SEARCH · Search PubMed

Results for “Compressed Air”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources

PubMed1985

Intellectual deterioration with excessive diving (punch drunk divers).

A survey was performed on a specific occupational group of compressed air divers--the professional abalone divers of New South Wales. One aspect of this survey included the use of psychometric screening tests to elicit evidence of impaired intellectual capacity, which may be related to the compressed air diving. Results of the survey indicate that there is suggestion of intellectual impairment in almost half of this diving population. The fact that this diving group exposed themselves to much greater decompression stress than the more conventional professional diving groups suggests that these results should not be extrapolated to other diving populations. The results are supportive of the anecdotal beliefs that exist regarding this highly selective diving group, i.e., that a syndrome of reduced intellectual capacity (dementia or "punch drunkenness") may be present.

Adult↗

PubMed1994

Technical study of some major parameters influencing the performance of an aerosol delivery equipment suitable for calves.

Aerosol delivery equipment, suitable for the treatment of bovine respiratory dysfunctions and including 2 parallelly positioned jet nebulizers, was studied in depth in order to determine the optimal working conditions in the field. Indeed, some factors might reasonably alter the performance of this equipment. Among these factors, the influences of the parallel position of jet nebulizers (in order to accommodate the breathing requirements of the cattle and achieve a rapid treatment), of the long feed pipe delivering compressed air (in order to keep the animal away from the compressor unit), and finally of the ambient temperature were studied, this equipment being essentially used during the winter season. This equipment could accommodate the breathing needs of cattle weighing up to 225 kg if a pressure of 600 kPa was developed upstream to the nebulizers. The rate of atomization was significantly reduced when working at ambient air temperatures (272.25 K < T < 274.65 K) close to those encountered in winter. This was especially true when pressure upstream to the nebulizers did not exceed 500 kPa. The immersion of the feed pipe for compressed air in hot water led to an increase in the rate of atomization without raising evaporative water losses, and reduced the drop in temperature in the nebulizer solution. Finally, the rate of atomization significantly increased when the face mask including the nebulizers was maintained so that the nebulizers were in a vertical position or at an angle not less than 60 degrees with respect to the ground.

Administration, Inhalation↗

PubMed1994

Effects of nitrous oxide on the brain catecholamines in rats.

The effects of nitrous oxide on the brain norepinephrine (NE), dopamine (DA), and metabolites of DA were studied in rats. Forty-eight male Wistar rats were divided into 2 groups and exposed to gas in Plexiglas tubes: compressed air or 75% nitrous oxide in oxygen. Each group was further divided into 4 subgroups, consisting of 6 rats each, according to the duration of exposure: 0.5, 1, 2 and 4 hours. The control group of 6 rats were kept in rat cages and exposed to room air. The animals were sacrificed with microwave irradiation after the exposure. Brain contents of NE, DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured with high-pressure liquid chromatography. Exposure to compressed air in the tube did not affect NE, DA, DOPAC nor HVA. Nitrous oxide did not change the brain content of NE or DA. Metabolites of DA increased with nitrous oxide: DOPAC and HVA increased after 0.5 h exposure (from 105 +/- 8 to 152 +/- 38 ng/g brain, from 120 +/- 9 to 175 +/- 27 ng/g brain, respectively, P < 0.05). Increased levels of DA metabolites indicate that nitrous oxide increases dopamine turnover. However, these increases attenuated during exposure. The attenuation indicates that the decline of DA turnover may correlate with a development of acute tolerance to nitrous oxide action(s) in the central nervous system.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2005

Flock workers' exposures and respiratory symptoms in five plants.

BACKGROUND: Sentinel cases of lymphocytic bronchiolitis in flock production and coating operations triggered a five-plant study of airborne respirable dust and fiber exposures and health symptoms. METHODS: Job histories from 219 current workers were linked to a job-exposure matrix derived from personal exposure measurements of respirable dust and fibers. Univariate group comparisons and multivariate modeling tested for relations between indices of cumulative and current exposure, and respiratory and systemic symptom outcomes. RESULTS: Respiratory symptoms and repeated flu-like illnesses were associated with use of compressed air to clear equipment (blow-downs) and with respirable dust exposure (current and cumulative) after controlling for smoking. Blow-downs had an equal or greater effect than smoking status on most symptoms. CONCLUSIONS: Eliminating compressed air cleaning, engineering control of dust exposure, and respirators are needed to limit exposures to particulates. Longitudinal follow up may provide guidance for a dust or fiber level without adverse respiratory health effects.

Adult↗

PubMed2004

Expected and unexpected head yaw movements result in different modifications of gait and whole body coordination strategies.

During locomotion we routinely make voluntary head movements, similar to those made during steering tasks, in order to scan our environment and obtain information about objects in the environment and our proximity to these objects. Given the importance that head segment orientation during locomotion has received in the recent literature, two studies were designed to investigate responses following a voluntarily generated and an unexpected, externally applied head turn. During a voluntary head turn, an efferent copy of the head movement could cancel the sensory effects of the head turn, effectively isolating the movement response to that segment. Alternatively, if the steering synergy is a part of our motor repertoire, as has been suggested, movement of the head could automatically release a steering "synergy" of segmental control and coordination. A unique head mounted air-jet apparatus, designed and developed at the University of Waterloo, was used for both studies to ensure that auditory stimuli and the physical presence of the apparatus on the head were similar for participants of the two experiments. During certain points in the gait cycle, this device was triggered and a short burst of compressed air (350 ms) was released to cue participants to make a voluntary head turn (Experiment 1). The same device was triggered in Experiment 2; however, in this experiment compressed air was released for a longer duration (1,500 ms) which resulted in an unexpected and quick turn of the participants' head to either the left or right. In these experiments, vision was also manipulated in certain trials with liquid crystal display glasses that occluded vision for the duration of the head turn. Data from the first experiment indicates that a subset of the steering synergy previously observed is released following the voluntary head movement; however, the travel trajectory path is preserved, suggesting that sensory input resulting from the head movement is partially nullified by the central nervous system. Overall safety is ensured by maintaining the same travel path. In the second experiment, an unexpected perturbation was applied to the head during locomotion to determine how the absence of an efferent copy of the movement pattern influences the level of control over body segments during locomotion. Whole body responses similar to those observed during steering tasks were observed following application of this unexpected head perturbation. It is proposed that the CNS interprets an unexpected yaw movement of the head as a change in the frame of reference, and global modifications of the walking trajectory, similar to that observed during steering tasks, are made in the perceived new direction of travel. Collectively this work extends our understanding of how the CNS establishes a head based orientation frame for locomotion. The CNS interprets and integrates anticipated and unexpected changes in sensory information from the head segment and subsequently modifies locomotion patterns according to the perceived whole body orientation in space. The sequence of control following these head movements appears to be part of a movement repertoire that is not immutable; maintaining whole body stability during locomotion is paramount.

Acoustic Stimulation↗

PubMed1992

Oxygen may improve dyspnea and endurance in patients with chronic obstructive pulmonary disease and only mild hypoxemia.

Oxygen (O2) has been reported to improve exercise tolerance in some patients with chronic obstructive pulmonary disease (COPD) despite only mild resting hypoxemia (PaO2 greater than 60 mm Hg). To confirm these prior studies and evaluate potential mechanisms of benefit, we measured dyspnea scores by numeric rating scale during cycle ergometry endurance testing and correlated the severity of dyspnea with right ventricular systolic pressure (RVSP) measured by Doppler echocardiography during a separate supine incremental exercise test. Both sets of exercise were performed according to a randomized double-blind crossover protocol in which patients breathed compressed air or 40% O2. We studied 12 patients with severe COPD (FEV1 0.89 +/- 0.09 L [mean +/- SEM], FEV1/FVC 37 +/- 2%, DLCO 9.8 +/- 1.5 ml/min/mm Hg[47% of predicted], PaO2 71 +/- 2.6 mm Hg). With endurance testing on compressed air, PaO2 did not change significantly in the group as whole (postexercise PaO2 63 +/- 5.1 mm Hg, p = NS), but did fall to less than 55 mm Hg in four patients from this group. Duration of exercise increased on 40% O2 from 10.3 +/- 1.6 to 14.2 +/- 1.5 min (p = 0.005), and the rise in dyspnea scores was delayed. Oxygen delayed the rise in RVSP with incremental exercise in all patients and lowered the mean RVSP at maximum exercise from 71 +/- 8 to 64 +/- 7 mm Hg (p less than 0.03). Improvement in duration of exercise correlated with decrease in dyspnea (r2 = 0.66, p = 0.001) but not with decreases in heart rate, minute ventilation, or RVSP.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-Blind Method↗

PubMed1982

Estimation of gas-phase diffusivities in hyperbaric environments.

Diffusion of a particular gas in a mixture of three or more gases depends on diffusion characteristics and concentrations of the other gases and also on environmental pressure. 1) Estimates of gas-phase diffusivities in hyperbaric environments can be calculated from binary coefficients by the Wilke equation. Sample calculations show that addition of carbon dioxide and water to inspired gas has very little effect on diffusivity of oxygen but that neglect of lesser components of a mixture, such as the nitrogen in "trimix" or the helium in crude neon, would lead to errors of 10% to 20%. 2) It is not possible to match a compressed air environment with a helium-oxygen or a helium-oxygen-nitrogen environment for both density and diffusivity. Diffusivities of oxygen and carbon dioxide in a helium mixture can be less than half the values in compressed air having the same density. In a plot of diffusivity vs. gas density, most useful mixtures are included in a hyperbolic-shaped band; diffusivity falls to below 25% of the room air value when density is 5 times normal.

Atmospheric Pressure↗

PubMed1999

Placement of a spring filter during interventional treatment of deep venous thrombosis to reduce the risk of pulmonary embolism.

PURPOSE: To assess the efficacy of the Spring filter during interventional treatment of deep venous thrombosis in vivo. MATERIAL AND METHODS: A model of inferior vena cava thrombosis was used. Part I: The thrombus was treated by the pulse-spray technique (PT) (urokinase 250,000 IU; n=7) or a rotatory basket catheter, Thrombolizer (MT) (activated with compressed air at 7 atm; n=5). Part II: Following placement of a Spring filter, the animal underwent PT (n=5) or MT (n=5). Based on the results of part I, the treatment protocol was modified (PT, urokinase 500,000 IU; MT, compressed air at 8 atm). Embolus volumes trapped by the filter and found in the lungs were calculated and the filtering efficacy quantified. RESULTS: Part I: Pulmonary emboli (1 to 4 mm in diameter) were observed in 3 animals in the PT group and 1 animal in the MT group, respectively. Median reduction in thrombus volume was 21% and 4% by PT and MT, respectively. Part II: In the PT group, 58% and 100% of the total embolus load was trapped in 2 animals, while the filter failed to trap emboli (1 to 1.5 mm in diameter) in 1 animal. In the remaining 2 animals, no embolus was found trapped by the filter or in the lungs. In the MT group, 55 97% (median 83%) of the embolus load was trapped. Emboli found in the lungs did not exceed 4 mm in diameter. CONCLUSION: Preceding interventional treatment of venous thrombosis with placement of the Spring filter reduced the embolic burden on the lungs.

Angiography↗

PubMed2000

Personal air sampling and biological monitoring of occupational exposure to the soil fumigant cis-1,3-dichloropropene.

OBJECTIVES: To assess exposure of commercial application workers to the nematocide cis-1,3-dichloropropene (cis-DCP). METHODS: The study was conducted during the annual application season, August to 15 November, in the starch potato growing region in The Netherlands. 14 Application workers collected end of shift urine samples on each fumigation day (n=119). The mercapturic acid metabolite N-acetyl-S-(cis-3-chloro-2-propenyl)-L-cysteine (cis-DCP-MA) in urine was used for biological monitoring of the cis-DCP uptake. Inhalatory exposure was assessed by personal air sampling during a representative sample (n=37) of the fumigation days. Extensive information was collected on factors of possible relevance to the exposure and the application workers were observed for compliance with the statutory directions for use. The inhalatory exposure during all fumigation days was estimated from the relation between the personal air sampling data and the biological monitoring data. Exposure levels were correlated with the general work practice. The fumigation equipment and procedures were in accordance with the statutory directions of use, with the exception of the antidrip systems. Two antidrip systems were used: antidrip nozzles or a compressed air system. RESULTS: The geometric mean exposure of the application workers was 2.7 mg/m(3) (8 hour time weighted average); range 0.1-9.5 mg/m(3). On 25 days (21%) the exposure exceeded the Dutch occupational exposure limit (OEL) of 5 mg/m(3). This could mainly be explained by prolonged working days of more than 8 hours. The general work practice of the application workers was rated by the observers as good or poor. No difference in exposure to cis-DCP was found in the use of none, one, or two antidrip systems. Malfunctioning of the antidrip systems and lack of experience with the compressed air system were identified as possible causes for the lack of effectiveness of these antidrip systems. The use of personal protection was not always in accordance with the statutory directions of use. Dermal exposure to liquid cis-DCP was found four times during repair and maintenance, but the biological monitoring data did not suggest a significant increase in cis-DCP uptake. CONCLUSIONS: The application of cis-DCP in the potato growing industry can be performed at exposure concentrations below the Dutch OEL of 5 mg/m(3) if the working days are limited to 8 hours. An injector equipped with either kind of antidrip system which is in good working order, as well as the consistent use of personal protection in accordance with the statutory directions of use, may ensure exposure concentrations below the Dutch OEL.

Adult↗

PubMed2000

Secondary hypoxemia exacerbates the reduction of visual discrimination accuracy and neuronal cell density in the dorsal lateral geniculate nucleus resulting from fluid percussion injury.

The purpose of this study was to determine the impact of secondary hypoxemia on visual discrimination accuracy after parasagittal fluid percussion injury (FPI). Rats lived singly in test cages, where they were trained to repeatedly execute a flicker-frequency visual discrimination for food. After learning was complete, all rats were surgically prepared and then retested over the following 4-5 days to ensure recovery to presurgery levels of performance. Rats were then assigned to one of three groups [FPI + Hypoxia (IH), FPI + Normoxia (IN), or Sham Injury + Hypoxia (SH)] and were anesthetized with halothane delivered by compressed air. Immediately after injury or sham injury, rats in groups IH and SH were switched to a 13% O2 source to continue halothane anesthesia for 30 min before being returned to their test cages. Anesthesia for rats in group IN was maintained using compressed air for 30 min after injury. FPI significantly reduced visual discrimination accuracy and food intake, and increased incorrect choices. Thirty minutes of immediate posttraumatic hypoxemia significantly (1) exacerbated the FPI-induced reductions of visual discrimination accuracy and food intake, (2) further increased numbers of incorrect choices, and (3) delayed the progressive recovery of visual discrimination accuracy. Thionine stains of midbrain coronal sections revealed that, in addition to the loss of neurons seen in several thalamic nuclei following FPI, cell loss in the ipsilateral dorsal lateral geniculate nucleus (dLG) was significantly greater after FPI and hypoxemia than after FPI alone. In contrast, neuropathological changes were not evident following hypoxemia alone. These results show that, although hypoxemia alone was without effect, posttraumatic hypoxemia exacerbates FPI-induced reductions in visual discrimination accuracy and secondary hypoxemia interferes with control of the rat's choices by flicker frequency, perhaps in part as a result of neuronal loss and fiber degeneration in the dLG. These results additionally confirm the utility of this visual discrimination procedure as a sensitive, noninvasive means of assessing behavioral function after experimental traumatic brain injury.

Animals↗

PubMed2004

[Changes of angiotensin II and its receptor during the development of chronic intermittent hypoxia-induced hypertension in rats].

OBJECTIVE: To observe the changes of angiotensin II (ATII) and ATII type-1 receptor (AT1R) during the development of chronic intermittent hypoxia (CIHO)-induced hypertension in rats, and the effect in the mechanism of CIHO-induced hypertension. METHODS: Seventy-two male Wistar rats were divided into three groups:intermittent hypoxia group (IH), sham control group (SC) and control group (UC). By using supply of nitrogen (30 s each cycle) followed by compressed air (30 s each cycle) into the exposure chambers (4% - 6% nadir ambient oxygen with return to 21%), IH rats were subjected to intermittent hypoxia every 60 s for 8 h/d during the diurnal sleep period. SC rats were similarly treated but received compressed air instead of nitrogen. UC rats were not treated. Mean arterial pressure (MAP), the levels of ATII and renin activity (RA) in plasma as well as the expression of AT1R mRNA in tissue were measured on day 7, 21 and 42 after experiment. RESULTS: MAP was significantly elevated in IH rats [(102.2 +/- 6.2) mm Hg, 1 mm Hg = 0.133 kPa] compared with initial MAP [(94.1 +/- 4.3) mm Hg, P < 0.01] and compared with that in SC [(95.7 +/- 3.6) mm Hg], UC [(97.2 +/- 3.6) mm Hg, all P < 0.05] on day 42. The levels of ATII and RA in plasma in IH rats increased gradually over time, and RA started to increase significantly on day 7 [(3.86 +/- 1.25) ng.ml(-1).h(-1)] compared with that in SC [(2.73 +/- 0.98) ng.ml(-1).h(-1)], UC [(2.55 +/- 0.87) ng.ml(-1).h(-1), all P < 0.05], and ATII started to increase significantly on day 21 [(214 +/- 41) ng/L] compared with that in SC [(124 +/- 21) ng/L], UC [(121 +/- 18) ng/L, all P < 0.01]. The RA and ATII levels in plasma showed positive correlation with MAP (r = 0.529, P = 0.008; r = 0.475, P = 0.019 respectively). The expression of AT1R mRNA in heart, kidney and aorta in IH rats showed no differences compared with that in SC and UC group (all P > 0.05). All indices were not different between SC and UC rats at any time point (all P > 0.05). CONCLUSION: CIHO can cause the levels of circulating RA and ATII to increase, but has no effects on AT1R mRNA expression in tissue, which suggests that activated renin-angiotensin system may contribute to the pathogenesis of CIHO-induced hypertension.

Angiotensin II↗

PubMed1995

Efficacy of XeCl-308 excimer laser in fusing hydroxyapatite to seal the root apex.

Sealing the root apex during apical surgery is important for a successful outcome. The effect of XeCl-308 nm excimer laser irradiation on the fusion and seal of hydroxyapatite to the root apex was tested in extracted human teeth. Twenty-four roots of intact single-rooted premolars were instrumented to size 30 K-file at the apex leaving a patent apical foramen. The apex of each tooth was covered with a freshly prepared paste of hydroxyapatite powder mixed with saline. The samples were then divided into two groups. In 12 teeth, the apical area was irridiated with XeCl-308 nm excimer laser at a fluence of 0.7 J/cm2 for 5 s with pulse repetition rate of 25 Hz and a spot size of 0.13 cm2 immediately after the hydroxyapatite application. In the other 12 teeth, no laser treatment was performed after the hydroxyapatite application. The roots were mounted on a model for the detection of radicular leakage of hydrogen peroxide. The hydrogen peroxide leakage of each sample was measured and the difference between the test groups compared. The ability of the hydroxyapatite plug to prevent hydrogen peroxide leakage at the apex was also tested by applying compressed air from the triple syringe on the coronal access preparation for 2 min. Apical leakage was found in four teeth in the lased group and in eight teeth in the non-plased group. However, the difference between the groups was not statistically significant. Compressed air applied to the coronal access caused hydrogen peroxide leakage in all the teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Chi-Square Distribution↗

PubMed1992

Dentin surface treatment and shear bond strength of a light-cured glass ionomer.

This study evaluated the effect of dentin surface treatment with polyacrylic acid on the shear bond strength of Fuji Lining LC light-cured glass ionomer lining cement (GIC). A total of 40 human, noncarious extracted permanent molars stored in distilled water were used. A flat buccal dentin surface was ground wet on 600-grit silicon carbide paper. The teeth were then randomly distributed into four groups of 10 teeth each: Group 1: dentin rinsed with distilled water, dried with oil-free compressed air, placement of cylindrical GIC samples and sheared at 15 minutes post-curing. Group 2: same as group 1, but sheared 7 days post-curing. Group 3: dentin treated with GC Conditioner for 10 seconds, rinsed with distilled water, dried with oil-free compressed air, placement of the GIC and sheared 15 minutes post-curing. Group 4: same as group 3, but sheared 7 days post-curing. The GIC was mixed in a 1:1 powder-liquid ratio. The samples were stored in distilled water until sheared with an Instron. The results revealed that dentin surface treatment with the polyacrylic acid significantly increased the shear bond strength to dentin when tested at 7 days post-curing.

Acid Etching, Dental↗

PubMed1994

An opponent-process interpretation of the anxiolytic effects of single inhalations of large concentrations of carbon dioxide.

Ten anxiety-disorder outpatients and 10 controls were monitored for heart rate and self reports of anxiety approximately 1 min before and 1 min after a single full-capacity inhalation of a gas consisting of either 65% CO2 + 35% O2 or compressed air. Under the CO2 + O2 condition, patients and controls showed almost identical reductions in anxiety and parallel reductions in heart rate. From an opponent-process point of view, these reductions were explained by the acute negative affective state being followed by the hedonically pleasant state that follows dissipation of CO2. Under the compressed air condition, only patients showed reductions of anxiety presumably because in them breathing an unknown gas via an inhalation mask, raised anxiety, followed by an opponent-process to anxiety after withdrawal of the mask.

Administration, Inhalation↗

PubMed2001

Clinical evaluation of Prime & Bond 2.1 for treating cervical dentin hypersensitivity.

PURPOSE: To evaluate the effectiveness of a "one-bottle" dentin adhesive for reducing or eliminating hypersensitivity in exposed cervical dentin. MATERIALS AND METHODS: Eight patients with hypersensitive teeth were enrolled in this clinical trial. The hypersensitive teeth included a total of 22 premolars and anterior teeth with exposed cervical dentin that was sensitive to cold or other stimuli. A single layer of Prime & Bond 2.1, an acetone-based "one-bottle" adhesive, was applied to the cervical dentin and was light-cured. Sensitivity to compressed air and cold stimuli was determined immediately before and after treatment, and at periods ranging to 24 wks after treatment. Patient responses to the stimuli were timed, and were also evaluated by the use of a visual analogue scale. RESULTS: Application of a single coat of Prime & Bond 2.1 significantly reduced cervical dentin hypersensitivity to both compressed air and cold stimuli immediately after treatment. The reduction in hypersensitivity remained significant at 24 wks after treatment.

Acetone↗

PubMed1985

The effect of maternal hyperoxia on breathing movements, body movements and rest-activity cycles of low-risk human fetuses.

The effects of maternal hyperoxia on fetal breathing and body movements, and on fetal activity state as reflected in the fetal heart rate pattern, were studied in 20 healthy gravida. Fetal breathing and trunk movements were observed by means of real-time ultrasound scanning, and the fetal heart rate was recorded continuously before, during and after 30 min of maternal oxygen inhalation by mask. Maternal transcutaneous oxygen tension (TcPO2) was measured in 9 subjects. The protocol was also carried out in ten of the gravidas with substitution of compressed air for oxygen. Maternal TcPO2 nearly doubled during oxygen breathing in the subjects in whom this was measured. There were no significant changes in the incidence of fetal breathing or trunk movements, or in the distribution of heart rate patterns, during maternal oxygen breathing. Also, no differences were observed in these variables between the oxygen and compressed-air experiments. We conclude that the normal level of fetal oxygenation does not limit fetal activity in uncomplicated pregnancies.

Female↗

PubMed1977

The significance of bone islands, cystic areas and sclerotic areas in dysbaric osteonecrosis.

Dysbaric osteonecrosis is a major hazard to compressed air workers and an increasing hazard to divers. Symptomless osteonecrosis is best recognised by radiology and it is of fundamental importance that interpretation be reliable and accurate. There is much controversy concerning the significance of bone islands and cystic areas; several authors report bone islands and cystic areas to be up to eight times more frequent in compressed air workers and divers and believe that these represent positive evidence of osteonecrosis. Skeletal radiographs of 100 Royal Navy divers, all of whom were at risk to osteonecrosis were matched for age and rank with 100 controls, none of whom had been exposed to high pressures. The radiographs were interpreted by three radiologists working independently without knowing whether the radiographs were in the diving or control group. It is concluded that bone islands, cystic areas and sclerotic areas, as described in this text, occur with equal frequency in divers as in the normal population and do not represent positive evidence of osteonecrosis. The report includes autopsy studies of the proximal femur and proximal humerus in six diving fatalities. Five bone islands in the proximal humerus and one in the femoral neck were studied in bones removed from five divers. In the sixth case a cyst was seen to develop radiologically in the femoral neck and then reduce in size over 3 years and 10 months. Slab radiographs and histological section in all cases show no evidence of osteonecrosis.

Adult↗

PubMed2003

Submaximal exercise with self-contained breathing apparatus: the effects of hyperoxia and inspired gas density.

BACKGROUND: The self-contained breathing apparatus (SCBA) used by firefighters, and other working in dangerous environments, adds an external resistance to expiration, which increases expiratory work during heavy exercise. HYPOTHESIS: Compressed air is typically used with the SCBA and we hypothesized that changing the inspired oxygen concentration and/or gas density with helium would reduce the external expiratory resistance. METHODS: On separate days, 15 men completed four 30-min bouts of treadmill exercise dressed in protective clothing and breathing the test gases through the SCBA. Four different gas mixtures were assigned in random order: [compressed air (NOX: 21% O2, 79% N2), hyperoxia (HOX: 40% O2, 60% N2), normoxic-helium (HE-OX: 21% O2, 79% He), and helium-hyperoxia (HE-HOX: 40% O2, 60% He)]. RESULTS: Compared with NOX, the two helium mixtures (but not HOX), decreased the external breathing resistance and all three gas mixtures decreased the peak expired mask pressure and the ventilatory mass moved. Both hyperoxic mixtures decreased blood lactate and the rating of perceived exertion was decreased at 30 min with HE-HOX. CONCLUSIONS: These results demonstrate that the helium-based gas mixtures, and to a lesser extent HOX, reduce the expiratory work associated with the SCBA during strenuous exercise.

Administration, Inhalation↗