The relationship between the degree of pulmonary inflation and the pulmonary vascular resistance was studied in an open-chested dog preparation. It was possible to control the state of inflation and the blood flow to the lung under study. Vascular resistance could then be observed under controlled conditions. In most cases the resistance at complete collapse was very slightly higher than at moderate levels of inflation. In a few instances collapse was associated with a more marked elevation of resistance. Higher levels of inflation resulted in elevation of vascular resistance. At high levels of pulmonary blood flow and pulmonary arterial pressure, the flow resistance curve is lower than at low levels of blood flow. The resistance values obtained during deflation of the lung were consistently different at equal transpulmonary pressures from those obtained during inflation. The possible reasons for this hysteresis are discussed. Evidence is presented that the increased resistance at high levels of lung inflation is due to the effect of transpulmonary pressure on the vessels surrounding the alveoli. Submitted on January 11, 1960

This approach informs decision makers about efficiency of interventions, conforms to the mandate and is consistent with basic economic principles. Empirical testing of its feasibility and usefulness is required.

Objectives: A mechanism to increase the influence of Health Technology Assessments (HTAs) on hospital policy decisions was developed.Methods: We describe the process and results of an experiment in which a local in-hospital HTA unit was created to provide sound evidence on technology acquisition issues, and to formulate locally appropriate policy recommendations. The Unit consists of a small technical staff that accesses and synthesizes the evidence incorporating local health and economic data, and a Policy Committee that develops policy recommendations based on this evidence. It represents administration, health-care professionals, patients, and representatives of the clinical disciplines affected by each issue. The level of success of the Unit was independently evaluated.Results: To date, 16 reports have been completed, each within 2–4 months. Five recommended unrestricted use, seven recommended rejection, and four recommended very limited use of the technology in question. All have been incorporated into hospital policy. Budget impact is estimated at approximately $3 million of savings per year.Conclusions: This local in-house HTA agency has had a major impact on the adoption of new technology. Probable reasons for success are (i) relevance (selection of topics by administration with on-site production of HTAs allowing them to incorporate local data and reflect local needs), (ii) timeliness, and (iii) formulation of policy reflecting community values by a local representative committee. Because over one third of all health-care costs are incurred in the hospital, diffusion of this model could have a significant effect on the quantity and quality of health-care spending.

Estimates of the risks associated with the use of radiologic contrast agents frequently are based on a subjective review of some of the numerous articles that have been published on the subject. We have chosen instead to synthesize the existing evidence in an objective, quantitative way by statistically combining the data from individual studies through meta-analysis. Although meta-analysis is subject to whatever biases may exist in the underlying data, and may inappropriately pool data from studies with significant differences, the estimates draw proportionately from each original study and, in addition, gain considerable precision owing to the increased amounts of data considered. Using this technique, we analyzed the data from all available original reports appearing since 1980. Crude rates derived from all reports were used to estimate risks with high-osmolality media. Weighted rate differences based on comparative studies only were used in the estimation of the reductions in risk obtainable with low-osmolality media. The risk of death with high-osmolality media was 0.9 per 100,000 uses (95% confidence interval, 0.3-2.6 per 100,000). The difference in risk produced by using lowosmolality media was 0 (95% confidence interval,-1.1 to 1.1 per 100,000). The risk of severe reactions associated with high-osmolality media was 157 per 100,000 uses (95% confidence interval, 144-172 per 100,000). The reduction in risk that can be obtained by the use of low-osmolality media was estimated to be 126 per 100,000 (95% confidence interval, 1 10-142 per 100,000). This meta-analysis shows that the risk of death is very low with either type of contrast material and that there is no difference between them. Severe nonfatal reactions with high-osmolality media, although more frequent, are still rare; approximately 80% of them can be prevented by using low-osmolality media.

Methodology for evaluation of impact of health technology assessments (HTAs) is outlined and its use illustrated by applying it to 21 HTAs produced by CETS. Impact on policies and technology diffusion was identified in documents, through interviews, questionnaires, and use of data banks. There was evidence that all but three reports influenced policy and that cost-minimization studies caused savings of between $16 million and $27 million annually. Precise estimates of impact will seldom be possible, but systematic documentation of effects is feasible.