Continuous positive airway pressure causes lung injury in a model of sepsis.

Continuous positive airway pressure, aimed at preventing pulmonary atelectasis, has been used for decades to reduce lung injury in critically ill patients. In neonatal practice, it is increasingly used worldwide as a primary form of respiratory support due to its low cost and because it reduces the need for endotracheal intubation and conventional mechanical ventilation. We studied the anesthetized in vivo rat and determined the optimal circuit design for delivery of continuous positive airway pressure. We investigated the effects of continuous positive airway pressure following lipopolysaccharide administration in the anesthetized rat. Whereas neither continuous positive airway pressure nor lipopolysaccharide alone caused lung injury, continuous positive airway pressure applied following intravenous lipopolysaccharide resulted in increased microvascular permeability, elevated cytokine protein and mRNA production, and impaired static compliance. A dose-response relationship was demonstrated whereby higher levels of continuous positive airway pressure (up to 6 cmH(2)O) caused greater lung injury. Lung injury was attenuated by pretreatment with dexamethasone. These data demonstrate that despite optimal circuit design, continuous positive airway pressure causes significant lung injury (proportional to the airway pressure) in the setting of circulating lipopolysaccharide. Although we would currently avoid direct extrapolation of these findings to clinical practice, we believe that in the context of increasing clinical use, these data are grounds for concern and warrant further investigation.

Effects of nasal continuous airway pressure on pulmonary and systemic output in preterm infants

Objective: Respiratory assistance with nasal continuous positive airway pressure (n-CPAP) is an effective treatment in premature newborns presenting respiratory distress. The aim of the study was to depict cardiac function, systemic (Qs) and pulmonary output (Qp) by echocardiography in stable premature infants requiring prolonged n-CPAP. Our hypothesis was that n-CPAP could reduce pulmonary blood flow. Patients and methods: All premature infants < 32 weeks gestation, > 7 days-old, requiring n-CPAP without severe respiratory compromise nor need for additional oxygen were prospectively included. Every patient had a first echocardiography while on n-CPAP. N-CPAP was then discontinued for two hours and a second echocardiography was performed. Results: 17 premature infants were included. Mean gestational age was 28 ± 2 weeks and mean weight 1.1 ± 0.3 kg. Following retrieval of n-CPAP we observed an increase in Qp of 53 ml/kg/min (95% CI 19-87 ml/kg/min), but no significant change in Qs. Consecutively a significant increase in Qp/Qs ratio of 16% was found (95% CI 7-29%). Conclusions: Nasal continuous positive airway pressure has hemodynamic effects in preterm infants in stable pulmonary and cardiac conditions. It reduces pulmonary output without interference with systemic output.

Altered high-energy phosphate metabolism predicts contractile dysfunction and subsequent ventricular remodeling in pressure-overload hypertrophy mice.

To study the role of early energetic abnormalities in the subsequent development of heart failure, we performed serial in vivo combined magnetic resonance imaging (MRI) and (31)P magnetic resonance spectroscopy (MRS) studies in mice that underwent pressure-overload following transverse aorta constriction (TAC). After 3 wk of TAC, a significant increase in left ventricular (LV) mass (74 +/- 4 vs. 140 +/- 26 mg, control vs. TAC, respectively; P < 0.000005), size [end-diastolic volume (EDV): 48 +/- 3 vs. 61 +/- 8 microl; P < 0.005], and contractile dysfunction [ejection fraction (EF): 62 +/- 4 vs. 38 +/- 10%; P < 0.000005] was observed, as well as depressed cardiac energetics (PCr/ATP: 2.0 +/- 0.1 vs. 1.3 +/- 0.4, P < 0.0005) measured by combined MRI/MRS. After an additional 3 wk, LV mass (140 +/- 26 vs. 167 +/- 36 mg; P < 0.01) and cavity size (EDV: 61 +/- 8 vs. 76 +/- 8 microl; P < 0.001) increased further, but there was no additional decline in PCr/ATP or EF. Cardiac PCr/ATP correlated inversely with end-systolic volume and directly with EF at 6 wk but not at 3 wk, suggesting a role of sustained energetic abnormalities in evolving chamber dysfunction and remodeling. Indeed, reduced cardiac PCr/ATP observed at 3 wk strongly correlated with changes in EDV that developed over the ensuing 3 wk. These data suggest that abnormal energetics due to pressure overload predict subsequent LV remodeling and dysfunction.

Washing and Dewatering of Different Starches in Pressure Filters

The main objective of this thesis was togenerate better filtration technologies for effective production of pure starchproducts, and thereby the optimisation of filtration sequences using created models, as well as the synthesis of the theories of different filtration stages, which were suitable for starches. At first, the structure and the characteristics of the different starch grades are introduced and each starch grade is shown to have special characteristics. These are taken as the basis of the understanding of the differences in the behaviour of the different native starch grades and their modifications in pressure filtration. Next, the pressure filtration process is divided into stages, which are filtration, cake washing, compression dewatering and displacement dewatering. Each stage is considered individually in their own chapters. The order of the different suitable combinations of the process stages are studied, as well as the proper durations and pressures of the stages. The principles of the theory of each stageare reviewed, the methods for monitoring the progress of each stage are presented, and finally, the modelling of them is introduced. The experimental results obtained from the different stages of starch filtration tests are given and the suitability of the theories and models to the starch filtration are shown. Finally, the theories and the models are gathered together and shown, that the analysis of the whole starch pressure filtration process can be performed with the software developed.

Isentropic Exergy and Pressure of the Shock Wave Caused by the Explosion of a Pressure Vessel

An accidental burst of a pressure vessel is an uncontrollable and explosion-like batch process. In this study it is called an explosion. The destructive effectof a pressure vessel explosion is relative to the amount of energy released in it. However, in the field of pressure vessel safety, a mutual understanding concerning the definition of explosion energy has not yet been achieved. In this study the definition of isentropic exergy is presented. Isentropic exergy is the greatest possible destructive energy which can be obtained from a pressure vessel explosion when its state changes in an isentropic way from the initial to the final state. Finally, after the change process, the gas has similar pressure and flow velocity as the environment. Isentropic exergy differs from common exergy inthat the process is assumed to be isentropic and the final gas temperature usually differs from the ambient temperature. The explosion process is so fast that there is no time for the significant heat exchange needed for the common exergy.Therefore an explosion is better characterized by isentropic exergy. Isentropicexergy is a characteristic of a pressure vessel and it is simple to calculate. Isentropic exergy can be defined also for any thermodynamic system, such as the shock wave system developing around an exploding pressure vessel. At the beginning of the explosion process the shock wave system has the same isentropic exergyas the pressure vessel. When the system expands to the environment, its isentropic exergy decreases because of the increase of entropy in the shock wave. The shock wave system contains the pressure vessel gas and a growing amount of ambient gas. The destructive effect of the shock wave on the ambient structures decreases when its distance from the starting point increases. This arises firstly from the fact that the shock wave system is distributed to a larger space. Secondly, the increase of entropy in the shock waves reduces the amount of isentropic exergy. Equations concerning the change of isentropic exergy in shock waves are derived. By means of isentropic exergy and the known flow theories, equations illustrating the pressure of the shock wave as a function of distance are derived. Amethod is proposed as an application of the equations. The method is applicablefor all shapes of pressure vessels in general use, such as spheres, cylinders and tubes. The results of this method are compared to measurements made by various researchers and to accident reports on pressure vessel explosions. The test measurements are found to be analogous with the proposed method and the findings in the accident reports are not controversial to it.

The global carbon budget:a conflicting claims problem

Despite global environmental governance has traditionally couched global warming in terms of annual CO2 emissions (a flow), global mean temperature is actually determined by cumulative CO2 emissions in the atmosphere (a stock). Thanks to advances of scientific community, nowadays it is possible to quantify the \global carbon budget", that is, the amount of available cumulative CO2 emissions before crossing the 2oC threshold (Meinshausen et al., 2009). The current approach proposes to analyze the allocation of such global carbon budget among countries as a classical conflicting claims problem (O'Neill, 1982). Based on some appealing principles, it is proposed an efficient and sustainable allocation of the available carbon budget from 2000 to 2050 taking into account different environmental risk scenarios. Keywords: Carbon budget, Conflicting claims problem, Distribution, Climate change. JEL classification: C79, D71, D74, H41, H87, Q50, Q54, Q58.

Predictive Factors for Intraocular Pressure Reduction after Phacoemulsification in Swiss Patients.

Background: Phacoemulsification is known to induce postoperative intraocular pressure (IOP) reduction, the degree of which varies according to glaucoma subtype and race. The authors set out to investigate the effect of cataract surgery on IOP, in a Swiss Caucasian population, and identify ocular predictive factors. Patients and Methods: 234 consecutive cases of 188 patients undergoing phacoemulsification between January 2011 and December 2012 were retrospectively reviewed and data collected. Exclusion criteria included acute angle closure, malignant glaucoma and pre-existing or subsequent glaucoma surgery. Pre- and post-operative visual acuity, IOP, gonioscopic findings, glaucoma medications, and laser treatments were recorded for eligible eyes. All eyes received the same postoperative regimen. Using multivariate analysis the predictive power of preoperative IOP, iridocorneal angle width, axial length on IOP reduction following phacoemulsification at months 3, 6 and 12 postoperatively were assessed. Eyes with narrow angles were compared against those with open angles. Results: 172 eyes of 121 patients met the inclusion criteria; mean age was 70.3 years (SD ± 10.7 years), with 77 males. Preoperatively median IOP was 16 mmHg (range 9-32 mmHg), mean number of glaucoma medications was 1.2 (SD ± 1.1), median visual acuity was 0.28 LogMAR (range 0-2.3LogMar). At 3 months post-operatively mean IOP decreased to 14 mmHg (p < 0.01) and remained statistically significantly reduced until 12 months, mean number of glaucoma medications was reduced to 1.0 and mean Snellen visual acuity increased to 0.8. Multivariate analysis revealed that pre-operative IOP and iridocorneal angle width (at 3 months) were significant predictive indicators of IOP reduction. At 12 months, IOP reduction was similar between open and narrow angle groups and total IOP reduction was no longer statistically significant. No intraoperative complications were recorded. Conclusions: Intraocular pressure reduction following phacoemulsification was greatest during the very early post-operative period, particularly in narrow angle patients. By one year, angle size was no longer predictive of IOP lowering, however pre-operative IOP and number of anti-glaucoma medications remained correlated with total IOP reduction.

Short-term effects of particulate matters on pulse pressure in two general population studies.

OBJECTIVES: To explore the association of short-term exposure to particulate matter with aerodynamic diameters less than 10 μm (PM10) with pulse pressure, SBP, and DBP taking outdoor temperature into account in two large population-based studies in Switzerland. METHODS: We used data from the Bus Santé study including 5605 adults in Geneva and the CoLaus study including 6183 adults in Lausanne. PM10 and meteorological data were measured from fixed monitoring stations. We analyzed the association of short-term exposure to PM10 (on the day of examination visit and up to 7 days before) with pulse pressure, SBP, and DBP by linear regression, controlling for potential confounders and effect modifiers. RESULTS: Average PM10 levels were 22.4 μg/m in Geneva and 31.7 μg/m in Lausanne. In adjusted models, for each 10 μg/m increase in 7-day PM10 average, pulse pressure and SBP increased by 0.583 (95% confidence interval, 0.296-0.870) mmHg and 0.490 (0.056-0.925) mmHg in Geneva, and 0.183 (0.017-0.348) mmHg and 0.036 (0.042-0.561) mmHg in Lausanne, respectively. Stronger associations of pulse pressure and SBP with PM10 were observed when outdoor temperature was above 5°C. CONCLUSION: Positive associations of pulse pressure and SBP with short-term exposure to PM10 were found and replicated in the Swiss adult population. Our results suggest that even low levels of air pollution may substantially impact cardiovascular risk in the general population.

A prospective observational study comparing a non-operator dependent automatic PWV analyser to pulse pressure, in assessing arterial stiffness in hemodialysis.

BACKGROUND: Chronic kidney disease (CKD) accelerates vascular stiffening related to age. Arterial stiffness may be evaluated measuring the carotid-femoral pulse wave velocity (PWV) or more simply, as recommended by KDOQI, monitoring pulse pressure (PP). Both correlate to survival and incidence of cardiovascular disease. PWV can also be estimated on the brachial artery using a Mobil-O-Graph; a non-operator dependent automatic device. The aim was to analyse whether, in a dialysis population, PWV obtained by Mobil-O-Graph (MogPWV) is more sensitive for vascular aging than PP. METHODS: A cohort of 143 patients from 4 dialysis units has been followed measuring MogPWV and PP every 3 to 6 months and compared to a control group with the same risk factors but an eGFR > 30 ml/min. RESULTS: MogPWV contrarily to PP did discriminate the dialysis population from the control group. The mean difference translated in age between the two populations was 8.4 years. The increase in MogPWV, as a function of age, was more rapid in the dialysis group. 13.3% of the dialysis patients but only 3.0% of the control group were outliers for MogPWV. The mortality rate (16 out of 143) was similar in outliers and inliers (7.4 and 8.0%/year). Stratifying patients according to MogPWV, a significant difference in survival was seen. A high parathormone (PTH) and to be dialysed for a hypertensive nephropathy were associated to a higher baseline MogPWV. CONCLUSIONS: Assessing PWV on the brachial artery using a Mobil-O-Graph is a valid and simple alternative, which, in the dialysis population, is more sensitive for vascular aging than PP. As demonstrated in previous studies PWV correlates to mortality. Among specific CKD risk factors only PTH is associated with a higher baseline PWV. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02327962.