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PubMed2004

Optimal oxygen pressure and time for reduced bubble formation in the N2-saturated decompressed prawn.

Bubbles that grow during decompression are believed to originate from preexisting gas micronuclei. We showed that pretreatment of prawns with 203 kPa oxygen before nitrogen loading reduced the number of bubbles that evolved on decompression, presumably owing to the alteration or elimination of gas micronuclei (Arieli Y, Arieli R, and Marx A. J Appl Physiol 92: 2596-2599, 2002). The present study examines the optimal pretreatment for this assumed crushing of gas micronuclei. Transparent prawns were subjected to various exposure times (0, 5, 10, 15, and 20 min) at an oxygen pressure of 203 kPa and to 5 min at different oxygen pressures (PO2 values of 101, 151, 203, 405, 608, and 810 kPa), before nitrogen loading at 203 kPa followed by explosive decompression. After the decompression, bubble density and total gas volume were measured with a light microscope equipped with a video camera. Five minutes at a PO2 of 405 kPa yielded maximal reduction of bubble density and total gas volume by 52 and 71%, respectively. It has been reported that 2-3 h of hyperbaric oxygen at bottom pressure was required to protect saturation divers decompressed on oxygen against decompression sickness. If there is a shorter pretreatment that is applicable to humans, this will be of great advantage in diving and escape from submarines.

Animals↗
PubMedDate not supplied

Clinical observation: Beau's lines on fingernails after deep saturation dives.

Transverse furrows, or Beau's lines, were noted in the fingernails of all 6 divers following a deep saturation dive to apressure equal to 1100 feet (335 meters) ofsea water (3,370 kPa), and in 2 of6 divers following a similar dive to 1000 feet (305 meters) of sea water (3,164 kPa). Both dives took place at the Ocean Simulation Facility of the Navy Experimental Diving Unit in Panama City, Florida. The divers breathed a partial pressure of 0.40 - 0.44 atm abs (40.5 - 44.6 kPa) oxygen, with the balance helium, during most of the time under pressure. All divers performed hard work on bicycle ergometers during the dives. Four of the divers on the first dive were treated during the dive for pain-only decompression sickness. Beau's lines have been reported in numerous medical conditions such as typhus, rheumatic fever, malaria, myocardial infarction, and other severe metabolic stresses. To the author's knowledge this is the first report of Beau's lines associated with saturation diving.

Decompression↗
PubMed1986

An effect of CO2 on the maximum safe direct decompression to 1 bar from oxygen-nitrogen saturation.

An investigation into the maximum safe decompression step from oxygen nitrogen saturation to 1 bar was carried out with and without the presence of 0.02 bar carbon dioxide. The series, Islander 1, involved 13 teams of 5, fully informed, male volunteers carrying out simulated dives. One group of 6 teams carried out dives in an atmosphere of 0.4 bar oxygen, balance nitrogen (O2-N2); another group of 7 teams used an atmosphere of 0.38 bar oxygen, 0.02 bar carbon dioxide, balance nitrogen (O2-N2-CO2). The dives consisted of a 48-h stay at 1.7 or 1.8 bar to saturate the tissues, followed by decompression to 1 bar air at 0.5 bar/min. Two decompression parameters were studied; the incidence of decompression sickness (DCS) in the 24 h postdecompression, and the incidence and grade of venous gas emboli (VGE) in the first 6 h postdecompression. The grade of VGE was assessed using the Kisman-Masurel scoring system which produces a bubble grade with the subject at rest and after movement. No significant difference was found in the incidence of DCS between the two groups. Twenty subjects were decompressed from 1.7 bar using each mixture, without signs or symptoms of DCS. However, after decompression from 1.8 bar there were 2 cases of DCS in 10 subjects in the O2-N2 group and 2 cases in 15 subjects in the O2-N2-CO2 group. The incidence of detectable VGE was always lower in the O2-N2-CO2 group at both saturation pressures; at 1.7 bar the VGE incidence was lower by 40% (P less than 0.05) at rest and by 55% (P less than 0.001) after movement. At 1.8 bar the reduction was 3% (NS) at rest and 30% (NS) after movement. The results indicate that decompression from 1.8 bar to 1 bar, with or without the presence of 0.02 bar carbon dioxide, is likely to produce more than 5% DCS.

Adult↗
PubMed1991

The effect of the menstrual cycle and of decompression stress on arachidonic acid-induced platelet aggregation and on intrinsic platelet thromboxane production in women compared with men.

Menstrual cycle variations in platelet aggregation and thromboxane production in association with sex steroids have been reported. External stimuli such as decompression sickness have been associated with clotting activity changes, specifically, increased platelet aggregation. Differences in response of platelets from women and men, when subjected to such a stress, have been observed. This study evaluated the ability of washed platelets from women in the proliferative and secretory phases of the menstrual cycle to aggregate in response to arachidonic acid and the aggregation difference between washed platelets from women and men in response to decompression stress and arachidonic acid. Additionally, platelet thromboxane production differences between the assessed platelet populations were compared. Our results indicate no difference in platelet aggregability between phases of the menstrual cycle. A significant aggregation difference between platelets from women and men was noted. Platelets from women were more sensitive to arachidonic acid aggregation. These differences were not affected by decompression stress. No difference in thromboxane B2 production was noted between the platelet populations evaluated.

Adult↗
PubMedDate not supplied

Blood biochemical parameters in women during long-term simulated hyperoxic diving up to 8 ATA.

Nowadays an increasing number of women are participating in recreational diving. A special recompression treatment table for delayed pulmonary barotrauma or decompression sickness was developed by V.V. Smolin in the Institute for Biomedical Problems (IBMP, Russia). The aim of our study was to investigate the effect of simulated dives (similar to this recompression treatment table) on biochemical parameters of healthy women. Three healthy female volunteers participated in long-term simulated diving to 8 ATA (0.8 MPa). Blood samples for determination of the biochemical substrate levels and activity of blood enzymes using a Reflotron analyzer were obtained at the control period, at the beginning of decompression and at the post dive period. No significant changes of serum levels of glucose, triglycerides, cholesterol, HDL cholesterol and urea were found during this experimental period or in comparison with the predive values. There were no significant changes in ALT activity in two volunteers but there was some tendency for an insignificant decrease in AST activity. One of the volunteers had a considerable increase in AST and ALT activities 15 h after the dive, probably due to a modified diet outside the experiment conditions. Thus, the long-term simulated diving recompression treatment table did not lead to a shift in the woman's serum biochemical status. However, it remains necessary to consider probable dysfunction of liver due to hyperbaric exposure.

Adult↗
PubMed1982

Air embolism: possible role of surfactant on recompression.

The relationship between surface tension and surface area has been measured on each of three common pulmonary surfactants - dipalmitoyl lecithin (DPL), dipalmitoyl phosphatidylethanolamine, and sphyngomyelin-under simultaneously simulated physiological conditions. These are selected to simulate the state of any surfactant that has migrated onto the surface of venous bubbles filtered by the pulmonary vasculature. It is concluded that, in the absence of shunt vessels, only DPL could reduce surface tension enough to allow pulmonary gas emboli to escape into arterial blood and then only after compression. This finding is discussed in relation to the delay in any appearance of bubbles in arterial blood and the possible facilitation of the release of asymptomatic lung bubbles by recompression therapy. The suggestion is made to reconsider stopping recompression of a subject with peripheral decompression sickness (the bends) at the depth of relief rather than risk releasing pulmonary gas emboli by further recompression. It is also demonstrated how the introduction of 1-min stops into compression can avoid surface tension falling to the low values at which it is theoretically possible for venous bubbles to escape into arterial blood during pulmonary hypertension.

Decompression↗
PubMed1976

Assessment of vertical excursions and open-sea psychological performance at depths to 250 fsw.

A series of 10 two-man descending vertical excursion dives was carried out in the open sea from an ocean-floor habitat off the coast of Puerto Rico by four aquanauts saturated on a normoxic-nitrogen breathing mixture at a depth of 106 fsw. The purpose of these dives was two-fold: to validate laboratory findings with respect to decompression schedules and to determine whether such excursions would produce evidence of adaptation to nitrogen narcosis. For the latter, tests designed to measure time estimation, short-term memory, and auditory vigilance were used. The validation of experimental excursion tables was carried out without incidence of decompression sickness. Although no signs of nitrogen narcosis were noted during testing, all subjects made significantly longer time estimates in the habitat and during the excursions than on the surface. Variability and incomplete data prevented a statistical analysis of the short-term memory results, and the auditory vigilance proved unusable in the water.

Analysis of Variance↗
PubMed2001

Cerebral gas embolism absorption during hyperbaric therapy: theory.

Cerebral gas embolism is a serious consequence of diving. It is associated with decompression sickness and is assumed to cause severe neurological dysfunction. A mathematical model previously developed to calculate embolism absorption time based on in vivo bubble geometry is used in which various conditions of hyperbaric therapy are considered. Effects of varying external pressure and inert gas concentrations in the breathing mixtures, according to US Navy and Royal Navy diving treatment tables, are predicted. Recompression alone is calculated to reduce absorption times of a 50-nl bubble by up to 98% over the untreated case. Lowering the inhaled inert gas concentration from 67.5% to 50% reduces absorption time by 37% at a given pressure. Bubbles formed after diving and decompression with He are calculated to absorb up to 73% faster than bubbles created after diving and decompression with air, regardless of the recompression gas breathed. This model is a useful alternative to impractical clinical trials in assessing which initial step in hyperbaric therapy is most effective in eliminating cerebral gas embolisms should they occur.

Absorption↗
PubMed2004

Brain magnetic resonance imaging, aerobic power, and metabolic parameters among 30 asymptomatic scuba divers.

The aim of the study was to evaluate the presence of cerebral lesions in asymptomatic scuba divers and explain the causes of them: potential risk factors associating cardiovascular risk factors, low aerobic capacity, or characteristics of diving (maximum depth, ascent rate). Experienced scuba divers, over 40 years of age, without any decompression sickness (DCS) history were included. We studied 30 scuba divers (instructors) without any clinical symptoms. For all of them, we carried out a clinical examination with fatty body mass determination and we questioned them about their diving habits. A brain Magnetic Resonance imaging (MRI), an assessment of maximal oxygen uptake, glycemia, triglyceridemia, and cholesterolemia were systematically carried out. Cerebral spots of high intensity were found at 33 % in the scuba diving group and 30 % in the control group. In the diving group, abnormalities were related to unsafe scuba-diving or metabolic abnormalities. In our study, we did not find a significant relationship between the lesions of the central nervous system, and the age, depth of the dives, number of dives, and ergometric performances (maximal oxygen uptake, V.O (2max), serum level of blood lactate). Nevertheless, we found a significant relationship between the lesions of the central nervous system and ascent rate faster than 10 meters per minute (r = 0.57; p = 0.003) or presence of high level of cholesterolemia (r = 0.6; p = 0.001). We found concordant results using the Cochran's Test: meaningful link between the number of brain lesions and the speed of decompression (Uexp = 14 < Utable = 43; alpha = 0.05, p < 0.01). We concluded that hyperintensities can be explained by preformed nitrogen gas microbubbles and particularly in presence of cholesterol, when the ascent rate is up to 10 meters per minute. So, it was remarkable to note that asymptomatic patients practicing scuba diving either professionally or recreationally, presented lesions of the central nervous system. This survey permitted us to highlight in a population of professional divers, neurological and also cardiovascular abnormalities (ventricular arrhythmias); although none of them present any symptoms today. It seems therefore important to us to propose in the future, for a better prevention of neurological injuries, a systematic follow-up by maximal oxygen consumption measure, brain MRI, and cholesterolemia. In the same way, our results suggest a modification of the diving tables with a maximal decompression rate at 9 m . mn (-1).

Brain↗
PubMed1994

Diving pattern of fishermen in the Pescadores.

Professional diving fishermen in the Pescadores Archipelago (119.30 degrees W, 23.30 degrees N) dive with a simple hookah system. Although they use modern equipment, such as wet suit, face mask, mouth piece with demand valve, spear gun, weight belt, and fins, their lack of knowledge of diving medicine is apparent. On the average, 180 cases of decompression sickness (DCS) per year were reported to occur in the Pescadores. We conducted studies in 1990 and 1992 on three islands of the Archipelago. At the time of our study, an estimated 140 diving fishermen resided on these three islands. Of the 62 fishermen interviewed, 14 volunteered for the recording of dive profiles using a diver-carried data logger. In the summer of 1990, a group of eight fishermen dived, on the average, to a depth of 17.8 +/- 5.3 m (mean +/- SD; range, 8-27 m) for 26.9 +/- 19.7 min (5-66 min). Although the diving depth was similar to that of the average recollections of 43 divers, 20.1 +/- 4.4 m (15-30 m), the actual diving time was far shorter than that of their recollections, 426 +/- 138 min (240-630 min). The post-typhoon sea floor conditions may have shortened their diving time. In the summer of 1992, a group of six fishermen dived to 20.5 +/- 3.8 m (15-26 m) for 56.4 +/- 21.2 min (18-84 min). Again, the diving depth matched that of their recollection well, 22.2 +/- 2.5 m (20-26 m), but their bottom time was far shorter than they believed, 270 +/- 108 min (120-480 min). They used no decompression procedures, regardless of the bottom time and diving depth. In the 1990 group, 5 out of 10 equivalent single dive bottom times (ESDBT) exceeded U.S. Navy no-decompression (No-D) air dive limits; whereas in the 1992 group, 7 out of 9 ESDBTs exceeded No-D limits. Eight of the 38 discrete dives exceeded the No-D limits, even if we underestimate their decompression stress by disregarding their repetitive dive history. However, no symptoms of DCS were observed in either the 1990 or 1992 groups of 14 divers, despite 63% of the ESDBTs and 21% of discrete dives having exceeded the No-D limits. Adaptation to diving work may have allowed them to exceed the established No-D limits. The existing records of incidence of DCS from this region suggest that previously they must have dived longer or deeper or both during times of abundant resources.

Adult↗
PubMed2005

A physiological model of gas pockets in crevices and their behavior under compression.

The formation of bubbles in the body from dissolved gases during decompression causes a range of symptoms, often referred to as Decompression Sickness. It is likely that these bubbles grow from pre-existing nuclei. It has been proposed that such nuclei are pockets of gas that are stabilized against collapse under raised pressure, such as that experienced by deep-sea divers. This work explores the stabilization of gas pockets in crevices, in its application to the nucleation of bubbles in blood vessels. A model has been derived to describe the dynamics of a bubble in a crevice, assuming that gases diffuse in and out of the bubble via the crevice wall from the body tissues surrounding the crevice. The time-varying behavior of the bubble has been examined and it has been shown that a crevice bubble can survive compression by temporary variations in the gas-liquid interface curvature or by shrinking, its behavior being found to be strongly dependent upon the model parameters.

Animals↗
PubMed1980

Dose-responses of guinea pigs to diazepam at recompression depths.

Dose-responses to diazepam were studied in guinea pigs at the recompression pressures used for the treatment of gas embolism and decompression sickness. The conditions and the doses were randomly assigned. Sufficient exposure to 6 ATA air, 3 ATA oxygen, or 1 ATA air was allowed in the hyperbaric chamber before diazepam was administered intravenously. Loss of righting reflex and its return were the end points for sleep and awakening, respectively. The data were analyzed with a mathematical model for dose-response and duration of effect. Results were: (1) in 1 ATA air, widely varying doses induced sleep of long duration; (2) in 6 ATA air, sleep was induced with small doses; and (3) in 3 ATA oxygen, sleep was induced with large doses. The duration of sleep under hyperbaric conditions was shorter than at sea level pressure. The null hypothesis, which assumed similar dose-responses and durations of sleep under these three conditions, was rejected. The dose and duration of diazepam's effect during recompression apparently depend on the pressure and the gas composition used.

Animals↗
PubMedDate not supplied

[Results of the psychophysiological investigations of female test-subjects during long-term stay in pressurized chamber under the regime of therapeutic recompression].

IBMP has developed and applied protocols of therapeutic recompression of patients with delayed admission after the onset of decompression sickness or pulmonary barotraumas the occurrence of which increases among recreational divers including females. Experiment Rusalka-2004 was performed to validate a therapeutic recompression protocol with participation of female test-subjects subjected to experimental descents at air pressure of 40 and 80 m H2O (training) and of 70 m H2O (experimental) followed by 4 days at 40 to 0 m H2O in a hyperoxic (pO2 = 0.45-0.5 kgs/cm2) helium-oxygen-nitrogen atmosphere. Psychophysiological investigations during the experiment revealed only weak changes of the parameters evaluated by the well-being - activity - mood, Spilberg - Khanin, Luscher, and proof-read tests. Significant deviations in self-feeling (modified method by Dembaut - Rubinstein) and mental performance assessment (Krepelin's tables) were associated with the air pressure elevation to 40-80 m H2O both during the training and experimental descents, and symptoms of nitrogen narcosis. Based on these results, the therapeutic recompression protocol can be recommended for treatment of as males, so females.

Adaptation, Psychological↗
PubMed1975

Gas transport and blood acid-base balance in diving sea snakes.

The values of hemoglobin concentration, Hb-O2 affinity and buffering capacity of the blood of six sea snake species considerably overlap values from terrestrial squamates. Decreased blood pH had little effect on the P50 but increased the n-value of Hb-O2 equilibrium curves. The O2 saturation of blood in the dorsal aorta varied between about 30 and 70% during voluntary diving in Acalyptophis peronii and Lapemis hardwickii. Voluntary dives ended when the lung PP02 was about 50 mm Hg and the arterial PO2 about 30 mm Hg indicating that roughly half of the O2 reserves had been used. In conjunction with relatively stable blood lactate concentration and pH, this indicates that voluntary dives occurred largely aerobically. In contrast, forced dives resulted in depletion of O2 reserves and large changes in blood acid-base balance. Long recovery periods following forced dives are inconsistent with field observations and thus suggest that extensive anaerobic metabolism does not normally occur in sea snakes. Bradycardia was not evident during forced dives. Large differences in PO2 between the lung and dorsal aorta indicated considerable right to left shunting either in the heart or in the lung. Venous blood represented over 50% of the systemic flow when there was considerable O2 in the lung. Therefore blood PO2 may remain relatively low despite elevated lung PO2 resulting from diving. In view of substantial capability for extra-pulmonary gas exchange, high shunting reduces the possibility of losing O2 through the skin and also may help prevent decompression sickness following deep dives.

Acid-Base Equilibrium↗
PubMedDate not supplied

MR imaging of the central nervous system in divers.

A group of 70 professional divers and 47 healthy control subjects who had never dived were examined with magnetic resonance (MR) imaging to determine the prevalence of focal white matter changes in the brain. Spots of high signal intensity in white matter on proton density- and/or T2-weighted spin-echo images were detected in 42% of the control subjects and in 34% of the divers. In the control subjects, the prevalence of more than three changes was related to smoking, use of alcohol, head trauma, age of more than 35 years, and a combination of several cerebrovascular risk factors. This relationship was not present in the divers. The prevalence of changes in divers was inversely related to diving depth, amount of diving, participation in "unsafe diving," and decompression sickness. The reasons for these results could not be ascertained. The results are compared with those of MR imaging studies of white matter changes recently presented by other research groups.

Adult↗
PubMed1982

Delayed infarction of spinal cord white matter following x-irradiation.

The thoraco-lumbar spinal cord of 4 cats were subjected to 4000 RADS of X-irradiation. Between 3 and 5 mth afterwards the animals developed weakness of the hind-legs and became uncoordinated. Small infarcts were found in the white matter of the irradiated area of spinal cord, accompanied by neuronal death and oedema of the grey matter close to the central canal. Ultrastructurally the infarcts were shown to stem from necrosis and thrombosis of small blood vessels. Comparison is made with the pathogenesis of spinal cord infarction that occurs in decompression sickness.

Animals↗
PubMed1998

Osteonecrosis of the knee: current clinical concepts.

Osteonecrosis of the knee should be differentiated into two main categories: (1) primary, spontaneous, or idiopathic osteonecrosis and (2) secondary osteonecrosis (e.g., secondary to factors such as steroid therapy, systemic lupus erythematosus, alcoholism, Caisson decompression sickness, Gaucher's disease, hemoglobinopathies, etc.). Spontaneous or primary osteonecrosis of the knee presents with an acute knee pain in elderly patients. It is three times more common in women than in men. Traumatic and vascular theories have been proposed as a causative factor of osteonecrosis of the knee, but the precise etiology still remains speculative. High index of clinical awareness and a good history and physical examination are essential to make an early, accurate diagnosis. Plain radiographs are often normal during the early course of the disease and, in such instances, radioisotope bone scan and magnetic resonance imaging may be helpful. In the early stage of the disease, nonoperative treatment is indicated and many patients, if diagnosed early, have a benign course with a satisfactory pain relief and a good knee function. In patients with advanced stage of the disease, treatment options include arthroscopic debridement, curettage or drilling of the lesion, bone grafting, high tibial osteotomy, use of osteochondral allograft, and unicompartmental or total knee arthroplasty. The choice of treatment should be based on factors such as age of the patient, severity of symptoms, activity level and functional demands on the knee, site and stage of the lesion, and extent of deformity and secondary osteoarthritis. The clinical features and treatment of steroid-induced osteonecrosis of the knee are briefly discussed. In recent years, "postmeniscectomy" osteonecrosis has been reported, but at present its prevalence and pathophysiology remain unknown. It is possible that this may be a preexisting condition that was not recognized at the time of initial consultation or osteonecrosis may develop after meniscectomy in occasional cases.

Adrenal Cortex Hormones↗