Working ability between air and trimix breathing gas under 8 ATA air condition

Pneumatic caisson work in Japan has come into operation since 1924. Afterward, this technique of compressed air work has been widely utilized in the construction of foundation basements, shafts of the bottom tunnel shields for subway and so forth. While using this technique of compressed air work means that workers have to be exposed to hyperbaric environment, this technique has risks of not only decompression sickness (DCS) but also toxicity of poisonous gas and/or oxygen deficiency. However, this technique is independent of city construction work and the operation of compressed air work higher than 5ATA (4.0 kg/cm2G) is actually been planning recently. Accordingly unmanned caisson work is considered as a better technique for such higher pressurized work, even though workers must enter into hyperbaric working fields for maintenance or repair of unmanned operated machinery and materials. This research is to establish the safe work under hyperbaric air environment at 8ATA.     

Man Under Pressure

Current achievements in environments at pressures higher than atmospheric are reviewed, ranging from the uses of hyperbaric oxygen for treatment to the concept of residence at high pressure for extended Continental Shelf exploration and very deep caisson work.A case is made for the use of high oxygen pressures in the treatment of hypoxias of acute onset, of certain infections, and as an adjunct to radiotherapy. Achievement of the desired high tissue tensions of oxygen while avoiding toxicity requires careful choice of both pressure and duration of exposure.Man has successfully dived to 1000 feet in the sea, and has remained for weeks at high pressures. Adequate prophylactic decompression remains a major problem, since current recompression procedures are to a large extent empirically derived. There are grounds for expecting improved prophylactic and therapeutic procedures when present studies are completed.     

Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

ObjectiveTo test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air breathing as assessed by intravascular bubble formation after decompression.MethodsHuman volunteers underwent a first simulated dive breathing compressed air to include subjects prone to post-decompression venous gas bubbling. Twelve subjects prone to bubbling underwent a double-blind, randomized, cross-over trial including one simulated dive breathing compressed air, and one dive breathing EAN (36% O₂) in a hyperbaric chamber, with identical diving profiles (28 msw for 55 minutes). Intravascular bubble formation was assessed after decompression using pulmonary artery pulsed Doppler.ResultsTwelve subjects showing high bubble production were included for the cross-over trial, and all completed the experimental protocol. In the randomized protocol, EAN significantly reduced the bubble score at all time points (cumulative bubble scores: 1 [0–3.5] vs. 8 [4.5–10]; P < 0.001). Three decompression incidents, all presenting as cutaneous itching, occurred in the air versus zero in the EAN group (P = 0.217). Weak correlations were observed between bubble scores and age or body mass index, respectively.ConclusionEAN breathing markedly reduces venous gas bubble emboli after decompression in volunteers selected for susceptibility for intravascular bubble formation. When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing.

Trial Registration

ISRCTN 31681480     

Continuous enzymatic cooking and liquefaction of starch using the technique of direct resistive heating

Continuous cooker prototypes of very simple design, using electricity as a primary energy source, were developed for the process of cooking and liquefaction of starch suspensions. Previous work on equipment using microwave dielectric heating has already been reported. Results of energy consumption as low as 330 kcal/kg based on starch content were achieved. Considering these results and looking for new solutions or engineering concepts, the authors have been investigating the possibility of using electric energy at 60 Hz for direct resistive heating, in which the starch suspension is the proper "resistor."The most important results of energetic yield obtained until now, working in a continuous process of cooking-liquefaction, are not larger than 235 kcal (272 Wh)/kg based on starch content. These results were obtained using a commercial grade alpha-amylase from B. subtillis, working with temperatures ranging from 70 to 75 degrees C, and with residence times in the reactor not greater than 1.5 min. The experiments of saccharification and fermentation accomplished as a test for the efficiency of this heating technique gave good results (as with a conventional technique) and thus enabled us to proceed with the studies.     

Modulation of decompression sickness risk in pigs with caffeine during H(2) biochemical decompression.

In H(2) biochemical decompression, H(2)-metabolizing intestinal microbes remove gas stored in tissues of animals breathing hyperbaric H(2), thereby reducing decompression sickness (DCS) risk. We hypothesized that increasing intestinal perfusion in pigs would increase the activity of intestinal Methanobrevibacter smithii, lowering DCS incidence further. Pigs (Sus scrofa, 17-23 kg, n = 20) that ingested caffeine (5 mg/kg) increased O(2) consumption rate in 1 atm air by ~20% for at least 3 h. Pigs were given caffeine alone or caffeine plus injections of M. smithii. Animals were compressed to 24 atm (20.5-23.1 atm H(2), 0.3-0.5 atm O(2)) for 3 h, then decompressed and observed for signs of DCS. In previous studies, DCS incidence in animals without caffeine treatment was significantly (P < 0.05) lower with M. smithii injections (7/16) than in controls (9/10). However, contrary to our hypothesis, DCS incidence was marginally higher (P = 0.057) in animals that received caffeine and M. smithii (9/10) than in animals that received caffeine but no M. smithii (4/10). More information on gas kinetics is needed before extending H(2) biochemical decompression to humans.     

Changes in pain sensitivity under increased atmospheric pressure]

It has been established that augmentation of air pressure from 0.1 to 1.1 MPa (with 0.1 MPa intervals) was accompanied in rats with the development of progressive analgesia which was measured according to the threshold of vocalization in the test of electrical stimulation of the tail. The highest analgesic response arose at 0.7-1.1 MPa. All the animals might be divided into two groups: group 1-72% of the animals with a 200% increase of the threshold, group 2--animals with such an increase by 15%. The augmentation of the pressure of heliox (79.1% of helium, 20.9% of oxygen) also caused analgesia, but not so strong. In patients pain thresholds to the mechanical nociceptive stimulation also increased by about 43-67% and 95-100% under the influence of increased air pressure of 0.4 and 0.7 MPa, respectively. In group 1 patients (67%) pain threshold increased by 50-100%, in group 2 by 15-25%. Pretreatment with naloxone (1 mg/kg), atropine (1 mg/kg), yohimbine (1 mg/kg), parachloramphetamine (5 mg/kg) and prasosin (1 mg/kg) decreased hyperbaric analgesia in rats by 41-56, 41-56, 17-19, 17-19%, respectively. The role of increased partial pressure of nitrogen in hyperbaric analgesia and possible neurochemical mechanisms of its realization are discussed.     

Effects of Hyperbaric Oxygen at 1.25 Atmospheres Absolute with Normal Air on Macrophage Number and Infiltration during Rat Skeletal Muscle Regeneration

Use of mild hyperbaric oxygen less than 2 atmospheres absolute (2026.54 hPa) with normal air is emerging as a common complementary treatment for severe muscle injury. Although hyperbaric oxygen at over 2 atmospheres absolute with 100% O₂ promotes healing of skeletal muscle injury, it is not clear whether mild hyperbaric oxygen is equally effective. The purpose of the present study was to investigate the impact of hyperbaric oxygen at 1.25 atmospheres absolute (1266.59 hPa) with normal air on muscle regeneration. The tibialis anterior muscle of male Wistar rats was injured by injection of bupivacaine hydrochloride, and rats were randomly assigned to a hyperbaric oxygen experimental group or to a non-hyperbaric oxygen control group. Immediately after the injection, rats were exposed to hyperbaric oxygen, and the treatment was continued for 28 days. The cross-sectional area of centrally nucleated muscle fibers was significantly larger in rats exposed to hyperbaric oxygen than in controls 5 and 7 days after injury. The number of CD68- or CD68- and CD206-positive cells was significantly higher in rats exposed to hyperbaric oxygen than in controls 24 h after injury. Additionally, tumor necrosis factor-α and interleukin-10 mRNA expression levels were significantly higher in rats exposed to hyperbaric oxygen than in controls 24 h after injury. The number of Pax7- and MyoD- or MyoD- and myogenin-positive nuclei per mm² and the expression levels of these proteins were significantly higher in rats exposed to hyperbaric oxygen than in controls 5 days after injury. These results suggest that mild hyperbaric oxygen promotes skeletal muscle regeneration in the early phase after injury, possibly due to reduced hypoxic conditions leading to accelerated macrophage infiltration and phenotype transition. In conclusion, mild hyperbaric oxygen less than 2 atmospheres absolute with normal air is an appropriate support therapy for severe muscle injuries.     

Probing the limits of human deep diving

Divers breathing compressed air are restricted to 45 m depth because of the narcotic effects of nitrogen and toxic action of oxygen at increased pressures. Substitution of oxygen-helium for compressed air has permitted divers to reach 600 m. However, at depths greater than 160 m, signs and symptoms of the high pressure nervous syndrome (h.p.n.s.) occur, with tremors, myoclonic jerking, nausea, vomiting, fatigue, somnolence, e.e.g. changes, dyspnoea, and poor sleep with nightmares. It has been the objective of this Laboratory to ameliorate the symptoms of pressure-induced h.p.n.s. by the addition of small amounts of 'narcotic' nitrogen to the oxygen-helium mixture to form the Trimix breathing gas. In 1973, comparative experiments with oxygen-helium and the same divers, during compressions in only 33 min to 219.5 m and 305 m, showed such Trimix to be effective with 10% (by volume) nitrogen. Simulated dives, termed ATLANTIS, have been made with Trimix over the last 4 years to depths in excess of 610 m for 11 days, 650 m for 4 days and 686 m for 1 day. The objectives were to determine the effects of either slow or rapid rates of compression, and either 5% or 10% (by volume) nitrogen in Heliox, on the presence of h.p.n.s. or nitrogen narcosis. Measurements were made of intellectual and psychomotor performance, electrophysiological function of the brain and reflexes, lung and cardiovascular function, including arterial gas analysis at rest and work, blood chemistry and psychiatric and psychological status. The results permit the conclusion that divers may be compressed safely to depths as great as 686 m. The technique requires a slow exponential compression over days, with frequent stages lasting 14 h or more, the use of 5-8% (by volume) nitrogen in Heliox and careful selection of the divers.     

Diving: barometric pressure and neurochemical mechanisms

The studies of Paul Bert, presented in his book "La Pression Barométrique" in 1878, were at the origin of the modern hyperbaric physiology. Indeed his research demonstrated the effects of oxygen at high pressure, that compression effects must be dissociated from decompression effects, and that neurological troubles and death of divers during or after decompression were due to the fast rate of decompression. However, it is only in 1935 that the work of Behnke et al. attributed the complaints reported at 3 bars and above in compressed air or nitrogen-oxygen mixture to the increase in partial pressure of nitrogen which induces nitrogen narcosis. Little is known about the origins and mechanisms of this narcosis. The traditional view was that anaesthesia or narcosis occurred when the volume of a hydrophobic membrane site was caused to expand beyond a critical amount by the absorption of molecules of a narcotic gas. The observation of the pressure reversal effect during general anaesthesia has long supported this lipid theory. However, recently, protein theories have met with increasing recognition since results with gaseous anaesthetics have been interpreted as evidence for a direct gas-protein interaction. The question is to know whether inert gases, that disrupt dopamine and GABA neurotransmissions and probably glutamatergic neurotransmission, act by binding to neurotransmitter protein receptors.     

金黄色葡萄球菌肠毒素检测的研究进展

金黄色葡萄球菌(Staphylococcus aureus)是一种重要的人畜共患致病菌,广泛存在于自然界中,其产生的肠毒素(staphylococcal enterotoxins,SE)可通过污染食物而导致食物中毒。目前,随着人们对食品安全重视度的加深,国际上已将肠毒素的检测列入食品检验法规,因此建立灵敏、快速的肠毒素检测方法,是食品安全检测的一项重要研究内容。     

Salicylate hypothermia in rats exposed to hyperbaric air and helium.

Rectal temperatures of salicylate-treated and untreated rats were observed in 21-23 degrees C air at 1, 3, 6, and 8 ATA, in 21-23 degrees C helium at 1 and 6 ATA, and in 1 ATA thermal neutral air (28 degrees C). Significant dose-related temperature decreases occurred in 21-23 degrees C 1 ATA air with 180 and 300 mg/kg of salicylate; 60 mg/kg had no effect. However, in thermal neutral air, 300 mg/kg significantly elevated temperatures. Hyperbaric air and helium had temperature-lowering effects which were correlated with thermal properties of these environments, and in them the hypothermic effects of salicylate were similar to those in 1 ATA air, the total temperature decreases being the sum of the salicylate hypothermia and that caused by the hyperbaric air or helium. These additive temperature effects are unlike previously reported results in which the temperature lowering effects of 5 degrees C cold exposure and salicylate together were greater than the sum of the two individual effects.     

Select agent regulations

In recent years, there has been an increase in research with biological agents, particularly those that pose a potential for use by terrorists. In this environment, laws have been enacted and regulations developed to ensure the appropriate use of specified "select agents and toxins" for legitimate research. Within this regulatory environment, it has been necessary for institutions and investigators to adapt to an entirely new set of requirements to begin or continue to work with these pathogens. Registration and approval for use of select agents and toxins, security and safety requirements, and daunting record-keeping requirements are only some of the regulatory challenges that researchers face in working with these agents. A brief overview of recent regulations is presented, as well as where to obtain additional information on regulations, standards, and guidelines related to work with select agents and toxins.     

Growth of the extreme thermophile Sulfolobus acidocaldarius in a hyperbaric helium bioreactor

The relationship between pressure and temperature as it affects microbial growth and metabolism has been examined only for a limited number of bacterial species. Because many newly-discovered, extremely thermophilic bacteria have been isolated from pressurized environments, this relationship merits closer scrutiny. In this study, the extremely thermophilic bacterium, Sulfolobus acidocaldarius, was cultured successfully in a hyperbaric chamber containing helium and air enriched with 5% carbon dioxide. Over a pressure range of approximately 1-120 bar and a temperature range of 67-80 degrees C, growth was achieved in a heterotrophic medium with the air mixture at partial pressures up to 3.5 bar. Helium was used to obtain the final, desired incubation pressure. No significant growth was noted above 80 degrees C over the same range of hyperbaric pressures, or at 70 degrees C when pressure was applied hydrostatically. Growth experiments conducted under hyperbaric conditions may provide a means to study these bacteria under simulated in situ conditions and simultaneously avoid the complications associated with hydrostatic experiments. Results indicate that hyperbaric helium bioreactors will be important in the study of extremely thermophilic bacteria that are isolated from pressurized environments.     

Biochemical indicators of oxygen poisoning]

Content of extra erythrocyte hemoglobin (EEH), total peroxidase activity (TPA), tseruloplasmin oxidase activity (TOA) and chemiluminescence intensity have been investigated in plasma. The dose-dependent changes of EEN, TPA, TOA are shown in experiments on the animals under hyperbaric oxygen (HBO) pressure (0.2, 0.3, 0.5, 0.7 MPa from 30 min. to 120 min.) and EEH, TPA--under hyperbaric air (1.1 MPa; 4 hours). All these parameters have been studied in patients treated with HBO for the assessment of HBO efficacy in the clinical investigations. These biochemical parameters may be used as informative tests of the functional state of the organism under HBO and hyperbaric air.     

The Potassium Iodide Method for Determining Protection Factors in Open-fronted Microbiological Safety Cabinets

A method for determining operator protection factors in Class I and Class II microbiological safety cabinets and for evaluating product protection factors in Class II cabinets, is described. The technique employs an aerosol of potassium iodide droplets produced by a spinning disc generator together with special centripetal air samplers detecting any aerosol escape. The method meets the requirements of British Standard (BS) 5726 and is an alternative to the microbiological technique.
The method has been used to evaluate the performance of a number of safety cabinets in relation to the requirements of BS 5726.
Working procedures and unsuitable environments have been shown to prejudice the containment performance of open-fronted cabinets by several orders of magnitude.
The relationship between inflow air velocity and protection factors in Class I safety cabinets has confirmed the optimum requirements defined in the British Standard.     

Hyperbaric oxygen toxicity and ribosome destruction in Escherichia coli K12

The viability of resting suspensions of Escherichia coli K12 Ymel exposed to air plus 300 psi (1 psi = 6.895 kPa) oxygen (hyperbaric oxygen) decreased as an apparent first-order process after an initial period of constant viability. Control suspensions exposed to air plus 300 psi nitrogen (hyperbaric nitrogen) did not lose viability over the 96 h of the experiment. It was observed that a decrease in the refractive index of the cells preceded the loss of viability in hyperbaric oxygen. This finding together with electron micrographs, which showed extensive loss of ribosomal particles in bacteria incubated in hyperbaric oxygen, led us to suspect that ribosome injury or disassociation might be important in hyperbaric oxygen toxicity. In support of this we found that cellular RNA, labeled with [5-3H]uridine, was much more rapidly and more completely degraded in hyperbaric oxygen than in hyperbaric nitrogen. Furthermore, a far greater proportion of RNA was degraded than was DNA or protein. A direct assay for ribosome particles by sucrose gradient centrifugation showed that only 34% of the 70S ribosome particles was lost during the first 24 h in hyperbaric nitrogen whereas in hyperbaric oxygen 99.6% of the 70S particles was degraded during the same period. In hyperbaric oxygen the rate of viability loss between 24 and 72 h was equal to the rate of 70S ribosome degradation during the first 24 h. If 70S ribosome disassociation in hyperbaric oxygen continues at the same rate after first 24 h, then cumulative 70S ribosome disassociation or injury may lead to and provide an explanation for irreversible bacterial cell injury and the loss of viability.     

Effect of a short-acting NO donor on bubble formation from a saturation dive in pigs.

It has previously been reported that a nitric oxide (NO) donor reduces bubble formation from an air dive and that blocking NO production increases bubble formation. The present study was initiated to see whether a short-acting NO donor (glycerol trinitrate, 5 mg/ml; Nycomed Pharma) given immediately before start of decompression would affect the amount of vascular bubbles during and after decompression from a saturation dive in pigs. A total of 14 pigs (Sus scrofa domestica of the strain Norsk landsvin) were randomly divided into an experimental (n = 7) and a control group (n = 7). The pigs were anesthetized with ketamine and alpha-chloralose and compressed in a hyperbaric chamber to 500 kPa (40 m of seawater) in 2 min, and they had 3-h bottom time while breathing nitrox (35 kPa O(2)). The pigs were all decompressed to the surface (100 kPa) at a rate of 200 kPa/h. During decompression, the inspired Po(2) of the breathing gas was kept at 100 kPa. Thirty minutes before decompression, the experimental group received a short-acting NO donor intravenously, while the control group were given equal amounts of saline. The average number of bubbles seen during the observation period decreased from 0.2 to 0.02 bubbles/cm(2) (P < 0.0001) in the experimental group compared with the controls. The present study gives further support to the role of NO in preventing vascular bubble formation after decompression.     

Legacy of implementing industrial health and safety in developing countries

Aiming to develop public attention to the hindrance of national and international efforts on industrial health and safety, this paper explores some important issues, such as the reasons for the lack of motivation to implement necessary measures in developing countries. Examples are likewise given to show why working people are significantly exposed to a number of occupational problems that are reflected in a deterioration of their health, safety and well being. In lieu thereof, an introduction of health and safety is not itself a solution, if certain changes are not rationalised according to the local need. While health and safety intervention is concerned, then local need is of prime importance. If individual situation is not clearly outlined, then preventive and control measures can be treated as a de facto measure. Hence immediate attention, collaboration and co-operation is needed from all the concerned parties such as local government authorities, semi-government or private organisations and international communities for proper implementation of work regulations as well as industrial acts and rules in various workplaces in each of the developing countries.