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PubMed2003

The maximum tissue half-time for nitrogen elimination from divers' body.

Both the longest tissue half-time (T1/2max) and the maximum allowable pressure gradient (deltaP) define the safe rate of decompression (DR) after saturation expositions. The mathematical relation between them (DR = -k x deltaP, where: k = ln(2)/(T1/2max)) suggests that experimentally established decompression rate can be hypothetically described by the infinite number of T1/2max and deltaP combinations. The observed number of decompression sickness after saturation decompressions forced to change those parameters subsequently and finally led to values far outside physiological range. Therefore the aim of this study was to compare values of the longest tissue half-time of nitrogen desaturation from diver's body published since 1908 in order to present the evolution of opinions concerning desaturation process. Non-physiological values of T1/2max (from 75 to 1280 minutes) have been published during historical evolution of decompression tables and systems. The currently accepted values of T1/2max (in the range of 320-480 minutes) for saturation and non-saturation air and nitrox divings and hypobaric decompressions, still need to be precised. The discrepancy between T1/2max values obtained using isobaric decompression method and decompressions after diving indicates different physiological phenomena during nitrogen elimination in both methods.

Decompression↗
PubMed2004

Paralysis and blindness during a balloon ascent to high altitude.

An account of the classic balloon ascent to over 29,000 ft (8840 m) by J. Glaisher and H. T. Coxwell on September 5, 1862, appeared in The Lancet and is reproduced here. Glaisher reported paralysis of his arms and legs and sudden loss of sight. Coxwell also lost the use of his hands and could only open the valve of the balloon to initiate its descent by seizing the cord with his teeth. These symptoms are unusual for acute hypoxia, and in a recent article Michael J. Doherty suggested that they may have been caused by decompression sickness. However, this seems unlikely based on many reported cases of subatmospheric decompression sickness.

Altitude Sickness↗
PubMed1976

Blood viscosity in man following decompression: correlations wiht hematocrit and venous gas emboli.

Whole blood viscosities were measured in U.S. Navy personnel before and after chamber compressions to 5 ATA (132FSW) and 7.4 ATA (210 FSW) by a new method described here. Bubble scores as a quantitative measure of venous gas emboli were determined during decompression and for 30 min thereafter. Hematocrit was measured both before and after each dive. There were five cases of decompression sickness in the two groups. No significant changes in whole blood viscosity, or hematocrit, were noted either in the group that was affected by decompression sickness or in all of the subjects taken as a group. No correlations between total bubble score and changes in viscosity or hematocrit could be made. These results imply that no major changes in viscosity occur in the usual forms of decompression sickness encountered in human beings.

Blood Viscosity↗
PubMed1984

Ultrasonic monitoring of decompression procedures.

p6rly detection of bubbles may provide clues to the mechanism of their formation, and a knowledge of their extent during a decompression may allow the prevention of decompression sickness. We have used ultrasound imaging to study bubble formation in peripheral tissues. The results suggest that: (a) a threshold supersaturation for bubble formation exists; (b) the earliest bubbles are intravascular; (c) before signs of decompression sickness a substantial accumulation of stationary bubbles occurs. Despite the success of Doppler methods in detecting moving bubbles after decompressions normally considered safe, recent studies have shown that the correlation between number of bubbles detected and symptoms of decompression sickness is often poor. We have used a time integral of the ultrasound images, which avoids laborious image analysis, to follow the extent of both moving and stationary bubbles. Human trials involving a wide variety of decompressions suggest that correct prediction of symptoms is possible.

Animals↗
PubMed2003

Health outcome following multi-day occupational air diving.

Acclimatization to decompression stress has been reported in caisson workers and helium-oxygen divers; however the alternative notion that the risk of decompression sickness increases with successive days of diving is widespread. We examined 201 multi-day series of 2 to 29 diving days identified retrospectively in a database of occupational air dives for evidence of acclimatization or sensitization. Decompression related health status was measured using a self-administered diver health survey; resulting scores were analyzed by linear modelling. Daily diving consisted of 1-3 dives each to mean maximum depth of 17.2 (SD 3.9) meters seawater for a mean duration of 23 (SD 17) min. Daily diver health scores increased with calculated daily risk of decompression sickness but were not influenced by the order of dives in multi-day series. Poor health outcome indicated by treated decompression sickness and diver health scores > 8 occurred early in multi-day series. There was no evidence of sensitization to decompression stress whereas the timing of poor health outcomes suggests an element of acclimatization.

Analysis of Variance↗
PubMed1995

[Neurologic accident of decompression: a new indication of transesophageal echocardiography].

Decompression sickness in a 33-year-old SCUBA diver led to neurological lesions with brain damage. The existence of a patent foramen ovale detected with a transoesophageal contrast echocardiography suggested paradoxal gas embolism. This observation emphasizes the intest of transoesophageal contrast echocardiography in decompression sickness as discussed in the literature. Its widely utilization would permit a better understanding of the pathophysiology of decompression sickness. It also may help the physician in deciding whether or not to authorize further diving.

Adult↗
PubMed1979

Effects of aspirin and dipyridamole on platelet function, hematology, and blood chemistry of saturation divers.

Twenty-four young male divers were assigned randomly to 4 treatment groups: Group I received aspirin (325 mg) three times daily; II received dipyridamole (75 mg) three times daily; III received both drug regimens; and IV received matching placebo. Double-blind procedures were followed. Treatment began 24 h prior to a 48-h saturation dive (inclusive of 17 h decompression) at a simulated depth of 18.3 m and continued throughout and for 3 days after the dive. A post-dive reduction in circulating platelet count was observed in all groups, except the group that received aspirin only. Platelet survival was shortened in all treatment groups. Five cases of Type I decompression sickness occurred and were treated by recompression, two in the aspirin plus dipyridamole group, two in the dipyridamole group, and one in the placebo group. Blood chemistry and hematology profiles showed that divers with decompression sickness had more elevated GOT, GPT, CPK, cholesterol and triglyceride levels, and greater reductions in platelet count, Platelet Factor 4 and Thrombin Clotting Time than most other subjects. Subjects receiving either aspirin or aspirin plus dipyridamole had fewer changes in these parameters. Failure of aspirin to potentiate, or add to, dipyridamole may be due to other actions of aspirin such as inhibition of prostacyclin synthesis. Further studies of the role of antiplatelet drugs in decompression sickness are warranted.

Adult↗
PubMed1998

Rapid decompression in the EA-6B.

A Grumman EA-6B aircraft experienced a rapid pressurization failure at 27,000 feet. All four crew members had removed their oxygen masks and were breathing cabin air pressurized to 8,000 feet before the incident. Although none of the crew members developed signs or symptoms of decompression sickness, the potential for adversity was realized by all. Altitude decompression sickness (DCS) and pulmonary overinflation syndrome (POIS) represent potentially fatal complications of rapid decompression or uncontrolled ascent in aircraft. The signs and symptoms of DCS range from mild joint pain to eventual cardiopulmonary collapse and death. The symptoms of POIS are usually more abrupt and lethal. The medical management of DCS and POIS includes (1) maintenance of airway and cardiopulmonary resuscitation if necessary: (2) administration of 100% oxygen; (3) descent as per Naval Aviation Training and Operating Procedures Standardization guidelines; (4) horizontal body position; (5) maintenance of fluid intake; and (6) early medical evaluation by a flight surgeon or other physician qualified in the management of DCS. Symptoms of DCS may appear up to 24 hours after decompression, and continued monitoring or grounding of exposed individuals during this time is essential. Many controllable factors may predispose to DCS/POIS, and preventive measures should be taken to ensure maximum reduction of risk.

Aerospace Medicine↗
PubMed1979

Increased blood-brain barrier permeability to tetracycline in rabbits under dysbaric conditions.

Alteration of the blood-brain barrier (BBB) by dysbaric exposure may have relevance in several areas of hyperbaric medicine. Drugs administered to persons exposed to dysbaric conditions, e.g., divers, compressed air workers, may penetrate the brain in amounts that could produce toxic or undesirable effects. Modification of the BBB may also have pathogenetic implications in decompression sickness. Furthermore, increased BBB permeability to certain potentially useful antitumor agents, antibiotics, and other compounds under dysbaric conditions may provide the basis for a new therapeutic approach. This report concerns the influence of dysbaric exposure on BBB permeability to an antibiotic. Tetracycline (5-40 mg/kg) was intravenously injected in 22 experimental rabbits (subjected to air compression-decompression) and 17 controls (kept at ambient pressure). Fluorescence microscopy and spectrometry revealed significantly greater tetracycline concentrations in 72.7% of the experimental brains. With the 5 mg/kg dose, the mean tetracycline concentrations was 0.17 micrograms/g in control brains and 0.33 micrograms/g in experimentals. These results indicate that dysbaric exposure increases BBB permeability to tetracycline. It appears that BBB alteration is related to intravascular gas bubbles but is independent of the development of decompression sickness. The conclusions of this investigation are pertinent to brain pharmacotherapy and may provide some new insight into the mechanism of decompression sickness. They also point to potential risks connected with drug administration under dysbaric conditions that can alter BBB permeability.

Animals↗
PubMed1985

Fetal and maternal bubbles detected noninvasively in sheep and goats following hyperbaric decompression.

Pregnant sheep and goats were compressed with air to an equivalent depth of 49 msw (160 fsw) for bottom times ranging from 5 to 15 min. Maternal (precordial) and fetal (umbilical artery) circulation were monitored transcutaneously with a Doppler ultrasound flowmeter to determine the presence of decompression gas bubbles. It was found that the number of bubbles detected precordially in the maternal circulation exceeded the number detected in the fetal umbilical artery for any given bottom line. Additionally, bubbles were found in the fetal circulation even when the mother did not display signs of decompression sickness. Thus, avoidance of symptoms of pain-only decompression sickness in the mother is not sufficient to preclude gas phase formation in the fetus.

Age Factors↗
PubMed1998

Diving pattern and work schedule of construction well divers in Taiwan.

Construction well divers in Taiwan reportedly suffer a high prevalence of dysbaric osteonecrosis. We studied five divers working at the same construction site. We recorded their diving methods, diving depths, bottom times, work patterns, water temperatures, and heart rates. We also monitored gas bubbles in the subclavian vein in selected dives. A crude but effective hot-water system protected divers against hypothermia and allowed them to work in 24 degrees-27 degrees C water. Divers worked approximately 6.6 h a day and progressed approximately 3.0 m a day while excavating an average of 148 buckets of sand and rock each weighing 49.5 kg. The divers sustained a heart rate increase of 49%. Sixty percent of their equivalent single dive bottom times exceeded the U.S. Navy's no-decompression limits. Two cases of venous bubbles were detected, and one of these divers showed symptoms of decompression sickness. The prolonged bottom time and lack of a decompression schedule probably contributed to a risk of decompression sickness and dysbaric osteonecrosis.

Adult↗
PubMed1976

Pressure-reduction limits for rats following steady-state exposures between 6 and 60 ATA.

The role of pressure reduction in the formation and growth of bubbles is universally recognized and its significance in decompression theory has been accepted. Yet the allowable limits of pressure reduction for man and animal are uncertain. This study sought to evaluate the pressure-reduction limits for rats following steady-state exposures at pressures greater than 1 atm. To define the relationship, 350 albino rats were exposed to 1 of 12 specified pressure levels between 6 and 60 ATA and then abruptly decompressed to a preselected reduced pressure level for observation. The pressure-reduction levels were selected to determine for each saturation-exposure level an ED-50 (i.e. the effective dose that will produce decompression sickness in 50% of the animals). The results demonstrate three consistent findings: (1) there is a linear relationship (r = .99) between the magnitude of a safe pressure reduction and the saturation exposures between 6 and 43 ATA; (2) at pressures greater than 43 ATA, there is a qualitative change in the decompression sickness symptoms and a reduction in the precision of the mathematical relationship (r = .44); and (3) the magnitude of the pressure change required to increase the incidence of decompression sickness from 10% to 90% is directly related to the magnitude of the exposure pressure. The implications of these results for deep operational diving are discussed.

Animals↗
PubMed1993

Dysbarism: the medical problems from high and low atmospheric pressure.

The most serious problems resulting from a change in ambient pressure are pulmonary barotrauma with air embolism and decompression sickness. The small differential pressures used in ventilators at atmospheric pressure may tear lung tissue and, in diving, deaths have occurred from the expansion of pulmonary gas on an ascent of less than two metres. The bubbles of respired gas that enter the systemic circulation often occlude cerebral arteries and may cause infarction. In decompression sickness, bubbles form in the tissues from supersaturation of the nitrogen or helium absorbed under pressure. Joint pain--the 'bends'--is associated with gas in particular connective tissue. Serious decompression sickness results from the entry of microbubbles into the systemic veins. Large numbers of bubbles trapped in the lung cause an acute respiratory syndrome known as 'chokes'. If the lung filter is overwhelmed, or microbubbles pass into the systemic arteries through an atrial septal defect, they may open the blood-brain barrier, affecting brain and spinal cord function. Untreated, demyelination with relative preservation of axons may occur, the pathological hallmarks of multiple sclerosis. Gas bubble disease requires urgent compression in a hyperbaric chamber and the use of high partial pressures of oxygen.

Atmospheric Pressure↗
PubMed1988

Neuroimaging of scuba diving injuries to the CNS.

Diving accidents related to barotrauma constitute a unique subset of ischemic insults to the CNS. Victims may demonstrate components of arterial gas embolism, which has a propensity for cerebral involvement, and/or decompression sickness, with primarily spinal cord involvement. Fourteen patients with diving-related barotrauma were studied with MR imaging of the brain and spinal cord and with CT of the brain. In four patients with presumed cerebral gas embolism, cranial MR was abnormal in three patients while CT was abnormal in only one. Twelve patients had decompression sickness and spinal cord symptoms. MR documented spinal cord abnormalities in three patients. However, scans obtained early in our study were frequently limited by technical constraints. MR of the brain is more sensitive than conventional CT scanning techniques in detecting and characterizing foci of cerebral ischemia caused by embolic barotrauma to the CNS. Although spinal MR may be less successful in the localization of spinal cord lesions related to decompression sickness, these lesions were previously undetectable by other neuroimaging methods.

Adolescent↗
PubMedDate not supplied

[Development of decompression regimens for excursion dives after a prolonged exposure to 21 ata].

Decompression regimens for excursion dives from a depth of 20, 50, 100 or 200 m were developed and tested in a dry altitude chamber. Each dive continued for about 2 weeks, during which test subjects performed 10 excursion dives to a lower depth. No cases of decompression sickness were observed during 246 man/excursions whereas two cases of decompression sickness occurred in a field study.

Adult↗
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↗
PubMed1996

Recreational scuba diving injuries.

Because of the increasing popularity of recreational scuba diving, primary care physicians should be familiar with common diving injuries. One form of barotrauma, middle ear squeeze, is the most common diving injury. Other important diving injuries include inner ear barotrauma and pulmonary barotrauma. Arterial gas embolism, a potentially life-threatening form of pulmonary barotrauma, requires hyperbaric treatment. Decompression sickness is the result of bubble formation in body tissue. Symptoms of decompression sickness range from joint pain to neurologic or pulmonary problems. Recompression is the mainstay of treatment.

Barotrauma↗
PubMed1988

Scuba diving injuries.

Scuba diving has become increasingly popular, and family physicians may encounter patients who have been injured in a dive. Manifestations of diving injuries may not occur until 12 hours or more after a dive. Initial treatment, based on knowledge of the pathophysiology of decompression sickness, lung expansion injuries and ear barotrauma, may prevent severe and permanent sequelae. Decompression sickness and air embolism are medical emergencies.

Air Pressure↗