Errors in Pressure Gradient Measurement in Prosthetic Aortic Valves Due To Pressure Recovery: Type, Size, and Flow Rate Effects In Vitro

We assessed errors in valvular pressure gradients due to pressure recovery, the variation in aortic pressure with distance from the valve, to explain errors in catheter measurements and simultaneous continuous-wave Doppler/catheter studies. Ten types and three sizes of valves were tested in vitro. Aortic pressure was measured by catheter between 1 and 6 cm from the valve. Pressure recovery was quantified as the slope of the gradient with distance from the annulus. Valve type, size, and flow rate effects were determined by analysis of variance. Relationships between Doppler and maximal catheter gradients were also analyzed statistically. The slope of pressure recovery was significantly higher in smaller valves (P< 0.01), in bioprosthetic rather than mechanical valves (P < 0.001), and at higher flows (P < 0.0001). Doppler I catheter slopes were dependent on valve type and size, with more overestimation by Doppler in mechanical (P < 0.01) and larger valves (P < 0.01). Errors due to catheter positioning are more likely wherever effects of pressure recovery are higher: in bioprosthetic valves, smaller valves, and at higher flow rates. Pressure recovery can explain overestimation by Doppler only if localized gradients closer than 1 cm from the valve exist. Clinicians should be aware of these effects of pressure recovery when making major diagnostic and therapeutic decisions.     

Understanding the recent evolution of the human genome: insights from human-chimpanzee genome comparisons

The sequencing of the chimpanzee genome and the comparison with its human counterpart have begun to reveal the spectrum of genetic changes that has accompanied human evolution. In addition to gross karyotypic rearrangements such as the fusion that formed human chromosome 2 and the human-specific pericentric inversions of chromosomes 1 and 18, there is considerable submicroscopic structural variation involving deletions, duplications, and inversions. Lineage-specific segmental duplications, detected by array comparative genomic hybridization and direct sequence comparison, have made a very significant contribution to this structural divergence, which is at least three-fold greater than that due to nucleotide substitutions. Since structural genomic changes may have given rise to irreversible functional differences between the diverging species, their detailed analysis could help to identify the biological processes that have accompanied speciation. To this end, interspecies comparisons have revealed numerous human-specific gains and losses of genes as well as changes in gene expression. The very considerable structural diversity (polymorphism) evident within both lineages has, however, hampered the analysis of the structural divergence between the human and chimpanzee genomes. The concomitant evaluation of genetic divergence and diversity at the nucleotide level has nevertheless served to identify many genes that have evolved under positive selection and may thus have been involved in the development of human lineage-specific traits. Genes that display signs of weak negative selection have also been identified and could represent candidate loci for complex genomic disorders. Here, we review recent progress in comparing the human and chimpanzee genomes and discuss how the differences detected have improved our understanding of the evolution of the human genome.     

Obesity and health in Europeans aged 50 years and older

BACKGROUND: Obesity is increasing globally across all population groups. Limited data are available on how obesity patterns differ across countries. OBJECTIVE: To document the prevalence of obesity and related health conditions for Europeans aged 50 years and older, and to estimate the association between obesity and health outcomes across 10 European countries. METHODS: Data were obtained from the 2004 Survey of Health, Ageing and Retirement in Europe, a cross-national survey of 22,777 Continental Europeans over the age of 50 years. The health outcomes included self-reported health, disability, doctor-diagnosed chronic health conditions and depression. Multivariate regression analysis was used to predict health outcomes across weight classes (defined by body mass index [BMI] from self-reported weight and height) in the pooled sample and individually in each country. RESULTS: The prevalence of obesity (BMI >or=30) ranged from 12.8% in Sweden to 20.2% in Spain for men and from 12.3% in Switzerland to 25.6% in Spain for women. Adjusting for compositional differences across countries changed little in the observed large heterogeneity in obesity rates throughout Europe. Compared with normal weight individuals, men and women with greater BMI had significantly higher risks for all chronic health conditions examined except heart disease in overweight men. Depression was linked to obesity in women only. Particularly pronounced risks of impaired health and chronic health conditions were found among severely obese people. The effects of obesity on health did not vary significantly across countries. CONCLUSIONS: Cross-country differences in the prevalence of obesity in older Europeans are substantial and exceed socio-demographic differentials in excessive body weight. Obesity is associated with significantly poorer health outcomes among Europeans aged 50 years and over, with effects similar across countries. Large heterogeneity in obesity throughout Europe should be investigated further to identify areas for effective public policy.     

An investigation of two multivariate permutation methods for controlling the false discovery proportion

Identifying genes that are differentially expressed between classes of samples is an important objective of many microarray experiments. Because of the thousands of genes typically considered, there is a tension between identifying as many of the truly differentially expressed genes as possible, but not too many genes that are not really differentially expressed (false discoveries). Controlling the proportion of identified genes that are false discoveries, the false discovery proportion (FDP), is a goal of interest. In this paper, two multivariate permutation methods are investigated for controlling the FDP. One is based on a multivariate permutation testing (MPT) method that probabilistically controls the number of false discoveries, and the other is based on the Significance Analysis of Microarrays (SAM) procedure that provides an estimate of the FDP. Both methods account for the correlations among the genes. We find the ability of the methods to control the proportion of false discoveries varies substantially depending on the implementation characteristics. For example, for both methods one can proceed from the most significant gene to the least significant gene until the estimated FDP is just above the targeted level ('top-down' approach), or from the least significant gene to the most significant gene until the estimated FDP is just below the targeted level ('bottom-up' approach). We find that the top-down MPT-based method probabilistically controls the FDP, whereas our implementation of the top-down SAM-based method does not. Bottom-up MPT-based or SAM-based methods can result in poor control of the FDP.     

The relationship between attendance at birth and maternal mortality rates: an exploration of United Nations' data sets including the ratios of physicians and nurses to population, GNP per capita and female literacy

The relationship between attendance at birth and maternal mortality rates: an exploration of United Nations' data sets including the ratios of physicians and nurses to population, GNP per capita and female literacy. BACKGROUND: This is the third and final paper drawing on data taken from United Nations (UN) data sets. The first paper examined the global distribution of health professionals (as measured by ratios of physicians and nurses to population), and its relationship to gross national product per capita (GNP) (Wharrad & Robinson 1999). The second paper explored the relationships between the global distribution of physicians and nurses, GNP, female literacy and the health outcome indicators of infant and under five mortality rates (IMR and u5MR) (Robinson & Wharrad 2000). In the present paper, the global distribution of health professionals is explored in relation to maternal mortality rates (MMRs). The proportion of births attended by medical and nonmedical staff defined as "attendance at birth by trained personnel" (physicians, nurses, midwives or primary health care workers trained in midwifery skills), is included as an additional independent variable in the regression analyses, together with the ratio of physicians and nurses to population, female literacy and GNP. AIM: To extend our earlier analyses by considering the relationships between the global distribution of health professionals (ratios of physicians and nurses to population, and the proportion of births attended by trained health personnel), GNP, female literacy and MMR. 相似文献   

A comparative study of the financing, provision and quality of care in nursing homes. The approach of four European countries: Belgium, Denmark, Germany and the Netherlands

A comparative study of the financing, provision and quality of care in nursing homes. The approach of four European countries: Belgium, Denmark, Germany and the Netherlands As result of an increase in the numbers of frail elderly people, most European countries are facing problems with the financing and provision of services by nursing homes. At the same time, the expectations of quality of these services continue to rise. The main question investigated in this study was that of how countries approach the problems of financing and service provision by nursing homes and, at the same time, attempt to increase the quality levels in these institutions. The study was conducted in Belgium, Denmark, Germany and the Netherlands. A study was made of the relevant literature and questionnaires were sent to experts in each country. The four countries are addressing the problems of financing and sufficient service provision by controlling the use of nursing home services. In addition, financial problems are approached by extending co-payments, encouraging cheaper forms of care and putting pressure on nursing homes to operate at lower costs. Problems in the provision of care are addressed by applying more selective admission criteria and offering alternative forms of care outside the nursing home. As a result nursing home beds are used for those with the greatest care-dependency. Nursing home services are adjusted to rising quality expectations by offering a greater range of provision, decreasing the number of residents per room, improving comfort and improving the training of nursing staff. Another way to increase the quality of care is to separate the housing and service functions. Many nursing homes nowadays collaborate intensively with other facilities for the elderly to cope with all these problems and changes. The workload for nursing home staff has increased because of the increasing care-dependency of residents, the demand for higher quality of services and the financial problems.     

Poverty and the extent of child obesity in Canada, Norway and the United States

The goal of this paper is to compare the extent of child obesity in Canada, Norway and the United States. As child poverty is an important correlate of child obesity, we wish to examine the potential role of international differences in child poverty in explaining international differences in the extent of child obesity. We use three representative microdata surveys containing parental reports of child height and weight collected in the mid-1990s in Canada, Norway and the US. We calculate both the prevalence and proportional severity of child obesity for 6-11-year-old children in each country, and represent the 'extent' of obesity diagrammatically. Differences in patterns of child poverty are similarly depicted. Obesity extent is also compared for poor and non-poor children in Canada and the US. Finally, child obesity in the three countries is compared using only non-poor children where we find that the extent of child obesity is much lower in Norway than in Canada or the US. The pattern apparent for obesity is remarkably similar to that found for child poverty. In Canada and especially in the US, we find a much greater extent of obesity for poor than non-poor children. However, when we compare only non-poor children in the three countries, although the magnitude of difference is smaller, it remains clear that Norwegian children are much less likely to be obese. Policy and research directed towards reducing the extent of child obesity in both Canada and the US should pay particular attention to issues of child poverty.     

Statistically comparing EEG/MEG waveforms through successive significant univariate tests: How bad can it be?

When making statistical comparisons, the temporal dimension of the EEG signal introduces problems. Guthrie and Buchwald (1991) proposed a formally correct statistical approach that deals with these problems: comparing waveforms by counting the number of successive significant univariate tests and then contrasting this number to a well‐chosen critical value. However, in the literature, this method is often used inappropriately. Using real EEG data and Monte Carlo simulations, we examined the problems associated with the incorrect use of this approach under circumstances often encountered in the literature. Our results show inflated false‐positive or false‐negative rates depending on parameters of the data, including filtering. Our findings suggest that most applications of this method result in an inappropriate familywise error rate control. Solutions and alternative methods are discussed.     

Pulmonary varix: report of a case with additional anomalies of the vascular pulmonary tree

A 65-year-old woman developed a bloody pleural effusion $\text{2-}\text{1}\text{2}\text{years}$ after the onset of Dressler's syndrome. Since an extensive evaluation failed to reveal a specific etiology, the effusion was presumed to be a manifestation of Dressler's syndrome. Because of the therapeutic implications involved, we are reporting this case to emphasize that pleural effusions may occur as a manifestation of Dressler's Syndrome in the distant post-infarction period.