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PubMed1982

Evaluation of radiation monitor effectiveness for the detection of 85Kr.

As part of the preparations for the purging of TMI Unit-2, the 85Kr sensitivity of 12 radiation detector systems or system combinations was determined. Eleven of these were evaluated using a cube-shaped polyethylene-walled room containing a volume of 5.6 m3 (200 ft3). Krypton-85 gas was added to produce a concentration of 6.7 x 10(-6) muCi/ml in the test room. It was found that none of the ion chambers and scintillation detector systems were able to detect this concentration of 85Kr. Detectors employing thin window GM pancake probes were found to be sensitive enough to monitor this gas down to the unrestrictive area maximum permissible concentration level (MPC) of 3 x 10(-5) muCi/ml, while a large window gas flow proportional counter was found to be sensitive enough to monitor down to about 09.1 MPC. At the end of this experiment, 2.3 m3 (80 ft3) of the gas in the test room was pumped into a compressed air cylinder (scuba bottle) and was used to calibrate The Pennsylvania State University (PSU) Noble Gas Monitor. The sensitivity of this system, which employs gas compression and Ge(Li) spectroscopy, was demonstrated to be between 0.1 and 0.03 times MPC, depending on the counting time employed.

Air Pollutants, Radioactive↗
PubMed1980

A simple and rapid method for postmortem radiographic investigation of lung fine structure.

Radiologic pathologic correlation of lung specimens requires a gas content identical to intravital conditions. Methods of air drying and formalin steam fixation are well known but time consuming. A new, rapid method is presented: the lungs are inflated with compressed air, frozen in liquid nitrogen, and cut into slices. Radiographs taken with soft tissue technique demonstrate structural details down to 200-300 mu. The excellent state of preservation also permits excellent quality of microscopic slides.

Air↗
PubMed1980

[Investigation of radiologic lung fine structure by freezing of inflated specimens in liquid nitrogen (author's transl)].

Radiologic pathologic correlation of lung specimens requires a gas content identical to intravital conditions. Methods of air drying and formalin steam fixation are well known but time consuming. A new, quick method is presented: The lungs are inflated with compressed air, frozen in liquid nitrogen, and cut into slices. Radiographs taken in soft tissue technique will demonstrate structural details down to 200--300 mu. The excellent state of preservation enables unusual quality of microscopic slides, as well.

Adult↗
PubMed1992

Cardiovascular responses to upright tilt in man during acute exposure to 3 atm abs air.

To examine the effect of acute hyperbaric exposure on cardiovascular response to orthostasis, a passive 70 degrees head-up tilt (HUT) test was performed for 15 min in a simulated compressed-air hyperbaric environment of 3 atm abs at ambient temperature of 31 degrees C (thermoneutral) on 8 male subjects. Heart rate (HR), blood pressure, cardiac output (CO) by impedance cardiography, forearm blood flow (FBF) by the occlusion plethysmography, and laser-Doppler skin blood flow (BFLD) on the thigh were measured for 15 min before, during, and after HUT. Esophageal temperature and HR data were recorded continuously. An identical test was performed in a 29 degrees C (thermoneutral) normal atmospheric condition. None of the subjects showed signs of syncope during HUT in either environment. Baseline HR was significantly lower (P less than 0.05) at 3 atm abs, and the increase in HR (delta HR) during HUT was of the same magnitude (15 beats/min) at both atmospheric pressures. The reduction of systolic blood pressure (delta SBP) was identical in both environments. Thus, the chronotropic response to HUT (delta HR/delta SBP) was the same. A marked reduction in CO (P less than 0.05) was attributed to a reduction of stroke volume during HUT, and the reduction was greater (P less than 0.05) at 3 atm abs. There were no pressure-dependent changes during HUT in FBF, forearm vascular resistance, and BFLD except for a greater increase (P less than 0.05) in total peripheral resistance at 3 atm abs. These observations suggest that orthostatic tolerance was maintained in the presence of lower CO at 3 atm abs, probably by a greater vasoconstrictor response in the splanchnic areas. We conclude that the substantial bradycardia which occurred at 3 atm abs did not interfere with a normal response to orthostasis in humans because of a peripheral vasoconstriction caused by the elevated oxygen pressure and an enhanced increase in total peripheral resistance which occurred during HUT in 3 atm abs.

Adult↗
PubMed1998

Comparison of carbon dioxide and air pneumoperitoneum for gamete intrafallopian transfer under conscious sedation and local anesthesia.

OBJECTIVE: To compare patient tolerance and pregnancy rates (PRs) between two cohorts that underwent GIFT under local anesthesia with air versus carbon dioxide (CO2) pneumoperitoneum. DESIGN: Retrospective study. SETTING: University clinic. PATIENT(S): Eighty-five patients who underwent 125 laparoscopies under conscious sedation for GIFT using air pneumoperitoneum were compared with 42 patients who had 70 GIFT procedures with CO2 pneumoperitoneum. INTERVENTION(S): Transvaginal ultrasound-guided egg retrieval followed by GIFT with compressed air or CO2 for pneumoperitoneum under local anesthesia and i.v. sedation. MAIN OUTCOME MEASURE(S): Patient tolerance and viable PR. RESULT(S): The percentage of patients scoring "very good" was lower in the CO2 group (73% for air versus 57% for CO2), but the combined percentage of those scoring "very good" or "good" was comparable at 89% and 87%. The difference in the viable PRs between the two groups (43% versus 37%) for patients < 40 years old was not statistically significant. CONCLUSION(S): Patient tolerance and PRs are similar for air and CO2 pneumoperitoneum during GIFT under local anesthesia. Given the theoretical risk of air embolus and lack of detrimental effect of CO2 on patient tolerance and success rate, it seems prudent to use CO2 in such a setting.

Adult↗
PubMed1990

Low-flow endobronchial insufflation with air for 2 hours of apnea provides ventilation adequate for survival.

We tested the efficacy of low-flow endobronchial insufflation (EI) with air, as it may be useful in emergency situations in which positive-pressure mechanical ventilation is not possible. The only equipment required is a source of compressed air with flow controller and a specially designed insufflation catheter. The insufflation catheter has forked ends that can be positioned blindly in the mainstem bronchi. In six anesthetized, apneic dogs averaging 9.6 kg, we determined that the average air flow needed to maintain PaO2 above 45 mm Hg and PaCO2 below 65 mm Hg after 30 min was 2.5 L/min. At these flow rates, all dogs survived 2 h of endobronchial insufflation with no neurologic dysfunction. The small internal diameters (0.8 mm) of the catheter ends increase gas exit velocity and allow for adequate oxygenation and CO2 removal at low flow rates. Endobronchial insufflation could also be employed with cricothyroidotomy and a compressor for emergency situations in the field involving mass casualties, where oxygen supplies and equipment are limited.

Animals↗
PubMed1990

Comparison of carbon-dioxide-enriched, oxygen-enriched, and normal air in treatment of acute mountain sickness.

Twenty mountaineers with acute mountain sickness (AMS) at an altitude of 4559 m were randomly allocated to treatment with oxygen-enriched (33% oxygen), carbon-dioxide-enriched (3% carbon dioxide), or normal compressed air. Treatment with oxygen significantly improved the arterial partial pressure of oxygen (PaO2), relieved symptoms of AMS, and reduced cerebral blood flow as estimated by transcranial doppler ultrasound examination of the median cerebral artery. The only significant effect of carbon dioxide was increased ventilation resulting in a slight rise in PaO2. Thus, in contrast to previous uncontrolled trials, this study does not support the usefulness of carbon dioxide treatment in AMS.

Acute Disease↗
PubMed1998

Effects of inhaled gases on the ultrasound contrast produced by microspheres containing air or perfluoropropane in anesthetized dogs.

RATIONALE AND OBJECTIVES: Inhaled gas mixtures with increased amounts of oxygen cause air containing ultrasound contrast agents to lose efficacy faster than during the inhalation of air. The authors hypothesized that contrast materials containing relatively insoluble gases would decrease the effects of inhaled gases on the ultrasound contrast. METHODS: Anesthetized dogs were ventilated with compressed air and different oxygen/nitrogen gas mixtures. Video densitometric analysis was performed on end diastolic ultrasound images of the heart after administration of Albunex (air-filled microspheres) or Optison (perfluoropropane-filled microspheres). RESULTS: Increased concentrations of oxygen caused no change in the contrast intensity produced by Optison in the left ventricular chamber. In the myocardium, however, increases in oxygen caused Optison to produce significantly less enhancement of the myocardial tissue. CONCLUSIONS: The use of perfluoropropane within albumin microspheres prevented the effects of inhaled gas mixtures on contrast produced within the left ventricular chamber. In the myocardium, increased concentrations of oxygen in the inhaled gas mixtures reduce contrast intensity.

Administration, Inhalation↗
PubMed1977

Hematologic changes after two exposures to 6.7 ATA air at three-day intervals.

Hematologic parameters were studied in human subjects exposed to various diving regimens. A series of exposures in a dry chamber to a simulated depth of 188 ft of seawater gauge (fswg), 6.7 ATA, utilizing compressed air, were carried out according to standard Navy diving tables. The subjects were serially followed for a control period prior to diving and subsequently for up to 1 wk. Little significant change occurred except for alterations in some platelet factors. In another series of experiments, the single excursion was followed by a second dive to 188 fswg 3 days later, again with appropriate hematologic monitoring. A pronounced eosinopenia and increased clotting times were observed soon after reaching the surface. Platelet depletion associated with increased clumping and elevated megathrombocyte levels persisted long after the second excursion. A latent hemodilution also developed 3--5 after the second dive. These findings clearly demonstrate that repeated hyperbaric exposures produce additive effects and further suggest that no diving procedure is completely innocuous.

Adult↗
PubMed2002

Using animal data to improve prediction of human decompression risk following air-saturation dives.

To plan for any future rescue of personnel in a disabled and pressurized submarine, the US Navy needs a method for predicting risk of decompression sickness under possible scenarios for crew recovery. Such scenarios include direct ascent from compressed air exposures with risks too high for ethical human experiments. Animal data, however, with their extensive range of exposure pressures and incidence of decompression sickness, could improve prediction of high-risk human exposures. Hill equation dose-response models were fit, by using maximum likelihood, to 898 air-saturation, direct-ascent dives from humans, pigs, and rats, both individually and combined. Combining the species allowed estimation of one, more precise Hill equation exponent (steepness parameter), thus increasing the precision associated with human risk predictions. These predictions agreed more closely with the observed data at 2 ATA, compared with a current, more general, US Navy model, although the confidence limits of both models overlapped those of the data. However, the greatest benefit of adding animal data was observed after removal of the highest risk human exposures, requiring the models to extrapolate.

Algorithms↗
PubMed2003

Benzene exposure assessment for use of a mineral spirits-based degreaser.

This study examines benzene emissions from the use of a metal parts washer ("degreaser") supplied with a mineral spirits solvent containing either 9 or 58 ppm benzene. Air samples were obtained during a one-hour session of relatively vigorous parts cleaning activity using a degreaser station equipped with wet brush and sprayer attachments and a compressed air hose. Two methods were utilized to assess airborne benzene levels: U.S. EPA TO-14 (summa stainless steel canister) and NIOSH 1501 (charcoal tube). Overall, both methods provided similar results, excepting detection limit differences. The first simulation was performed with recycled solvent (9 ppm benzene in solvent) showing average one-hour airborne benzene levels < or =33 ppbv in the worker's breathing zone and directly above the parts cleaning tank. Average airborne benzene concentrations 18 inches away from the tank were below 2 ppbv during the 60-minute cleaning protocol. The second simulation with benzene-spiked recycled solvent (58 ppm benzene) showed airborne benzene levels averaging 500 ppbv measured over the 60-minute cleaning period in the worker's breathing zone and directly above the tank, while average concentrations 18 inches from the tank perimeter were 63 ppbv. The data indicate that average and peak exposures to airborne benzene were roughly proportional to the solvent benzene content, although the brief peak exposures exhibited greater variance probably related to aerosol generation associated with the use of the brush and/or spraying attachment. Under this selected upper bound exposure simulation, we found that cleaning parts using a recycled mineral spirits-based solvent in an open warehouse setting did not result in exposures in excess of the current occupational exposure limit of 0.5 ppm averaged over 8 hours for solvent benzene content between 9 and 58 ppm.

Benzene↗
PubMed1980

In vivo resin impregnation of dentinal tubules.

This study investigated the in vivo resin impregnation of dentinal tubules on exposed dentin surfaces with transversely cut tubules and examined the effect of different pretreatment on impregnation of the dentin. The results have lead to the following conclusions: 1. There is no sound reason to routinely etch and impregnate the dentin with resin on cavity walls. 2. It is possible to impregnate flat areas of exposed dentin which are not close to the pulp and which have transversely sectioned dentinal tubules. This may block dentin sensitivity, preventing infection and irritation of the pulp. 3. The etching time with 37% phosphoric acid should be limited to 5 seconds. This is sufficient to open and enlarge the dentinal tubules at the surface. 4. The desiccation should be performed with the air nozzle near, and almost parallel to, a flat surface for at least 15 seconds. An uneven surface results in uneven impregnation of the dentinal tubules due to incomplete desiccation. Therefore, the compressed air should be applied from different directions. Better results are obtained if the dentin surface is smooth. This may be achieved by planing with a smooth fissure bur. 5. To obtain satisfactory desiccation of dentin walls in cavities, an air nozzle should be reduced in diameter enough to allow it to enter the cavity. It should be kept in motion while continuously air drying the cavity surface.

Acid Etching, Dental↗
PubMed1984

A cardiac output monitor and diagnostic unit for pneumatically driven artificial hearts.

The pneumatic artificial heart uses a flexible diaphragm to separate blood from air. The air space behind the diaphragm is connected to the atmosphere during diastole. Blood entering the heart during diastole displaces an equal volume of air into the atmosphere. A pneumotachograph is used to sense this flow of air. Integration of the airflow signal with respect to time yields the volume of air displaced during diastole, which is equal to the volume of blood entering the heart over the same period. This measured filling volume is equal to the cardiac output when averaged over a number of cardiac cycles. Allowance is made for regurgitant losses owing to the prosthetic heart valves. The output of the pneumotachograph is independent of absolute pressure, and so the device may also be used during the systolic (air compression) phase of the cardiac cycle. Analysis of the display of the airflow curves during diastole and systole has great diagnostic value. This device is accurate, easy to calibrate, stable, noninvasive, and does not require modification of any existing air-driven artificial hearts.

Air↗
PubMed1996

Formaldehyde exposure enhances inhalative allergic sensitization in the guinea pig.

Formaldehyde (FA), a common indoor air pollutant, has been associated with increased prevalence rates of asthmatic symptoms among exposed individuals in epidemiologic surveys. We studied the influence of FA exposure on inhalative allergic sensitization in the guinea pig. Three groups of guinea pigs (n = 12 each) were exposed to clean air or two different FA concentrations (0.13 and 0.25 ppm) over 5 consecutive days. Exposure was followed by inhalation of 0.5% ovalbumin (OA) as sensitizing allergen. Three weeks later, specific bronchial provocation with OA was performed with body plethysmographic measurement of compressed air (CA). Furthermore, specific anti-OA-IgGl (reaginic) antibodies were determined in serum. In a further six animals, the respiratory tract was examined histologically for signs of inflammation directly after the end of FA or clean air exposure. In the group exposed to 0.25 ppm FA, 10/12 animals were found to be sensitized to OA (positive reaction on specific provocation) vs. 3/12 animals in the control group (P < 0.01). Furthermore, CA measurements of specific bronchial provocation and serum anti-OA-antibodies were significantly higher in the 0.25 ppm FA group than in controls (CA 0.35 vs. 0.09 ml median, P < 0.01; anti-OA-IgGl 13 vs. < 10 EU median, P < 0.05), indicating enhanced sensitization. In the group exposed to 0.13 ppm FA, no significant difference was found compared to the control group. There was no sign of inflammation of the lower airways in FA-exposed guinea pigs other than mucosal edema, which was discovered by morphometry. We conclude that short-term exposure to a low concentration of FA (0.25 ppm) can significantly enhance sensitization to inhaled allergens in the guinea pig.

Allergens↗
PubMed1981

New Cataract removal instrumentation and techniques: i. the NASA-McGannon cataract fragmentor.

The instrument consists of a high-speed air turbine driven cutter combined with a pressure-regulated infusion system and a peristaltic pump evacuation system. The tool has an exposure control to vary the axial position of the cutter relative to its housing. The entire unit is controlled and powered by compressed air. A foot pedal start and stops all suction and cutting functions. The intraocular pressure is controlled by a flow-compensating pressure regulator that balances out the inflow system pressure drop and thereby provides essentially constant intraocular pressure.

Cataract Extraction↗
PubMed1996

Wet bonding: effect of drying time and distance.

PURPOSE: To examine the effect of various drying times and air syringe-to-tooth distances on the shear bond strength of a dentin adhesive that requires a wet surface for maximum effectiveness. MATERIALS AND METHODS: Seventy extracted human molars were acid etched. The surface of the etched dentin was rinsed and dried with compressed air for 1, 3, or 5 seconds from a distance from either a distance of 1 or 10 cm. The adhesive One-Step was then applied, composite cylinders were attached and shear bond strengths were obtained. RESULTS: Drying time and distance had a significant impact on the resultant shear bond strengths. Longer drying times and shorter syringe-to-tooth distances negatively affected the bond strength of the adhesive studied.

Acid Etching, Dental↗
PubMed2002

[High-pressure air-blast injury of the esophagus].

Blast injuries causing pneumatic damage to the oesophagus are very rare. Patients usually present with respiratory distress, subcutaneous and mediastinal emphysema, and may also have pneumothorax. Ruptures need early repair to avoid serious morbidity and potential lethal complications. We report about a successfully treated 47-year-old patient, who has been admitted to our department with compressed air injury of the oesophagus.

Air↗