Quadrupole mass filter: design and performance for operation in stability zone 3.

The predicted performance of a quadrupole mass filter (QMF) operating in Mathieu stability zone 3 is described in detail using computer simulations. The investigation considers the factors that limit the ultimate maximum resolution (Rmax) and percentage transmission (%Tx), which can be obtained for a given QMF for a particular scan line of operation. The performance curve (i.e., the resolution (R) versus number (N) of radio frequency (rf) cycles experienced by the ions in the mass filter) has been modeled for the upper and lower tip of stability zone 3. The saturation behavior of the performance curve observed in practice for zone 3 is explained. Furthermore, new design equations are presented by examining the intersection of the scan line with stability zone 3. Resolution versus transmission characteristics of stability zones 1 and 3 are compared and the dependence of performance for zones 1 and 3 is related to particular instrument operating parameters.

Issues in the economic evaluation of influenza vaccination by injection of healthy working adults in the US: a review and decision analysis of ten published studies.

The objective was to review recent economic evaluations of influenza vaccination by injection in the US, assess their evidence, and conclude on their collective findings. The literature was searched for economic evaluations of influenza vaccination injection in healthy working adults in the US published since 1995. Ten evaluations described in nine papers were identified. These were synopsized and their results evaluated, the basic structure of all evaluations was ascertained, and sensitivity of outcomes to changes in parameter values were explored using a decision model. Areas to improve economic evaluations were noted. Eight of nine evaluations with credible economic outcomes were favourable to vaccination, representing a statistically significant result compared with a proportion of 50% that would be expected if vaccination and no vaccination were economically equivalent. Evaluations shared a basic structure, but differed considerably with respect to cost components, assumptions, methods, and parameter estimates. Sensitivity analysis indicated that changes in parameter values within the feasible range, individually or simultaneously, could reverse economic outcomes. Given stated misgivings, the methods of estimating influenza reduction ascribed to vaccination must be researched to confirm that they produce accurate and reliable estimates. Research is also needed to improve estimates of the costs per case of influenza illness and the costs of vaccination. Based on their assumptions, the reviewed papers collectively appear to support the economic benefits of influenza vaccination of healthy adults. Yet the underlying assumptions, methods and parameter estimates themselves warrant further research to confirm they are accurate, reliable and appropriate to economic evaluation purposes.

A quadrupole mass spectrometer for resolution of low mass isotopes.

The qualitative and quantitative identification of low mass isotopes in the mass range 1-6 u poses certain difficulties when attempting to achieve the required resolution with an instrument suitable for deployment within a process environment. Certain adjacent species present in the process sample (HT and D(2)) require a resolution greater than 930 to achieve an accurate measurement. We demonstrate here through simulation techniques that this level of performance required is unachievable using commercially available instruments. Using previously reported simulation techniques, this article demonstrates how the required performance for resolving the low mass isotopes can be achieved by a quadrupole mass spectrometer (QMS), which incorporates a quadrupole mass filter (QMF) constructed from hyperbolic electrodes and operated in zone 3 of the Mathieu stability diagram.

An economic assessment of inhaled formoterol dry powder versus ipratropium bromide pressurized metered dose inhaler in the treatment of chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is debilitating and costly to manage. A recent clinical trial concluded that formoterol, a long-acting beta(2)-adrenoceptor agonist, was more clinically effective than inpratropium bromide in the management of COPD. OBJECTIVE: The aim of this study was to perform an economic assessment of the management of COPD with formeterol versus ipratropium bromide. METHODS: Assessment were based on the results of a previously published 12-week, multicenter, double-masked, randomized, parallel-group, placebo-controlled clinical trial comparing inhaled formoterol dry powder 12 and 24 microg BID with ipratropium bromide 40 microg QID pressurized metered dose inhaler and with placebo in 780 COPD patients. Treatment costs for study drugs and rescue medications were estimated from resource utilization and average wholesale prices. Costs were assessed with respect to forced expiratory lung volume in 1 second (FEV(1)) and patient-reported quality of life (QOL) as assessed via the St. George's Respiratory Questionnaire. Cost-effectiveness ratios were calculated for each treatment arm and incremental cost-effectiveness ratios (ICERs) were calculated for each treatment relative to the next best alternative. Economic efficiency frontiers were identified. Sensitivity analysis was conducted. RESULTS: Cost analysis with respect to FEV(1) revealed an economic efficiency frontier formed by placebo, ipratropium bromide 40 microg, and formoterol 12 microg at their respective FEV(1) levels, with cost-effectiveness ratios of $30.18, $53.50, and $142.04, respectively, per FEV(1). The ICER for ipratropium over placebo was $273.03; for formoterol 12 microg over ipratropium, $1611.32. Cost analysis with respect to QOL showed an economic efficiency frontier formed by placebo and formoterol 12 microg at their respective QOL outcomes, with cost-effectiveness ratios of $25.96 and $32.56, respectively, per QOL score change. The cost-effectiveness ratio for ipratropium was $69.40,which was not on the QOL economic efficiency frontier. The ICER for formoterol 12 microg over placebo was $34.51 per QOL score point. CONCLUSIONS: Formoterol 12 microg provided greater QOL outcome than ipratropium bromide at an additional cost of $554.28 per year. Further research would be necessary to assess whether the differences in outcomes, particularly QOL, observed in the short term with formoterol would lead to favorable long-term health and economic outcomes.

Antihypertensive treatment with and without benazepril in patients with chronic renal insufficiency: a US economic evaluation.

OBJECTIVE: To conduct an economic analysis in the US of antihypertensive treatment with and without benazepril in patients with chronic renal insufficiency. DESIGN: A four-state Markov model, using clinical data obtained from a 3-year randomised clinical trial [the Angiotensin-Converting-Enzyme Inhibition in Progressive Renal Insufficiency (AIPRI) study] plus its extension study (median 3.6 years), and cost data obtained from published US sources. The period of analysis was 7 years following randomisation. PERSPECTIVE: Healthcare payer. SETTING: Clinical data were obtained from multiple medical centres in three European countries as described in the published studies. Key economic data were obtained from the US Healthcare Financing Administration's End Stage Renal Disease programme. PATIENTS AND INTERVENTIONS: In the clinical studies on which this economic analysis was based, patients with chronic renal insufficiency of various aetiologies were randomised to antihypertensive therapy with or without concomitant benazepril. MAIN OUTCOME MEASURES AND RESULTS: Over 7 years of analysis, patients randomised to antihypertensive treatment with concomitant benazepril therapy incurred on average USD12991 (1999 values) lower medical costs than patients prescribed antihypertensive treatment without benazepril, and obtained an additional 0.091 quality-adjusted life years (QALYs). Costs and QALYs were greater for the benazepril arm than the placebo arm for all years of analysis after the first. Rank order stability of results favouring the benazepril therapy arm was found in sensitivity analyses of changes in key model parameters. Additional economic and health benefits favouring patients receiving benazepril would be seen if underlying model rates of dialysis and transplantation were increased, as may be appropriate to reflect treatment practice differences in the US relative to European countries. CONCLUSIONS: Benazepril therapy as a component of antihypertensive treatment of persons with chronic renal insufficiency initially costs money, but investment costs are recouped quickly and return on investment continues to grow. The impact of end-stage renal disease on patient health and healthcare costs is great. Thus, the quality-adjusted survival benefits and overall cost savings seen in benazepril recipients over a prolonged period (2 to 7 years) indicate that the strategy of prescribing benazepril to reduce progression of renal disease in patients with renal insufficiency is both clinically and economically beneficial compared with current antihypertensive regimens without ACE inhibition.