Volume Of Trapped Air Research Articles

The impact of increasing saline flush volume to reduce the amount of residual air in the delivery system of aortic prostheses-a randomized controlled trial.

Air embolism is a known risk during thoracic endovascular aortic repair (TEVAR) and is associated with an incomplete deairing of the delivery system despite the saline lavage recommended by the instructions for use (IFU). As the delivery systems are identical and residual air remains frequently in the abdominal aortic aneurysm sac, endovascular aortic repair (EVAR) can be used to examine the effectiveness of deairing maneuvers. We aimed to evaluate whether increasing the flush volume can result in a more complete deairing. Patients undergoing EVAR were randomly assigned according to flushing volume (Group A, 1× IFU; Group B, 4× IFU). The Terumo Aortic Anaconda and Treo and Cook Zenith Alpha Abdominal stent grafts were randomly implanted in equal distribution (10-10-10). The quantity of air trapped in the aneurysm sac was measured using a pre-discharge computed tomography angiography (CTA). Thirty patients were enrolled and equally distributed between the two groups, with no differences observed in any demographic or anatomical factors. The presence of air was less frequent in Group A compared to that in Group B [7 (47%) vs. 13 (87%), p = .02], and the air volume was less in Group A compared to that in Group B (103.5 ± 210.4 vs. 175.5 ± 175.0 mm3, p = .04). Additionally, the volume of trapped air was higher with the Anaconda graft type (p = .025). These findings suggest that increased flushing volume is associated with a higher amount of trapped air; thus, following the IFU might be associated with a reduced risk of air embolization. Furthermore, significant differences were identified between devices in terms of the amount of trapped air. [NCT04909190], [ClinicalTrials.gov].

WS06.05 The volume of trapped air (VTA) from multiple breath washout (MBW) substantially underestimates the extent of trapped air (TA) demonstrated with spirometry-controlled computed tomography

Objectives: A limitation of the lung clearance index (LCI) from MBW is that it may ‘overlook’ areas of TA, a major component of CF lung disease pathophysiology. Previous methodology addressed this by performing 5 inspiratory capacity (5IC) breaths after the standard end of washout to mobilise TA. In calculating the VTA, a fundamental assumption is that the gas mobilized has a [N2] of 78%. We assessed this assumption and the relationship of VTA to TA scores from CT scans.

Intraventricular Tension Pneumocephalus After Subarachnoid Hemorrhage and Removal of an External Ventricular Drain

Pneumocephalus is defined as an accumulation of air or gas in the intracranial space. It is a common complication after skull surgery or craniofacial trauma, sometimes also caused by gas-producing organisms in the context of an infection, and reported with cerebrospinal fluid draining procedures. Here we report a case of a large intraventricular tension pneumocephalus after removal of an external ventricular drain in a patient with subarachnoid hemorrhage. The acute management included therapy with normobaric oxygen. Despite the large volume of trapped air and its diffuse distribution inside the skull and spine, therapy with 100% normobaric oxygen appears to be safe and efficient for a rapid improvement of the patient's symptoms and the neuroradiological imaging.

An Easy Method for Pressure Measurement in Microchannels Using Trapped Air Compression in a One-End-Sealed Capillary.

Pressure is one basic parameter involved in microfluidic systems. In this study, we developed an easy capillary-based method for measuring fluid pressure at one or multiple locations in a microchannel. The principal component is a commonly used capillary (inner diameter of 400 μm and 95 mm in length), with one end sealed and calibrated scales on it. By reading the height (h) of an air-liquid interface, the pressure can be measured directly from a table, which is calculated using the ideal gas law. Many factors that affect the relationship between the trapped air volume and applied pressure (papplied) have been investigated in detail, including the surface tension, liquid gravity, air solubility in water, temperature variation, and capillary diameters. Based on the evaluation of the experimental and simulation results of the pressure, combined with theoretical analysis, a resolution of about 1 kPa within a full-scale range of 101.6–178 kPa was obtained. A pressure drop (Δp) as low as 0.25 kPa was obtained in an operating range from 0.5 kPa to 12 kPa. Compared with other novel, microstructure-based methods, this method does not require microfabrication and additional equipment. Finally, we use this method to reasonably analyze the nonlinearity of the flow-pressure drop relationship caused by channel deformation. In the future, this one-end-sealed capillary could be used for pressure measurement as easily as a clinical thermometer in various microfluidic applications.

Analysis of Optimum Performance of Air Vessels Used in Damping Water Hammer Pressure Wave

Transient flow or water hammer is the sudden change of flow conditions due to an unexpected event such as a sudden closing of a valve installed on the pipeline system. Water hammer can pose serious threats to the pipeline system, as the flow's pressure can be changed above or below the limits which the pipeline network can withstand. Controlling the water hammer pressure becomes indispensable, so a transient surge analysis is required to investigate the points of severe changes along with the pipeline system. Compressed air vessel (CAV) is a pressure control device that is used to control the positive and negative pressure changes. There are two parameters affect the sizing of the air vessel; the initial trapped air volume and throttling the aperture of the air vessel. A computer model based on the unsteady one-dimensional flow equations of momentum and continuity is established to examine the proper size of the two parameters. The equations are solved by the method of characteristics while the vessel is modeled as a quasi-one-dimensional flow system. An experimental test rig provided with a rapid closing magnetic valve and pressure sensors are used to validate the model results. Both the experimental and model results show the high capability of the air vessel to dampen water hammer pressure. In addition, the results show that the introduced throttling action has a wide effect on the size of the air vessel and that the diameter of the throttling shall not be less than 0.3 the diameter of the main pipe. Besides, the initial volume of the trapped air should be in the range of 53% to 78% of the total volume of the air vessel, so that the air vessel works effectively with optimum value of 60%.

Thermal effects of copper-graphene composite films in a human skin analogous for the application to clothing

PurposeThe purpose of the study was to explore heat-accumulative and thermal-conductive characteristics of copper-graphene composite film (Cu-G film) while applying it to a human-skin analogue.Design/methodology/approachIn the preliminary experiment, the authors evaluated the thermal conductive characteristics of the Cu-G film in three covered conditions (no film, copper film, and Cu-G film conditions). For the first factorial experiment, the heat-accumulative properties over heated pig skin were compared at air temperatures of 10, 25 and 35°C. For the second factorial experiment, 105 trials were conducted on pig skin by combining air temperatures, trapped air volumes, and numbers of film layers.FindingsThe results from the preliminary experiment showed that the Cu-G film distributed the surface heat to the outside of the Cu-G film, which resulted in even distribution of heat inside and outside the Cu-G film, whereas the copper film accumulated heat inside the copper film. The human-skin analogue of pig skin, however, showed the opposite tendency from that of the plastic. The pig-skin temperatures beneath the Cu-G film were higher than those beneath the copper film, and those differences were remarkable at the air temperature of 10°C. The accumulative heat was affected by the trapped air volume, fit to the skin, and number of Cu-G film layers.Originality/valueIn conclusion, the Cu-G film more effectively accumulated heat on the human-skin analogue than copper film, and those effects were more marked in cold environments than in mild or hot environments.

Firefighters’ protective jackets: Fit to female form and its effects on attributes relevant to thermal comfort

Often male and female workers wear protective garments of identical construction and style, with females typically wearing small-sized men’s garments. Consequently, the air spaces under garments worn by male and female wearers can substantially differ in size and distribution affecting the physiological comfort of firefighters’ protective clothing. The present study was designed to investigate the effects of varying dimensions and distributions of air spaces in the next-to-skin microclimate under firefighters’ protective jackets on attributes relevant to the thermal comfort of wearer, not only in relation to garment construction and fit, but also to human body geometry using 3D body scanning. Analysis of 20 scans demonstrated that jackets of the same size and construction create larger air spaces under them worn on a female as opposed to on a male body form. Both thermal and vapor resistance of clothing were affected significantly by the volume of trapped air.

Structured mixture proportioning for oil palm kernel shell concrete

Proportioning based on the principles of absolute volume method was used to obtain specific properties of lightweight concrete of oil palm kernel shells (OPKS). The sand content was determined depending on the cement content and OPKS/sand ratio. The trapped air volume of 5% and Water/cement ratio of 0.45 were fixed according to previous authors' works. The cement content ranged from 400 to 550kg/m3, and the OPKS/sand ratio ranged from 0.4 to 0.75. The mixture proportions of C:S:OPKS in weight of 1:1.60:0.96 and 1:1.53:0.99 with cement content of 450kg/m3 resulted in values for workability (≥20mm), density (1800≤d≤1900kg/m3) and cylindrical compressive strength (≥15MPa), which are recommended by ACI and British Code for structural lightweight concrete. This study, as part of efforts toward a structured method of proportioning of eco-friendly composite, demonstrates the possibility of linking mix proportions to properties of lightweight OPKS concrete.

Does exercise pulmonary hypertension exist?

The exercise definition of pulmonary hypertension using a mean pulmonary artery pressure threshold of greater than 30 mmHg was abandoned following the 4th World Pulmonary Hypertension Symposium in 2008, as this definition was not supported by evidence and healthy individuals frequently exceed this threshold. Meanwhile, the clinical value of exercise pulmonary hemodynamic testing has also been questioned. Recent data support the notion that an abnormal pulmonary hemodynamic response during exercise (or exercise pulmonary hypertension) is associated with symptoms and exercise limitation. Pathophysiologic mechanisms accounting for the development of exercise pulmonary hypertension include increased vascular resistance, excessive elevation in left atrial pressure and/or increased volume of trapped air during exercise, resulting in a steep rise in pulmonary artery pressure relative to cardiac output. Recent evidence suggests that exercise pulmonary hypertension may be defined by a mean pulmonary artery pressure surpassing 30 mmHg together with a simultaneous total pulmonary resistance exceeding 3 WU. Exercise pulmonary hypertension is a clinically relevant entity and an improved definition has been suggested based on new evidence. Exercise pulmonary hemodynamics may help unmask early or latent disease, particularly in populations that are at high risk for the development of pulmonary hypertension.

Break-up in formation of small bubbles: Break-up in a confined volume

Small bubbles play the critical role in flotation of providing the large interfacial area for collecting and transporting selected (hydrophobic) mineral particles. The generation of these bubbles is a physical process chemically assisted by addition of surfactants (frothers). The prime action of frothers is commonly considered to be coalescence inhibition. In contrast, the possible role of frothers in the initial air break-up has attracted little attention. In this paper, we investigate the effect of frothers on break-up. An experimental setup was designed to isolate break-up from coalescence. Single bubbles were produced through mechanically-induced deformation of a trapped air volume, the design aiming to mimic the break-up of the air cavity behind an impeller blade in a mechanical flotation machine. The results show that the bubble size produced at break-up is strongly affected by the presence of frother, but weakly by the input mechanical energy and the volume of trapped air. The proposed mechanism is that frothers induce surface tension gradients which increase the instabilities along the air/water interface. For a finite air volume, increasing the number of instabilities means that more and smaller bubbles will break away. Frothers of different types and concentrations were tested.

Reversibility of trapped air on chest computed tomography in cystic fibrosis patients

PurposeTo investigate changes in trapped air volume and distribution over time and compare computed tomography (CT) with pulmonary function tests for determining trapped air. MethodsThirty children contributed two CTs and pulmonary function tests over 2 years. Localized changes in trapped air on CT were assessed using image analysis software, by deforming the CT at timepoint 2 to match timepoint 1, and measuring the volume of stable (TAstable), disappeared (TAdisappeared) and new (TAnew) trapped air as a proportion of total lung volume. We used the difference between total lung capacity measured by plethysmography and helium dilution, residual volume to total lung capacity ratio, forced expiratory flow at 75% of vital capacity, and maximum mid-expiratory flow as pulmonary function test markers of trapped air. Statistical analysis included Wilcoxon's signed rank test and Spearman correlation coefficients. ResultsMedian (range) age at baseline was 11.9 (5–17) years. Median (range) of trapped air was 9.5 (2–33)% at timepoint 1 and 9.0 (0–25)% at timepoint 2 (p=0.49). Median (range) TAstable, TAdisappeared and TAnew were respectively 3.0 (0–12)%, 5.0 (1–22)% and 7.0 (0–20)%. Trapped air on CT correlated statistically significantly with all pulmonary function measures (p<0.01), other than residual volume to total lung capacity ratio (p=0.37). ConclusionTrapped air on CT did not significantly progress over 2 years, may have a substantial stable component, and is significantly correlated with pulmonary function markers.

Reversible thermo-pneumatic valves on centrifugal microfluidic platforms.

Centrifugal microfluidic systems utilize a conventional spindle motor to automate parallel biochemical assays on a single microfluidic disk. The integration of complex, sequential microfluidic procedures on these platforms relies on robust valving techniques that allow for the precise control and manipulation of fluid flow. The ability of valves to consistently return to their former conditions after each actuation plays a significant role in the real-time manipulation of fluidic operations. In this paper, we introduce an active valving technique that operates based on the deflection of a latex film with the potential for real-time flow manipulation in a wide range of operational spinning speeds. The reversible thermo-pneumatic valve (RTPV) seals or reopens an inlet when a trapped air volume is heated or cooled, respectively. The RTPV is a gas-impermeable valve composed of an air chamber enclosed by a latex membrane and a specially designed liquid transition chamber that enables the efficient usage of the applied thermal energy. Inputting thermo-pneumatic (TP) energy into the air chamber deflects the membrane into the liquid transition chamber against an inlet, sealing it and thus preventing fluid flow. From this point, a centrifugal pressure higher than the induced TP pressure in the air chamber reopens the fluid pathway. The behaviour of this newly introduced reversible valving system on a microfluidic disk is studied experimentally and theoretically over a range of rotational frequencies from 700 RPM to 2500 RPM. Furthermore, adding a physical component (e.g., a hemispherical rubber element) to induce initial flow resistance shifts the operational range of rotational frequencies of the RTPV to more than 6000 RPM. An analytical solution for the cooling of a heated RTPV on a spinning disk is also presented, which highlights the need for the future development of time-programmable RTPVs. Moreover, the reversibility and gas impermeability of the RTPV in the microfluidic networks are validated on a microfluidic disk designed for performing liquid circulation. Finally, an array of RTPVs is integrated into a microfluidic cartridge to enable sequential aliquoting for the conversion of dengue virus RNA to cDNA and the preparation of PCR reaction mixtures.

Theoretical and experimental investigation of the trapped air effect on air-sealed capacitive pressure sensor

This study presents the effect of the air trapped in the cavity on the performance of an air-sealed capacitive pressure sensor investigated by theoretical analysis and experimental validation. As a result, the sensitivity of a typical air-sealed capacitive pressure sensor can be improved significantly by adopting additional air chamber to increase the trapped air volume of the sensor. For theoretical analysis, the diaphragm deflection and the relative capacitance change of the sensor are formulated by considering the air pressure within the cavity affected by the diaphragm deflection and ambient temperature. In experiments, a passive wireless LC resonant telemetry scheme is employed to monitor the applied pressure by integrating an inductor coil with the fabricated sensor. The obtained result of the sensor having a flexible diaphragm such a natural rubber latex (NRL) shows the sensitivity improved more than 15 times by employing additional air chamber at room temperature compared to that of the sensor without it. Consequently, the test result of the NRL sensor with additional air chamber shows a pressure sensitivity of 8986ppm/kPa and a pressure responsivity of 1.391MHz/kPa in the pressure range of 1–10kPa. In addition, the effect of ambient temperature on the response of the air-sealed capacitive pressure sensor is measured and examined through comparison with the analytical results.

Thermo-hydro-mechanical response of granite to temperature changes

This paper examines the thermo-hydro-mechanical behaviour of a granitic rock. The cylindrical sample of granite contained a sealed fluid-filled cavity which was subjected to a cycle of temperature changes on its outer surface. The temperature and fluid pressure changes in the fluid-filled cavity were measured. Since the measurement of fluid pressure and temperature in the sealed cavity is experimentally feasible, the technique is a common feature in thermo-hydro-mechanical experiments. However, it was observed that regardless of how precisely the cavity was filled with de-aired water, air bubbles can still exist in the cavity and influence the fluid pressure changes. A novel technique is suggested for taking into account the influence of the volume of trapped air and eliminating its effect in the estimation of permeability. The experiment was computationally modelled using the finite element code COMSOL Multiphysics™ and the experimental results were compared with the computational estimates.

Measurement of the interface tension of smectic membranes in water

A simple method is proposed to measure the interfacial tension of a smectic liquid crystal (LC) in freely suspended film geometry in aqueous environment. The method is based upon the evaluation of the deformation of smectic bubbles by the buoyancy of a trapped air volume. The advantages over classical suspended smectic droplet experiments in water are the considerably shorter equilibration times, and most important, the much larger density differences between the fluids. The latter allow a much more accurate force determination. Bulk elastic force contributions can be practically neglected in the thin smectic films. Values for a smectic C mixture of two disubstituted phenylpyrimidines are reported.

Diagnosis-related deterioration of lung function after extracorporeal membrane oxygenation

The aim of the study was to assess lung function longitudinally after neonatal extracorporeal membrane oxygenation (ECMO), and to identify any effects of diagnosis and perinatal characteristics. 121 neonatal ECMO-treated children (70 with meconium aspiration syndrome, 20 congenital diaphragmatic hernia and 31 with other diagnoses) performed a total of 191 lung function measurements at 5, 8 and/or 12 yrs. We assessed dynamic and static lung volumes, reversibility of airway obstruction and diffusion capacity. Mean SDS forced expiratory volume in 1 s (FEV(1)) at 5 yrs before and after bronchodilation (-0.51 and 0.07) was significantly higher than at 8 (-0.79 and -0.4; p<0.04) and 12 yrs (-1.10 and -0.52; p<0.003). Mean SDS for all spirometric parameters before and after bronchodilation were significantly lower in the congenital diaphragmatic hernia group compared with the other diagnostic groups (all p ≤ 0.025). A significant volume of trapped air was observed in 86% patients with congenital diaphragmatic hernia, 50% with meconium aspiration syndrome and 58% with other diagnoses. After bronchodilation, mean SDS FEV(1) and forced vital capacity were negatively influenced by duration of ventilation (both p<0.001) and duration of ECMO (p=0.003 and p=0.02, respectively). Long-term pulmonary sequelae after neonatal ECMO-treatment mainly occur in congenital diaphragmatic hernia patients and tend to deteriorate over time.

Determining Atmospheric Pressure with a Eudiometer and Glycerol

We consider a volume of air trapped over a glycerol column in a eudiometer. We demonstrate that there is an approximately linear relationship between the volume of trapped air and the height of the glycerol column. Simply by moving the eudiometer up and down, we cause the glycerol-column height and trapped-air volume to vary. The plot of volume versus height has a slope that depends on atmospheric pressure. We show how to determine atmospheric pressure from the plot of trapped-air volume versus glycerol-column height. This exercise allows students to use a familiar instrument in an unfamiliar way, while improving their understanding of pressure measurements and Boyle’s law.

Experimental verification of numerical predictions for the optimum plunger speed in the slow phase of a high-pressure die casting machine

An experimental study of the optimum maximum plunger speed in the slow phase of a high-pressure die casting machine with horizontal cold chamber is presented. A special apparatus that uses a photoelectric sensor to determine the instant at which the working fluid reaches the runner was developed and installed in the injection chamber. The measured volumes of air remaining in the chamber at this instant for various maximum plunger speeds were compared with those predicted by a three-dimensional numerical model based on a finite element formulation and the volume of fluid method for treating the free surface. Very good agreement was found between experimental and numerical results, except for maximum plunger speeds higher than the optimal, for which very complex fluid flow phenomena (that would require a more detailed numerical analysis of the air entrapment mechanisms) tend to be produced. The optimum maximum plunger speed at which the measured volume of trapped air is minimum was found to be very close to that predicted numerically.

A CHRONIC PNEUMOTHORAX AND FITNESS TO FLY

According to Boyle’s law, as the pressure falls, the volume of gas rises in an inversely proportional manner. This means that during an aircraft flight, the volume of trapped air in gas filled body chambers will increase. As a consequence, it is fairly well established that individuals with an untreated pneumothorax should not participate in commercial flying due to the risk of it enlarging and the possible development of tension. However, whether this also applies to individuals who have a long-standing, clinically stable pneumothorax is uncertain. The following article describes two adult patients each with a chronic pneumothorax who asked whether they would be fit to fly in an aircraft. We outline their histories and subsequent evaluation which consisted of clinical assessment, computed tomographic imaging, a hypoxic challenge test and exposure to a hypoxic hypobaric environment in a decompression chamber.

Tiotropium bromide. A review of its use as maintenance therapy in patients with COPD.

Tiotropium bromide. A review of its use as maintenance therapy in patients with COPD.