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PubMed2003

Simulated high altitude diving experiment for the underwater construction operation.

The simulated dive experiments were conducted at the high altitude of 4500 meters and 5000 meters, for the requirement of diving operation in the lakes at the altitude of 4442 meters for the construction of large-scale hydroelectric power station. The high & low pressure chamber-complex was used, and 15 professional divers participated in the experiment. The divers were stayed at the altitude of 4500 and 5000 meters for 7-9 days. Totally 85 persons-times of dives to the depths of 30-50 meters were operated; they stayed under the water for 30-90 minutes while processing physical activities. During the experiment, we studied the pressurization procedure, decompression table, and physiological functions of the divers. The results indicate that, although the relative pressure differences between the surface and underwater was larger at high altitude than at sea level, the appropriate prolongation of the compression time was able to prevent the difficulty in pressure regulation for the divers to avoid the injury of middle ear. Four tables of the decompression A, B, C and D was calculated with Haldane's theory, and the speed of decompression increased in the order from A to D. The safest procedure was C, and there was no decompression sickness and bubbles in body of the divers. The methods of decompression included underwater stage decompression, surface decompression, oxygen-breathing decompression, and repetitive diving decompression. The surface decompression was the most suitable method for the high altitude, as it could greatly decrease the time in the cold water for the divers. The power spectrum analysis of EEG (electroencephalogram) indicated that, when the divers were exposed to the altitude of 5000 meters, the delta activity in EEG increased, alpha and beta activity decreased. And the delta activity decreased, the alpha and beta activity increased while diving during a dry condition. According to the diving and decompression procedure studied under simulated conditions, 272 person-times of diving training and underwater operations were processed in a high altitude hydroelectric power station at the altitude of 4442 meters, including photographing, video-recording, measuring, and drilling. There were no signs and symptoms of decompression sickness and bubbles.

Adaptation, Physiological↗
PubMed2006

Vascular distribution of an ultrasound contrast agent used to simulate decompression bubbles.

OBJECTIVE: The objectives of this preliminary work were to evaluate the distribution of an ultrasound contrast agent (UCA) (microbubbles) in different arterial regions (brain, kidney, lower limbs) using the Doppler spectrum brightness analysis and to discuss the results in the context of decompression physiology. METHOD: There were four patients who instrumented with two pulsed Doppler sensors in order to monitor in real-time the spectrum of the middle cerebral femoral arteries. Renal arteries were investigated using an echo-Doppler probe handled by a sonographer. Measurements of the systolic mean, diastolic frequencies, qualitative, and quantitative analysis of the spectrum brightness intensity were performed before and after intravenous injection of a UCA. RESULTS: All of the systolic mean and diastolic arterial frequencies remained constant during the experiment. Some seconds after the first injection, the cerebral spectrum was heterogeneously enhanced with strong flashes over the entire spectrum. The renal and femoral spectrums were homogeneously reinforced. The spectrum brightness patterns did not change during the first 10 min. DISCUSSION: This work shows that the distribution of the UCA microbubbles within the vessel sections changed according to the distance from the heart, as suggested by the spectrum recorded at different sites. By mixing the blood, the heart could re-aggregate the UCA particles, even when they returned from the distal vascular regions where they were homogeneously distributed. The circulating microbubbles and their distribution within the arteries should be considered in decompression procedures with repetitive dives.

Adult↗
PubMed1981

[Considerations on 209 cases of decompression sickness treated in Italian hyperbaric centers in 1978 and 1979].

Results of an epidemiological study on the incidence and aethiology of the cases of Decompression Sickness treated in eleven Italian Hyperbaric facilities during 1978 and 1979 are reported 209 cases were treated; 186 recovered completely, 92 improved, 5 had no advantage from treatment, 2 died. The majority of cases were in the age-range 25-29 years (15-55) and in the depth-range 40-50 msw (12-100). Decompression was mandatory in 207 cases and was not respected, mainly because the divers ascended at a wrong rate (20 msw/min in the majority, 10 cass "ballooned" to the surface, 2 cases surfaced at 1-2 msw/min). In a significant number of times decompression was aborted due to exhaustion of compressed air in the bottles. 55% of the 1979 cases referred to repetitive diving (2nd or 3rd dive of the day). The Authors conclude that human error in by far the most recurring aethiological agent in this study and point out the coincidence of the high incidence of D.S. cases south of Rome with the relative lack of diving schools in that area.

Adult↗
PubMed1996

Neurologic decompression illness: a gravity score.

Treatment of neurologic decompression accidents consists of various hyperbaric oxygen (HBO) protocols. To facilitate such comparisons between different protocols we developed a gravity score. A group of 96 divers was used to establish the score. On admission we first identified signs and symptoms that had possible predictive value (chi 2 test). The parameters included were repetitive dive, clinical course before HBO, objective sensory disorder, motor impairment, and urinary disturbances. Each parameter was assigned a coefficient. The sum of the coefficients for each accident, based on the most severe manifestations before decompression therapy, yielded a score for each diver. A multivariate analysis was used to evaluate the overall agreement between the model prediction and clinical observations, which was 78.7%. A second group (66 divers) was used to validate the score; this group showed a significant difference in the gravity score between the divers who had sequelae and those who did not (P = 0.0001), and between the divers who had incapacitating sequelae and those who had mild sequelae (P = 0.04). Eighty-six percent of the divers with a score above 7 developed sequelae. This index remains to be validated in a prospective multicenter study. If endorsed, valid comparisons can be made between the different therapeutic protocols.

Adult↗
PubMed2000

Neurological accidents caused by repetitive breath-hold dives: two case reports.

We report two Japanese male professional breath-hold divers (33 and 39 years of age) who experienced neurological disorders during repetitive dives to over 20 m of seawater. One patient had right homonymous hemianopsia, and the other presented with right hemiparesis with facial involvement and sensory deficit. In addition, they each had a history of neurological problems following such dives. Magnetic resonance images of their brains disclosed multiple T2-weighted hyperintensities corresponding to their neurological symptoms. Their brain lesions suggest a multiple cerebral infarction caused by occlusion of the cerebral arteries. We conclude that the repetitive deep breath-hold dives induced the brain involvement.

Adult↗
PubMed1987

Failure of heparin, superoxide dismutase, and catalase to protect against decompression sickness.

The effects of heparin (HEP), superoxide dismutase (SOD), and catalase (CAT) on the course of decompression sickness (DCS) were studied in anesthetized dogs (Canis familiaris). Animals were divided into 4 groups: a drug assay group (n = 4) received HEP + SOD or HEP + SOD + CAT but were not dived; a control group (n = 14) was dived without drug treatment; a HEPSOD group (n = 11) received HEP + SOD predive and postdive; and a HEPSODCAT group (n = 15) received HEP + SOD + CAT before diving. All dived animals were subjected to repetitive air dives to 10 ATA until pulmonary artery pressure at least doubled within 10 min postdive. Physiologic variables were measured for 3 h postdive or until death. Animals were not recompressed. More early deaths occurred in the HEPSOD (7/11) and HEPSODCAT (8/15) groups than in the control group (5/14). All dived animals developed pulmonary hypertension, systemic hypotension, hemoconcentration, acidosis, hypoxemia, and interstitial pulmonary edema postdive. Drug therapy did not alter these responses to decompression. We conclude that without recompression, treatment with either HEP + SOD OR HEP + SOD + CAT does not improve the outcome of severe DCS in this animal model.

Animals↗
PubMed1992

Cardiovascular responses elicited by simulated diving and their habituation in man.

The cardiovascular responses of 24 subjects were investigated under various simulated diving conditions. Muscle blood flow in forearm and calf, arterial pressure, heart rate and intrathoracic pressure were monitored. Breath holding with face immersion in water at 18 degrees C gave a typical diving response at intrathoracic pressure of 0 and 20 mmHg, (23% bradycardia, greater than 60% muscle vasoconstriction). Breath holding alone at 20 mmHg intrathoracic pressure resulted in vasoconstriction (50%) and bradycardia (4%). Breath holding at 0 mmHg intrathoracic pressure induced a muscle vasoconstriction (5%). These results indicate that both increased intrathoracic pressure and facial immersion can produce a typical diving response individually but that the full 'diving response' requires the presence of both conditions. Diving often activated two responses, the typical 'diving response' and a superimposed defence reaction. Cardiovascular components of the defence reaction (muscle vasodilatation and tachycardia) which was elicited in some divers masked the diving response. In those subjects in whom the diving response was initially absent during repetition of diving manoeuvres the cardiovascular components of the defence reaction were habituated and the characteristic diving response gradually emerged: the initial tachycardia diminished and was replaced by bradycardia, while vasodilatation in the forearm and calf was replaced by vasoconstriction.

Adolescent↗
PubMed2006

Neurological disorders after repetitive breath-hold diving.

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.

Adult↗
PubMed1979

Dolphin lung collapse and intramuscular circulation during free diving: evidence from nitrogen washout.

Intramuscular nitrogen tensions in Tursiops truncatus after a schedule of repetitive ocean dives suggest a lung collapse depth of about 70 meters and suggest that intramuscular circulation is maintained during unrestrained diving in the open ocean. Therefore, the bottle-nosed dolphin is not protected by lung collapse from the decompression hazards of dives to depths shallower than 70 meters.

Adipose Tissue↗
PubMed2026

Adaptations to breath-hold diving: from traditional divers to elite athletes.

Breath-hold diving exposes humans to repeated episodes of profound hypoxia and hypercapnia, eliciting physiological adaptations that enable prolonged underwater performance. This article summarises current knowledge on chronic adaptations in elite breath-hold athletes and traditional diving populations, including the Bajau sea nomads of Southeast Asia and the Korean Haenyeo divers. Evidence indicates that repeated apnoea induces adaptations across multiple physiological systems. Haematological changes include increased spleen size and enhanced splenic contraction, augmenting circulating haemoglobin and oxygen stores during apnoea. In elite divers, structured training can increase resting spleen volume, whereas the Bajau exhibit genetically associated splenic enlargement linked to variants near the PDE10A gene. Cardiopulmonary adaptations include modified pulmonary vascular responses to hypoxia, improved oxygen conservation, and metabolic shifts favoring efficient mitochondrial energy production. Molecular adaptations involve enhanced antioxidant defenses and activation of hypoxia-responsive pathways that may mitigate oxidative stress associated with repeated hypoxia-reoxygenation cycles. Emerging evidence also suggests neural plasticity and possible structural brain adaptations, although the long-term neurological consequences of chronic intermittent hypoxia exposure remain uncertain. Studies of traditional diving populations indicate that both phenotypic plasticity and genetic selection contribute to diving capacity, highlighting interactions between training and evolution. Despite these benefits, breath-hold diving also carries risks, including hypoxic blackout, decompression sickness, and potential neurological injury. Understanding the mechanisms underlying human tolerance to extreme hypoxia may have implications beyond diving physiology, including applications in cardiovascular medicine, hypoxic diseases, and rehabilitation. Further longitudinal, genomic, and mechanistic studies are needed to clarify the limits, benefits, and clinical relevance of these adaptations.

Humans↗
PubMed2001

Can eustachian tube ventilatory function impairment after oxygen diving be influenced by application of free radical scavenger vitamins C and E?

OBJECTIVES/HYPOTHESIS: To evaluate the influence of free radical scavenger vitamins C and E on eustachian tube ventilatory function changes related to oxygen dives. STUDY DESIGN: Prospective, randomized, double-blind, placebo-controlled study of middle ear impedance changes of oxygen divers being orally treated with free radical scavenger vitamins C and E. METHODS: Fifteen divers were allocated to two groups. Before diving on oxygen on consecutive days (days 1 and 2), divers in group 1 took a daily dose of 1 g ascorbic acid and 600 International Units d-alpha-tocopherol and divers in group 2 were given placebo. Before diving and 2 and 24 hours after diving on days 1 and 2, middle ear impedance was measured. RESULTS: Impedance decreased overnight after dive 1 (P =.04) but not after dive 2 (P =.31). No impedance differences were found between groups after the dive on day 1 (P =.83). Twenty-four hours after the dive on day 1 and after the dive on day 2, impedance values in both groups were different (P =.02 vs. P =.07), emphasizing slightly more negative pressures in the vitamin group. CONCLUSION: Vitamins C and E did not reduce eustachian tube ventilatory function impairment overnight after the dive on day 1, suggesting no evidence of free radical-mediated toxicity affecting the eustachian tube or middle ear mucosa. Repetitive oxygen dives may cause tissue adaptation suggesting other than antioxidant defense mechanisms.

Administration, Oral↗
PubMed1981

[Effects of variations in the ascending speed on the production of circulating gas bubbles after compressed-air diving].

Ninety-seven compressed air divers at depths of 20 to 52 msw were done. Every dive reached a tissue nitrogen saturation level greater than or equal to M value according to U.S. Navy decompression schedules and respected all prescribed decompression stop. Dives were divided in two groups according to the speed of ascent:--1st group: 33 dives (18 simulated, 15 open water) with ascent at 18 msw/min. for the first half of the distance and 10 msw/min. for the second half. No work on the bottom. Average ascent rate 14 msw/min. This profile was due to the flow limits of the outlet of our chamber during the second part of the ascent, and it was repeated in open water diving.--2nd group: 64 dives (4 simulated, 60 open water) with linear ascent at 10 msw/min. Half the open water dives were repetitive within 4 hours from the first one. Medium to heavy work on the bottom. Ultrasound Doppler bubble detection at rest and after exercise was performed at five minutes intervals and during 40 minutes after surfacing.

Diving↗
PubMedDate not supplied

Decompression sickness following breath-hold diving.

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.

Decompression Sickness↗
PubMed1990

Splenic contraction during breath-hold diving in the Korean ama.

Major increases of hemoglobin concentration and hematocrit, possibly secondary to splenic contraction, have been noted during diving in the Weddell seal. We sought to learn whether this component of the diving response could be present in professional human breath-hold divers. Splenic size was measured ultrasonically before and after repetitive breath-hold dives to approximately 6-m depth in ten Korean ama (diving women) and in three Japanese male divers who did not routinely practice breath-hold diving. Venous hemoglobin concentration and hematocrit were measured in nine of the ama and all Japanese divers. In the ama, splenic length and width were reduced after diving (P = 0.0007 and 0.0005, respectively) and calculated splenic volume decreased 19.5 +/- 8.7% (mean +/- SD, P = 0.0002). Hemoglobin concentration and hematocrit increased 9.5 +/- 5.9% (P = 0.0009) and 10.5 +/- 4% (P = 0.0001), respectively. In Japanese male divers, splenic size and hematocrit were unaffected by repetitive breath-hold diving and hemoglobin concentration increased only slightly over baseline (3.0 +/- 0.6%, P = 0.0198). Splenic contraction and increased hematocrit occur during breath-hold diving in the Korean ama.

Adult↗
PubMed2002

Pharmacological blockade of the dive response: effects on heart rate and diving behaviour in the harbour seal (Phoca vitulina).

While diving, harbour seals (Phoca vitulina) manage their oxygen stores through cardiovascular adjustments, including bradycardia, a concurrent reduction in cardiac output, and peripheral vasoconstriction. At the surface, post-dive tachycardia facilitates rapid reloading of oxygen stores. Although harbour seals can tolerate >20 min of submergence, the majority of their natural dives are only 2-6 min and are usually followed by surface intervals that are <1 min, so they spend approximately 80% of their time submerged. Given that harbour seals meet their ecological needs through repetitive short aerobic dives, we were interested in the functional role, if any, of the dive response during these short dives. During voluntary diving in an 11 m deep tank, the cardiovascular responses to submergence of five harbour seals were manipulated using specific pharmacological antagonists, and the effects on diving behaviour were observed. Effects of pharmacological blockade on heart rate were also examined to assess the autonomic control of heart rate during voluntary diving. Heart rate was recorded using subcutaneous electrodes and data loggers, while diving behaviour was monitored using a video camera. The muscarinic blocker methoctramine blocked diving bradycardia, the alpha-adrenergic blocker prazosin blocked diving vasoconstriction, and the beta-adrenergic blocker metoprolol blocked post-dive tachycardia. Heart-rate analysis indicated that diving bradycardia is primarily modulated by the vagus, while post-dive tachycardia results from parasympathetic withdrawal as well as increased sympathetic stimulation of the heart. None of the pharmacological blockers had any effect on average dive or surface interval duration. Seals maintained a high percentage of time spent diving in all treatments. Thus, harbour seals do not appear to need the dive response during short dives in order to maintain an efficient dive strategy.

Adrenergic alpha-Antagonists↗
PubMed2002

The incidence of venous gas emboli in recreational diving.

From 1989-91, the Divers Alert Network monitored recreational divers for Doppler-detected venous gas emboli (VGE) and depth-time profiles following multi-day, repetitive, multi-level exposures. A Spencer score >0 occurred in 61 of 67 subjects (91%) and 205 of 281 dives (73%). No subject developed decompression sickness (DCS) on monitored days although 102 dives (36.3%) scored at Spencer Grades 2 or 3 (High Bubble Grade, HBG). We recorded the depth-time profiles with Suunto dive computers and estimated exposure severity with a probabilistic decompression algorithm. The HBG incidence increased 53% over the range of exposure severity (p < 0.001) in the divers, was approximately 20% higher for repetitive dives than for first dives, and decreased approximately 25% over the 6-8 days of multi-day diving (p < 0.001) suggesting a phenomenon similar to DCS adaptation. The observed HBG incidence was approximately 20% higher for males than females. Older male divers had a 25% increase in observed incidence of HBG while older female divers showed a 55% increase when compared to their younger counterparts.

Adult↗
PubMed2001

Ocular tear film bubble counts after recreational compressed air diving.

Other authors have demonstrated an increase in tear film bubble counts following dry, compressed air dives. We examined the lower tear film meniscus for the presence of bubbles in 42 divers after compressed air dives on a single day and in 11 divers undergoing repetitive, multi-day diving exposures over 5 days. After diving, bubble counts increased significantly (P < 0.01) from predive values. From a predive median (inter-quartile range) of 0 (0-0.33) bubbles/eye, single-day divers reached a maximum bubble count at 48 h after diving of 1 (0-2.25) bubbles/eye. Similarly, from a predive count of 0.33 (0-1) bubbles/eye, multi-day divers had increased bubble counts from 24 h following their first dive until 24 h following their final dive when counts were 1.67 (0.92-3.08) bubbles/eye. Bubble counts were not significantly correlated with inert gas load, body mass index, age, or diving experience. We confirm that tear film bubble counts are raised after wet compressed air diving as previously described following dry diving.

Adult↗