Sample size: How many is enough?

Sample size is an element of research design that significantly affects the validity and clinical relevance of the findings identified in research studies. Factors that influence sample size include the effect size, or difference expected between groups or time points, the homogeneity of the study participants, the risk of error that investigators consider acceptable and the rate of participant attrition expected during the study. Appropriate planning in regard to each of these elements optimises the likelihood of finding an important result that is both clinically and statistically meaningful

Health status after traumatic injury

BACKGROUND: This study explored the relationships between health-related quality of life and postacute factors such as patients’ perceived access to information and support, perceptions of illness and ability to provide self-care after traumatic injury. METHODS: Adults (18 years or older) admitted to hospital for ≥24 hours for the acute treatment of trauma in two hospitals in Queensland, Australia, were enrolled in a prospective cohort study. Questionnaires completed at hospital discharge and 3 months and 6 months incorporated the following: demographic data; psychological factors (Revised Illness Perception Questionnaire, Information, Autonomy and Support Scale, and Therapeutic Self-Care Scale); and outcome data (medical short form-36). Data on injury and hospital stay were obtained from health care records and the Queensland Trauma Registry. RESULTS: One hundred ninety-four patients with a median Injury Severity Score 9 (interquartile range, 5–14) were enrolled, with 125 (64%) completing questionnaires at 6 months. More than half the cohort reported symptoms of pain, fatigue, stiff joints, sleep difficulties, and loss of strength. All subscale scores on the short form-36 were below Australian norms 6 months after injury. Predictors of poor physical health included older age, lower extremity injury, and increased perceived consequences of their injuries, whereas predictors of poor mental health included younger age, female gender, and lower perceived control over their environment. CONCLUSIONS: Patients with minor to moderate injury based on anatomic injury scoring systems have ongoing challenges with recovery including problematic symptoms and low quality of life. Interventions aimed toward assisting recovery should not be limited to trauma patients with major injury. LEVEL OF EVIDENCE: Prognostic study, level III

Effects of interaction on an adiabatic quantum electron pump

We study the effects of inter-electron interactions on the charge pumped through an adiabatic quantum electron pump. The pumping is through a system of barriers, whose heights are deformed adiabatically. (Weak) interaction effects are introduced through a renormalisation group flow of the scattering matrices and the pumped charge is shown to {\it always} approach a quantised value at low temperatures or long length scales. The maximum value of the pumped charge is set by the number of barriers and is given by $Q_{\rm max} = n_b -1$. The correlation between the transmission and the charge pumped is studied by seeing how much of the transmission is enclosed by the pumping contour. The (integer) value of the pumped charge at low temperatures is determined by the number of transmission maxima enclosed by the pumping contour. The dissipation at finite temperatures leading to the non-quantised values of the pumped charge scales as a power law with the temperature ($Q-Q_{\rm int} \propto T^{2\alpha}$), or with the system size ($Q-Q_{\rm int} \propto L_s^{-2\alpha}$), where $\alpha$ is a measure of the interactions and vanishes at $T=0 ~(L_s=\infty)$. For a double barrier system, our result agrees with the quantisation of pumped charge seen in Luttinger liquids.Comment: 9 pages, 9 figures, better quality figures available on request from author

Demonstration of 3-port grating phase relations

We experimentally demonstrate the phase relations of 3-port gratings by investigating 3-port coupled Fabry-Perot cavities. Two different gratings which have the same 1st order diffraction efficiency but differ substantially in their 2nd order diffraction efficiency have been designed and manufactured. Using the gratings as couplers to Fabry-Perot cavities we could validate the results of an earlier theoretical description of the phases at a three port grating

Diffractive Optics for Gravitational Wave Detectors

All-reflective interferometry based on nano-structured diffraction gratings offers new possibilities for gravitational wave detection. We investigate an all-reflective Fabry-Perot interferometer concept in 2nd order Littrow mount. The input-output relations for such a resonator are derived treating the grating coupler by means of a scattering matrix formalism. A low loss dielectric reflection grating has been designed and manufactured to test the properties of such a grating cavity

In-hospital cardiac arrests: Effect of amended Australian Resuscitation Council 2006 guidelines

Objective: To evaluate cardiac arrest outcomes following the introduction of the Australian Resuscitation Council (ARC) 2006 amended guidelines for basic and advanced life support. Methods: A retrospective study of all consecutive cardiac arrests during a 3-year phase pre-implementation (2004–06) and a 3-year phase post-implementation (2007–09) of the ARC 2006 guidelines was conducted at a tertiary referral hospital in Brisbane, Australia. Results: Over the 6-year study phase 690 cardiac arrests were reported. Resuscitation was attempted in 248 patients pre-implementation and 271 patients post-implementation of the ARC 2006 guidelines. After adjusting for significant prognostic factors we found no significant change in return of spontaneous circulation (ROSC) (odds ratio 1.21, 95% confidence interval 0.80–1.85, P = 0.37) or survival to discharge (odds ratio 1.49, 95% confidence interval 0.94–2.37, P = 0.09) after the implementation of the ARC 2006 guidelines. Factors that remained significant in the final model for both outcomes included having an initial shockable rhythm, a shorter length of time from collapse to arrival of cardiac arrest team, location of the patient in a critical-care area, shorter length of resuscitation and a day-time arrest (0700–2259 hours). In addition the arrest being witnessed was significant for ROSC and younger age was significant for survival to discharge. Conclusions: There are multiple factors that influence clinical outcomes following an in-hospital cardiac arrest and further research to refine these significant variables will assist in the future management of cardiac arrests. What is known about this topic?: The evaluation of outcomes from in-hospital cardiac arrests focuses on immediate survival expressed as ROSC and survival to hospital discharge. These clinical outcomes have not improved substantially over the last two decades. What does this paper add?: This paper identifies the factors that are related to ROSC and survival to discharge following the implementation of the ARC 2006 guidelines, which included a refocus on providing quality cardiopulmonary resuscitation with minimal interruptions. What are the implications for practitioners?: Given that multiple factors can influence clinical outcomes following an in-hospital cardiac arrest, focusing on maximising a range of factors surrounding cardiopulmonary resuscitation is essential to improve outcomes

Maternal Feeding Goals and Restaurant Menu Choices for Young Children

Background: Childhood obesity remains a major public health issue. One recent effort to improve the obesogenic environment is mandating that restaurants provide calorie and other nutritional content on menus. Little is known about whether maternal feeding for young children is influenced by calorie disclosure on menus. This study examined (1) whether maternal feeding goals associate with mothers' food selections for their young children and (2) whether mothers change entrée and side selections for their children when calories/fat grams are listed on menus. Methods: One-hundred seventy mothers of children ages of 3?6 years participated in an online survey. Most participants identified as white (76.5%), with a mean BMI of 25.68 (standard deviation=5.94). Mothers were presented two menus (one with and one without calorie/fat information). Results: The goal of feeding for the child's familiarity with the food was significantly associated with mothers' selection of original side dish and entrées, with greater endorsement of this goal associated with choosing high-calorie/-fat sides and entrées. Feeding for natural content was associated with mothers' selection of original entrée, with greater endorsement of this goal associated with choosing low-calorie/-fat entrées. Significantly fewer mothers chose a higher-calorie entrée when there was menu labeling. Conclusions: Maternal feeding goals are associated with mothers' selection of entrée and side dishes on restaurant menus. Results from this study suggest that menu labeling of calories and fat grams may influence entrée choices by mothers. Targeting mothers' feeding goals and labeling restaurant menus may improve the diets of young children.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140340/1/chi.2015.0014.pd

Protocol-directed sedation versus non-protocol-directed sedation to reduce duration of mechanical ventilation in mechanically ventilated intensive care patients

Background The sedation needs of critically ill patients have been recognized as a core component of critical care and meeting these is vital to assist recovery and ensure humane treatment. There is growing evidence to suggest that sedation requirements are not always optimally managed. Sub-optimal sedation incorporates both under- and over-sedation and has been linked to both short-term (e.g. length of stay) and long-term (e.g. psychological recovery) outcomes. Various strategies have been proposed to improve sedation management and address aspects of assessment as well as delivery of sedation. Objectives To assess the effects of protocol-directed sedation management on the duration of mechanical ventilation and other relevant patient outcomes in mechanically ventilated intensive care unit (ICU) patients. We looked at various outcomes and examined the role of bias in order to examine the level of evidence for this intervention. Search methods We searched the Cochrane Central Register of Controlled trials (CENTRAL) (2013; Issue 11), MEDLINE (OvidSP) (1990 to November 2013), EMBASE (OvidSP) (1990 to November 2013), CINAHL (BIREME host) (1990 to November 2013), Database of Abstracts of Reviews of Effects (DARE) (1990 to November 2013), LILACS (1990 to November 2013), Current Controlled Trials and US National Institutes of Health Clinical Research Studies (1990 to November 2013), and reference lists of articles. We re-ran the search in October 2014. We will deal with any studies of interest when we update the review. Selection criteria We included randomized controlled trials (RCTs) conducted in adult ICUs comparing management with and without protocol-directed sedation. Data collection and analysis Two authors screened the titles and abstracts and then the full-text reports identified from our electronic search. We assessed seven domains of potential risk of bias for the included studies. We examined the clinical, methodological and statistical heterogeneity and used the random-effects model for meta-analysis where we considered it appropriate. We calculated the mean difference (MD) for duration of mechanical ventilation and risk ratio (RR) for mortality across studies, with 95% confidence intervals (CI). Main results We identified two eligible studies with 633 participants. Both included studies compared the use of protocol-directed sedation, specifically protocols delivered by nurses, with usual care. We rated the risk of selection bias due to random sequence generation low for one study and unclear for one study. The risk of selection bias related to allocation concealment was low for both studies. We also assessed detection and attrition bias as low for both studies while we considered performance bias high due to the inability to blind participants and clinicians in both studies. Risk due to other sources of bias, such as potential for contamination between groups and reporting bias, was considered unclear. There was no clear evidence of differences in duration of mechanical ventilation (MD -5.74 hours, 95% CI -62.01 to 50.53, low quality evidence), ICU length of stay (MD -0.62 days, 95% CI -2.97 to 1.73) and hospital length of stay (MD -3.78 days, 95% CI -8.54 to 0.97) between people being managed with protocol-directed sedation versus usual care. Similarly, there was no clear evidence of difference in hospital mortality between the two groups (RR 0.96, 95% CI 0.71 to 1.31, low quality evidence). ICU mortality was only reported in one study preventing pooling of data. There was no clear evidence of difference in the incidence of tracheostomy (RR 0.77, 95% CI 0.31 to 1.89). The studies reported few adverse event outcomes; one study reported self extubation while the other study reported re-intubation; given this difference in outcomes, pooling of data was not possible. There was significant heterogeneity between studies for duration of mechanical ventilation (I2 = 86%, P value = 0.008), ICU length of stay (I2 = 82%, P value = 0.02) and incidence of tracheostomy (I2 = 76%, P value = 0.04), with one study finding a reduction in duration of mechanical ventilation and incidence of tracheostomy and the other study finding no difference. Authors' conclusions There is currently insufficient evidence to evaluate the effectiveness of protocol-directed sedation. Results from the two RCTs were conflicting, resulting in the quality of the body of evidence as a whole being assessed as low. Further studies, taking into account contextual and clinician characteristics in different ICU environments, are necessary to inform future practice. Methodological strategies to reduce the risk of bias need to be considered in future studies