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PubMed1987

Possible role of vacuum systems and compressed air generators in cross-infection in the ICU. A radioactive tracer study.

Cross-contamination between a hospital's vacuum and compressed air systems was demonstrated using xenon-133 as a tracer. A xenon-133 bolus was introduced to the vacuum system in the intensive care unit. Calculations based on the amount of radioactive tracer recovered from the compressed air outlet at the same location as that at which the tracer was introduced indicated that 17% of the tracer had entered the compressed air system. The contamination was caused because the vacuum and compressed air systems were located in the same machine room. This could conceivably provide a route for respiratory tract contamination in patients receiving ventilatory assistance with air-oxygen mixtures.

Air↗
PubMed1981

[Effects of variations in the ascending speed on the production of circulating gas bubbles after compressed-air diving].

Ninety-seven compressed air divers at depths of 20 to 52 msw were done. Every dive reached a tissue nitrogen saturation level greater than or equal to M value according to U.S. Navy decompression schedules and respected all prescribed decompression stop. Dives were divided in two groups according to the speed of ascent:--1st group: 33 dives (18 simulated, 15 open water) with ascent at 18 msw/min. for the first half of the distance and 10 msw/min. for the second half. No work on the bottom. Average ascent rate 14 msw/min. This profile was due to the flow limits of the outlet of our chamber during the second part of the ascent, and it was repeated in open water diving.--2nd group: 64 dives (4 simulated, 60 open water) with linear ascent at 10 msw/min. Half the open water dives were repetitive within 4 hours from the first one. Medium to heavy work on the bottom. Ultrasound Doppler bubble detection at rest and after exercise was performed at five minutes intervals and during 40 minutes after surfacing.

Diving↗
PubMed1990

Effect of exposure to compressed air and elevated oxygen levels on bone blood flow in the rabbit.

As the pathogenesis of dysbaric osteonecrosis is not fully understood, we investigated the effects of compressed air, decompression, and elevated oxygen levels on bone blood flow. Bone blood flow was measured in 4 groups of rabbits using the radioactive-labeled microsphere technique. In the Control and Oxygen groups it was measured at normal pressure (1 ATA) at the end of 4-h exposures to air and 100% oxygen, respectively. In the Pressure group it was measured "at pressure" at the end of a 4-h exposure to compressed air (3 ATA) and in the Decompression group it was measured after decompression following a 3.5-h exposure to compressed air (3 ATA). Femoral head blood flow was significantly lower (P = 0.027) in both the Pressure (7.5 ml.100 g-1.min-1) and Decompression (7.1 ml.100 g-1.min-1) groups than in the Control group (13.0 ml.100 g-1.min-1). Moreover, the distribution of blood flow between the cortex and marrow of the humerus differed significantly (P = 0.044) between the Control and Pressure groups. No differences were found between the bone blood flow rates of the Control and Oxygen groups. It is concluded that femoral head blood flow is reduced by prolonged exposure to compressed air (without decompression) and that this is not solely an effect of the high partial pressure of oxygen.

Animals↗
PubMed2001

Ocular tear film bubble counts after recreational compressed air diving.

Other authors have demonstrated an increase in tear film bubble counts following dry, compressed air dives. We examined the lower tear film meniscus for the presence of bubbles in 42 divers after compressed air dives on a single day and in 11 divers undergoing repetitive, multi-day diving exposures over 5 days. After diving, bubble counts increased significantly (P < 0.01) from predive values. From a predive median (inter-quartile range) of 0 (0-0.33) bubbles/eye, single-day divers reached a maximum bubble count at 48 h after diving of 1 (0-2.25) bubbles/eye. Similarly, from a predive count of 0.33 (0-1) bubbles/eye, multi-day divers had increased bubble counts from 24 h following their first dive until 24 h following their final dive when counts were 1.67 (0.92-3.08) bubbles/eye. Bubble counts were not significantly correlated with inert gas load, body mass index, age, or diving experience. We confirm that tear film bubble counts are raised after wet compressed air diving as previously described following dry diving.

Adult↗
PubMed1999

Compressed air as a source of inhaled oxidants in intensive care units.

Exhaled gas from mechanically ventilated preterm infants was found to have similar oxidant concentrations, regardless of lung disease, leading to the hypothesis that wall outlet gases were an oxidant source. Oxidants in compressed room air and oxygen from wall outlets were assessed in three hospitals. Samples were collected by flowing wall outlet gas through a heated humidifier and an ice-packed condenser. Nitric oxide (NO) was measured in intensive care room air and in compressed air with and without a charcoal filter using a Sievers NOA280 nitric oxide analyzer (Boulder, CO). Oxidants were measured by spectrophotometry and expressed as nMol equivalents of H2O2/mL. The quantity of oxidant was also expressed as amount of Vitamin C (nMol/mL) added until the oxidant was nondetectable. This quantity of Vitamin C was also expressed in Trolox Equivalent Antioxidant Capacity (TEAC) units (mMol/L). Free and total chlorine were measured with a Chlorine Photometer. Oxidants were not found in compressed oxygen and were only found in compressed air when the compression method used tap water. At a compressed room air gas flow of 1.5 L/min, the total volume of condensate was 20.2 +/- 1 mL/hr. The oxidant concentration was 1.52 +/- 0.09 nMol/mL equivalents of H2O2/mL of sample and 30.8 +/- 1.2 nMol/hr; 17.9% of that found in tap water. Oxidant reduction required 2.05 +/-0.12 nMol/mL vitamin C, (1.78 +/- 0.1 x 10(-3) TEAC units). Free and total chlorine in tap water were 0.3 +/- 0.02 mg/mL and 2.9 +/- 0.002 mg/mL, respectively. Outlet gas contained 0.4 +/- 0.06 mg/mL and 0.07 + 0.01 mg/mL total and free chlorine, respectively; both 14% of tap water. When a charcoal filter was installed in the hospital with oxidants in compressed air, oxidants were completely removed. Nursery room air contained 12.4 +/- 0.5 ppb NO; compressed wall air without a charcoal filter, 8.1 +/- 0.1 ppb and compressed air with a charcoal filter 12.5 +/- 0.5 ppb. A charcoal filter does not remove NO. (Table 3) We recommend that all compressed air methods using tap water have charcoal filters at the compression site and the gases be assessed periodically for oxidants.

Administration, Inhalation↗
PubMed1978

Nitrogen-oxygen saturation therapy in serious cases of compressed-air decompression sickness.

Decompression sickness and arterial air embolism which follow exposure to raised environmental pressures of compressed air are usually adequately treated by accepted recompression procedures of relatively short durations. With serious cases, however, conventional treatment may not allow sufficient time at depth for the complete resolution of manifestations because of the need to avoid pulmonary oxygen toxicity which is associated with a prolonged period of breathing compressed air. Treatment by nitrogen-oxygen saturation at a pressure equivalent of 30 m (100 ft) sea water is proposed. Based upon the success of three refractory cases treated by this procedure, recommendation are made for the conversion of standard compressed-air chambers into an emergency saturation mode for therapy.

Adult↗
PubMed1977

Shallow habitat air dives I and II: human hematologic responses to compressed air saturation diving.

Two subjects each were exposed to pressure equivalents of 50 (SHAD I) and 60 (SHAD II) feet of sea water gauge (FSWG) for 30 and 28 d, respectively. Red blood cell (RBC) count, hemoglobin (Hb) content, and reticulocyte count of venous blood from divers were measured before, during, and after these exposures. RBC count of the divers decreased a maximum of 7.1% in the 50-ft dive and 10.7% in the 60-ft dive compared to surface control values. Hb content fell 7.7% and 11.1% in the 50- and 60-ft dives, respectively, when compared to nondiving subjects. Reticulocyte counts tended to increase late in the pressurization phase and during the recovery. The total month-long responses of Hgb in SHAD I, and RBC, Hgb, and reticulocyte count in SHAD II were significantly altered when compared to those of the surface control subjects. The changes in these factors were directly attributable to the month-long exposure to the total hyperbaric environment. The threshold for hematological effects of chronic exposure to compressed air would seem to lie between 50 and 60 FSWG.

Air↗
PubMed1992

Dysbaric osteonecrosis in a compressed air tunnelling project in Hong Kong.

In the largest compressed air tunnelling project using the Blackpool Decompression Tables in Hong Kong, 912 men had radiological examination of major joints and 12 definite and 30 suspected cases of dysbaric osteonecrosis were detected by the compressed air physician. Distribution of the lesions was symmetrical and 43.1 per cent were juxta-articular. All the cases were asymptomatic. The infrequent occurrence of osteonecrosis in Hong Kong in general and in this project in particular suggests that the Blackpool Tables were relatively effective in preventing the disease. Definite and suspected cases were pooled together for the study of risk factors for osteonecrosis. Logistic regression analysis showed that the number of bends ever experienced, number of hours worked in the present contract, age and obesity were important independent risk factors. Because of the impossibility of a suitably long follow-up for all workers, the prevalence of osteonecrosis may be under-reported in Hong Kong.

Adult↗
PubMed2002

Safety in the use of compressed air versus oxygen for the ophthalmic patient.

Oxygen, routinely administered during surgery to avoid hypoxia, poses risks including increased likelihood of surgical room fires and predisposition to retinal phototoxicity in patients. Compressed air to supplement ventilation may be safer than oxygen. The purpose of this study was to determine whether hypoxia occurs more frequently when compressed air replaces supplemental oxygen during ophthalmic surgery. A convenience sample of 111 patients was randomly assigned to receive supplemental oxygen (group 1) or compressed air (group 2). Patients with serious cardiac or pulmonary disease were excluded. Blood oxygen levels were monitored during surgery by pulse oximetry. Oxygen was administered to all group 2 patients whose oxygen saturation fell to less than 90% or by more than 5% below baseline. No differences were observed between groups in age, ASA classification, type of surgery, or anesthetic drugs or doses. Minor, but statistically higher oxygen values were observed in group 1. The frequency with which oxygen saturation decreased below 90% or below 5% of baseline was similar in both groups. Supplemental oxygen is not required routinely in selected patients undergoing ophthalmic surgery. By using compressed air, the risk of operating room fires and retinal phototoxicity may be reduced.

Air↗
PubMed2004

Investigation on wind energy-compressed air power system.

Wind energy is a pollution free and renewable resource widely distributed over China. Aimed at protecting the environment and enlarging application of wind energy, a new approach to application of wind energy by using compressed air power to some extent instead of electricity put forward. This includes: explaining the working principles and characteristics of the wind energy-compressed air power system; discussing the compatibility of wind energy and compressor capacity; presenting the theoretical model and computational simulation of the system. The obtained compressor capacity vs wind power relationship in certain wind velocity range can be helpful in the designing of the wind power-compressed air system. Results of investigations on the application of high-pressure compressed air for pressure reduction led to conclusion that pressure reduction with expander is better than the throttle regulator in energy saving.

Air↗
PubMed1987

[Research on the incidence of decompression sickness in compressed air works. The development of its recent five years' study].

Compressed air works have been used as the safest construction work for the basic underground or underwater compressed shield or caisson works in Japan; however, the workers who were exposed to the compressed fields must have put themselves at risk of decompression sickness. Decompression sickness is generally considered to be due to the bubble effects and the bubbles originate from the supersaturated gas dissolved in the blood and other tissues. The standard decompression schedule by the Ministry of Labor has been practically applied at the end of compressed air works, and the laborers decompress slowly from the bottom pressure to the surface according to the schedule. It is difficult to completely prevent the sickness and the average percentage of contracting "bends," using the Japanese standard decompression schedule, is considered to be 0.54%. But previous papers reported higher incidences from 1.42 to 3.3% or more. We have continued an actual investigation on the incidence, and the number of the exposed trials amounted to nearly a hundred thousand. These data were compared between recent five years' group and before. Eventually, it was ascertained that the incidence has been significantly decreased in the recent five years; however, greater care in occupational safety control is still needed.

Adult↗
PubMedDate not supplied

Hydrofluoric acid burn resulting from ignition of gas from a compressed air duster.

A young female suffered burns to her hand after the ignition of gas from a compressed air duster. After debridement and dressing, the patient continued to have pain out of proportion to injury that was refractory to intravenous morphine. The material safety data sheet revealed that the chemical used was 1,1-difluoroethane. High temperatures can cause decompensation to form hydrofluoric acid. Calcium gluconate gel was applied topically to the patient's burns, which caused prompt and complete relief of her pain. A review of different compressed air duster products revealed that the main ingredient in each was a halogenated hydrocarbon. Although not considered flammable, all products have warnings regarding the possibility of ignition under various circumstances. Ignition of the gas in compressed air cleaners not only can cause flame burns, it can also cause chemical damage from exposure to hydrogen and fluoride ions. Prompt recognition and treatment is necessary to prevent severe injury.

Adult↗
PubMed2006

Compressed air injection technique to standardize block injection pressures.

PURPOSE: Presently, no standardized technique exists to monitor injection pressures during peripheral nerve blocks. Our objective was to determine if a compressed air injection technique, using an in vitro model based on Boyle's law and typical regional anesthesia equipment, could consistently maintain injection pressures below a 1293 mmHg level associated with clinically significant nerve injury. METHODS: Injection pressures for 20 and 30 mL syringes with various needle sizes (18G, 20G, 21G, 22G, and 24G) were measured in a closed system. A set volume of air was aspirated into a saline-filled syringe and then compressed and maintained at various percentages while pressure was measured. The needle was inserted into the injection port of a pressure sensor, which had attached extension tubing with an injection plug clamped "off". Using linear regression with all data points, the pressure value and 99% confidence interval (CI) at 50% air compression was estimated. RESULTS: The linearity of Boyle's law was demonstrated with a high correlation, r = 0.99, and a slope of 0.984 (99% CI: 0.967-1.001). The net pressure generated at 50% compression was estimated as 744.8 mmHg, with the 99% CI between 729.6 and 760.0 mmHg. The various syringe/needle combinations had similar results. CONCLUSION: By creating and maintaining syringe air compression at 50% or less, injection pressures will be substantially below the 1293 mmHg threshold considered to be an associated risk factor for clinically significant nerve injury. This technique may allow simple, real-time and objective monitoring during local anesthetic injections while inherently reducing injection speed.

Air Pressure↗
PubMed1987

Compressed air injury of the colon, a case report.

A case of compressed air injury to the bowel resulting in large bowel perforation necessitating resection is presented. The mechanism of injury is discussed and the attention of health care delivery personnel is drawn to this new type of industrial accident in Nigeria. The need for education of the workers handling compressed air appliances in a developing country like Nigeria is emphasized.

Adult↗
PubMed1997

Contamination of hospital compressed air with nitric oxide: unwitting replacement therapy.

BACKGROUND: Inhaled nitric oxide (NO) at levels between 5 and 80 ppm has been used experimentally to treat a variety of conditions. NO also is a common environmental air pollutant in industrial regions. As compressed hospital air is drawn from the local environment, we speculated that it may contain NO contamination, which, if present, would provide unwitting inhaled NO therapy to all subjects respiring this compressed gas. METHODS: NO levels were measured twice daily from ambient hospital air and compressed gas sources driving positive pressure ventilation from two adjacent hospitals and compared with NO levels reported daily by local Environmental Protection Agency sources. An NO chemiluminescence analyzer (Sievers 270B; Boulder, Colo) sensitive to > or =2 parts per billion was used to measure NO levels in ambient air and compressed gas. RESULTS: NO levels in ambient air and hospital compressed air covaried from day to day, and absolute levels of NO differed between hospitals with the difference never exceeding 1.4 ppm (range, 0 to 1.4 ppm; median, 0.07 ppm). The hospital with the highest usage level of compressed air had the highest levels of NO, which approximated ambient levels of NO. NO levels were lowest on weekends in both hospitals. We also documented inadvertent NO contamination in one hospital occurring over 5 days, which corresponded to welding activity near the intake port for fresh gas. This contamination resulted in system-wide NO levels of 5 to 8 ppm. CONCLUSION: Hospital compressed air contains highly variable levels of NO that tend to covary with ambient NO levels and to be highest when the rate of usage is high enough to preclude natural degradation of NO in 21% oxygen. Assuming that inhaled NO may alter gas exchange, pulmonary hemodynamics, and outcome from acute lung injury, the role of unwitting variable NO of hospital compressed air needs to be evaluated.

Air↗
PubMed1987

[Medical aspects of the environmental sanitation of workplaces in compressed air work in Japan].

Actual follow-up investigations were made for a period of 5 yr and 10 months since February 1980 on 55 places of caisson and shield work. The maximum bottom pressure in caisson work was 3.6 kg/cm2 (4.6 ATA) and that of shield work was 1.6 kg/cm2. The number of exposures of workers was 23,737 in caisson work and 75,244 in shield work. The items of geomedical measurements were temperature (degrees C), humidity, dust, illumination, noise, oxygen, carbonic acid gas and others. In compressed air work, it is most important to prevent decompression sickness (bends) from the view of occupational health. The incidence of bends has decreased in recent years because of strict control by regulations. Environmental hygiene, however, has seldom been discussed in this field and little geomedical control has been made on compressed air work. In view of this situation, we have, therefore, studied, observed, and measured the hygienic factors of this work during the past five years. This investigation is without doubt the first of its kind in Japan and the areas covered most of the regions where compressed air works have been made in the past. From these results, it can be concluded as follows: The working temperature was controlled, but humidity was too high (nearly 90%). Illumination was insufficient. Dust was a problem, but high humidity played an important role in decreasing the volume. The environment was noisy. It is therefore natural that environmental studies should be continued and hygienic consideration be further emphasized in compressed air work.

Atmospheric Pressure↗
PubMed1985

Preemployment medical examinations in a compressed air tunneling project in Hong Kong.

One thousand workers intended to be employed in a compressed air tunneling project in Hong Kong had preemployment medical examinations for fitness to work in compressed air. Only 69.3% were declared fit and the overall unfit rate was 22.1%. The major disqualifying medical conditions were lung and heart abnormalities and chronic otitis media. Chest x-ray was found to be the most useful procedure in detecting the disqualifying conditions. The type I bends rate of the contract during the same period of examination was low: 1.39% at maximum working pressure of 2.45 kg/cm2, and there was no case of type II decompression sickness. Although many factors may affect the bends rate, it is suggested that the strict criteria adopted in the selection of workers might have contributed to the satisfactory outcome in the prevention of decompression sickness.

Decompression Sickness↗