Gas Delivery System Research Articles

Blood‐oxygen level dependent MRI measures of cerebrovascular reactivity using a controlled respiratory challenge: Reproducibility and gender differences

To evaluate the reproducibility and gender differences in cerebrovascular reactivity (CVR) measurements obtained using the blood-oxygen level dependent (BOLD) response to controlled changes in end-tidal partial pressure of carbon dioxide (PETCO(2)). We obtained ethical approval to image 19 healthy volunteers (10 men, 9 women) on a 1.5 Tesla (T) MRI scanner twice on two separate days using identical procedures. CVR images were generated by collecting BOLD MRI data during controlled changes in PETCO(2) induced by a sequential gas delivery system. Using the intraclass correlation coefficient (ICC), we demonstrated excellent within-day CVR measures in gray matter (GM) (ICC = 0.92) and white matter (WM) (ICC = 0.88) regions, excellent between-day reproducibility in GM (ICC = 0.81), and good between-day reproducibility in the WM (ICC = 0.66). CVR values between men and women were significantly different in the GM and WM. Men exhibited a 22 +/- 2% greater CVR in GM and a 17 +/- 2% greater CVR in WM compared with females. Our results demonstrate the reliability of BOLD MRI CVR measurements obtained using a controlled cerebrovascular challenge. Using this technique, we also revealed significantly increased BOLD response to CO(2) in males compared with females.

Shape Optimization of a Showerhead System for the Control of Growth Uniformity in a MOCVD Reactor Using CFD-based Evolutionary Algorithms

A steady state, laminar flow coupled with heat transfer, gas-phase and surface chemistry, is numerically solved for the optimal design of a showerhead gas delivery system in an axis-symmetrical MOCVD reactor. The design method involves an evolutionary algorithm based on CFD simulations. A finite-volume CFD code for aluminum growth provides the numerical predictions of the growth rate and its spatial variation over the substrate. A multilevel evolutionary algorithm is used to continuously adjust the shape of the shower plate so as to minimize the spatial variation of the growth rate. A 5-variable parameterization of the shower plate is investigated and a near-optimal solution is proposed and compared to the original configuration of the shower plate.

A reply

Barema welcomes the opportunity to respond to this letter from Drs Campbell and Sellers on behalf of all suppliers of anaesthetic machines, and not just GE Healthcare (formally Datex–Ohmeda). Putting aside the question of checking equipment prior to the starting a case, this letter raises a number points, including the application of standards and regulations on: Hypoxic guards on the anaesthetic machines, Oxygen alarm level on the respiratory gas monitors, Manufacturer responsibility under the provisions of the European Union Medical Devices Directive (93/42/EEC, 2007/47 EEC). The latest revision of BS EN ISO 60601-2.13 states that ‘The anaesthetic gas delivery system shall be provided with a protection device to prevent the unintentional selection of a mixture of oxygen and other gases having an oxygen concentration below 19%.’ This hypoxic protection device is mandated as an integral part of the anaesthetic machine, and not just an alarm. The rationale is to further reduce the risk for accidental error, such as turning off the oxygen delivery valve instead of the nitrous oxide valve. The latest revision contained in EN ISO CD 80601-2.55 allows the user to set the oxygen level. The wording is ‘For each gas reading alarm condition with which the RGM is equipped, the alarm limit(s) shall be operator adjustable. The high gas level for inspired nitrous oxide shall be exempt from this requirement. Deliberate action shall be required on the part of the user to adjust the alarm limits. It shall not be possible to set the low alarm of the inspired oxygen gas reading below 18% without an additional deliberate action’. All medical device manufacturers must comply with the Essential Requirements of the European Union Medical Devices Directive in order to be able to affix the CE Mark to the device. A means of achieving this compliance is by the use of published standards, the standards listed above are two such examples. All suppliers of anaesthetic machines in United Kingdom meet these requirements, with the intention that users will give a safe anaesthetic to patients whatever the circumstances. At the same time, suppliers recognise it is essential to allow users to make adjustments to equipment to meet particular needs. If users believe the default settings on equipment should be revised, then Barema is of the opinion this should be raised with the Safety Committee of the Association of Anaesthetists of Great Britain and Ireland in the first instance.

Pharmaceutical preparation of oxygen-15 labelled molecular oxygen and carbon monoxide gasses in a hospital setting

Clinical positron emission tomography (PET) requires safe and effective PET radiopharmaceuticals. Tracers used for measuring oxygen consumption and blood volume are [(15)O]O(2) and [(15)O]CO, respectively. In general, these oxygen-15 labelled tracers are produced using a cyclotron that accelerates deuterons onto a target filled with (14)N(2) containing a trace of oxygen. In recent years, cyclotrons have been developed that only are capable of accelerating protons. The purpose of this study was to validate and assess such a cyclotron for production and administration of oxygen-15 labelled gasses in an hospital setting. An RDS111 cyclotron (Siemens-CTI, Knoxville, USA) was validated for bolus production of [(15)O]O(2) and [(15)O]CO gasses. In addition, equipment was developed to administer these tracers to patients. Both [(15)O]O(2) and [(15)O]CO gasses could be produced in sufficient amounts, whilst meeting European Pharmacopeia requirements. Although produced oxygen-15 gasses contained a minor level of (11)C contamination, in clinical studies it was possible to correct for this contamination by delayed blood counting. An 11 MeV proton cyclotron combined with an in-house developed gas delivery system allows for the production and administration of sufficient amounts of [(15)O]-gasses for routine clinical PET studies in an hospital setting.

Vapour liquid equilibria data for a range of new carbon dioxide absorbents

Carbon dioxide (CO2) is now recognised as the greenhouse gas contributing most to global warming and implicated in climate change model predictions. Electricity generation from fossil fuel combustion is a major source of CO2 emissions both internationally (32% of total CO2 emissions) and nationally (50% of total CO2 emissions). To effectively reduce CO2 emissions in the short to medium term requires CO2 capture and storage from these and other point sources as a part of the solution. The CSIRO Division of Energy Technology has undertaken a major CO2 capture research program covering many aspects of the technology. On the laboratory scale, the chemical reactions involved in CO2 capture and release by chemical absorption are being investigated and modelled to identify where and how improvements in efficiency can be made. A large scale screening study in which the CO2 absorption capacity of over 100 30% w/w amine solutions at 40 ∘C and ∼13 kPa CO2 partial pressure has been carried out. This study has identified a number of novel amines as having outstanding CO2 carrying capacity. An apparatus has been developed used a stirred glass batch reactor, capable of withstanding pressures up to 1100 kPa, coupled to a pressure controller and gas delivery system from a high pressure reservoir. The apparatus has been used to collect vapour liquid equilibria (VLE) data by measurement of CO2 consumption from the high pressure reservoir. VLE data has been collected for three amines identified in the screening study at 1 mol L−1 and 40 ∘C over the pressure range ∼0.3 to 900 kPa. The VLE results will be presented along with a comparison with MEA and an interpretation of the behaviour of the amines.

The effect of solids and dispersant loadings on the suspension viscosities and deposition rates of suspension plasma sprayed YSZ coatings

Suspension plasma spraying (SPS) is a promising modification of traditional plasma spraying techniques that uses small (≤ 2 μm) particles suspended in a liquid to fabricate coatings with fine microstructures and controlled porosity rapidly and without the need for post-deposition heat treatments. These qualities make SPS an interesting new technique to manufacture solid oxide fuel cell (SOFC) active layers. However, in order to be able to manufacture layers with good microstructures, the properties of the feedstock suspension must be optimized to enhance particle dispersion and improve feedability. This study uses a pressurized gas delivery system to feed aqueous YSZ suspensions containing an organic dispersant to a Northwest Mettech Axial III axial injection suspension plasma spray system. Three different dispersant types (polyacrylic acid (PAA), polyethylene imine (PEI) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)) were characterized and the effects of solid loadings, dispersant type, and dispersant concentration on suspension properties such as viscosity and feedability, and layer characteristics such as microstructure and deposited thickness were examined.

The great gas pipeline game: monopolistic expansion of Russia's Gazprom into European markets

Purpose – Russian dominance of the Eurasian natural gas delivery system has put the independence of the EU's foreign policy at risk. Although Europe is struggling to counteract the threat, Russia appears to be winning the game. This paper aims to recommend significant measures to reverse the trend.Design/methodology/approach – This is a discussion paper exploring the issues involved.Findings – Russia's stranglehold already has acquired 25 percent of the European market. Moreover, it is installing four new pipelines, and plans to increase its market share substantially. In response, Europe is building or planning three new pipelines. The author recommends additionally: strategic gas reserves, anti‐trust prosecution, financial and political inducements, and offering WTO membership to Russia in exchange for concessions.Practical implications – Europe can win the great natural gas pipeline game if it is played with commitment. Europe must focus on the big prize, natural gas independence.Originality/value – Th...

Practice Advisory for the Prevention and Management of Operating Room Fires

Practice Advisory for the Prevention and Management of Operating Room Fires: An Updated Report by the American Society of Anesthesiologists Task Force on Operating Room Fires Jeffrey Apfelbaum;Robert Caplan;Steven Barker;Richard Connis;Charles Cowles;Jan Ehrenwerth;David Nickinovich;Donna Pritchard;David Roberson;Robert Caplan;Steven Barker;Richard Connis;Charles Cowles;Albert de Richemond;Jan Ehrenwerth;David Nickinovich;Donna Pritchard;David Roberson;Gerald Wolf; Anesthesiology

Gas delivery system in patients with type 1 diabetes mellitus

The aim of the study was to investigate the effect of diabetes mellitus on the lung diffusing capacity for carbon monoxide (TLCO) and oxygen status of arterial blood in 141 young (of them, 66 female) patients with type 1 diabetes mellitus (IDDM) (mean age, 26.2 ± 6.2 yrs; mean duration of the disease, 12.6 ± 7.3 yrs) in comparison with 36 age-, sex-, weight-, and height-matched healthy controls (C). Diabetic patients were divided into 4 groups: 1) 46 diabetic patients without microvascular complications (DP1); 2) 48 diabetic patients with mild late complications (simple and preproliferative diabetic retinopathy, II to III stage nephropathy (DP2); 3) 34 diabetic patients with advanced late complications (proliferative retinopathy, IV stage nephropathy) (DP3); 4) 13 diabetic patients with end-stage renal failure (V stage nephropathy), not treated with dialysis (DP4). Spirometry with assessment of bronchodilator response, body plethysmography were performed, TLCO and transfer-factor (KCO) were measured in sitting position by the single-breath (TLCOsb) and the steady-state (TLCOss) methods. Gas exchange and lung volumes did not differ between DP1 and C. We found a significant reduction in TLCOsb, TLCOss, KCO in DP2patients compared to controls. Severe diabetic microangiopathy (DP3, DP4) was associated with significant decrease in TLCO and total lung capacity (TLC), progressive fall in arterial pO 2 and total oxygen concentration in arterial blood (ctO2). TLCO, TLC, pO 2 and ctO 2 were particularly low in the group with end-stage renal failure (DP4). Conclusion. Diabetes mellitus alters pulmonary gas exchange and causes reduction in lung volumes. Our data suggest that this abnormalities could be considered as manifestations of late diabetic complications and the lungs are one of the target organs affected by diabetes.

The Effect of Nitrogen Partial Pressure on Microstructure of Reaction Bonded Silicon Nitride

The interaction between gas atmosphere and silicon during reaction bonded silicon nitride(RBSN)process leads to a non-uniform band formation of alpha silicon nitride. The reaction layer, α -Si3N4, was formed near the surface of the sample in the early stage of RBSN. Reactive nitrogen gas was supplied as static state using computer controlled gas delivery system. The formation of α -Si3N4 band near the surface of the sample can be explained thermodynamically, based on the nitrogen partial pressure in the gas mixtures.

Ozone air levels adjacent to a dental ozone gas delivery system

Objective. Ozone (O3) has been suggested as an anti-microbial treatment in dentistry, with an ozone gas delivery system introduced for the treatment of fissure and root caries. The aim of this study was to investigate the sealing capacity of the novel delivery system and its re-suction capacity during accidental displacement of the cup at different stages of ozone delivery. Material and methods. Ozone leakage was studied in vitro after application on a flat metal surface and on buccal and occlusal tooth surfaces. An ozone analyzer was used to measure ozone gas concentrations adjacent to the delivering cups when adapted to the target surfaces during and after 10–20 s application cycles. The measured levels were compared with the background concentrations in the room. Measurements were performed 1) after complete ozone application cycles, 2) within the cycle before the start of the suction period, and 3) after displacements of the cup during the cycles. Results. Ozone air values varied between 8 and 166 µg·m−3 for the flat metal surface and between 0 and 108 µg·m−3 for the tooth surfaces. Ozone leakage levels were 7.6 µg·m−3 for the flat and 7.4 µg·m−3 and 5.6 µg·m−3 for the buccal and occlusal surfaces, respectively, and 5.2 µg·m−3 and 9.8 µg·m−3 for the premolar and molar surfaces, respectively. Cycles with displacement showed significantly higher leakage levels than continuous complete cycles (p=0.03). Conclusions. Ozone application cycles with displacements showed significantly higher leakage levels than continuous complete cycles. The largest ozone delivery cups showed the highest leakage values. A change in background levels was seen with similar change in adjacent ozone levels. The overall measured ozone leakage values were low after normally functioning delivery cycles and after repeated displacements. The delivery system can be considered safe.

Compact toroid injection system for JFT-2M

The compact toroid (CT) injection system for JFT-2M is composed of a CT injector, a gas delivery and vacuum system, a power supply system, and a diagnostics system. In particular, the power supply system delivers high performance for CT formation and acceleration. The CT formation capacitor bank unit achieved a formation current of 350 kA with a rise time less than 10 μs. Although the CT acceleration bank units are equipped with 14 ignitron switches instead of gap switches to attenuate the discharge noise level, an acceleration current of 400 kA with a short rise time of 9 μs is controlled within a jitter of much less than 1 μs. The resulting CT velocity and mass density satisfy the requirements for CT penetration into the tokamak plasma core at a toroidal field of 1 T. This CT injection system is thus suitable for CT injection in a middle-sized tokamak plasma such as the JFT-2M tokamak.

Novel methodology to comprehensively assess retinal arteriolar vascular reactivity to hypercapnia

Purpose (1) Describe a new methodology that permits the comprehensive assessment of retinal arteriolar vascular reactivity in response to a sustained and stable hypercapnic stimulus. (2) Determine the magnitude of the vascular reactivity response of the retinal arterioles to hypercapnic provocation in healthy, young subjects. Methodology Eleven healthy subjects of mean age 27 years (SD 3.43) participated in the study and one eye was randomly selected. A mask attached to a sequential rebreathing circuit, and connected to a gas delivery system, was fitted to the face. To establish baseline values, subjects breathed bottled air for 15 min and at least 6 blood flow measurements of the supero-temporal arteriole were acquired using the Canon Laser Blood Flowmeter (CLBF). Air flow was then decreased until a stable increase in fractional end-tidal CO 2 concentration (F ETCO 2) of 10–15% was achieved. CLBF measurements were acquired every minute (minimum of 6 measurements) during the 20-minute period of elevated F ETCO 2. F et CO 2 was then reduced to baseline levels, and 6 further CLBF measurements were acquired. Respiratory rate, blood pressure, pulse rate and oxygen saturation were monitored continuously. Results Retinal arteriolar diameter, blood velocity and blood flow increased during hypercapnia relative to baseline ( p = 0.0045, p < 0.0001 and p < 0.0001, respectively). Group mean F ETCO 2 showed an increase of 12.0% (SD 3.6) relative to baseline ( p < 0.0001). Conclusions This study describes a new methodology that permits the comprehensive assessment of retinal arteriolar vascular reactivity in response to a sustained and stable hypercapnic stimulus. Retinal arteriolar diameter, blood velocity and blood flow increased significantly in response to a hypercapnic provocation in young, healthy subjects.

Effects of coal syngas and H 2S on the performance of solid oxide fuel cells: Single-cell tests

The performance of single-cell planar solid oxide fuel cells using coal syngas, with and without hydrogen sulfide (H 2S), was studied. A state-of-the-art gas delivery system, data acquisition system, and test stand were designed and assembled for experimentation. All cells were tested at 850 °C with a constant current load of 14.3 A (current density of 0.20 A cm −2). The results from using syngas with no H 2S indicated no degradation after 290 h of operation. After immediately injecting CO (and water) in the H 2–N 2 mixture, there was a slight tendency of improving performance (power) and then the behavior remained steady. On the other hand, results for the test with syngas in the presence of H 2S (200–240 ppm) indicated good performance over 570 h (650 h total operation time) with 10–12.5% degradation. The results suggest these cells can be used for extended periods of time for syngas applications, and in the presence of H 2S the cells show no major degradation.

Development of a microfabricated impinger for on-chip gas phase sampling

The design and development of a glass fabricated microimpinger for gas phase sampling of hydrogen cyanide is described. Using standard glass microfabrication techniques, a microimpinger consisting of a gas sample inlet, gas delivery arms, and an extraction reservoir was used to extract dilute hydrogen cyanide vapor from a gas delivery system using a basic aqueous trapping buffer. A Teflon membrane was utilized for containing the liquid sample in the extraction reservoir. Extraction efficiency for sampling hydrogen cyanide was monitored by forming a fluorescent cyanide isoindole in the reaction of cyanide with naphthalene-2,3-dicarboxaldehyde and taurine. Experiments using a flow of 2 mL min −1 and a sampling time of 1 min were used to measure cyanide vapors as low as 1.9 mg m −3, with a calculated limit of detection of 0.486 mg m −3. The effects of the vacuum flow rate and sampling time were also investigated.

Microstructure of reaction-bonded silicon nitride fabricated under static nitrogen pressure

In this study, reaction-bonded silicon nitride (RBSN) was fabricated using static nitriding system. This technique may be advantageous in commercialization. Reactive nitrogen gas was supplied as a static state using computer-controlled gas delivery system instead of a dynamic flowing state. Nitridation rates obtained at the early stage of reaction rate were proportional to the reactive gas pressures. The sequence of the nitridation reactions was as follows: (1) outside, (2) inside and (3) intermediate region of the specimen. The results were obtained from the coloration of the cross-sectioned specimens that had various nitridation rates.

Air Embolism during Intraoperative Endoscopic Localization and Surgical Resection for Blue Rubber Bleb Nevus Syndrome

Air Embolism during Intraoperative Endoscopic Localization and Surgical Resection for Blue Rubber Bleb Nevus Syndrome

An investigation of pipeline materials for continuous hyperpolarized 129Xe gas spectroscopy

In order to establish a continuous hyperpolarized xenon-129 (HP-129Xe) gas delivery system for MR imaging, the effect of the metallic materials in the gas pipeline on the signal intensity was investigated. In the gas pipeline, an appropriate surface is needed to minimize wall relaxation by the HP-129Xe gas caused by the interaction between the HP gas and the surface, which can lead to signal loss. Although Pyrex glass is a popular material for the HP gas chamber, it is fragile under heat or physical stress. In this study, five stainless steel tubes (STs) prepared with different surface film-forming processes were examined. The MR signal intensities of HP-129Xe gas that passed through each tube were then compared. The film passivated by iron fluoride maintained the highest level of hyperpolarization, whereas that passivated by chromium oxide maintained the lowest. A ST with an appropriate passive film may be a useful alternative to a Pyrex glass pipeline.

Behavioral correlates of olfactory and trigeminal gaseous stimulation in chickens, Gallus domesticus

Despite growing evidence of avian olfactory abilities, there are few reports of behavioral correlates of chemosensory stimulation in birds. The present study aimed to determine how the behavioral responses of hens to selected gases might be affected by input from different chemosensory systems. We also hoped to relate electrophysiological thresholds previously measured in our laboratory to behavioral evidence of perception. Immediate behavioral responses to ascending series of short (7 s) pulses of olfactory (hydrogen sulphide), trigeminal (carbon dioxide) and combining (ammonia) gaseous stimulants were measured in 12 partially restrained adult hens ( Gallus domesticus) using a purpose built gas delivery system. The concentration ranges applied matched those used in our previous electrophysiological studies of olfactory bulb responses. Consistent and specific behavioral responses were observed in response to stimulation with each gas. While significant increases in mandibulation (a distinctive rapid bout of bill movements), interruption of ongoing behavior, orientation to the end of the stimulus, and struggling were seen during stimulation with all three gases, orientation towards the stimulus occurred only in response to the olfactory stimulants, ammonia and hydrogen sulphide. The only gas to elicit significant avoidance was hydrogen sulphide, while gasping and headshaking were elevated in response to stimulation with carbon dioxide. Approximate threshold values for some types of behavior related reasonably well to receptor thresholds determined electrophysiologically, but perception may have occurred at lower concentrations without overt behavioral consequences. The diversity of the behavioral responses observed supports the notion that the gases selectively stimulated different sensory pathways.

A direct nitric oxide gas delivery system for bacterial and mammalian cell cultures

Nitric oxide (NO) is the smallest known gaseous signaling molecule released by mammalian and plant cells. To investigate the pathophysiologic role of exogenous NO gas (gNO) in bacterial and mammalian cell cultures, a validated in vitro delivery method is required. The system should be able to deliver gNO directly to bacterial and/or cell cultures in a continuous, predictable, and reproducible manner over a long period of time (days). To accomplish this, a gas delivery system was designed to provide optimal growth conditions for bacteria and/or mammalian cells. Parameters for cell exposure, such as concentration of gNO, nitrogen dioxide (NO(2)), oxygen (O(2)), temperature, and relative humidity (RH) were continuously monitored and evaluated. Uptake of gNO into various media was monitored by measuring the nitrite concentration using the Griess reagent technique. A selection of standard growth media [saline, tryptic soy broth (TSB), Middlebrook 7H9 (MB 7H9), and Dulbecco's modified Eagle's medium (DMEM)] exposed to various concentrations of gNO revealed a steady and consistent transfer of gNO into the aqueous phase over a 48-h period. Validation of optimal growth conditions within the device, as compared to a conventional incubator, were accomplished by growing and observing viability of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and human fibroblast cultures in the absence of gNO. These results indicate that an optimal growth environment for the above tested cells was accomplished inside the proposed delivery system. Dose-dependent toxicological data revealed a significant bacteriostatic effect on P. aeruginosa and S. aureus with continuous exposure to 80 ppm gNO. No toxic effects were observed on dermal fibroblast proliferation at concentrations up to 400 ppm gNO for 48 h. In conclusion, the designed gNO exposure system is capable of supporting cellular viability for a representative range of prokaryote and eukaryotic cells. The exposure system is also capable of obtaining toxicological data. Therefore, the proposed device can be utilized to continuously expose cells to various levels of gNO for up to 72 h to study the in vitro effects of gNO therapy.