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PubMed1980

Effects of low concentrations of nitrous oxide on rat fetuses.

The long-term inhalation of air polluted with nitrous oxide has been implicated in spontaneous abortions and fetal abnormalities in operating room personnel. Studies with 1% and 0.5% N2O in air have confirmed the adverse effects of dilute concentrations of N2O in pregnant rats. The present study was designed to determine the threshold concentration of nitrous oxide necessary to produce adverse responses in pregnant rats. Wistar albino rats were mated in an environmental chamber and conception confirmed by vaginal smears. Immediately thereafter, the rats were randomly divided into control and experimental groups. The control rats were exposed for 19 days to oil-free compressed air in an environmental chamber at a flow rate of 8.5 air changes per hour. Experimental animals were exposed continuously under identical conditions to concentrations of 0.0, 0.1%, 0.5%, or 0.025% N2O. On day 19 the gravid rats were killed. The corpora lutea of pregnancy were counted and related to the number of fetuses in the uterus. Fetuses were fixed, cleared, and their skeletons stained with alizarin red. Litter size, frequency of fetal resorption, and fetal crown rump measurements were significantly different following exposure to 0.1% N2O than they were in control rats or in rats exposed to 0.05% or 0.025% nitrous oxide, neither of which had any fetal effects. The suggested threshold level of 30 ppm (0.03%) N2O in humans may be unrealistically low.

Abnormalities, Drug-Induced↗
PubMed1977

[Significance of model studies for explanation of the pathogenesis of the mechanically induced birth trauma (author's transl)].

We have studied the propotions of displacements from fetal cerebral parts during simulated intrauterine pressure. Stillborn children from the death to the experiments last only some hours, were put in cephalic position in our birth model. The cavum uteri was simulated by a metal cylinder, in which we gave compressed air for simulating the labor. The pressure was held about 100 mm Hg. A rubber cuff was fixed on the metal cylinder and let an opening of 8 cm, simulating the cervix uteri. The model with the death infant in it was frozen and than the fetal head sectioned in slides of 1,5 cm in the right of the birth pressure axis. We found, that the gyri occipital were widened, opposite the gyri frontal were compressed. Parieto-occipital we found a venous blood congestion. The brain stem was kinked and displaced dorsal. In one case we carried out in the meantime an aniogram. The cerebral vessels became under the pressure elongated. This was reversible by decrease of the pressure. The limitation of such model studies are give in some facts. We do not know, how much the loosening of the skull, following the fetal death, leads to a more than normal shifting. We further do not know, which proportions of the displacements of the cerebral substance during labor from the fetus could be compensated. Our findings suggest, that it is possible, that cerebral blood flow will be altered by displacements of the cerebral masses during intrauterine pressure. But we have not exact informations about it.

Birth Injuries↗
PubMed1996

Effect of hyperbaric oxygenation on peripheral nerve regeneration in adult male rabbits.

Oxygen environments were used to study the regenerative effects of hyperbaric oxygen on crushed sciatic nerves in 30 adult male rabbits. Six different oxygen environments were used, and treatments were initiated 4 days post injury. Transmission electron microscopy and light microscopy were used to evaluate the regenerative morphology of crushed nerves. The morphology of crushed nerves after 7 wk of treatment with compressed oxygen at 202, 242, and 303 kPa resembled normal uncrushed nerves, with nerve fibers uniformly distributed throughout the section. The treatment groups receiving 202 kPa compressed air, 100% normobaric oxygen, or ambient air did not display morphologies similar to normal uncrushed nerve. The nerves in these animals were edematous and contained disarrayed nerve fibers. Myelination in the animals receiving 100% O2 at high pressures resembled undamaged nerves. Collagen and blood vessels were more evident in the lower pressure/oxygen tension treatments than in the animals receiving 100% O2 at higher pressures. The neurofilamentous material inside the crushed control axons was dense, whereas in the axons of animals treated with compressed O2 it was loosely packed. These differences in morphology suggest that treatments consisting of 100% O2 under pressure can accelerate a peripheral nerve's recovery from a crush injury.

Animals↗
PubMed1989

Effect of adhesive thickness on the shear bond strength of Scotchbond 2/Silux to dentin.

Seventy-five extracted human permanent molars were embedded in brass cups with cold-cure acrylic. Immediately prior to the preparation of a test specimen, the occlusal surface was ground wet on 180 followed by 600 grit SiC to expose dentin. The Scotchprep Dentin Primer was applied to the dried dentin surface with a brush for 60 seconds, and dried with compressed air for 15 seconds. The tooth was mounted in a special device containing a split Teflon mold with a circular hole, 3.5 mm in diameter and 5 mm deep, and A:0.5 microL (50 microns), B:1.0 microL (100 microns), C:2.5 microL (250 microns), D:5 microL (500 microns) or E:10 microL (1000 microns) Scotchbond 2 pipetted into the teflon mold. The adhesive was cured by visible light for 30 seconds. Three increments of Silux were transferred to the Teflon mold, compressed firmly, and each cured for 30 seconds. The test specimens were disassembled 15 minutes after cure and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied via a knife-edge rod in an Instron machine. The shear bond strength was expressed in MPa. The data were analyzed by ANOVA and Duncan's multiple range test. The mean (+/- SD) of the shear bond strengths were: A: 8.8 (3.5), B: 7.9 (2.7), C: 6.8 (2.5), D: 8.1 (4.2), E: 5.3 (2.4). Adhesive thickness from 50 microns to 500 microns (A, B, C and D) had no significantly different effect on shear bond strength. An adhesive thickness of 1000 microns resulted in a significant reduction in shear bond strength.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2006

The effects of positive and negative middle ear pressures on auditory threshold.

HYPOTHESIS: To assess the effects of positive and negative middle ear pressures on auditory threshold. BACKGROUND: Nonatmospheric middle ear pressures can alter auditory threshold by their effects on tympanic membrane and ossicular chain mobility. METHODS: Experiments were conducted on guinea pigs by inducing alterations in pressure (positive and negative) with a syringe connected to the middle ear bulla cavity, the magnitude of the pressure being assessed with a water manometer. Elevated middle ear fluid pressures were also induced by attaching a saline-filled vertical tube to the saline-filled middle ear. The effect of these altered middle ear air and fluid pressures were assessed by recording auditory nerve-brainstem evoked responses. RESULTS: There was no effect on auditory threshold of positive middle ear air pressures (up to 250 mm H2O). A negative middle ear air pressure of -50 mm H2O induced a significant 9.5-dB threshold elevation, whereas more negative pressures (up to -150 mm H2O) did not induce an additional threshold elevation. Filling the middle ear cavity with saline induced a 10- to 16-dB elevation, whereas additional fluid pressures (up to 200 mm H2O) did not induce further elevations. CONCLUSION: The major factor inducing threshold elevation in serious otitis media is not the alteration in middle ear pressure but rather the reduction in the volume of compressible air in the middle ear by the fluid.

Air Pressure↗
PubMed1999

An Australian study to evaluate worker exposure to chrysotile in the automotive service industry.

A study was conducted in Sydney, Australia, in 1996 to investigate the current exposure levels, control technologies, and work practices in five service garages (four car and one bus), three brake bonding workshops, and one gasket processing workshop. This study formed part of the assessment of chrysotile as a priority existing chemical under the Australian National Industrial Chemicals Notification and Assessment Scheme. A total of 68 (11 personal and 57 area) air samples were collected, in accordance with the Australian standard membrane filter method. Fiber concentrations were determined by the traditional phase contrast microscopy (PCM) method and 16 selected samples were analyzed by the more powerful transmission electron microscopy (TEM). Chrysotile exposure of car mechanics measured by PCM was typically below the reportable detection limit of 0.05 f/mL, irrespective of whether disc brake, drum brake, or clutch was being serviced. These low levels can be attributed to the wet cleaning or aerosol spray methods used in recent years to replace the traditional compressed air jet cleaning. In the three brake shoe relining workshops, task-specific exposure reached up to 0.16 f/mL in the processes of cutting and radius grinding. TEM results were generally higher, due to its higher resolution power. The median diameter on samples taken from the service garages (passenger cars), as determined by TEM, was 0.5-1.0 micron; and was between 0.2-0.5 micron for the brake bonding and gasket processing workshops, while that for the bus service depot was 0.1-0.2 micron. Most of the respirable fibers (84%, mainly forsterite) from the bus service depot were below 0.2 micron in diameter which is the resolution limit of PCM. In the brake bonding and gasket cutting workshops, 34 percent and 44 percent of the chrysotile fibers were below 0.2 micron in diameter.

Air Pollutants, Occupational↗
PubMed2003

Effects of oxygen administration on the circulating vascular endothelial growth factor (VEGF) levels in patients with obstructive sleep apnea syndrome.

OBJECTIVE: Repeated nocturnal hypoxia is implicated in the pathogenesis of cardiovascular complications in obstructive sleep apnea syndrome (OSAS). We hypothesized that circulating vascular endothelial growth factor (VEGF) levels are affected by nocturnal hypoxemia in patients with OSAS. METHODS: We examined the serum VEGF levels in patients with OSAS and in control subjects. We also tested the effects of oxygen or air administration on the subjects' VEGF levels. PATIENTS AND MATERIALS: Twenty-four OSAS patients (mean age 54.2 +/- 3.6 years) and 24 age-matched control subjects (53.2 +/- 3.6 years). Their serum samples were tested. RESULTS: Serum VEGF levels at 8:00 AM were significantly higher in OSAS patients than in controls (p<0.01). VEGF levels decreased from 515 +/- 31 (pg/ml) to 178 +/- 16 (pg/m) (p<0.01) in OSAS patients whose nocturnal hypoxemia was found to be improved by administration of 2 l/min of oxygen during the night. However, the administration of compressed air affected neither the VEGF level nor nocturnal oxygen desaturation in OSAS patients. CONCLUSION: These results indicate that circulating VEGF levels are elevated in OSAS patients, primarily due to nocturnal hypoxemia.

Adult↗
PubMedDate not supplied

Recent neurochemical basis of inert gas narcosis and pressure effects.

Compressed air or a nitrogen-oxygen mixture produces from 0.3 MPa nitrogen narcosis. The traditional view was that anaesthesia or narcosis occurs when the volume of a hydrophobic site is caused to expand beyond a critical amount by the absorption of molecules of a narcotic gas. The observation of the pressure reversal effect on general anaesthesia has for a long time supported the lipid theory. However, recently, protein theories are in increasing consideration since results have been interpreted as evidence for a direct anaesthetic-protein interaction. The question is to know whether inert gases act by binding processes on proteins of neurotransmitter receptors. Compression with breathing mixtures where nitrogen is replaced by helium which has a low narcotic potency induces from 1 MPa, the high pressure nervous syndrome which is related to neurochemical disturbances including changes of the amino-acid and monoamine neurotransmissions. The use of narcotic gas (nitrogen or hydrogen) added to a helium-oxygen mixture, reduced some symptoms of the HPNS but also had some effects due to an additional effect of the narcotic potency of the gas. The researches performed at the level of basal ganglia of the rat brain and particularly the nigro-striatal pathway involved in the control of the motor, locomotor and cognitive functions, disrupted by narcosis or pressure, have indicated that GABAergic neurotransmission is implicated via GABAa receptors.

Anesthetics↗
PubMed1994

Perception of thermal comfort during narcosis.

We examined the perception of thermal comfort in six male subjects immersed in water at 28 degrees C (study I) and 15 degrees C (study II), breathing either room air (AIR) or a normoxic mixture containing 30% N2O (N2O). Immersions were terminated if esophageal temperature (Tes) decreased by 2 degrees C from resting levels or to 35 degrees C. At regular intervals, subjects rated their perception of thermal comfort on a 21-point scale (thermal comfort vote, TCV; +10 = very, very hot, 0 = neutral, -10 = very, very cold). For similar decreases in Tes from resting preimmersion values (mean +/- SD = -0.90 degrees +/- 0.13 degrees C and -0.92 degrees +/- 0.15 degrees C during the AIR and N2O trials in study I, and -0.90 degree +/- 0.22 degree C and -0.89 degree +/- 0.27 degree C during the AIR and N2O trials in study II), subjects perceived the immersions as less cold during the N2O trials. The median TCVs for the AIR condition of -5 in study I and -7.75 in study II, were significantly lower than those reported by the subjects for the respective N2O conditions (1.75 in study I and -5.5 in study II). It is concluded that behavioral adjustments required for maintaining thermal balance may be diminished during narcosis due to the altered perception of thermal discomfort. Assuming that the effect of inert gas narcosis on thermoregulatory responses is similar to that of N2O, then combined with the significant attenuation of heat gain mechanisms by anesthetic gases, the attenuation of the perception of thermal comfort may represent a significant factor in the etiology of hypothermia observed in compressed air divers.

Body Temperature Regulation↗
PubMed1976

[Changes in intracranial pressure and impedance in the presence of air and gad embolism].

In biophysical models and in acute experiments on animals, the air was administered in measured volumes into the artificial blood flow and into the common carotid artery in dogs. When air bubbles get into the electric field between electrodes, specific changes of impedance depending on the bubbles size could be recorded. A lot of small bubbles sharply increased the impedance according to their total volume. Ih the air compression up to 10 kgs/cm2 and in following decompression, the intracranial impedance and pressure smoothly changed according to barogram. After 15 min of stying under pressure the dogs developed during decompression a sharp increase of the intracranial impedance and pressure which, similarly to the results of the model experiments, should be regarded as the consequence of formation of a free gas phase in the system of intracranial circulation.

Animals↗
PubMed1983

Storage cabinet for volatile toxic chemicals.

It is common practice to store toxic volatile chemicals in a laboratory fume hood. Although this provides safe storage, it becomes necessary to operate the hood continuously, resulting in a continuous loss of conditioned air from the building. Often, bottles containing highly toxic chemicals are few in numbers and small in size so that the storage volume required for this purpose is modest. This makes it possible to utilize a small auxiliary storage cabinet in place of a chemical hood for this purpose, provided all the vapors from the stored chemicals can be retained. We have constructed and tested a passive storage cabinet consisting of a metal box, 30 X 30 X 30 cm, with a front-opening latchable door, a false bottom for catching and retaining liquid spills, and an open top completely covered with a 5-cm depth of tightly packed, gas-adsorbing, activated charcoal. All vapors released inside the cabinet must pass through the charcoal before reaching the outside and are retained on the charcoal. Means are provided to purge the box of residual vapors before opening the door by compressed air line or a hand-operated squeeze bulb. The incoming fresh air sweeps through the chamber and exists through the charcoal filter.

Drug Storage↗
PubMed1984

Perfluorochemicals as a treatment of decompression sickness in rats.

Perfluorodecalin and perfluorotripropylamine which have N2 solubility coefficients of 28.4 and 35.7 ml/dl, respectively, were used for treatment of decompression sickness in this study. Rats with chronically implanted venous catheters were held for 30 min at 800 kPa (7 bar, 8 ATA) by introducing compressed air into a chamber in which they were kept; a relatively short period of decompression followed (200 kPa/min). Immediately thereafter injections of the perfluorochemicals (PFCs) in a dose of 10 g/kg were given, controls received saline in the same volume or remained without treatment. An observation period of 2 h followed; after this time the incidence of death amongst the experimental animals (as compared with controls tested by the chi 2-test) showed that PFC treatment increased the likelihood of survival. Probit-log time relationship for the incidence of death also revealed a significant decrease in lethality in treated rats 30 min after the end of decompression. The mean lethal times Lt50 differed significantly, too. A still greater effect might be expected if the PFC emulsion were deprived of its normal nitrogen content by oxygenation before administration. Under the conditions of the present experiments PFCs produced an improvement in N2 exhalation at least in terms of the survival rate after compression followed by a very short decompression time.

Animals↗
PubMed1999

Cerebral arterial gas embolism in air force ground maintenance crew--a report of two cases.

Two cases of cerebral arterial gas embolism (CAGE) occurred after a decompression incident involving five maintenance crew during a cabin leakage system test of a Hercules C-130 aircraft. During the incident, the cabin pressure increased to 8 in Hg (203.2 mm Hg, 27 kPa) above atmospheric pressure causing intense pain in the ears of all the crew inside. The system was rapidly depressurized to ground level. After the incident, one of the crew reported chest discomfort and fatigue. The next morning, he developed a sensation of numbness in the left hand, with persistence of the earlier symptoms. A second crewmember, who only experienced earache and heaviness in the head after the incident, developed retrosternal chest discomfort, restlessness, fatigue and numbness in his left hand the next morning. Both were subsequently referred to a recompression facility 4 d after the incident. Examination by the Diving Medical Officer on duty recorded left-sided hemianesthesia and Grade II middle ear barotrauma as the only abnormalities in both cases. Chest X-rays did not reveal any extra-alveolar gas. Diagnoses of Static Neurological Decompression Illness were made and both patients recompressed on a RN 62 table. The first case recovered fully after two treatments, and the second case after one treatment. Magnetic resonance imaging (MRI) of the brain and bubble contrast echocardiography performed on the first case 6 mo after the incident were reported to be normal. The second case was lost to follow-up. Decompression illness (DCI) generally occurs in occupational groups such as compressed air workers, divers, aviators, and astronauts. This is believed to be the first report of DCI occurring among aircraft's ground maintenance crew.

Adult↗
PubMed1999

Effect of water, saliva and blood contamination on bonding of metal brackets with a 4-META/MMA/TBB resin to etched enamel.

PURPOSE: To investigate the influence of contamination by water, human saliva, and blood on the bonding of metal brackets with a 4-META/MMA/TBB resin to etched enamel. MATERIALS & METHODS: For compressive shear bond strength measurements, the surfaces of bovine enamel were prepared either by etching with 37% phosphoric acid solution for 10, 30, or 60 s and then dried with oil-free compressed air for 10 s, or by contaminating with water, human saliva, and blood. Brackets were applied with Super Bond under loads of 200, 400, or 600 g. The bonded samples were immersed in water for 1 d or thermo-cycled for 500 cycles, and the mean shear bond strengths were compared using two-way ANOVA and Scheffé's multiple comparisons test at P = 0.05. RESULTS: The bond strengths to enamel etched for 60 s were independent of the variable load, regardless of the type of contamination. A short etching duration provided higher bond strengths than extended etching of samples contaminated with saliva and blood. The bond strengths to enamel etched for 10 s after thermal stress and immersion in water were from 11.4 to 30.4 MPa. The samples contaminated by saliva showed the lowest bond strength, and thermal stress did not reduce the bond strengths.

Acrylic Resins↗
PubMed1986

New instrument for vitreoretinal membrane surgery.

We have designed a new instrument that dissects and cuts complex vitreoretinal membranes. It is a modified hook with a wedge-shaped front end. An anvil-like platform serves as a "chopping block." An oscillating knife, housed in the hollow shaft of the hook, is driven against the anvil to cut the membrane. The instrument is powered by compressed air and controlled by a multifunctional, portable console and universal pedal. We evaluated the system in 125 cases of complicated retinal detachment and found it to be effective, safe, reliable, and durable. The console and pedal can also serve to activate other instruments used in all intraocular microsurgical procedures, including vitrectomy and cataract surgery, and to interface with diathermy, cryosurgery, endolaser, and phacofragmentation machines.

Evaluation Studies as Topic↗
PubMed1994

Treatment of burned mice with hyperbaric oxygen reduces mesenteric bacteria but not pulmonary neutrophil deposition.

OBJECTIVE: Hyperbaric oxygen (HBO) is used but unproven for many conditions, including burns. We hypothesized that HBO therapy might increase oxygen delivery to intestine during burn shock and decrease mucosal injury. SETTING: University research laboratory. DESIGN AND STUDY PARTICIPANTS: We studied the effects of HBO therapy (100% oxygen at 2.4 atm absolute) on mesenteric bacterial colonies (MBCs) in mice following 32% total body surface area burns. MBCs were counted 24 or 48 hours postburn by culturing mesenteric tissue. Intestinal histologic features were examined, acid-base balance was measured, and pulmonary neutrophil deposition was estimated by lung myeloperoxidase content. INTERVENTIONS: HBO delivered in a compression chamber. MAIN OUTCOME MEASURE: Numbers of mice with MBCs. RESULTS: With twice-daily HBO treatments, each treatment lasting 1.5 or 2 hours, fewer burned mice had MBCs. Three HBO treatments within 24 hours produced seizures, death, and increased numbers of mice with MBCs. Numbers of mice with MBCs were not influenced when compressed air (2.4 atm absolute) or 100% oxygen (1 atm absolute) was used. Villus histologic findings showed less damage in burned mice that received HBO therapy than in controls. Metabolic acidosis was not affected by HBO therapy, nor were lung myeloperoxidase levels. CONCLUSION: HBO therapy was associated with reduced numbers of mice with MBCs after burn injury and reduced histologic evidence of mucosal damage, but lung myeloperoxidase levels and metabolic acidosis were not affected. HBO therapy may increase oxygen delivery to ischemic intestine and improve cellular metabolism; alternatively, increased tissue oxygen may augment killing of translocated bacteria by phagocytic cells. HBO deserves further investigation for burn treatment, but because of the narrow therapeutic window and continued neutrophil sequestration in the lungs, we should proceed cautiously.

Acid-Base Equilibrium↗
PubMed1979

Respiratory therapy. Current practice in ambulatory patients with chronic airflow obstruction.

The role of respiratory therapy in treating ambulatory patients with chronic obstructive pulmonary disease is becoming more clearly defined. Oxygen therapy on a continuous basis is needed for patients with arterial PO2 values below 45 mm Hg and should be considered for patients with arterial PO2 values between 45 and 55 mm Hg who have chronic cor pulmonale, erythrocytosis with hematocrit value greater than 55%, and disturbances of cognition and sleep. Concentrated bronchodilator and corticosteroid aerosols have established roles in therapy; the place of bland aerosols is less clear They may increase ease of expectoration and should be given by simple compressed-air nebulizer systems; their administration by brief periods of intermittent positive-pressure breathing is rarely justified. Three-positional, postural drainage with chest percussion and vibration may be helpful in mobilizing secretions in patients with severe disease.

Aerosols↗
PubMed2002

A world-to-chip socket for microfluidic prototype development.

We report a prototype for a standard connector between a microfluidic chip and the macroworld. This prototype is the first to demonstrate a fully functioning socket for a microchip to access the outside world by means of fluids, data, and energy supply, as well as providing process visibility. It has 20 channels for the input and output of liquids or gases, as well as compressed air or vacuum lines for pneumatic power lines. It also contains 42 pins for electrical signals and power. All these connections were designed in a planar configuration with linear orthogonal arrays. The vertical space was opened for optical measurement and evaluation. The die (29.1 mm x 27.5 mm x 0.9 mm) can be easily mounted and dismounted from the socket. No adhesives or solders are used at any contact points. The pressure limit for the connection of working fluids was 0.2 MPa and the current limit for the electrical connections was 1 A. This socket supports both serial and parallel processing applications. It exhibits great potential for developing microfluidic systems efficiently.

Electrochemistry↗