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Pressure Support (pressure + support)
Selected AbstractsProbing cosmology and galaxy cluster structure with the Sunyaev,Zel'dovich decrement versus X-ray temperature scaling relationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009Cien Shang ABSTRACT Scaling relations among galaxy cluster observables, which will become available in large future samples of galaxy clusters, could be used to constrain not only cluster structure, but also cosmology. We study the utility of this approach, employing a physically motivated parametric model to describe cluster structure and applying it to the expected relation between the Sunyaev,Zel'dovich decrement (S,) and the emission-weighted X-ray temperature (Tew). The slope and normalization of the entropy profile, the concentration of the dark matter potential, the pressure at the virial radius and the level of non-thermal pressure support as well as the mass and redshift dependence of these quantities are described by free parameters. With a suitable choice of fiducial parameter values, the cluster model satisfies several existing observational constraints. We employ a Fisher matrix approach to estimate the joint errors on cosmological and cluster structure parameters from a measurement of S, versus Tew in a future survey. We find that different cosmological parameters affect the scaling relation differently: predominantly through the baryon fraction (,m and ,b), the virial overdensity (w0 and wa for low- z clusters) and the angular diameter distance (w0 and wa for high- z clusters; ,DE and h). We find that the cosmology constraints from the scaling relation are comparable to those expected from the number counts (dN/dz) of the same clusters. The scaling-relation approach is relatively insensitive to selection effects and it offers a valuable consistency check; combining the information from the scaling relation and dN/dz is also useful to break parameter degeneracies and help disentangle cluster physics from cosmology. Our work suggests that scaling relations should be a useful component in extracting cosmological information from large future cluster surveys. [source] On the morphologies, gas fractions, and star formation rates of small galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007Tobias Kaufmann ABSTRACT We use a series of N -body/smoothed particle hydrodynamics simulations and analytic arguments to show that the presence of an effective temperature floor in the interstellar medium at TF, 104 K naturally explains the tendency for low-mass galaxies to be more spheroidal, more gas rich, and less efficient in converting baryons into stars than larger galaxies. The trend arises because gas pressure support becomes important compared to angular momentum support in small dark matter haloes. We suggest that dwarf galaxies with rotational velocities , 40 km s,1 do not originate as thin discs, but rather are born as thick, puffy systems. If accreted on to larger haloes, tenuous dwarfs of this kind will be more susceptible to gas loss or tidal transformation than scaled-down versions of larger spirals. For a constant temperature floor, pressure support becomes less important in large haloes, and this produces a tendency for massive isolated galaxies to have thinner discs and more efficient star formation than their less-massive counterparts, as observed. [source] Ventilatory strategies for the extremely premature infantPEDIATRIC ANESTHESIA, Issue 5 2008ANNE GREENOUGH Summary Bronchopulmonary dysplasia (BPD), which has long-term adverse outcomes, is common following extremely premature birth. BPD has a multifactorial etiology, including a high level or prolonged use of mechanical ventilation. Numerous research studies, therefore, have attempted to identify ventilatory techniques which reduce the likelihood of baro/volutrauma and hence BPD; these have been critically examined in this review, particularly with regard to their relevance to the extremely prematurely born infant. This has highlighted that few randomized studies of ventilatory strategies have concentrated exclusively on those high-risk infants. Overall, in prematurely born infants, advantages have been suggested by the results of studies examining pressure support, proportional assist and volume-targeted ventilation. In addition, High-Frequency Oscillatory Ventilation (HFOV) may reduce the deterioration seen in lung function of prematurely born infants over the first year after birth. In conclusion, more randomized studies are required which concentrate exclusively on the extremely prematurely born population who are at highest risk of BPD. It is essential in such studies that long-term follow-up assessment is inbuilt so that the benefits/adverse effects can be appropriately identified. [source] Recurrent pneumothoraces associated with nocturnal noninvasive ventilation in a patient with muscular dystrophyPEDIATRIC PULMONOLOGY, Issue 1 2002Lee R. Choo-Kang MD Abstract Although a common complication of mechanical ventilation in acute respiratory failure, spontaneous pneumothorax has been rarely reported among patients on chronic, intermittent, noninvasive positive pressure support. We report the first case of recurrent pneumothoraces associated with nocturnal bilevel positive airway pressure ventilation via a nasal mask. A 26-year old man with chronic respiratory failure secondary to an unclassified neuromuscular condition suffered four separate episodes of spontaneous pneumothorax over a 12-month period. Two episodes occurred while he was asleep on bilevel positive airway pressure support. He was found to have numerous subpleural blebs, and we propose a mechanism for their development. Following open pleurodesis and blebectomy, the patient has not had another pneumothorax. Given the increasing utilization of chronic nocturnal bilevel positive airway pressure ventilation, we suggest that healthcare providers and patients be made aware of this potentially life-threatening complication. Pediatr Pulmonol. 2002; 34:73,78. © 2002 Wiley-Liss, Inc. [source] Effect of intra-operative pressure support vs pressure controlled ventilation on oxygenation and lung function in moderately obese adults*ANAESTHESIA, Issue 2 2010M. Zoremba Summary Obesity impairs peri-operative lung function. To evaluate the impact of pressure support ventilation vs pressure controlled ventilation in moderately obese adults upon early postoperative lung function, we randomly assigned 68 moderately obese patients (body mass index 25,35 kg.m,2) undergoing minor surgery to receive intra-operative ventilation either with pressure support or pressure controlled ventilation. We performed intra-operative blood gas analysis and measured pulse oximetry saturation, spirometry values at pre-operative assessment (baseline) and at 10 min, 30 min, 2 h and 24 h after extubation. The intra-operative oxygenation index (arterial partial pressure of oxygen/fraction of inspired oxygen) in the pressure support ventilation group was significantly improved over time (p < 0.0001). Postoperatively, the pressure support ventilation group also had better lung function and oxygenation values than did the pressure controlled ventilation group (p < 0.005). We conclude that pressure support ventilation better maintains lung function than pressure controlled ventilation in moderately overweight patients scheduled for minor surgery. [source] Blood pressure support in extremely premature infants is affected by different courses of antenatal steroidsACTA PAEDIATRICA, Issue 9 2009GV Nair Abstract Objective:, To examine the effects of partial, single and multiple courses of antenatal corticosteroids (ANS) on the need for blood pressure support in extremely premature infants. Methods:, Extremely premature infants with gestational age of 24 to 28 weeks were included in this study during a 5-year period. The main outcome measure of the study was the amount of blood pressure support during the first 3 days of life. Results:, The study infants (n = 163) were divided into: infants not exposed (ANS; n = 27) and exposed to ANS (ANS; n = 136). Blood pressure support was significantly lower in ANS compared with No ANS (65% vs 96%; p = 0.003) and in single course (SANS; n = 73) and ,2 courses (MANS; n = 34) compared with partial course of ANS (PANS; n = 29) (62%, 56% vs 86%; p = 0.03). The number of infants who received volume support and the amount of volume support were significantly lower in ANS compared with that in No ANS (p < 0.001) and in SANS and MANS compared with that in PANS (p < 0.02). Conclusion:, Exposure to multiple courses of ANS was as beneficial as single course of ANS in decreasing the need for blood pressure support in extremely premature infants. [source] | ||||||||||