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PubMed1993

Oxy-helium treatment of severe spinal decompression sickness after air diving.

Spinal cord injury in DCS after air diving is relatively frequent and often has late sequelae. U.S. Navy oxygen tables are sometimes not satisfactory. The advantage of using helium in these cases is based theoretically on its physical properties and has been demonstrated in animal models. We have introduced the Comex-30 (CX-30) oxy-helium table as an integral part of our treatment protocol for severe spinal DCS. We summarize here our clinical experience with seven cases. A case was considered severe if clinical assessment suggested progressive neurologic injury to the spinal cord or roots. Except for one case, the initial treatment was CX-30 followed by HBO sessions as indicated. Of the seven patients treated, five made a full recovery and the remaining two were left with mild neurologic sequelae.

Adult↗
PubMed1983

Role of lung surfactant in cerebral decompression sickness.

Five dogs have been embolized by air infusion into the venous system, then sacrificed and the pulmonary vasculature isolated by ligatures while ventilation was maintained for a further hour. In a sixth animal, the embolization was omitted. The lungs were back-perfused with plasma from the same dog and successive aliquots of the back-flushings analysed by thin-layer chromatography (TLC), each spot being removed for phosphorus determination. The results showed that the major lipid component was the phosphatidyl cholines, while lysophosphatidyl cholines, phosphatidyl ethanolamines, and sphingomyelins were also identified in significant quantities. A phosphorus balance for the lungs showed a significant migration of phospholipids from the tissue into pulmonary blood, phosphatidyl cholines increasing by a factor of 10.6. This migration of surfactant is discussed as an important factor in determining whether trapped pulmonary air emboli are released into the arterial system when their surface area is reduced by pressurization, suggesting that recompression should not be too rapid.

Animals↗
PubMed1993

Effect of severity, time to recompression with oxygen, and re-treatment on outcome in forty-nine cases of spinal cord decompression sickness.

For systematic study of the effects of clinical severity, time to recompression with oxygen, and re-treatment on outcome from spinal cord DCS, case records from the recompression chamber at the U.S. Naval Station Subic Bay were reviewed. Forty-nine cases of spinal cord DCS were classified using a numerical severity index and time to recompression with oxygen. Cases were divided by initial severity into mild, moderate, and severe groups and by time to recompression with oxygen into less than 12-h, 12-24-h, and greater than 24-h groups. Re-treatment effect was analyzed by severity after the first treatment and by the depth of the re-treatment table used. Severity after all treatment is strongly correlated with initial severity (r = 0.88) and moderately correlated with time to recompression with oxygen (r = 0.58). Response to treatment is significantly different among initial severity groups (P < 0.001). Delay to treatment worsens outcome for severely injured divers (P = 0.008). Residual severity after all treatments is highly correlated with severity after the first treatment (r = 0.97). There is no difference in re-treatment outcome by groups defined by severity after the first treatment or by 60- or 45-ft re-treatment tables.

Adult↗
PubMed1996

Left ventricular gas emboli in six cases of altitude-induced decompression sickness.

BACKGROUND: Ultrasonic techniques have demonstrated venous gas emboli (VGE) during exposure to high altitude. VGE per se have not been considered clinically hazardous. Arterial gas emboli (AGE), however, are viewed with great concern. The crossing-over of venous gas to the arterial circulation has not previously been seen in human subjects at altitude. This transfer may occur via either intracardiac defects, pulmonary shunts, or the pulmonary microcirculation. METHODS: A non-invasive ultrasonic echo imaging Doppler system was used to monitor volunteer human subjects for gas emboli simultaneously in the right and left sides of the heart at simulated altitude in a chamber. Subjects found to have gas cross-over were evaluated for septal defects with either transthoracic or transesophageal echocardiography. RESULTS: Previously unreported left ventricular gas emboli were observed with echo imaging in six subjects at altitude. In all six cases, at the time of AGE onset, the VGE scores were high from all monitored sites. Three subjects had no septal defect, another had a small sinus venosus defect, a third had a patent foramen ovale, and one was not available for evaluation. Five of the cases became symptomatic at the time of AGE onset. CONCLUSIONS: Operational altitude exposures known to elicit high VGE counts in the majority of people should be avoided because of an increased risk of right-to-left gas cross-over and resulting potential for severe cerebral symptomatology.

Aerospace Medicine↗
PubMed1993

[Normobaric oxygenation as a first-aid measure in decompression sickness].

Most divers and diving medicine specialists know that application of normobaric oxygen as first aid after a bubble disease incident is highly effective. However, as yet technical difficulties acted as a deterrent to using normobaric oxygen at the diving site. This can now be overcome by a newer technique. To be efficient, any therapy of bubble disease should follow three main principles: maximal partial pressure of inhaled oxygen (i.e. 100 kpa in normobaric, and 280 kpa in hyperbaric conditions); minimal partial pressure of inhaled nitrogen, which should ideally be near zero; immediate start of therapy, if possible at the diving site, but not later than 2 hours after the onset of the first symptoms. However, it has to be borne in mind that for an efficient normobaric oxygenation (100%), the standard apparatus design without oxygen reservoir is obsolete, for it offers at most 40% oxygen to the lungs. Currently the following technical approaches for an efficient normobaric oxygenation are available: open one-way systems with tightly fitting mask and oxygen reservoir bag (type Ambu or Leardal, etc.); open systems with on-demand regulation and tightly fitting mouth piece (type SCUBA, or Bird-respirator); closed systems with CO2 absorber (type oxygen rebreathing diving gear). The closed system is a genuine technical advance, because it needs 15 times less oxygen than open systems (about 90 liters oxygen for a 3-hours oxygenation run). Such an apparatus is thus of light weight, far less cumbersome, and nevertheless highly efficient. The therapy should start immediately at the site of the mishap and be maintained during the transport to the next HBO-unit (usually 3 to 6 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Atmospheric Pressure↗
PubMed2006

Numerical modeling of the transport to an intravascular bubble in a tube with a soluble/insoluble surfactant.

Using a newly developed algorithm in conjunction with the front tracking scheme, we have evaluated the transport associated with a deformable bubble moving in a tube in the presence of a soluble or an insoluble surfactant. Such evaluations are useful to the understanding of gas embolism--a common syndrome for decompression sickness. Decompression sickness may be encountered in performing extravehicular activity during space exploration. The numerical evaluations indicate that as the location of the adsorptive interface gets closer to the vessel wall, the surfactant amount on the wall gets depleted. The implication is that the process by which a bubble occluding a vessel dislodges may depend both on the strength of the diffusivity of the surfactant and the adsorption process. More detailed study is needed to clarify this observation. The numerical results evaluated include Marangoni flow, which causes a bubble to propel out of its initial static location, and bubble motion in Poiseuille flow. The presence of a soluble/insoluble surfactant slows down the bubble motion. For identical surface concentrations of the surfactant, the effect of the presence of a soluble surfactant is more severe on the retardation of the bubble motion than that of an insoluble surfactant.

Algorithms↗
PubMed1997

Environmental emergencies.

This article reviews the pearls and pitfalls of high-altitude sickness, decompression sickness, and barotrauma; new findings relevant to the near-drowning patient; continued controversies on hyperbaric oxygen for carbon monoxide poisoning; pitfalls in hypothermia management; and updates on the management of venomous snakebites.

Altitude Sickness↗
PubMed1975

Sudden hearing loss due to diving and its prevention with heparin.

Vascular embolic and thrombotic problems postulated to be the cause of inner ear sudden deafness have been reported with decompression sickness also. Decompression sickness has been found to lead to cochlear potential loss in the guinea pig, and these losses are minimized by the prophylactic administration of heparin. Preliminary results show that inner ear hemorrhage may be associated with diving deafness, but plasma protein leakage into the perilymph of the ear may precede the hemorrhage. Inner ear hemorrhage in diving deafness seems to be restricted to the microcirculation. Until we gain a better understanding of the pathophysiology of diving induced deafness, it would be premature to consider agents such as heparin for the treatment of the problem in man.

Animals↗
PubMed2003

James Glaisher's 1862 account of balloon sickness: altitude, decompression injury, and hypoxemia.

In 1862, James Glaisher and Henry Coxwell ascended to 29,000 feet in an open hot-air balloon. During the ascent, Glaisher described marked neurologic compromises: appendicular and later truncal paralysis, blindness, initially preserved cognition, and subsequent loss of consciousness. The author examines Glaisher's account of balloon sickness by comparing it with other balloonists' observations and discussing it in the context of altitude sickness, decompression injury, and hypoxemia.

Aerospace Medicine↗
PubMed1998

[Decompression sickness-one of the vital problems of aerospace medicine].

The author reviews the literature on decompression sickness (DCS) constituting one of the major problems of aerospace medicine. He speculates on the terms describing this health condition and offers the retrospective of hypothesised causes for DCS development. The paper outlines main DCS symptoms and reports statistics on the DCS incidence rate in flying personnel when piloting aircraft and training in altitude chambers, and in volunteered test-subjects during physiological experiments with simulated ascents in order to mimic the extravehicular activities of cosmonauts and to test the altitude gear. Underlined is the value of publications by many Russian and foreign investigators who contributed significantly to development of the scientific and applied aspects of this problem. The currently available and theoretically possible countermeasures against DCS in cosmonauts during EVA are considered.

Aerospace Medicine↗
PubMed1977

Supersaturation by counterperfusion and diffusion of gases.

Gaseous supersaturation can be induced under steady-state conditions when two inert gases are transmitted in opposite directions across any system comprising a diffusion barrier adjacent to a zone of limited convective capacity. This has many implications for bubble formation in vivo and can explain the occurence of symptoms of decompression sickness without decompression.

Decompression Sickness↗
PubMed2003

Field trials of no-decompression stop limits for diving at 3500 m.

INTRODUCTION: In 1990, Boğaziçi University (Istanbul, Turkey) launched an altitude diving program to develop techniques and safe decompression profiles for diving at high terrestrial altitudes. Following pioneering diving expeditions to lakes at high elevations in 1990-1992, it was deemed necessary to calculate new tables. METHODS: Bottom time limits for dives requiring no decompression stops (no-d) were calculated for 3500 m using linear extrapolation of U.S. Navy M-values decreased by 4 ft of sea water (M4 limits). These limits were tested for 15, 18, 21, 24, 27, and 30 m of depth by diving in the Great Sea Lake at Mt Kaçkar (3412 m) with 10 dives per profile. RESULTS: The mean decompression sickness (DCS) risk estimated from precordial bubble scores (Spencer Scale) ranged from 0.3% to 2.8% per profile. After three expeditions, 165 dives had been achieved with a cumulative bottom time of 3199 min. No DCS occurred in dives that adhered to the M4 no-d limits. However, two cases of Type I and one case of Type II DCS were encountered where the divers accidentally exceeded those limits. DISCUSSION: Considering the estimated risk of DCS and the relatively small number of trials, a more conservative approach was used to develop a final set of high altitude dive tables. This conclusive approach used continuous compartment half-lives. It is based on fitting a surface of allowable supersaturation limits using the empirical M-values from existing tables as well as our altitude diving data, together with an added constraint that forces calculated M-values to stay below the available M-value data.

Adult↗
PubMed1995

Complement levels and exposure in the hypobaric chamber.

Decompression sickness sometimes occurs in routine hypobaric chamber runs. Susceptibility to decompression sickness has been correlated with increases in C3a and C5a metabolites of complement activation by air bubbles. If personnel susceptible to decompression sickness show changes in C3a and C5a after decompression, then measurement of these metabolites may be useful in assisting diagnosis. C3a and C5a metabolites of complement activation were measured in 11 male and 2 female volunteers 1 h before (A), 1 h after (B), and 24 h after (C) exposure in routine hypobaric chamber runs to 25,000 ft equivalent altitude. The results were compared with 4 controls (3 males and 1 female). A one-way analysis of variance showed no significant difference between the experimental and control groups overall (p = 0.308; p > 0.05; N = 17). T-tests at each of the results further suggest non-significant differences between the experimental and control groups (p = 0.473; p = 0.341; p = 1.051; p > 0.05; N = 17) at results A, B, and C, respectively. The C5a assay was less than 10 micrograms.L-1 in all individuals, and the particular kit used was not sensitive below 10 micrograms.L-1. As none of the participants developed decompression sickness, it would be useful to determine levels of C3a and C5a in individuals who subsequently develop decompression sickness. One member of the experimental group who had undergone many chamber runs had much higher pre- and post-chamber run levels of C3a. This raises the question of the effect of repeated exposure in low pressure chambers on complement activation, and requires further study.

Adult↗
PubMed1984

Decompression from a deep nitrogen/oxygen saturation dive--a case report.

Ten divers participated in a 4.5 d nitrogen/oxygen saturation dive to 165 fsw. There were daily 2 h excursions to 61 msw (200 fsw). The divers breathed air during the excursions and 0.51 bar (0.5 atm) oxygen in nitrogen at 50.3 msw (165 fsw). The final decompression began 6 h after the last excursion. The oxygen partial pressure was 0.51 bar (0.5 atm) from 50.3 to 13.7 msw (165 to 45 fsw), and air was used from 13.7 msw (45 fsw) to the surface. By 6.1 msw (20 fsw), four divers had developed decompression sickness. A fifth diver developed decompression sickness during a commercial air flight 68 h after surfacing. Comparison of ascent rates for this dive and for air or nitrogen/oxygen saturation dives reported in the literature suggests that deeper dives require slower rates of ascent. Dives shallower than 30.5 msw (100 fsw) had a mean ascent rate of 1 msw/h (3.2 fsw/h) and 14 decompression incidents in 107 man-exposures. Dives deeper than 30.5 msw (100 fsw) had a mean rate of 0.76 msw/h (2.5 fsw/h) and 14 incidents in 45 man-exposures.

Adaptation, Physiological↗
PubMed1995

Diving at altitude: a review of decompression strategies.

Diving at altitude requires different tables from those at sea level due to the reduction in surface ambient pressure. Several algorithms extrapolating sea-level diving experimental data have been proposed to construct altitude diving tables. The rationale for these algorithms is reviewed together with the conservatism of the resulting tables and decompression computer outputs. All algorithms are based on the adaptation of critical tissue tensions to altitude. These are linear extrapolation (LEM), constant ratio translation (CRT), and constant ratio extrapolation (CRE) of maximum permissible tissue tensions (M values). Either new tables using the altitude-adapted M values were put forward or sea-level tables are to be used through an operation called correction. In this review it is shown that for a given set of M values, CRT and CRE give the same result for no-decompression-stop dives; they always yield more conservative results than LEM. When decompression stops are used, CRT is more conservative than CRE. When applied to different sets of M values, the conservatism becomes a function of bottom time, depth, and altitude. The analysis shows that the tables derived using CRT of U.S. Navy (USN) schedules and CRE Boni et al. tables give more conservative results than LEM Bühlmann tables for higher altitude, longer bottom time, and deeper dives. Aviation altitude exposure decompression sickness (DCS) data are also addressed to compare different model outputs. When applied to USN and Royal Navy tables, LEM yields an altitude DCS limit of 8,581 and 8,977 m, respectively. On the other hand, the altitude limit calculated using CRE applied to USN M values and LEM Bühlmann tables is found to be below 6,000 m.

Aerospace Medicine↗
PubMed1998

Effect of oxygen tension and rate of pressure reduction during decompression on central gas bubbles.

Reduction in ascent speed and an increase in the O2 tension in the inspired air have been used to reduce the risk for decompression sickness. It has previously been reported that decompression speed and O2 partial pressure are linearly related for human decompressions from saturation hyperbaric exposures. The constant of proportionality K (K = rate/partial pressure of inspired O2) indicates the incidence of decompression sickness. The present study investigated the relationship among decompression rate, partial pressure of inspired O2, and the number of central gas bubbles after a 3-h dive to 500 kPa while breathing nitrox with an O2 content of 35 kPa. We used transesophageal ultrasonic scanning to determine the number of bubbles in the pulmonary artery of pigs. The results show that, for a given level of decompression stress, decompression rate and O2 tension in the inspired air can be traded off against each other by using pulmonary artery bubbles as an end point. The results also seem to confirm that decompressions that have a high K value are more stressful.

Animals↗
PubMed1991

Ten years of diving-related illness in the Royal Navy.

The period from 1 January 1980 to 31 December 1989 produced a total of 244 training and operational diving accident reports involving Royal Navy and Royal Marines personnel. Because the incidence figures fluctuated widely year by year, a clear trend over the decade failed to emerge. However, the incidence of Type II decompression sickness, as a percentage of total decompression sickness, was greater in the second half of the decade than in the first, a trend similar to, although more moderate than, recent experience of dysbaric illness amongst sport divers. Student divers were disproportionately highly represented in the statistics, particularly with regard to pulmonary barotrauma and near-drowning.

Accidents, Occupational↗