Medicare has a legislative mandate for quality assurance, but the effectiveness of its population-based quality improvement programs has been difficult to establish.
To improve the quality of care ...for Medicare patients with acute myocardial infarction.
Quality improvement project with baseline measurement, feedback, remeasurement, and comparison samples.
All acute care hospitals in the United States.
Preintervention and postintervention samples included all Medicare patients in Alabama, Connecticut, Iowa, and Wisconsin discharged with principal diagnoses of acute myocardial infarctions during 2 periods, June 1992 through December 1992 and August 1995 through November 1995. Indicator comparisons were made with a random sample of Medicare patients in the rest of the nation discharged with acute myocardial infarctions from August 1995 through November 1995. Mortality comparisons involved all Medicare patients nationwide with inpatient claims for acute myocardial infarctions during 2 periods, June 1992 through May 1993 and August 1995 through July 1996.
Data feedback by peer review organizations.
Quality indicators derived from clinical practice guidelines, length of stay, and mortality.
Performance on all quality indicators improved significantly in the 4 pilot states. Administration of aspirin during hospitalization in patients without contraindications improved from 84% to 90% (P< .001), and prescription of beta-blockers at discharge improved from 47% to 68% (P < .001). Mortality at 30 days decreased from 18.9% to 17.1% (P = .005) and at 1 year from 32.3% to 29.6% (P < .001). These improvements in quality occurred during a period when median length of stay decreased from 8 days to 6 days. Performance on all quality indicators except reperfusion was better in the pilot states than in the rest of the nation in 1995, and the differences were statistically significant for aspirin use at discharge (P < .001), beta-blocker use (P < .001), and smoking cessation counseling (P = .02). Postinfarction mortality was not significantly different between the pilot states and the rest of the nation during the baseline period, although it was slightly but significantly better in the pilot states during the follow-up period (absolute mortality difference at 1 year, 0.9%; P = .004).
The quality of care for Medicare patients with acute myocardial infarction has improved in the Cooperative Cardiovascular Project pilot states. Performance on the defined quality indicators appeared to be better in the pilot states than in the rest of the nation in 1995 and was associated with reduced mortality.
We present semianalytic dynamical models for giant molecular clouds evolving under the influence of H II regions launched by newborn star clusters. In contrast to previous work, we neither assume ...that clouds are in virial or energetic equilibrium, nor do we ignore the effects of star formation feedback. The clouds, which we treat as spherical, can expand and contract homologously. Photoionization drives mass ejection; the recoil of cloud material both stirs turbulent motions and leads to an effective confining pressure. The balance between these effects and the decay of turbulent motions through isothermal shocks determines clouds' dynamical and energetic evolution. We find that for realistic values of the rates of turbulent dissipation, photoevaporation, and energy injection by H II regions, the massive clouds where most molecular gas in the Galaxy resides live for a few crossing times, in good agreement with recent observational estimates that large clouds in Local Group galaxies survive roughly 20-30 Myr. During this time clouds remain close to equilibrium, with virial parameters of 1-3 and column densities near 10 super(22) H atoms cm super(-2), also in agreement with observed cloud properties. Over their lives they convert 5%-10% of their mass into stars, after which point most clouds are destroyed when a large H II region unbinds them. In contrast, small clouds like those found in the solar neighborhood only survive 61 crossing time before being destroyed.
Bondi-Hoyle Accretion in a Turbulent Medium Krumholz, Mark R; McKee, Christopher F; Klein, Richard I
The Astrophysical journal,
02/2006, Letnik:
638, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Bondi-Hoyle formula gives the approximate accretion rate onto a point particle accreting from a uniform medium. However, in many situations accretion onto point particles occurs from media that ...are turbulent rather than uniform. In this paper we give an approximate solution to the problem of a point particle accreting from an ambient medium of supersonically turbulent gas. Accretion in such media is bimodal, at some points resembling classical Bondi-Hoyle flow, and in other cases being closer to the vorticity-dominated accretion flows recently studied by Krumholz, McKee, & Klein. Based on this observation, we develop a theoretical prediction for the accretion rate and confirm that our predictions are highly consistent with the results of numerical simulations. The distribution of accretion rates is lognormal, and the mean accretion rate in supersonically turbulent gas can be substantially enhanced above the value that would be predicted by a naive application of the Bondi-Hoyle formula. However, it can also be suppressed by the vorticity, just as Krumholz, McKee, & Klein found for non-supersonic vorticity-dominated flows. Magnetic fields, which we have not included in these models, may further inhibit accretion. Our results have significant implications for a number of astrophysical problems, ranging from star formation to the black holes in galactic centers. In particular, there are likely to be significant errors in results that assume that accretion from turbulent media occurs at the unmodified Bondi-Hoyle rate or that are based on simulations that do not resolve the Bondi-Hoyle radius of accreting objects.
We present a method for simulating the evolution of H II regions driven by point sources of ionizing radiation in magnetohydrodynamic media, implemented in the three-dimensional Athena MHD code. We ...compare simulations using our algorithm to analytic solutions and show that the method passes rigorous tests of accuracy and convergence. The tests reveal several conditions that an ionizing radiation hydrodynamic code must satisfy to reproduce analytic solutions. As a demonstration of our new method, we present the first three-dimensional, global simulation of an H II region expanding into a magnetized gas. The simulation shows that magnetic fields suppress sweeping up of gas perpendicular to magnetic field lines, leading to small density contrasts and extremely weak shocks at the leading edge of the H II region's expanding shell.
This study explores gender differences in symptom presentation associated with coronary heart disease (CHD). In this prospective study, nurse data collectors directly observed 550 patients as they ...presented to the Emergency Department (ED) of Yale-New Haven Hospital. The final sample included 217 patients (41% women) diagnosed with CHD (acute coronary ischemia or myocardial infarction). Chest pain was the most frequently reported symptom in women (70%) and men (71%). Unadjusted analyses revealed that women were more likely than men to present with midback pain (odds ratio OR 9.61, 95% confidence interval CI 2.10 to 44.11, p = 0.001), nausea and/or vomiting (OR 2.29, 95% CI 1.19 to 4.42, p = 0.012), dyspnea (OR 1.82, 95% CI 1.05 to 3.16, p = 0.032), palpitations (OR 3.42, 95% CI 1.02 to 11.47, p = 0.036), and indigestion (OR 2.13, 95% CI 1.03 to 4.44, p = 0.040). After adjustment for age and diabetes, women were more likely to present with nausea and/or vomiting (OR 2.43, 95% CI 1.23 to 4.79, p = 0.011) and indigestion (OR 2.13, 95% CI 1.10 to 4.53, p = 0.048). Women (30%) and men (29%) were equally likely to present without chest pain, and dyspnea was the most common non–chest pain symptom. In the subgroup of patients without chest pain, unadjusted analyses revealed that women were more likely to report nausea and/or vomiting compared with men (OR 4.40, 95% CI 1.30 to 14.84, p = 0.013). Although we found some significant gender differences in non–chest pain symptoms, we conclude that there were more similarities than differences in symptoms in women and men presenting to the ED with symptoms suggestive of CHD who were later diagnosed with CHD.
Bondi Accretion in the Presence of Vorticity Krumholz, Mark R; McKee, Christopher F; Klein, Richard I
The Astrophysical journal,
01/2005, Letnik:
618, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The classical Bondi-Hoyle formula gives the accretion rate onto a point particle of a gas with a uniform density and velocity. However, the Bondi-Hoyle problem considers only gas with no net ...vorticity, while in a real astrophysical situation accreting gas invariably has at least a small amount of vorticity. We therefore consider the related case of accretion of gas with constant vorticity, for the cases of both small and large vorticity. We confirm the findings of earlier two-dimensional simulations that even a small amount of vorticity can substantially change both the accretion rate and the morphology of the gas flow lines. We show that in three dimensions the resulting flow field is nonaxisymmetric and time-dependent. The reduction in accretion rate is due to an accumulation of circulation near the accreting particle. Using a combination of simulations and analytic treatment, we provide an approximate formula for the accretion rate of gas onto a point particle as a function of the vorticity of the surrounding gas.
We analyze the mixed-frame equations of radiation hydrodynamics under the approximations of flux-limited diffusion and a thermal radiation field and derive the minimal set of evolution equations that ...includes all terms that are of leading order in any regime of nonrelativistic radiation hydrodynamics. Our equations are accurate to first order in v/e in the static diffusion regime. In contrast, we show that previous lower order derivations of these equations omit leading terms in at least some regimes. In comparison to comoving-frame formulations of radiation hydrodynamics, our equations have the advantage that they manifestly conserve total energy, making them very well suited to numerical simulations, particularly with adaptive meshes. For systems in the static diffusion regime, our analysis also suggests an algorithm that is both simpler and faster than earlier comoving-frame methods. We implement this algorithm in the Orion adaptive mesh refinement code and show that it performs well in a range of test problems.
Background Recently, acute kidney injury defined by small changes in serum creatinine levels was associated with worse short-term outcomes; however, the precision and variability of this association ...was not fully explored. Study Design Systematic review and meta-analysis. Setting & Participants Hospitalized patients. Selection Criteria for Studies MEDLINE and EMBASE databases were searched for observational cohort studies and randomized controlled trials published from 1990 through February 2007 that provided information for small changes in serum creatinine levels. Predictor Small acute changes in serum creatinine levels by absolute and percentage of changes in serum creatinine levels (lower threshold for increase in serum creatinine <0.5 mg/dL or <25%). Outcome Short-term mortality (≤30 days). Results Compared with controls, patients with a 10% to 24% increase in creatinine levels had a relative risk (RR) of death of 1.8 (95% confidence interval CI, 1.3 to 2.5). By comparison, subjects with a 25% to 49% acute change in creatinine levels had an RR of death of 3.0 (95% CI, 1.6 to 5.8), and those with the largest change (≥50%) had the greatest RR of death (RR, 6.9; 95% CI, 2.0 to 24.5). Results were similar when absolute changes in creatinine levels were considered and when pooled estimates of adjusted RR were used. Limitations Individual patient data were unavailable; thus, only group-level data were pooled for meta-analysis. Results showed a significant degree of statistical heterogeneity that was only partially ameliorated by separating studies into subsets based on clinical setting. Conclusions Short-term mortality and acute decreases in renal function are associated through a graded relationship such that even mild changes in serum creatinine levels portend worse outcome in a variety of clinical settings and patient-types.
Low-risk limits recommended for alcohol consumption vary substantially across different national guidelines. To define thresholds associated with lowest risk for all-cause mortality and ...cardiovascular disease, we studied individual-participant data from 599 912 current drinkers without previous cardiovascular disease.
We did a combined analysis of individual-participant data from three large-scale data sources in 19 high-income countries (the Emerging Risk Factors Collaboration, EPIC-CVD, and the UK Biobank). We characterised dose–response associations and calculated hazard ratios (HRs) per 100 g per week of alcohol (12·5 units per week) across 83 prospective studies, adjusting at least for study or centre, age, sex, smoking, and diabetes. To be eligible for the analysis, participants had to have information recorded about their alcohol consumption amount and status (ie, non-drinker vs current drinker), plus age, sex, history of diabetes and smoking status, at least 1 year of follow-up after baseline, and no baseline history of cardiovascular disease. The main analyses focused on current drinkers, whose baseline alcohol consumption was categorised into eight predefined groups according to the amount in grams consumed per week. We assessed alcohol consumption in relation to all-cause mortality, total cardiovascular disease, and several cardiovascular disease subtypes. We corrected HRs for estimated long-term variability in alcohol consumption using 152 640 serial alcohol assessments obtained some years apart (median interval 5·6 years 5th–95th percentile 1·04–13·5) from 71 011 participants from 37 studies.
In the 599 912 current drinkers included in the analysis, we recorded 40 310 deaths and 39 018 incident cardiovascular disease events during 5·4 million person-years of follow-up. For all-cause mortality, we recorded a positive and curvilinear association with the level of alcohol consumption, with the minimum mortality risk around or below 100 g per week. Alcohol consumption was roughly linearly associated with a higher risk of stroke (HR per 100 g per week higher consumption 1·14, 95% CI, 1·10–1·17), coronary disease excluding myocardial infarction (1·06, 1·00–1·11), heart failure (1·09, 1·03–1·15), fatal hypertensive disease (1·24, 1·15–1·33); and fatal aortic aneurysm (1·15, 1·03–1·28). By contrast, increased alcohol consumption was log-linearly associated with a lower risk of myocardial infarction (HR 0·94, 0·91–0·97). In comparison to those who reported drinking >0–≤100 g per week, those who reported drinking >100–≤200 g per week, >200–≤350 g per week, or >350 g per week had lower life expectancy at age 40 years of approximately 6 months, 1–2 years, or 4–5 years, respectively.
In current drinkers of alcohol in high-income countries, the threshold for lowest risk of all-cause mortality was about 100 g/week. For cardiovascular disease subtypes other than myocardial infarction, there were no clear risk thresholds below which lower alcohol consumption stopped being associated with lower disease risk. These data support limits for alcohol consumption that are lower than those recommended in most current guidelines.
UK Medical Research Council, British Heart Foundation, National Institute for Health Research, European Union Framework 7, and European Research Council.
There are two dominant models of how stars form. Under gravitational collapse, star-forming molecular clumps, of typically hundreds to thousands of solar masses (M ), fragment into gaseous cores that ...subsequently collapse to make individual stars or small multiple systems. In contrast, competitive accretion theory suggests that at birth all stars are much smaller than the typical stellar mass (∼0.5M ), and that final stellar masses are determined by the subsequent accretion of unbound gas from the clump. Competitive accretion models interpret brown dwarfs and free-floating planets as protostars ejected from star-forming clumps before they have accreted much mass; key predictions of this model are that such objects should lack disks, have high velocity dispersions, form more frequently in denser clumps, and that the mean stellar mass should vary within the Galaxy. Here we derive the rate of competitive accretion as a function of the star-forming environment, based partly on simulation, and determine in what types of environments competitive accretion can occur. We show that no observed star-forming region can undergo significant competitive accretion, and that the simulations that show competitive accretion do so because the assumed properties differ from those determined by observation. Our result shows that stars form by gravitational collapse, and explains why observations have failed to confirm predictions of the competitive accretion model.
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