Studies of the human oropharyngeal airspaces using magnetic resonance imaging IV--the oropharyngeal retention effect for four inhalation delivery systems.

Magnetic resonance imaging (MRI) of the oropharyngeal region from 20 adult volunteers using four model inhalation devices (varying mouthpiece diameters, airflow resistances) and tidal breathing was carried out. Statistical analysis (convex hull method) selected 12 scans from 80 data sets representing the extremes of all dimensions in the population. Twelve physical mouth-throat models were made by stereolithography using the exact scan data. The aim was to produce models with varying dimensions to span the adult population, and to investigate if oropharyngeal dimensions affected throat retention for different delivery systems. In an in vitro analysis, the models were used to determine the retention effect of the oropharyngeal airspaces when drug aerosols were administered from four inhalation delivery systems: a pressurised metered dose inhaler (pMDI), two different dry powder inhalers (DPIs A and B), and a nebulizer. The aims of this work were to determine the key parameters governing mouth-throat retention and whether retention was dependent on the delivery system used. Characterizing the throat models by measuring 51 different dimensional variables enabled determination of the most influential variables for dose retention for each inhalation delivery system. Throat model retention was found to be dependent on the delivery system (pMDI approximately DPI(A) > DPI(B) > Neb.). The most influential variable was the total throat model volume. Throat models representing high, median, and low oropharyngeal filtration in healthy adults have been identified.     

Medical technology in the United States. The last decade.

This paper reviews the evolution of U.S. policy toward medical technology in areas such as cost containment, regulation of devices and drugs, and third party reimbursement. In addition the authors chronicle the diffusion of major medical technologies, procedures, and organizational innovations in the United States. Finally, the article provides tentative observations on the effect of recent policy changes and concludes with some recommendations for the future.     

The stability of atracurium in clinical practice

Atracurium has an unusual intrinsic Hofmann elimination which is increased by an alkaline environment and increased temperature. Normally the relaxant is stored at pH 3.3 and kept at a temperature of 4 degrees C. However, it is convenient to have a reasonable quantity available within the operating theatre. This study examined the rate of degradation of atracurium in the operating theatre environment of 20 degrees C. Atracurium within one month of its expiry date was placed in the drawer for anaesthetic drugs in each of three operating theatres. At the end of each month, further drug was added to the stock. At the end of the study, atracurium which had been stored continuously at 4 degrees C, was at 102.9% of nominal strength, having started with 113.5% at manufacture. Atracurium which had been at room temperature for one, two and three months respectively retained 99%, 95% and 92% strength respectively. These results show that even three months' exposure to room temperature does not cause enough deterioration to be clinically significant.     

Continuous parathyroid hormone induces cortical porosity in the rat: effects on bone turnover and mechanical properties.

We examined the time course effects of continuous PTH on cortical bone and mechanical properties. PTH increased cortical bone turnover and induced intracortical porosity with no deleterious effect on bone strength. Withdrawal of PTH increased maximum torque to failure and stiffness with no change in energy absorbed. INTRODUCTION: The skeletal response of cortical bone to parathyroid hormone (PTH) is complex and species dependent. Intermittent administration of PTH to rats increases periosteal and endocortical bone formation but has no known effects on intracortical bone turnover. The effects of continuous PTH on cortical bone are not clearly established. MATERIALS AND METHODS: Eighty-four 6-month-old female Sprague-Dawley rats were divided into three control, six PTH, and two PTH withdrawal (WD) groups. They were subcutaneously implanted with osmotic pumps loaded with vehicle or 40 microg/kg BW/day human PTH(1-34) for 1, 3, 5, 7, 14, and 28 days. After 7 days, PTH was withdrawn from two groups of animals for 7 (7d-PTH/7d-WD) and 21 days (7d-PTH/21d-WD). Histomorphometry was performed on periosteal and endocortical surfaces of the tibial diaphysis in all groups. microCT of tibias and mechanical testing by torsion of femora were performed on 28d-PTH and 7d-PTH/21d-WD animals. RESULTS AND CONCLUSIONS: Continuous PTH increased periosteal and endocortical bone formation, endocortical osteoclast perimeter, and cortical porosity in a time-dependent manner, but did not change the mechanical properties of the femur, possibly because of addition of new bone onto periosteal and endocortical surfaces. Additionally, withdrawal of PTH restored normal cortical porosity and increased maximum torque to failure and stiffness. We conclude that continuous administration of PTH increased cortical porosity in rats without having a detrimental effect on bone mechanical properties.     

Comparison of fibre optic transillumination with clinical and radiographic caries diagnosis

Fibre optic transillumination (FOTI) has been employed during the course of a 3-yr clinical dentifrice trial which initially involved 3003 children. At the initial examination, a subgroup of 813 13-yr-olds, and at the following annual visit, 2247 14-yr-olds, were examined using a 150 W lamp and 0.5 mm diameter probe. Routine clinical and radiographic examinations were performed separately. Compared to the clinical scores for anterior teeth, FOTI detected an additional 64% of interproximal lesions at the first visit while, for the larger number of children at the second visit, the increase in lesion detection level using FOTI was 37%. For the posterior teeth the comparable figure at the second examination was 92%. When FOTI data were compared to radiographic data for more than 52,000 posterior interproximal surfaces, FOTI could only detect 17% of radiographic Grade 2 lesions and 48% Grade 3 lesions. Thus any assumption that FOTI diagnoses may be a substitute for bitewing radiography appears premature.     

Dietary fatty acids, hemostasis, and cardiovascular disease risk

The cause of many myocardial infarctions is occlusive thrombosis, or a blood clot that stops blood flow in a coronary artery. Hemostasis involves a complex system of factors, which normally form and degrade blood clots, that work within a delicate balance. Emerging evidence suggests that some hemostatic factors, including factor VII, fibrinogen, and plasminogen activator inhibitor-1, are associated with increased risk for cardiovascular disease (CVD). Accumulating evidence suggests a relationship between dietary fatty acids and emerging hemostatic CVD risk factors, although much of this evidence is incomplete or conflicting. Dietary supplementation with marine n-3 fatty acids prolongs bleeding time and may decrease risk for thrombosis. Factor VII coagulant activity modestly decreases with reductions in saturated fatty acid (SFA) intake and thereby may contribute to the beneficial effects of low SFA diets. Large triglyceride-rich particles formed during postprandial lipemia can support the assembly and function of coagulation complexes and seem to play a role in the activation of factor VII, and thus may partially explain increased CVD risk associated with increased postprandial triglyceridemia. As our understanding of the role of dietary fatty acids and hemostasis evolves, it is likely that we will be able to make specific dietary recommendations to further decrease CVD risk. At this juncture, however, increasing marine n-3 fatty acids and decreasing certain SFAs are leading strategies to reduce hemostatic CVD risk factors. An array of dietary strategies that target multiple CVD risk factors could have a greater impact on CVD than a single risk factor intervention strategy.