic, diastolic, and pulse pressures. Serum myoglobin concentration was elevated 40 and 150 min after the incident, whereas there were no changes in CK-MB or TnT. The ultimate cause of syncope in this diver probably was a decrease in cerebral perfusion following glossopharyngeal insufflation. The asystolic periods r...

PMID: 4690448 [PubMed - indexed for MEDLINE]
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It is well accepted that hyperventilation before breath hold swimming and diving makes it possible for a person to extend the time under water. Less well known is the fact that this maneuver can cause loss of consciousness due to hypoxia. This accident happens almost exclusively to males (56 cases). The most common age group was 16-20 years (range 12-33 years). All were known to be good swimmers or divers. Approximately 80f the cases occurred in guarded pools. Thirty-five subjects survived the accident and of the twenty-three fatalities, there was only one good autopsy report. In this instance the findings were those associated with classical drowning preceded by hypoxia and hypercapnia. Breath holding experiments indicated that the times between loss of consciousness and death may be no longer than 2.5 minutes. The patterns associated with these cases suggest that those who are responsible for aquatic safety as supervisors or guards of pools could prevent most accidents by watching for youn

PMID: 8578720 [PubMed - indexed for MEDLINE]

In work influence of various temporary modes of free hyperventilation of the lungs was investigated, usually used by the sportsmen before diving on reduction of the contents of CO2 in exhaling air of healthy men-divers. Attention was paid to the opportunity of occurrence of posthyperventilation apnea and loss of consciousness. It is shown, that washing away CO2 from organism at hyperventilation is limited. Hyperventilation (their depth and frequency was chosen arbitrary), spent during 60, 120, 180, 360 seconds causes in healthy trained men apnea and loss of consciousness.

OBJECTIVE: To examine the causes and circumstances of snorkelling deaths in Australia from 1987 to 1996. DESIGN: Retrospective case extraction. CASES AND DATA SOURCES: 60 snorkelling deaths extracted from an ongoing diving fatality survey and from coroners' reports. Further details were obtained from police reports, diving industry (incorporating commercial operators, relevant government departments and instructors' organisations) inquiries and coronal inquests. MAIN OUTCOME MEASURES: Cause of death (determined by the authors from information obtained and from detailed autopsy findings) and the circumstances surrounding death. RESULTS: 15 of the 60 snorkellers who died were female. The three major causes of death were drowning (27 cases), cardiac events (18) and hypoxia with breath-holding after hyperventilation and/or during ascent producing unconsciousness then drowning (12). Overseas tourists were notable among those who drowned, while middle-aged men dominated the group who died of cardiac

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 first official world championships in breath-hold diving (1996), a sport has developed where the athletes compete in various disciplines of breath-hold diving. One of the rules is that the diver should surface from a dive without showing any signs of hypoxia. Depending on the severity of hypoxia, a diver may suffer disqualifying signs such as loss of consciousness (LOC) or loss of motor control (LMC), the latter including signs such as confusion, affected postural control, spasms or speech problems. Data was collected from the results of the major international competitions following AIDA guidelines (Association International pour le Dévelopment de l'Apnée) in 1998, 2001-2004. The data was analyzed for frequency of LOC and LMC during constant weight diving and during static apnea. In constant weight diving, the diver swims down (and up) as deeply as possible along a vertically suspended rope (current record 105 m). In static apnea, the diver strives for maximum duration, floating motionless face down in a pool (current record 8.58 min). A total of 601 static apnea (SA) performances and 596 constant weight dives were judged in the six competitions. On average, 10 % of SA, and 11 % of CW performances were disqualified due to signs of hypoxia. For the competitions in 2002-2004, a distinction was made in the rules between LOC and LMC; of a total number of 355 SA performances, 1.1 % resulted in LOC, while 9.6 % resulted in LMC. For CW, the number was 344 with 6.1 % LOC and 6.1 % LMC. Despite the relatively high incidence of dramatic signs, it is noteworthy that there have been no reports of fatal accidents or permanent injuries from any of the above-mentioned competitions. This descriptive paper shows a relatively high incidence of disqualifications due to signs of hypoxia in breath-hold competitions 1998-2004.

Description from freediving.biz

In 2001 I filmed Hubert Myer blacking out at 10-15 meters in the Ibiza world cup. I remember his twisting body with air flowing out of him - the safetydivers lifting up his limp lifeless body on to the boat and the pink foam coming out of his mouth. He had been down to70 meters.

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Description from www.freedive.net:

Note to the reader: In the interest of freediver safety, I have elected to include the entire chapter on the subject of shallow-water blackout—probably the most serious threat to freediver safety. For a more in-depth discussion on this condition, please see our newest book Freedive! by myself and co-author David Sipperly.

Every year we lose too many divers to shallow-water blackout. Almost everyone I interviewed for this book has a story to tell about this frightening but all too common occurrence. Shallow-water blackout (SWB) is the sudden loss of consciousness caused by oxygen starvation. Unconsciousness strikes most commonly within 15 feet (five meters) of the surface, where expanding, oxygen-hungry lungs literally suck oxygen from the diver s blood.

SWB conjures up images from the movie Invasion of the Body Snatchers. Once you lose consciousness you die. The blackout occurs quickly, insidiously and without warning. Mercifully, the victims of this condition die without any idea of their impending death. Beginning breath-hold divers, because of their lack of adaptation, are not generally subject to this condition. It is the intermediate diver who is most at risk. He is in an accelerated phase of training, and his physical and mental adaptations allow him to dive deeper and longer with each new diing day sometimes too deep or too long. Advanced divers are not immune.

I blacked out once and had two near misses before the age of 22. Jerry Stugen, my early mentor, remembers me at age 16 coming up from a dive with purple lips. Unaware of my oxygen depleted state, I was rapidly preparing to dive again to remove a large fish holed up below. Jerry yanked the snorkel from my mouth and commanded me to stop diving for the day. When I was 18 years old, I passed out in a swimming pool during an underwater endurance test for my physical education class. The second I stopped swimming my coach jumped into the water and brought me to the pool deck where I regained consciousness. Aside from being frightened, the only other problem I had was painful legs lasting two days. My last near miss happened at age 22. I entered a Florida spearfishing contest with a borrowed gun. Ascending after a 70-foot dive, I shot a large jack which took off in a blur. Not wanting to lose the gun, I remember fighting the fish to within a few feet of the surface. The next thing I remember was being awakened by bumping my head against our anchored boat.

Description from scuba-doc.com:

Free Diving and Shallow Water Blackout

Discusses free diving, shallow water blackout (latent hypoxia)

Shallow water blackout (SWB) is the sudden loss of consciousness caused by oxygen starvation following a breath holding dive. This was first described by S. Miles as 'latent hypoxia', shallow water blackout is the term he ascribed to unexplained loss of consciousness in divers using closed-circuit oxygen breathing apparatus at shallow depths. Unconsciousness strikes most commonly within 15 feet (five meters) of the surface, where expanding, oxygen-hungry lungs literally suck oxygen from the divers blood. Once you lose consciousness you are likely to drown. The blackout occurs quickly, insidiously and without warning. The victims of this condition die without any idea of their impending death.

Description from www.freedive.net:

Freedivers Safety Vest

Well-trained freedivers who know the risks of shallow water blackout (SWB) die at an alarming and predictable rate. The vast majority of SWB victims are found on the bottom with their weight belt firmly in place. Why is this?

For some answers, download the pdf file linked below.

Related Items

• website: Freedivers Safety Vest

Novel observations collected from video, acoustic and conductivity sensors showed that Antarctic fur seals consistently exhale during the last 50-85% of ascent from all dives (10-160 m, n > 8000 dives from 50 seals). The depth of initial bubble emission was best predicted by maximum dive depth, suggesting an underlying physical mechanism. Bubble sound intensity recorded from one seal followed predictions of a simple model based on venting expanding lung air with decreasing pressure. Comparison of air release between dives, together with lack of variation in intensity of thrusting movement during initial descent regardless of ultimate dive depth, suggested that inhaled diving lung volume was constant for all dives. The thrusting intensity in the final phase of ascent was greater for dives in which ascent exhalation began at a greater depth, suggesting an energetic cost to this behaviour, probably as a result of loss of buoyancy from reduced lung volume. These results suggest that fur seals descend with full lung air stores, and thus face the physiological consequences of pressure at depth. We suggest that these regular and predictable ascent exhalations could function to reduce the potential for a precipitous drop in blood oxygen that would result in shallow-water blackout.