Muscle power is related to tibial bone strength in older women

Summary  We enrolled 65 to 75 year-old community-dwelling women and measured muscle power, strength, physical activity using accelerometry and tibial bone strength using peripheral quantitative computed tomography (pQCT). Muscle power contributed 6.6% of the variance in the bone strength–strain index and 8.9% in the section modulus after accounting for age, height, weight, and physical activity; moderate to vigorous physical activity was related to muscle power in the lower extremity. Introduction  Muscle power is associated with DXA measurements of bone mass, but it is not known whether muscle power is associated with bone strength. There are no reports of investigations that have tested the effect of muscle power on bone compartments using advanced imaging. Methods  We enrolled 74 community-dwelling women aged 65–75 years. We measured muscle power and strength of leg extension using Keiser air-pressure resistance equipment. All participants wore a waist-mounted Actigraph accelerometer to record physical activity. We used peripheral quantitative computed tomography (pQCT) to measure tibial mid-shaft (50% of the site) bone strength (strength–strain index, section modulus). We used Pearson correlations and multi-level linear regression to investigate the associations between muscle and bone. Results  Muscle power contributed 6.6% (p = 0.007) of the variance in the bone strength–strain index and 8.9% (p = 0.001) the variance in the section modulus in older women after accounting for age, height, weight, and physical activity. Moderate to vigorous physical activity was significantly related to muscle power in the lower extremity (r = 0.260; p = 0.041). Conclusion  Muscle power significantly contributed to the variance in estimated bone strength. Whether power training will prove to be a more effective stimulus for bone strength than conventional strength training will require further studies.     

Acute normovolemic hemodilution, intraoperative cell salvage and PulseCO hemodynamic monitoring in a Jehovah's Witness with placenta percreta

A Jehovah’s Witness who had had four previous cesarean deliveries was referred to our institution for management of a complete placenta previa at 34 weeks of gestation. A subsequent ultrasound scan was suggestive of placenta percreta with bladder involvement. After erythropoietin and iron supplementation, cesarean hysterectomy was performed. Using PulseCO technology for continuous hemodynamic monitoring, preoperative acute normovolemic hemodilution and intraoperative cell salvage were used resulting in a successful cesarean hysterectomy with a 5500-mL estimated blood loss. The PulseCO system provides continuous, real-time hemodynamic data by applying pulse power analysis to the arterial pressure waveform. A bolus of oxytocin given after delivery produced profound hypotension, the hemodynamics of which were elucidated with the PulseCO system. To our knowledge, the combined use of acute normovolemic hemodilution, intraoperative cell salvage and PulseCO hemodynamic monitoring for cesarean hysterectomy has not been reported previously. These techniques may be particularly useful in managing patients who refuse blood products and/or in whom the baseline hemoglobin is suboptimal.     

Proper inference from Simon's two-stage designs

Simon's two-stage designs are very popular for phase II clinical trials. A literature review revealed that the inference procedures used with Simon's designs almost always ignore the actual sampling plan used. Reported P-values, point estimates and confidence intervals for the response rate are not usually adjusted for the design's adaptiveness. In addition, we found that the actual sample size for the second stage is often different from that planned. We present here a method for inferences using both the planned and the actual sample sizes. The conventional and the preferred inference procedures usually yield similar P-values and confidence intervals for the response rate. The conventional inference, however, may contradict the result of the corresponding hypothesis testing.     

Robust Bayesian sample size determination in clinical trials

This article deals with determination of a sample size that guarantees the success of a trial. We follow a Bayesian approach and we say an experiment is successful if it yields a large posterior probability that an unknown parameter of interest (an unknown treatment effect or an effects-difference) is greater than a chosen threshold. In this context, a straightforward sample size criterion is to select the minimal number of observations so that the predictive probability of a successful trial is sufficiently large. In the paper we address the most typical criticism to Bayesian methods-their sensitivity to prior assumptions-by proposing a robust version of this sample size criterion. Specifically, instead of a single distribution, we consider a class of plausible priors for the parameter of interest. Robust sample sizes are then selected by looking at the predictive distribution of the lower bound of the posterior probability that the unknown parameter is greater than a chosen threshold. For their flexibility and mathematical tractability, we consider classes of epsilon-contamination priors. As specific applications we consider sample size determination for a Phase III trial.     

The impact of a misspecified random-effects distribution on the estimation and the performance of inferential procedures in generalized linear mixed models

Estimation in generalized linear mixed models (GLMMs) is often based on maximum likelihood theory, assuming that the underlying probability model is correctly specified. However, the validity of this assumption is sometimes difficult to verify. In this paper we study, through simulations, the impact of misspecifying the random-effects distribution on the estimation and hypothesis testing in GLMMs. It is shown that the maximum likelihood estimators are inconsistent in the presence of misspecification. The bias induced in the mean-structure parameters is generally small, as far as the variability of the underlying random-effects distribution is small as well. However, the estimates of this variability are always severely biased. Given that the variance components are the only tool to study the variability of the true distribution, it is difficult to assess whether problems in the estimation of the mean structure occur. The type I error rate and the power of the commonly used inferential procedures are also severely affected. The situation is aggravated if more than one random effect is included in the model. Further, we propose to deal with possible misspecification by way of sensitivity analysis, considering several random-effects distributions. All the results are illustrated using data from a clinical trial in schizophrenia.     

The power to shape decisions? An exploration of young people's power in participation

The participation of children and young people in social care decision-making in England is now widely accepted, supported by statute and enhanced by specific practice guidance. Drawing on data from 24 semistructured interviews with young people, local politicians, managers and front-line workers in three English social services departments, this paper explores the theoretical basis of young people's participation in the local policy process. In particular, a typology devised by Levin is used to explain what types of power each stakeholder group can exercise. Levin describes three types of power: power to do, literally what an individual is actually able to do; power over, the power of a group over another group; and power to achieve, the power to realise one's will. This paper concludes that the mechanisms used to facilitate participation and the culture of the organizations where participation takes place are important factors in the process, and that a clearer understanding of power could be used to help agencies improve their policy-making.     

Perspectives on midwifery power: an exploration of the findings of the inquiry into peripartum hysterectomy at Our Lady of Lourdes Hospital, Drogheda, Ireland

The Lourdes Hospital Inquiry: An inquiry into peripartum hysterectomy at Our Lady of Lourdes Hospital, Drogheda , Ireland, of 2006 recounts in detail the circumstances within which 188 peripartum hysterectomies were carried out at the hospital between 1974 and 1998. The findings of the inquiry have serious ramifications for Irish healthcare delivery and have implications for many professional groups, including midwives. The findings prompt clear questions about the relative position or power of midwives within maternity care. These questions are examined in this article, through the analysis and application of various theoretical perspectives on power. Critical views of power focus on the socio-political nature of oppressive structures within society and seek mechanisms to address these. Stemming from structure versus agency debates, Giddens's structuration theory examines the agency-structure interaction and stresses the centrality of agents' roles in the social reproduction of structures. Postmodernism, particularly drawing on the work of Michel Foucault, focuses on a fluid conception of power while also describing the nature of disciplinary power. It offers midwives a way of viewing power as productive and dispersed. Drawing on different aspects of these perspectives on power, helps us to understand midwives' relative positions and power relations and how to enhance these to prevent future tragic outcomes such as those reported in the inquiry report.     

Working with communities, governments and academic institutions to make pregnancy safer

The major medical causes of maternal death and the effective interventions to prevent maternal death due to these causes are known. Yet, every year, an estimated 529,000 women die during and following pregnancy and childbirth. Most of these deaths occur in developing countries where other non-medical determinants of maternal health influence the accessibility to these interventions. Improvements in maternal health can be achieved through a health systems approach. Care should be provided as a continuum throughout the life cycle and across health facilities through the health system. Communities, professional organizations and academic institutions should work actively with the government to: provide a package of service, based on population health needs, that is close to home; ensure availability of essential medicines and commodities; address financial barriers to receiving care; strengthen the health workforce; and gather and use information to improve maternal health.