High Suction Pressure Research Articles

Study on localised wind pressure development in gable roof buildings having different roof pitches with experiments, RANS and LES simulation models

In this study, the influence of different roof pitches on the mean pressure distributions around isolated buildings subject to different wind directions were investigated with wind tunnel tests, 3D steady Reynolds-averaged Navier-Stokes (RANS) simulation and large eddy simulation (LES). Wind tunnel experiments were conducted to obtain mean pressure distributions around buildings having three commonly used roof pitches, namely, 1:5, 2:5 and 3:5. The critical high suction areas created by conical vortices were identified, and the influence of roof pitch on these critical areas with high localised pressures was investigated under various wind directions. In addition, computational fluid dynamics (CFD) analysis was performed, and the performance of RANS and LES were evaluated and compared with the results measured from the wind tunnel tests by considering both the accuracy of results and computational cost. The assessment on RANS and LES was used to determine the best guidelines for the flow problems involved in this study.Results from the RANS show good agreement with the experimental results on pressure distribution when the building is subject to perpendicular wind directions. However, a significant improvement was found using LES over RANS in the prediction of near-building flow field and localised pressure under oblique wind directions but with an increased computational cost by a factor of more than 80. Furthermore, the high suction pressures are observed to be more critical on buildings with a lower roof pitch under both perpendicular and oblique wind directions. This indicates that a low roof pitch should be applied with caution especially in windstorm-prone areas.

Rotor wake interactions with an obstacle on the ground

ABSTRACTAn investigation of the flow around an obstacle positioned within the wake of a rotor is described. A flow visualisation survey was performed using a smoke wand and particle image velocimetry, and surface pressure measurements on the obstacle were taken. The flow patterns were strongly dependent upon the rotor height above the ground and obstacle, and the relative position of the obstacle and rotor axis. High positive and suction pressures were measured on the obstacle surfaces, and these were unsteady in response to the passage of the vortex driven rotor wake over the surfaces. Integrated surface forces are of the order of the rotor thrust, and unsteady pressure information shows local unsteady loading of the same order as the mean loading. Rotor blade-tip vortex trajectories are responsible for the generation of these forces.

07.05: Fatigue life assessment of cold‐formed steel roof battens

ABSTRACTMetal roofs of low‐rise buildings are exposed to highly fluctuating and prolonged suction wind uplift pressures during cyclones. The high suction pressures on roofs lead to premature, low cycle fatigue failures of roof members. Steel roof batten made of thin, high strength cold‐formed steel (CFS) is one of the vulnerable roof members that fails prematurely during cyclones. Pull‐through failure in the vicinity of batten to rafter connection is one of its common failure modes. A preliminary study on this topic revealed that the fatigue pull‐through capacity of a commonly used industrial roof batten is 45% of its static pull‐through capacity. Therefore, in order to assess the fatigue capacity and performance of all available CFS roof battens, a series of constant amplitude cyclic tests was conducted on thin‐walled steel roof battens. Critical parameters which influence the pull‐through failure, such as the steel batten grade, thickness and screw fastener diameter, were considered in the test series. S‐N curves were developed for each combination of the selected critical parameters, and the respective fatigue limits were obtained. Test results led to a simple modification to the recently developed static pull‐through capacity equations in order to include the effects of fatigue. They also improved the understanding of the fatigue behaviour of roof battens. In addition, a series of multi‐level cyclic tests was included in this study to investigate the suitability of the currently available Low‐High‐Low (LHL) cyclic test method. This paper presents the details of this study, and the results.

Inorganic characteristics of cake layer in A/O MBR for anaerobically digested leachate from municipal solid waste incineration plant with MAP pretreatment

Inorganic characteristics of cake layer in an anoxic/oxic membrane bioreactor (A/O MBR) for anaerobically digested leachate from a municipal solid waste incineration plant with MAP (magnesium ammonium phosphate precipitation) pretreatment was reported. During 90days of operation, the A/O-MBR had formed a thick cake layer, causing severe fouling. BCR (European Community Bureau of Reference) results showed that Fe, Al, Ca, Mg, Si were the dominant inorganic components (especially residual Si and Al) in the cake layer. X-ray diffraction (XRD) analysis further presented that the cake layer contained complex inorganic substances with FeSiO3, CaAl2O3, Ca5(PO4)3OH, CaCO3, CaPO3OH, Mg2(PO4)OH, etc., while Si-Al crystal was the major inorganic component in the cake layer. Additionally, SEM-EDX showed a consistent distribution of inorganics along the front cross-section of the cake layer, indicating that the stable particles and metal ions led to the steady inorganic accumulation onto the membrane surface. However, it was revealed that high suction pressure aggravated the inorganic particle accumulation, especially for the Si-Al crystals, at the end of the cake layer.

Safety and Quality Concern of In-Home Suction Equipment Failure Over Time

Portable suction machines are widely implemented in both clinical and home care settings. Two identical new machines were tested at 3 different levels of pressure settings operating at intermittent intervals. The study uncovered that noncalibrated portable suction triggers an additional 17% higher suction pressure than the actual most efficient and desired pressure setting. There are statistically significant differences between the calibrated suction machine and noncalibrated suction machine at 3 levels of settings: 80, 100, and 120 mm Hg. This emphasizes the need for fundamental safety redesign of clinical calibration measures for clinical engineering.

Experimental Approach to an Efficient and Versatile Water Filtration Vacuum Cleaner

AbstractA simple and robust suction technique is proposed for vacuum cleaning based on an innovative water filtration method for dry, wet, and water swab modes. The technique relies on applying vacuum above the free surface of water to drive the dust‐laden airstream to be released at constant depth below the water surface. Unlike conventional vacuum cleaner types, experimental measurements revealed that a high negative suction pressure availability and low exhaust air temperature with negligible and irrelevant increase in humidity levels were maintained regardless of the filling state. The proposed technique thus ensures more efficient utilization and conservation of energy.

Effects of wing shape, aspect ratio and deviation angle on aerodynamic performance of flapping wings in hover

This numerical study is focused on assessing the effect on the aerodynamic hovering performance of wing shapes defined by the radius of the first moment of the wing area (r1¯) and aspect ratio (AR). In addition, the effect of introducing a deviation angle in the kinematics is examined. The performance of r1¯=0.43, 0.53, and 0.63 wings with AR of 1.5, 2.96, 4.5, and 6.0 is investigated at Reynolds numbers (Re) = 12, 400, and 13 500. The performance trends of the wing shapes have been observed to be independent of Re for both 2-angle and 3-angle kinematics. This is because high suction pressures associated with the leading-edge vortex are predominantly spread in the distal (away from the wing root) and leeward regions (towards the trailing-edge) of high flapping velocities for all the cases. While the deviation angle is detrimental to the production of lift and power economy (PE, defined as the ratio of the mean lift coefficient to the mean aerodynamic power coefficient) at Re = 12 due to strong viscous effects, it improves PE at Re = 400 and 13 500. A high instantaneous angle of attack at the stroke reversal results in high lift peak for 3-angle kinematics but its effect at Re = 400 and 13 500 is attenuated by strong vortical structures on the underside of the wing. Maximum PE is achieved at AR = 2.96, as a low AR wing does not produce enough lift and high AR wings consume more aerodynamic power. Although the lift is maximized using high r1¯ and AR wings, our results show that low r1¯ and high AR wings are best for maximizing PE for a given lift in insects.

Are Prolactin Levels Linked to Suction Pressure?

Suction pressure has been reported to be a key driving force of lactation. An infant's sucking at its mother's breasts is the major stimulus to post-natal prolactin (PRL) secretion, and PRL is the essential hormone for lactation and milk production. It is unknown what role suction pressure has in PRL secretion and milk supply postnatally. To explore the relationship between the suction pressure, PRL level, lactation, and milk supply in breastfeeding mother-infant dyads. Healthy women with normal full-term infants were enrolled (n = 122). Data collection included suction pressure, PRL level, and the mother's perception of both the onset of her lactation and her milk supply at 1 month. Suction pressure was measured with a pressure sensor connected to a tube placed alongside the nipple. The chemiluminescence method was used to quantify maternal serum PRL level both before and after a breastfeed to explore the effect of suckling on PRL increment. The mother's perception of the onset of her lactation was evaluated by the mother's sense of fullness in her breast. The mother's perception of milk supply was evaluated by using the H&H Lactation Scale. Data from 117 participants were included in this analysis. Low suction pressure, a shorter gestational age, a high pre-gestational body mass index (BMI), and high infant birth weight were associated with a smaller than average PRL increment. High suction pressure, longer sucking duration, and a low gestational weight gain were related to a mother's perception of an earlier onset of her lactation. However, low suction pressure, a high frequency of giving formula, a small PRL increment, and the mother's perception of a later onset of her lactation were correlated with her perception of an insufficient milk supply. Suction pressure varied directly with the post-natal PRL increment. Suction pressure was associated with the timing of the mother's perception of her lactation. Strong suction pressure by the infant is likely to enhance the mother's confidence in her lactation. Additionally, sucking duration, frequency of giving formula, maternal BMI, and infant birth weight played a role in early breastfeeding success.

Cirurgia de vitrectomia com equipamento de 27 gauge

In the following video, we will show two pars plana vitrectomies using a 27-gauge system. The equipment used was the constellation® (Alcon, USA). These are the first two surgeries performed using this system in Brazil. They were undertaken at the Parana Eye Hospital (Hospital dos Olhos do Parana) in Curitiba, Parana State, and at the Brazilian Vision Center (Centro Brasileiro de Visao) in Brasilia, Distrito Federal. The 27-gauge system is thinner and more delicate compared with other such systems. It allows making incisions as small as 0.4 mm. Previously, the thinnest system available was the 25gague system, allowing 0.55-mm incisions. Smaller incisions induce less inflammation, do not require suturing, and allow faster recovery. The first case presented is that of a patient with vitreous hemorrhage due to proliferative diabetic retinopathy, an operation which was completed using only the new 27-gauge system. Contrary to what is expected, dense vitreous opacities can be removed with an instrument with a smaller-diameter opening. To do so, we simply follow Poiseuille's law that states that the flow velocity of a fluid in a system is directly related to the pressure exerted for its withdrawal and has an inverse correlation with the viscosity of the material. The new 27-gauge systems exhibit a high suction pressure, reaching up to 600 mmHg. In addition, their cutting speed is up to 7500 cuts per minute, i.e., if we perform the vitrectomy using these systems, we can achieve a flow rate similar to that achieved with devices with larger diameters, such as the 25- or 23gauge systems. It is the cutting speed on the vitreous that allows dense vitreous to be removed quickly. Note that the surgery is in real time and all bleeding is aspirated at a constant rate; this is similar to previously used systems. Although the 27-gauge system is more delicate, it allows performing peripheral vitrectomy without bending the tip of the device. Experienced surgeons will have no difficulty performing this procedure. In addition to the thinner cutter tip, the 27-gauge system comes with all accessories with the same diameter, including the laser that is used at the end of the procedure. In the second case, we show the surgery on a patient with a macular hole. With the high vacuum pressure exerted on the vitreous, the posterior hyaloid membrane is removed easily and safely. Once the posterior hyaloid is removed, the inner limiting membrane is stained with brilliant blue so that it may be removed using suitable forceps. At the end of the surgery, fluid–gas exchange is performed.

Predicting performance of axial pump inducer of LOX booster turbo-pump of staged combustion cycle based rocket engine using CFD

For low cost, high thrust, space missions with high specific impulse and high reliability, inert weight needs to be minimized and thereby increasing the delivered payload. Turbopump feed system for a liquid propellant rocket engine (LPRE) has the highest power to weight ratio. Turbopumps are primarily equipped with an axial flow inducer to achieve the high angular velocity and low suction pressure in combination with increased system reliability. Performance of the turbopump strongly depends on the performance of the inducer. Thus, for designing a LPRE turbopump, demands optimization of the inducer geometry based on the performance of different off-design operating regimes. In this paper, steady-state CFD analysis of the inducer of a liquid oxygen (LOX) axial pump used as a booster pump for an oxygen rich staged combustion cycle rocket engine has been presented using ANSYS® CFX. Attempts have been made to obtain the performance characteristic curves for the LOX pump inducer. The formalism has been used to predict the performance of the inducer for the throttling range varying from 80% to 113% of nominal thrust and for the different rotational velocities from 4500 to 7500 rpm. The results have been analysed to determine the region of cavitation inception for different inlet pressure.

Liquid Velocity and Local Fouling in Coagulation-submerged Microfiltration Module for Drinking Water Treatment

Effects of aeration intensity on local fouling were investigated in submerged membrane modules. Higher liquid velocities were observed at the section with the lower fiber packing density. The liquid velocity is increased with increasing the gas-liquid injection factor. The high shear stress coincided with the high liquid velocity. The shear stress increases with the increasing of gas-liquid injection factor and the liquid velocity improves with the increasing of gas-liquid injection factor. Irreversible fouling resistance (Rir) of the fiber position is significant in a local region of high suction pressure near the suction point of the fiber (position 1). The ratio of Rir/Rm and Rir/Rr of position 1 was highest compared to the position 2 and 3. Irreversible fouling resistances results confirmed the preferential deposition of foulants near the suction part of the fiber where the local suction pressure is the highest and correspondingly, more particles are accumulated to the membrane surface. The effects of local fouling along the fiber length are significant factors to optimize the design of submerged modules.

Moisture Release Behaviour of Orange-Growing Soils Developed from Different Parent Materials in Jhalawar District of Rajasthan

Variation in water retention characteristics has been evaluated in soils developed on Vindhyan scarplands and Malwa plateau from sandstone and shale with band of limestone and basaltic parent materials, respectively. Six typifying pedons from Vindhyan scarplands and eight from Malwa plateau representing dominant landforms have been studied for their physicochemical properties and water retention at various suctions. The higher values of water retention (0.69 and 0.38 m3 m−3) at 0.03 and 1.5 MPa were recorded in soils of basaltic origin (P12), whereas the corresponding values were very low (0.32 and 0.13 m3 m−3) in soils of sandstone and shale with band of limestone (P6 and P5). The variability in water retention at various suctions (0.03, 0.1, 0.3, 0.5, 1.0 and 1.5 MPa) was governed by clay content and associated soil properties. In general, water retention increased down the depth of profile in the pedons, which have increasing pattern of clay content in both the parent materials, at lower and higher suction pressures. The available water content ranged from 0.15 to 0.29 m3 m−3 with mean value of 0.20 m3 m−3 in soils of sandstone and shale with band of limestone, while in basaltic soils it varied from 0.14 to 0.31 m3 m−3 with mean content of 0.20 m3 m−3.

Absence of suction feeding ichthyosaurs and its implications for triassic mesopelagic paleoecology.

Mesozoic marine reptiles and modern marine mammals are often considered ecological analogs, but the extent of their similarity is largely unknown. Particularly important is the presence/absence of deep-diving suction feeders among Mesozoic marine reptiles because this would indicate the establishment of mesopelagic cephalopod and fish communities in the Mesozoic. A recent study suggested that diverse suction feeders, resembling the extant beaked whales, evolved among ichthyosaurs in the Triassic. However, this hypothesis has not been tested quantitatively. We examined four osteological features of jawed vertebrates that are closely linked to the mechanism of suction feeding, namely hyoid corpus ossification/calcification, hyobranchial apparatus robustness, mandibular bluntness, and mandibular pressure concentration index. Measurements were taken from 18 species of Triassic and Early Jurassic ichthyosaurs, including the presumed suction feeders. Statistical comparisons with extant sharks and marine mammals of known diets suggest that ichthyosaurian hyobranchial bones are significantly more slender than in suction-feeding sharks or cetaceans but similar to those of ram-feeding sharks. Most importantly, an ossified hyoid corpus to which hyoid retractor muscles attach is unknown in all but one ichthyosaur, whereas a strong integration of the ossified corpus and cornua of the hyobranchial apparatus has been identified in the literature as an important feature of suction feeders. Also, ichthyosaurian mandibles do not narrow rapidly to allow high suction pressure concentration within the oral cavity, unlike in beaked whales or sperm whales. In conclusion, it is most likely that Triassic and Early Jurassic ichthyosaurs were ‘ram-feeders’, without any beaked-whale-like suction feeder among them. When combined with the inferred inability for dim-light vision in relevant Triassic ichthyosaurs, the fossil record of ichthyosaurs does not suggest the establishment of modern-style mesopelagic animal communities in the Triassic. This new interpretation matches the fossil record of coleoids, which indicates the absence of soft-bodied deepwater species in the Triassic.

Influence of sinter grate suction pressure (flame front speed) on microstructure, productivity and quality of iron ore sinter

From a sinter production point of view, it is important to optimise the sintering process with regard to both sinter quality and production rate. In sintering, airflow rate within the sinter bed decides the production rate and its physical and metallurgical properties. To study the influence of airflow rate (flame front speed) on sinter production and sinter quality, pot grate sintering experiments were conducted at sinter grate suction pressures ranging from 900 to 1700 mm water column over the sinter bed. During sintering, time–temperature data were recorded, and mineralogical studies were carried out. This study reveals that increase in sinter grate suction pressure through the sinter bed from 900 to 1700 mm water column significantly improved the sinter productivity from 34·37 to 48·90 t/m2/day; however, the physical and metallurgical properties of the sinter at higher suction pressure were not optimum with respect to blast furnace requirements. The maximum sinter productivity with desired physical and metallurgical properties was obtained at suction pressure 1300 mm water column. At this pressure, improvement in sinter quality was due to optimum firing temperature and enough retention time available for formation of mineral phases. At an airflow rate 1300 mm water column, sinter productivity was 41·0 t/m2/day, sinter strength (TI) was 73·10%, reduction degradation index was 25·0 and reducibility was 71·50%.

Usefulness of High Suction Pressure for Sufficient Tissue Collection During Endobronchial Ultrasound Guided Transbronchial Needle Aspiration

IntroductionThe optimal suction pressure during endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) remains to be determined. The aim of this study was to compare suction pressures for performance in collecting sufficient tissue specimens from mediastinal and hilar lymph nodes during EBUS-TBNA.MethodsRetrospective analysis of consecutive patients with mediastinal and hilar lymphadenopathy who underwent EBUS-TBNA over a 3-year period. Results from patients who underwent EBUS-TBNA using a dedicated 20-mL VacLoc (Merit Medical Systems, Inc, South Jordan, UT) syringe (conventional method, group C) were compared with results from patients in whom a disposable 30-mL syringe (high pressure group, group H) was used. The yield for sufficient histologic specimen retrieval and amount of tissue obtained were compared between the 2 groups.ResultsOf 178 patients who underwent EBUS-TBNA, 131 had lung cancer confirmed by EBUS-TBNA: 35 in group C and 96 in group H. There were 7 patients in group C and 6 in group H who received final diagnoses by cytology alone. There were 28 in group C and 90 in group H who were diagnosed by both cytology and histology. There was a statistically significant difference between the groups in terms of the rate of sufficient sampling for histological specimens (p = 0.04). The H group revealed a tissue area approximately twice that of the C group (p = 0.003). There were no major procedure-related complications in either group.ConclusionHigher suction pressures with larger syringe volumes during EBUS-TBNA may be useful for safely collecting sufficient tissue specimens.

The fanfolding modification for removing chest tube clogging after cardiac surgery

Karimov et al. [1] emphasize an interesting subject ignored by surgeons in many aspects compared with surgical procedures. However, when not followed seriously, chest tube (CT) clogging can result in catastrophic complications [2, 3]. We congratulate the authors to draw attention to CT drainage, which is as important as ‘operative planning’. Duncan and Erickson [4] state that ‘When the full length of CTs was stripped (135 cm), intrathoracic pressure increased to −400 cmH2O (=294 mmHg) (whereas 5 cm of tubing resulted in a mean pressure of −87 cmH2O (=63.9 mmHg))’. However, it may not be clinically applicable. Because when the internal volume of 135-cm-long CTs with inner diameter of 0.952 cm (3/8 inch) is measured, its volume is determined to be no more than 130 ml. According to Pascal’s Law, if a U-tube is filled with water and subsequently, the air at the top of the one arm is evacuated by a piston, the height difference between two arms represents suction pressure. The same principle can be applied to chest drainage system (CDS). Namely, if the reservoir of the CDS is completely filled with water and 130 ml of air is evacuated from the connector end of CT, the height of water column within the CT is measured about 120 cmH2O, which is much less than 400 cmH2O. Likewise, if a 5-cm-long tube is stripped, the evacuated volume is 4.4 ml, creating a suction pressure of 4.06 cmH2O (=2.9 mmHg) in the thoracic cavity. Briefly, it can be said that such high suction pressures cannot be created by stripping/milking (S/M). Otherwise, the clinical implications of high negative suction pressure created by S/M would have been observed, since the pressure change in the thoracic cavity may not transient as the authors declared in the study [1]. The supporting point is that the CDS uses an under water seal which cannot allow flow through the thoracic cavity after S/M. It was suggested in the systematic Cochrane review that techniques, including stripping, milking and fanfolding, used for removing clots from tubes are not superior to each other [5]. The fanfolding technique involves folding sections of the tube over each other and squeezing [5]. According to our clinical experience, we would like to talk about the ‘Fanfolding modification’. In this technique, the tube is clamped distally before fanfolding, subsequently the fanfolded segment is released suddenly after squeezing and the clamp is removed. The manoeuvre is continued until oscillation is approved, especially in pericardial CT. Cardiac tamponade has never been observed with the manoeuvre at the intensive care duty during our residency course ( 1640 cases in a 6-years period). While avoiding volume changes in the chest, the main effect is the removal of clot and maintaining the oscillation for intact flow to the reservoir. Although the modification is clearly beneficial, the more sophisticated systems described by the co-authors [6] are quite good, and would gain wide acceptance by many surgeons.

Study on the operating performance of cross hot-gas bypass defrosting system for air-to-water screw heat pumps

Large-scale air-to-water screw heat pumps often operate with substantial frost formation on the air side of evaporators in winter, and the frost layer has to be melted away periodically. This paper presents a defrosting method for air-to-water screw heat pumps, i.e. the cross hot-gas bypass defrosting method, which uses two air heat exchangers for hot air from one air heat exchanger to melt the frost and absorb heat from another heat exchanger through the corresponding four-way reversing valve. The principle and process of this method are illustrated. The dynamic characteristics are experimentally investigated on a 359 kW air-to-water screw heat pump. The discharge temperature of the unit is at the normal range and the pressure varies little. A higher suction pressure is needed to achieve low pressure protection. The time period needed for the combination of heating and defrosting processes is short and it is not necessary to shutdown the compressor for defrosting so that a longer heating time period is possible. The inlet & outlet water temperature can be kept at around 30 °C and high heating COP is obtained. The test results show that the units work as expected.

Cylinder Syringe Suction

Subcutaneous hematoma is commonly caused by trauma or surgery. Proper treatment of the condition is needed to avoid severe complications. The present paper introduces a simple technique of hematoma evacuation, called cylinder syringe suction (CSS). Experiments were also performed to determine the detailed mechanism underlying its effectiveness. The CSS procedure was performed as follows. A cylindrical plastic cylinder syringe was used. Either a few stitches were removed or a very small incision was made on the site of the hematoma. The edge of the syringe was compressed to the skin, which was covered by a thin hydrocolloid dressing. Vacuum aspiration was enforced at the site of the wound or incision, and the hematoma was gradually aspirated.For the experiment, house rabbits were used. Hematoma evacuation was performed in 4 different ways, including needle aspiration alone (group 1), needle puncture followed by CSS (group 2), and creation of a small wound (5 mm) followed by needle aspiration (group 3) or CSS (group 4). The amount of evacuated hematoma and the suction pressure created by each of the 4 methods were compared. Group 4 showed the highest suction pressure and the greatest evacuated amount of hematoma. High suction pressure was also obtained in group 1; however, the amount of evacuated hematoma was small as the other 2 groups. The CSS technique becomes effective mainly by creating high suction pressure, and the opening of a small wound enables the viscous coagula to pass through the skin.

The Effect of Pressure and Shear on Autologous Fat Grafting

Fat grafting has become routine in plastic surgery because of low donor-site morbidity, a low complication rate, and fast recovery time. The optimal technique, however, has yet to be defined. Two critical variables are pressure and shear, both defined as force divided by area. In this study, the authors examined the effect of pressure and shear on human fat grafts in a nude mouse model. For negative pressure, tumescent liposuction was performed on fresh panniculectomy specimens. Suction pressure was either -15 inHg or -25 inHg. Lipoaspirate was centrifuged at 1200 g and injected into the flanks of nude mice. For positive pressure, positive pressure was applied to lipoaspirate up to 6 atm for up to 3 minutes and then injected into nude mice. For shear stress, lipoaspirate was centrifuged at 1200 g for 3 minutes and then injected with a fast flow rate (3 to 5 cc/second) or slow flow rate (0.5 to 1 cc/second). After 4 weeks, the fat grafts were analyzed for weight and histology. For negative pressure, there were no differences in weight or histology with high versus low suction pressures. For positive pressure, application of positive pressures up to 6 atm for up to 3 minutes did not create a significant difference in graft weight or histology at 4 weeks. For shear stress, in vivo, a slow injection pressure yielded a 38 percent increase in weight (p < 0.001) compared with fast injection. Histology was similarly affected. Higher aspiration pressures up to -0.83 atm did not affect fat graft viability in vivo. Positive pressure up to 6 atm also did not affect fat graft viability. The degree of shear stress, which is a function of flow rate, did significantly affect fat graft viability. Fat grafts injected slowly with low shear stress significantly outperformed fat injected with high shear stress. These data suggest that shear stress is a more important variable regarding fat graft viability than pressure.

Examining the Use and Outcomes of a New Hospital-Grade Breast Pump in Exclusively Pumping NICU Mothers

To determine whether exclusively pumping mothers of preterm infants could achieve full milk production while using the Ameda Platinum breast pump the first 14 days postpartum. Twenty-six mothers who delivered infants between 26 and 32 weeks' gestation at 2 Intermountain Healthcare hospitals completed the study. Mothers could not take milk-enhancing or milk-reducing substances, feed directly at the breast, have had breast surgery, or use any other breast pump during the study. Nonexperimental, descriptive study. Mothers were instructed to use the Ameda Platinum breast pump exclusively 8 times daily, for 14 days. They recorded milk volumes, suction pressures, cycle speeds, and time spent pumping. A "Performance Questionnaire" was completed at the end of the study with questions about the ease of use, preferred speed and suction settings, and overall performance of the pump. Full milk production was defined as 700 mL/d. Speed and suction settings, as well as average pumping session length, were analyzed in relation to categories of maximum milk volumes expressed. The average maximum daily milk volume for all mothers was 817 mL/d. Sixteen mothers produced milk volumes more than 700 mL/d and 9 of these mothers were able to express more than 1000 mL/d. Those with daily milk production more than 700 mL/d used lower suction pressure settings to stimulate the milk ejection reflex and to empty the breast. These higher-producing mothers also chose ending speeds of 50 to 60 cycles per minute, similar to the nutritive sucking pattern of a healthy newborn. Mothers producing less than 500 mL/d used higher suction pressures, faster ending cycle speeds, and longer pumping times. Suction pressures varied widely among all of the mothers and were influenced by the mothers' nipple or breast sensitivity, which varied from mother to mother and day to day. Mothers reported liking separate controls for speed and suction and used them to achieve maximum comfort and milk volume. The Ameda Platinum breast pump is an effective hospital-grade pump for exclusively pumping mothers to establish full milk production by 14 days postpartum. Separate control of speed and suction allows mothers a wide range of options to achieve greater comfort and multiple milk ejections, both of which contribute to optimal milk expression.