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[A comparison of two delivery methods on the bronchodilator effects of beta 2-stimulant].

The airway response to a bronchodilator, salbutamol delivered by a new handy ultrasonic nebulizer and the compressed air nebulizer was studied in a blind manner. Patients by the ultrasonic nebulizer had better percent increase in FVC and FEV1 significantly and in other parameters showed a tendency to being better than those by the compressed air nebulizer. These results suggest that this ultrasonic nebulizer may be more useful than the compressed air nebulizer as inhalation therapy for bronchial asthma. This ultrasonic nebulizer has several advantages over the compressed air nebulizer. This nebulizer is compact size, light weight and has dry batteries as power source, making it more convenient for travel and use at workplace.

Administration, Inhalation↗

[Great depth pneumatic caisson and its load work involved with the efficiency of respiratory protection].

Pneumatic caisson work in Japan has been in operation since 1924. Afterward, this technique of compressed air work has been utilized in the constructions like as foundation works, the basements, and shafts of the bottom tunnel or shields for subway and so forth. While, it means for people to be exposed to hyperbaric environment that they use compressed air work, this technique has risks to be suffered from not only decompression sickness (DCS) but toxicity of poisonous gas or oxygen deficiency. However, this technique is necessary for urban civil engineering and recent compressed air works over than 1.0 kg/cm2 has been increased in 1.5 times more than in 1970's and the higher compressed air work more than 4.0 kg/cm2 will be actually planned in near future. So unmanned caisson work is considered as a better technique for such high pressure work, even though people must enter into hyperbaric working fields for maintenance or repair of unmanned operated machinery and materials. This research is to establish the safety work under hyperbaric environment within 7 kg/cm2. It is necessary for us to establish the system not only to keep safety but to maintain working efficiency. According to obtain the purpose, the effect of respiratory protection has been investigated and work load under hyperbaric caisson work has also been studied.

Adult↗

Medical support for the North East Line Mass Rapid Transit project by the Republic of Singapore Navy's Naval Medicine Hyperbaric Centre.

Naval Medicine Hyperbaric Centre (NMHC) was approached by the Land Transport Authority (LTA) to provide medical support for the North Eastern Line MRT Project. The medical support provided by NMHC focused on providing training, audits and ensuring that safety and health infrastructure were in place even before the commencement of compressed air tunnelling. The extensive use of the EPBM (Earth Pressure Balance Machine) tunnelling machines for the first time in Singapore necessitated a reassessment of the medical support system and paradigm that was based primarily on the older form of tunnelling. The survey results showed that human exposure to compressed air works with the use of EPBM was minimal and no decompression illness was reported. However, there was still a total of 28 cases of barotrauma that were reported which were mainly from the tunnels dug using the open face compressed air tunnelling method. As such, medical providers should still exercise careful planning for the medical support of compressed air works.

Atmospheric Pressure↗

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

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

Adult↗

[Accidental decrease in the air flow during air/oxygen sevoflurane anesthesia].

We describe our experience of an accidental decrease in the air flow during air/oxygen sevoflurane anesthesia. According to the malfunction of an air compressor system, dehydration of the compressed air was inadequate, and the wet air was delivered to the anesthesia machine. The moisture was formed at a flow control valve to cause a gradual decrease in the air flow. The low-pressure alarm did not work at that time, because the pressure of the air supply was normal. There are two types of medical air, one is produced from the ambient air by air compressor system and another is the synthetic air which is a mixture of oxygen and nitrogen. Although the synthetic air is always dry and clean, the former contains dust, bacteria, and moisture. There is a possibility that all of these particles cannot be excluded before use. Accordingly, we must check the air compressor system routinely when a source of the compressed air is used.

Air↗

Cardiovascular changes during acute episodic repetitive hypoxic and hypercapnic breathing in rats.

It has been shown that chronic repetitive ambient hypoxia, simulating pulmonary gas disturbances observed in apnoea, leads to systemic hypertension in rats. However, the relative roles of hypoxia (HO), hypercapnia (HC), gas stress and vigilance on the cardiovascular changes have not yet been demonstrated. The aim of this study was to investigate the acute haemodynamic changes observed during the repetitive inhalation of various gas mixtures in rats for HO alone and HO+HC, and to analyse the effects of vigilance and of the stress of gas administration. We studied 6 unanaesthetized Wistar rats chronically instrumented with an aortic catheter. Nitrogen, nitrogen+CO2 mixtures and compressed air were randomly administered in a Plexiglass chamber for 10 s and then flushed by compressed air for 20 s. Two cycles were repeated every min for 10 to 12 min. The inhaled gas fractions (FI,O2,FI,CO2) were monitored by O2 and CO2 analysers. Blood pressure (BP) was measured by a P23XL transducer. The blood gases were analysed by a 1306 IL meter. In control experiments, with compressed air alone, there were no significant acute changes in heart rate (HR) and BP. During HO there were no changes in HR or BP at FI,O2 values from 0.05-0.14, whilst at FI,O2 values from 0-0.05 systolic blood pressure (SBP) rose significantly (+25.3 +/- 25.7 (SD) mmHg) and HR decreased (-93.8 +/- 124.1 bpm). During HOHC, SBP rose (+35.1 +/- 26.4 mmHg) and HR decreased (-139.3 +/- 75.7 bpm), significantly more than in HO alone. SBP was linearly correlated with Pa,O2 during HO (r = 0.53) and also during HOHC (r = 0.44) and was not directly related to Pa,CO2 which has, nevertheless, an additive effect to HO. SBP rose with each challenge significantly more when the rats were awake than when asleep (behavioural sleep). We conclude that in this acute repetitive inhalation model, the rise in SBP is not related to gas stress or to Pa,CO2 but to a decrease in Pa,O2 and is enhanced by wakefulness.

Acute Disease↗

Effects of 100% oxygen on lung vascular function in awake sheep.

The purpose of this study was to define the time course of pulmonary toxicity during continuous breathing of 100% oxygen in adult sheep. Sheep were prepared for chronic measurement of vascular pressures, cardiac output, gas exchange, and for collection of lung lymph. Tracheostomies allowed accurate delivery of either 100% oxygen, compressed air, or hypoxic gas. Six sheep breathed 100% oxygen for 72-96 h, and four sheep breathed compressed air for 96 h. In addition to hypoxic challenges [fractional concentration of inspired O2 (FIo2) = 0.12], some sheep received prostaglandin H2 (PGH2)-analogue infusions to further assess pulmonary vascular reactivity. Lung lymph and blood chemotactic activity were measured by granulocyte migration in modified Boyden chambers. Postmortem lung water content and light microscopy were used to measure pulmonary edema. All sheep breathing 100% oxygen died between 72 (n = 2) and 96 h (n = 4). Sheep breathing oxygen demonstrated lung toxicity by measurements of 1) a fourfold increase in flow of protein-rich lung lymph, 2) increased alveolar-arterial difference in Po2 (greater than 20 Torr on FIo2 = 0.21) and hypercapnic acidemia, and 3) a mean extravascular lung water/dry lung weight of 5.7 (controls = 3.3), and histological evidence of interstitial and alveolar edema. Chemotactic activity in lung lymph at base line increased eightfold within 72-96 h of oxygen breathing. In sheep breathing oxygen, the hypoxic pressor response decreased by 50% at 48 h, and by 72-96 h there was a total absence of hypoxic vasoconstriction. There was no increase in lung lymph prostacyclin metabolite, and sodium meclofenamate did not restore the pressor response. In sheep breathing compressed air none of these changes in pulmonary vascular reactivity, lymph flow, or chemotactic activity occurred. We conclude that prolonged breathing of pure oxygen causes pulmonary edema by increasing lung vascular permeability and that respiratory failure results from both edema and loss of pulmonary vascular reactivity.

Animals↗

Acquired sensitivity to relevant physiological activity in patients with chronic health problems.

The hypothesis that biased symptom perception toward excessive symptoms is common when relatively normal chronic patients enter symptom-relating situations, irrespective of emotional variables, was tested in 19 women with severe asthma, 18 with somatization-like characteristics, and 18 controls. Each underwent three experimental conditions: mental stress, resting, and physical exercise. Each condition included three breathing conditions: breathing normally, normal compressed air, and 5.5% CO2-enriched compressed air. Results yielded no group differences in physiological measures, e.g. elevated CO2 in exhaled air (end-tidal partial pressure of CO2, PetCO2), or lung function. Asthma patients experienced more breathlessness, and somatization-like participants more breathlessness, miscellaneous symptoms, and subjective stress than controls. Although these differences suggested acquired biased symptom perception, as it turned out, breathlessness in asthmatics was more influenced by PetCO2 and less by subjective stress compared to controls. Likewise, breathlessness in somatization-like participants was similarly influenced by PetCO2 and subjective stress compared to controls, and miscellaneous symptoms were even more influenced by PetCO2 and less by subjective stress compared to controls. It was concluded that acquired sensitivity to physiological activity associated with habitual symptoms may account for excessive symptoms in patients with chronic health problems.

Asthma↗

Effects of methylprednisolone on lung oxygen toxicity in awake sheep.

The purpose of this study was to measure the effects of high doses of corticosteroids on the response to breathing 100% O2 in sheep. Sheep were prepared for chronic measurement of vascular pressures, cardiac output, gas exchange, and for collection of lung lymph. Tracheostomies were made for accurate delivery of gas mixtures. Eight sheep received methylprednisolone 30 mg/kg body wt every 6 h for eight doses, four for the first 48 h, and four for the final 24-48 h of 100% O2 breathing. Eight control sheep breathed 100% O2 without methylprednisolone, four sheep breathed compressed air without methylprednisolone, and two breathed compressed air and received methylprednisolone. Sheep had daily measurements of hypoxic vasoconstriction (fractional concentration of O2 in inspired gas = 0.12), gas exchange, lymph flow, and lymph and plasma protein concentration. Polymorphonuclear leukocyte (granulocyte) function in experimental and control sheep was assessed ex vivo by tests of chemotaxis, aggregation, and superoxide production. The number of granulocytes in peripheral lung was measured in biopsy tissue taken at the time of original surgery and postmortem. Methylprednisolone did not affect the time course nor magnitude of gas exchange abnormality, lymph flow and composition, loss of hypoxic vasoconstriction, lung granulocyte accumulation, nor postmortem lung water caused by 100% O2 breathing. Sheep receiving methylprednisolone had a shorter survival by several h, independent of the timing of the drug. Granulocytes from methylprednisolone-treated sheep showed normal function ex vivo by all three assays. We conclude that high doses of methylprednisolone unfavorably affect the rate and progression of lung injury in sheep breathing 100% O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Principles of nebulizer-delivered drug therapy for asthma.

The principles of aerosol drug delivery by compressed-air nebulization are described, and the therapeutic agents administered by this process for management of asthma are reviewed. For therapy of acute and chronic asthma, aerosol inhalation has become the primary method of drug administration. Aerosolized particles with aerodynamic diameters of 1 to 5 microns are most efficiently deposited in the lower respiratory tract. Delivery systems for therapeutic aerosols include compressed-air nebulizers and metered-dose inhalers. Compressed-air nebulizers are less efficient than metered-dose inhalers; therefore, the drug dosages recommended for nebulizer solutions are 3 to 10 times higher than those delivered by a metered-dose inhaler. Because many asthma patients are treated with nebulization drug therapy at home, both patients and pharmacists must understand how to use the equipment correctly. Drugs used in aerosol therapy of acute and chronic asthma include the beta 2-receptor agonists epinephrine, isoproterenol, isoetharine, metaproterenol, terbutaline, and albuterol; cromolyn sodium; and the anticholinergic agents atropine and ipratropium bromide. Terbutaline and albuterol have longer durations of action and greater beta 2-receptor selectivity than metaproterenol, isoetharine, and isoproterenol. Cromolyn is a first-line prophylactic agent for asthma management. Atropine is indicated for maintenance therapy of chronic asthma and in combination with the beta 2-receptor agonists for therapy of acute asthma; ipratropium bromide is a new agent similar to atropine but with substantially fewer adverse effects. Acute and chronic asthma may be managed by aerosol administration of beta 2-receptor agonists, cromolyn, and atropine, alone or in combination. Inhalation is the preferred route of drug delivery because small doses of medication provide maximal therapeutic benefit with minimal adverse effects.

Aerosols↗

Latency in onset of decompression sickness on direct ascent from air saturation.

Twenty-four human subjects were exposed to compressed air at simulated depths ranging from 45 ft seawater gauge (fsw) (2.36 ATA) to 75 fsw (3.27 ATA) for periods of time sufficient to allow saturation of most tissues with inert gas. From each of four depths (45, 55, 65 and 75 fsw), subjects ascended directly to 1 ATA, where they remained for 30, 17, 13, and 10 min, respectively. During this time the onset of Doppler detected venous gas emboli (VGE), pruritus, and any other symptomatology was monitored and recorded. In the ascending excursion from 45 fsw (n = 18), the mean appearance times of pruritus and VGE were 19.3 +/- 7.5 (mean +/- SD) and 21.9 +/- 7.4 min, respectively, with one case of pain-only decompression sickness (DCS). The excursion from 55 fsw (n = 17) shortened these times to 9.2 +/- 3.3 and 14.4 +/- 3.2 min, respectively, with two cases of DCS, one each of pain-only and serious types. In the excursion from 65 fsw (n = 23), mean pruritus and VGE appearance times were 6.3 +/- 1.4 and 10.8 +/- 1.9 min, respectively, with no cases of DCS. The excursion from 75 fsw (n = 6) resulted in appearance times of 4.8 +/- 0.8 and 8.2 +/- 1.2, respectively, with one case of pain-only DCS. Sufficient cases of DCS did not occur in any of the excursions to allow determination of mean appearance times. The relationship between pressure reduction and appearance times of pruritus and VGE, and the threshold time of DCS, can be described mathematically. We conclude that latency in the development of DCS on direct ascent from air saturation exists and is of sufficient magnitude to permit practical application in emergency decompressions or unpressurized transfers between compressed air or N2-O2 environments.

Adult↗

Enhanced lung C-fiber responsiveness in sensitized adult guinea pigs exposed to chronic tobacco smoke.

Tobacco smoke (TS) exposure induces bronchoconstriction and increases airway secretions and plasma extravasation in certain sensitive individuals, particularly those with asthma. C-fiber activation also induces these effects. Although the mechanism by which chronic TS exposure induces airway dysfunction is not well understood, TS exposure may enhance C-fiber responsiveness. To investigate the effect of chronic TS exposure on C-fiber responsiveness to capsaicin and bradykinin, especially in atopic individuals, we exposed ovalbumin (OA)-sensitized guinea pigs to TS (5 mg/l air, 30 min/day for 7 days/wk) or to compressed air. Nonsensitized guinea pigs were also exposed to either compressed air or TS. Beginning after 120 days of exposure, C fibers and rapidly adapting receptors (RARs) were challenged with capsaicin and bradykinin. TS exposure enhanced sensory receptor and airway responsiveness to both intravenous capsaicin and bradykinin challenge. C-fiber, RAR, and airway responsiveness to capsaicin challenge was greatest in OA-sensitized guinea pigs exposed to TS. OA alone induced capsaicin hyperresponsiveness at 5 microg. Airway responsiveness to bradykinin was also greatest in OA-sensitized guinea pigs exposed to TS. OA alone enhanced C-fiber responsiveness to bradykinin at 5 and 10 microg. C-fiber activation by either agonist appeared direct, whereas RAR activation appeared indirect. Therefore, a mechanism of airway hyperirritability induced by the combination of OA sensitization and chronic TS exposure may include hyperirritability of lung C fibers.

Administration, Inhalation↗

Effects of breathing supplemental oxygen before progressive exercise in patients with chronic obstructive lung disease.

A study was carried out to determine whether supplemental oxygen before exercise would improve maximum exercise performance and relieve exertional dyspnoea in 20 patients with chronic obstructive lung disease (mean FEV1 0.79 l; forced vital capacity 2.30 l). Patients performed two progressive treadmill exercise tests to a symptom limited maximum, with at least 30 minutes rest between tests. They received compressed air or supplemental oxygen from nasal prongs for 10 minutes before exercise in a double blind randomised trial with a crossover design. Heart rate and breathlessness score on a visual analogue scale were compared between tests at 75% of the maximum distance walked in the compressed air test. The mean arterial oxygen saturation (SaO2) after oxygen (93%) was significantly higher than after compressed air (91%). There was no significant change, however, in maximum distance walked or maximum heart rate, or in the breathlessness score or heart rate at 75% of maximum distance walked. The study had a power of 93% for detecting an increase of 50 metres in maximum distance walked. There was an order effect, with better performance on the second test; but the magnitude of the difference was small. It is concluded that administration of supplemental oxygen sufficient to raise SaO2 above 90% for 10 minutes before exercise is unlikely to improve maximum exercise performance or breathlessness on exertion in patients with chronic obstructive lung disease.

Adult↗

Effects of nitrogen and helium at pressure on drug-induced stereotypy and locomotion in mice.

Stereotyped behavior was induced in mice by apomorphine (5-50 mg X kg-1 s.c.) and d-amphetamine (3-5 mg X kg-1 i.p.), and increased locomotor activity was induced by d-amphetamine (8 and 10 mg X kg-1 i.p.) and by morphine sulfate (15 and 30 mg X kg-1 i.p.). Experiments were conducted at 1, 4, and 7 ATA. All mice were myringotomized under ether anesthesia 3 d before behavioral studies to minimize disturbances due to pressure differences across the tympanic membrane during compression. Compressed air significantly increased locomotor activity induced by d-amphetamine and morphine sulfate whereas He/O2 had no effect, suggesting that the change was due to the narcotic effect of N2. Drug-induced stereotyped behavior was affected variably (usually depressed) by compressed air and not by He/O2. Since both stereotypy and locomotor activity induced by these drugs involve dopamine receptor systems, the results suggest that compressed air does not influence all such membrane receptors in like manner. Evidence for receptor plasticity is discussed.

Air Pressure↗

Improved venous return by elliptical, sequential and seamless air-cell compression.

AIM: The risk of deep vein thrombosis (DVT) in the peri-operative period is significant, but can be reduced with the use of mechanical intermittent pneumatic compression (IPC). These devices have reached widespread use in hospitals and have been found to be effective prophylactic measures against DVT. This study evaluates the latest design features of one particular IPC device in comparison to current models. METHODS: Duplex ultrasound scanning was performed on 40 lower extremities of 20 healthy volunteers before and during the application of the IPC device (VenaFlow System, Aircas, NJ, USA. Two hemodynamic parameters were measured, acceleration time from spontaneous baseline venous flow and peak vein velocity. All measurements were obtained by scanning proximal to the saphenofemoral junction in the common femoral vein in both extremities for each subject. Data were obtained from 3 compression cycles and averaged for each extremity. Results were compared with a recent prospective study form our center using a slow-filling and a rapid-filling sequential IPC devices. RESULTS: The medians for spontaneous average peak velocities at rest of the right and left lower extremities were 26 cm/s and 24.1 cm/s. The median augmented peak velocities during the compression cycle of the device in the right and left side were 79.6 cm/s and 79.0 cm/s. This represented a 306.2% increase in average peak velocity on the right side and a 327.8% increase on the left side. The median acceleration time was 305 ms +/- 40 in the left and 310 ms +/- 50 in the right limb. There was no statistically significant difference in the spontaneous and augmented velocities between the right and left lower extremities in each subject. In comparison to existing slow- and rapid-filling IPC devices the VenaFlow System had superior peak velocities and shorter acceleration times. CONCLUSION: The use of elliptical, sequential and rapid-filling compression of the leg with overlapping air-cells produces significant hemodynamic changes in the common femoral vein, which are superior to other sequential slow- or rapid-filling IPC devices. Randomized studies should be performed to determine the efficacy of this new device in DVT prevention.

Adult↗

Impregnation of ground, acid etched dentin in vivo, using five commercial resins.

Resin impregnation of dentin was studied in vivo in 64 pairs of contralateral dentin surfaces. One of the surfaces in each pair was randomly selected to be impregnated with Concise Enamel Bond, the other with one of four commercial resins; namely Concise White Sealant, Clearfil Bonding Agent, Estilux Glaze and Uvio Seal. Before impregnation, the dentin surface was ground flat with a flat fissure bur, etched for 5 seconds with Concise Etching Liquid and compressed air desiccated for 15 seconds holding the compressed air near and parallel to the surface. A bulk of composite material was added to facilitate lateral removal of the resin. Enamel and peritubular dentin were removed with acid after extraction to enable the separation of the resin from the softened dentin. A withinpair analysis of the inner resin surfaces was conducted, based on micrographs taken in the scanning electron microscope (SEM). A good and equivalent impregnation of the dentinal tubules was obtained with all the materials except Uvio Seal. Inadequate or no impregnation at all occurred only in areas near the pulp or close to the DE-junction. Short tags, often with concave endings, were constantly obtained with Uvio Seal.

Acid Etching, Dental↗

[Tissue regression as occupational disease. Character, causes, and assessment].

The most frequent of the so-called vocational diseases "Attrition of brachial joints after working with compressed-air-tools" and "Change of the miner's menisci" have only a loose causal connection with the occupations they are named for: By far the majority of such workers are not affected-even though they handle compressed-air-tools, or do the labor of miners all during their working life. This study explains, that the cause for these diseases is not to be sought in any external influences typical for these activities but rather in some negative tendency of patient's tissue--a definite morbidity towards tissue-regression. Patients are born with this inclination, with, therefore, is not insurable. The conditions for public accident incurance are fulfilled only if work with compressed-air-tools or labour of miners aggravates these negative tendencies. The somewhat indirect causal connection between diseases and occupations, do bring up certain problems and make it rather difficult, to judge these "tissue-regressions as vocational diseases".

Expert Testimony↗

[Scintigraphic assessment of pulmonary deposition of pentamidine administered by aerosol].

Isotopic techniques enable to determine the best conditions to aerosolize pentamidine as a preventive treatment of pneumocystis. An original labelling technique of pentamidine isethionate has led into a feasibility study of pentamidine scintigraphy in the monkey, and then to a clinical study. A tracer dose of 2 mg of pentamidine isethionate was diluted into 200 mg of pentamidine mesylate. An ultrasonic nebulizer (TV 6000) and a jet nebulizer (Venticis II) were first compared in four baboons. With the two nebulisers the curves of pulmonary kinetic activity showed a peak 10-15 minutes after the beginning of inhalation and then a plateau. With the ultrasonic TV6000 the pulmonary dose was on average 0.8 mg or 0.4% of the pentamidine aerosolized and the gastric contamination 3.1%. With the Venticis II compressed air apparatus the amount of pentamidine delivered to the deep lung was a mean of 4.2 mg or 2.1% of the aerosolized dose whereas the gastric contamination was only 0.5%. The delivery of the aerosol by the ultrasonic inhaler TV 6000 was then compared with two compressed air inhalers Venticis II and Respirgard II in four patients infected with HIV virus who were submitted to a preventative therapy against pneumocystis. With the ultrasonic TV 6000 the pulmonary dose was 0.8 mg or 0.3%-0.5% of the dose of pentamidine aerosolized and the digestive contamination was 3.1%. The performance of the two compressed air nebulizers Venticis II and Respirgard II were similar. The amount of pentamidine delivered to the deep lung was respectively 12 and 14 mg or 6 and 8% of the dose of pentamidine aerosolized and the digestive activity was 0.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗