The psychometric validation of the quality practical experience (QPE) instruments (nurses and student nurse) to evaluate clinical supervision of undergraduate student nurses.

It is important to evaluate stakeholder feedback regarding any change to a clinical supervision model to maintain quality. The Quality Practical Experience (QPE) instruments offer both the nurse on the ward involved with supervising student learning and the student nurse the opportunity to evaluate their satisfaction with the supervision model. This paper reports on the evaluation of the construct validity and the reliability of the QPE instruments measuring nurse and nursing student satisfaction with the clinical supervision model. Methodological design for the reliability and validation of a measuring instrument. The nurse and the student QPE instruments were tested with convenience samples of 488 nurses and 1116 student nurses, respectively. Psychometric tests included internal reliability, test-retest reliability and factor analyses. Exploratory factor analysis for both QPEs supported a three-factor solution; the nurse QPE explained 48% and student nurse QPE 45% of variance. Internal reliability and test-retest reliability were stable over time (nurse QPE ICC = 0.82; student nurse QPE ICC = 0.71). Both QPE instruments were found to be valid and reliable. Feedback from all stakeholders involved with supporting student nurses during clinical placement is important.

Trans-ethnic analysis of metabochip data identifies two new loci associated with BMI.

OBJECTIVE: Body mass index (BMI) is commonly used to assess obesity, which is associated with numerous diseases and negative health outcomes. BMI has been shown to be a heritable, polygenic trait, with close to 100 loci previously identified and replicated in multiple populations. We aim to replicate known BMI loci and identify novel associations in a trans-ethnic study population. SUBJECTS: Using eligible participants from the Population Architecture using Genomics and Epidemiology consortium, we conducted a trans-ethnic meta-analysis of 102 514 African Americans, Hispanics, Asian/Native Hawaiian, Native Americans and European Americans. Participants were genotyped on over 200 000 SNPs on the Illumina Metabochip custom array, or imputed into the 1000 Genomes Project (Phase I). Linear regression of the natural log of BMI, adjusting for age, sex, study site (if applicable), and ancestry principal components, was conducted for each race/ethnicity within each study cohort. Race/ethnicity-specific, and combined meta-analyses used fixed-effects models. RESULTS: We replicated 15 of 21 BMI loci included on the Metabochip, and identified two novel BMI loci at 1q41 (rs2820436) and 2q31.1 (rs10930502) at the Metabochip-wide significance threshold (P<2.5 × 10-7). Bioinformatic functional investigation of SNPs at these loci suggests a possible impact on pathways that regulate metabolism and adipose tissue. CONCLUSION: Conducting studies in genetically diverse populations continues to be a valuable strategy for replicating known loci and uncovering novel BMI associations.

Bacterial expression, correct membrane targeting and functional folding of the HIV-1 membrane protein Vpu using a periplasmic signal peptide.

Viral protein U (Vpu) is a type-III integral membrane protein encoded by Human Immunodeficiency Virus-1 (HIV- 1). It is expressed in infected host cells and plays several roles in viral progeny escape from infected cells, including down-regulation of CD4 receptors. But key structure/function questions remain regarding the mechanisms by which the Vpu protein contributes to HIV-1 pathogenesis. Here we describe expression of Vpu in bacteria, its purification and characterization. We report the successful expression of PelB-Vpu in Escherichia coli using the leader peptide pectate lyase B (PelB) from Erwinia carotovora. The protein was detergent extractable and could be isolated in a very pure form. We demonstrate that the PelB signal peptide successfully targets Vpu to the cell membranes and inserts it as a type I membrane protein. PelB-Vpu was biophysically characterized by circular dichroism and dynamic light scattering experiments and was shown to be an excellent candidate for elucidating structural models.

Generalization and fine mapping of European ancestry-based central adiposity variants in African ancestry populations.

BACKGROUND/OBJECTIVES: Central adiposity measures such as waist circumference (WC) and waist-to-hip ratio (WHR) are associated with cardiometabolic disorders independently of body mass index (BMI) and are gaining clinically utility. Several studies report genetic variants associated with central adiposity, but most utilize only European ancestry populations. Understanding whether the genetic associations discovered among mainly European descendants are shared with African ancestry populations will help elucidate the biological underpinnings of abdominal fat deposition. SUBJECTS/METHODS: To identify the underlying functional genetic determinants of body fat distribution, we conducted an array-wide association meta-analysis among persons of African ancestry across seven studies/consortia participating in the Population Architecture using Genomics and Epidemiology (PAGE) consortium. We used the Metabochip array, designed for fine-mapping cardiovascular-associated loci, to explore novel array-wide associations with WC and WHR among 15 945 African descendants using all and sex-stratified groups. We further interrogated 17 known WHR regions for African ancestry-specific variants. RESULTS: Of the 17 WHR loci, eight single-nucleotide polymorphisms (SNPs) located in four loci were replicated in the sex-combined or sex-stratified meta-analyses. Two of these eight independently associated with WHR after conditioning on the known variant in European descendants (rs12096179 in TBX15-WARS2 and rs2059092 in ADAMTS9). In the fine-mapping assessment, the putative functional region was reduced across all four loci but to varying degrees (average 40% drop in number of putative SNPs and 20% drop in genomic region). Similar to previous studies, the significant SNPs in the female-stratified analysis were stronger than the significant SNPs from the sex-combined analysis. No novel associations were detected in the array-wide analyses. CONCLUSIONS: Of 17 previously identified loci, four loci replicated in the African ancestry populations of this study. Utilizing different linkage disequilibrium patterns observed between European and African ancestries, we narrowed the suggestive region containing causative variants for all four loci.

Will diminishing cochlear delay affect speech perception in noise?

OBJECTIVE: Normal auditory systems appear well habituated to time/phase delays inherent to sound encoding along the hearing organ, sending frequency information non-simultaneously to the central auditory system. Eliminating, or simply perturbing, the cochlear delay might be expected to decrease speech recognition ability, especially under demanding listening conditions. Resources of a larger-scale investigation permitted a preliminary examination of this issue, particularly on a relevant timescale of empirically demonstrated cochlear delays. DESIGN: In a randomized controlled trial study, word recognition was tested for mono-syllabic tokens treated digitally to exacerbate, if not diminish/nullify, such delays. Speech-weighted noise was used to interfere with listening to time-frequency reversed (nominally no delay) versus non-reversed (natural timing) transforms under three treatments of speech tokens: (1) original-digitally recorded; digitally processed to emphasize (2) transient versus (3) quasi-steady-state components. STUDY SAMPLE: Ten normal-hearing young-adult females. RESULTS: The findings failed to demonstrate statistically significant differences between delay conditions for any of the three speech-token treatments. CONCLUSIONS: An algorithm putatively diminishing frequency-dependent cochlear delays failed to systematically deteriorate performance in all subjects for the fixed time-frequency transform, stimulus parameters, and test materials employed. Yet, trends were evident such that some effect of perturbing cochlear delays could not be ruled out completely.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates: profile in children vs. adults.

OBJECTIVE: Auditory steady-state responses (ASSR) evoked by recurrent brief tones were assessed over a wide range of stimulus repetition rates apropos the traditionally measured obligatory, transient, auditory evoked potentials. Repetition rates of ≤ 10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach, speculated to provide technical advantages/additional information over more traditional transient stimulus-response paradigms. DESIGN: Magnitudes were measured at repetition rates from 0.75 to 80 Hz, using trains of repeated tone-burst stimuli. STUDY SAMPLE: Twelve normal-hearing children and a reference sample of 25 young adults. RESULTS: Results show that response magnitudes were significantly larger in children than adults at repetition rates of ≤ 5 Hz. Magnitudes were largest at the two lowest repetition rates, following the trends expected from the transient auditory evoked potential (AEP) literature. The harmonic sum is proposed as a more appropriate measure of response magnitude than amplitude of the fundamental alone. CONCLUSIONS: The analysis methods used in this paper may give information that will have applications for clinical testing. Of pragmatic importance is that the stimulus rate profile could be determined without subjective wave identification and/or interpretation, and thus by a method that is inherently more objective than conventional AEP analysis.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates in awake vs. natural sleep.

OBJECTIVE: Auditory steady-state responses (ASSR) evoked by recurrent tones were assessed over a wide range of stimulus repetition rates embracing well the traditionally measured transient AEPs. Repetition rates of ≤ 10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach which is speculated to provide technical advantages, if not additional/supplemental information, over more traditional transient stimulus-response paradigms. DESIGN: Magnitudes were measured at repetition rates from 0.75 to 80 Hz, using trains of recurrent tone-burst stimuli. STUDY SAMPLE: Twenty-five normal-hearing adults during sleep and awake. RESULTS: Results show that response magnitudes for adults tested during sleep were significantly larger than those for adults while awake at repetition rates <5 Hz. Magnitudes were largest at the two lowest repetition rates, as expected from corresponding results obtained using conventional methods. CONCLUSIONS: The analysis methods used in this paper may give information that will have applications for clinical testing. Results confirm and extend knowledge of the effects of repetition rate on AEPs over a range embracing the gamut of responses as traditionally classified, specifically at the beginning stages of natural sleep.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates: profile in adults.

OBJECTIVE: Quasi-steady-state responses were assessed over a wide range of stimulus repetition rates embracing well the traditionally measured transient AEPs (obligatory auditory evoked potentials of all latencies). Repetition rates of ≤10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach which is speculated to provide technical advantages, if not additional information, over more traditional transient stimulus-response paradigms. DESIGN: A measure introduced and defined as the sum of the response at the stimulus frequency and its harmonics. The magnitude of steady-state responses were measured at repetition rates from 0.75 to 80 Hz, using trains of repeated tone-burst stimuli. STUDY SAMPLE: Twenty-five normal-hearing adults. RESULTS: Results show that the magnitudes of the response across repetition rates are largest at the two lowest rates, following trends expected from the transient AEP literature. Good reliability overall was observed for the harmonic sum. CONCLUSIONS: The analysis methods used in this paper may give information that will have application for clinical testing. Of pragmatic importance is that the rate profile could be determined without subjective wave identification and/or interpretation, and thus by a method that is inherently more objective than conventional AEP tests.

A control system for rotary blood pumps based on suction detection.

A control system for rotary ventricular assist devices was developed to automatically regulate the pumping speed of the device to avoid ventricular suction. The control system comprises a suction detector and a fuzzy logic controller (FLC). The suction detector can correctly classify pump flow patterns, using a discriminant analysis (DA) model that combines several indices derived from the pump flow signal, to classify the pump status as one of the following: no suction (NS), moderate suction (MS), and severe suction (SS). The discriminant scores, which are the output of the suction detector, were used as inputs to the FLC. Based on this information, the controller updates pump speed, providing adequate flow and pressure perfusion to the patient. The performance of the control system was tested in simulations over a wide range of physiological conditions, including hypertension, exercise, and strenuous exercising for healthy, sick, and very sick hearts, using a lumped parameter model of the circulatory system coupled with a left ventricular assist device. The controller was able to maintain cardiac output and mean arterial pressure within acceptable physiologic ranges, while avoiding suction, demonstrating the feasibility of the proposed control system.

Classifying subgroups of chronic low back pain patients based on lifting patterns.

OBJECTIVE: To compare self-reported measures of chronic lower back pain (CLBP) patients who were assigned to 2 subgroups based on their lifting patterns performed during a repetitive lifting task. DESIGN: Cross-sectional study. SETTING: Research laboratory PARTICIPANTS: CLBP subjects (n=81) and pain-free controls (n=53). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Measures of lifting patterns and self-reported disability, pain, and psychosocial aspects. RESULTS: Two CLBP subgroups were found: 1 group that lifts similarly to control subjects (n=35) and 1 group that lifts very differently from controls (n=46). The CLBP group that lifted differently than controls reported higher pain intensity (P=.005), higher pain severity (P=.025), and lower self-efficacy (P=.013) than the CLBP group that lifted similarly to controls. CONCLUSIONS: A classification system based on lifting patterns identified 2 CLBP subgroups that were significantly different on lifting and self-reported measures, indicating the importance of physical functioning measures in classification systems.

A rule-based controller based on suction detection for rotary blood pumps.

A rule-based controller for rotary ventricular assist devices was developed to automatically regulate the pumping speed of the device without introducing suction in the ventricle. The control approach is based on a discriminant analysis function that detects the occurrence of suction, providing the input for the rule-based controller. This controller has been tested in simulations showing the ability to autonomously adjust pump flow according to the patient's level of activity, while sustaining adequate perfusion pressures. The performance of the system (suction detector and controller) was tested for several levels of activity and contractility state of the left ventricle, using a lumped parameter model of the circulatory system coupled with a left ventricular assist device. In all cases, the controller kept cardiac output and mean arterial pressure within acceptable physiologic ranges.

Speech signal modification to increase intelligibility in noisy environments.

The role of transient speech components on speech intelligibility was investigated. Speech was decomposed into two components--quasi-steady-state (QSS) and transient--using a set of time-varying filters whose center frequencies and bandwidths were controlled to identify the strongest formant components in speech. The relative energy and intelligibility of the QSS and transient components were compared to original speech. Most of the speech energy was in the QSS component, but this component had low intelligibility. The transient component had much lower energy but was almost as intelligible as the original speech, suggesting that the transient component included speech elements important to speech perception. A modified version of speech was produced by amplifying the transient component and recombining it with the original speech. The intelligibility of the modified speech in background noise was compared to that of the original speech, using a psychoacoustic procedure based on the modified rhyme protocol. Word recognition rates for the modified speech were significantly higher at low signal-to-noise ratios (SNRs), with minimal effect on intelligibility at higher SNRs. These results suggest that amplification of transient information may improve the intelligibility of speech in noise and that this improvement is more effective in severe noise conditions.

Hemodynamic controller for left ventricular assist device based on pulsatility ratio.

Hemodynamic control of left ventricular assist devices (LVADs) is generally a complicated problem due to diverse operating environments and the variability of the patients: both the changes in the circulatory and metabolic parameters as well as disturbances that require adjustment to the operating point. This challenge is especially acute with control of turbodynamic blood pumps. This article presents a pulsatility ratio controller for LVAD that provides a proper perfusion according to the physiological demands of the patient, while avoiding adverse conditions. It utilizes the pulsatility ratio of the flow through the pump and pressure difference across the pump as a control index and adjusts the pump speed according to the reference pulsatility ratio under the different operating conditions. The simulation studies were performed to evaluate the controller in consideration of the sensitivity to afterload and preload, influence of the contractility, and effect of suction sensitivity. The controller successfully adjusts the pump speed according to the reference pulsatility ratio, and supports the natural heart under diverse pump operating conditions. The resulting safe pump operations demonstrate the solid performance of the controller in terms of sensitivity to afterload and preload, influence of the contractility, and effect of suction sensitivity.

Towards the development of a pediatric ventricular assist device.

The very limited options available to treat ventricular failure in children with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device at the University of Pittsburgh (UoP) and University of Pittsburgh Medical Center (UPMC). Our effort involves a consortium consisting of UoP, Children's Hospital of Pittsburgh (CHP), Carnegie Mellon University, World Heart Corporation, and LaunchPoint Technologies, Inc. The overall aim of our program is to develop a highly reliable, biocompatible ventricular assist device (VAD) for chronic support (6 months) of the unique and high-risk population of children between 3 and 15 kg (patients from birth to 2 years of age). The innovative pediatric ventricular assist device we are developing is based on a miniature mixed flow turbodynamic pump featuring magnetic levitation, to assure minimal blood trauma and risk of thrombosis. This review article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

Validity and accuracy of electric response audiometry using the auditory steady-state response: evaluation in an empirical design.

The validity and accuracy of the application of the auditory steady-state response (ASSR) to electric response audiometry (ERA) was tested further in a study permitting subjects to be their own controls for hearing loss. Simulated sensorineural hearing loss (SSHL) of complex configuration and varying degrees was effected using filtered masking noise. Thresholds estimated via ASSR-ERA were compared to those measured via conventional pure-tone audiometry. Further, the slow vertex potential N1-P2 was recorded to permit a comparison with an evoked-response test of common content validity and known accuracy. Results in a homogeneous subject sample demonstrated strong interest correlation and agreement within 10 dB at 1000 to 4000 Hz (on average), but not at 500 Hz. The configurations determined by ASSR-ERA followed behavioral audiometric patterns well, except for the mildest degree of SSHL tested. Consequently, limitations of ERA remain, although ASSR-ERA appears to be quite valid overall and promises (justifiably) broad clinical applicability.

The PediaFlow pediatric ventricular assist device.

The very limited options available to treat ventricular failure in patients with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device (VAD). Our effort involves a consortium consisting of the University of Pittsburgh, Carnegie Mellon University, Children's Hospital of Pittsburgh, World Heart Corporation, and LaunchPoint Technologies, LLC. The overall aim of our program is to develop a highly reliable, biocompatible VAD for chronic support (6 months) of the unique and high-risk population of children between 3 kg and 15 kg (patients from birth to 2 years of age). The innovative pediatric VAD we are developing (PediaFlow) is based on a miniature mixed-flow turbodynamic pump featuring magnetic levitation, with the design goal being to assure minimal blood trauma and risk of thrombosis. This article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

Evaluating reliability of hidden Markov models that describe the lifting patterns of chronic lower back pain patients and controls.

Two hidden Markov models (HMMs) were designed to identify sub-groups of chronic lower back pain (CLBP) subjects based on time series of lifting parameters obtained during a repetitive lifting task. Two simulation studies were conducted to determine the reliability of this approach, using data from the repetitive lifting study. The first simulation verifies that control and CLBP HMMs based on these data can reliably identify sequences that were generated from that model. The second simulation determines whether the HMMs can reliably identify sequences that are intentionally misclassified (CLBP lifting sequences included in the control group and visa versa). The kappa statistic is used to quantify reliability. The simulation results show that the HMMs provide a reliable technique to analyze time series of lifting patterns and can be used to identify misclassified subjects as a subgroup.

A discriminant-analysis-based suction detection system for rotary blood pumps.

A new suction detection system for rotary blood pumps used in left ventricular assist devices is presented. The system can correctly classify pump flow patterns, based on a discriminant analysis (DA) model that combines several indices derived from the pump flow signal to make a decision about the pump status. The indices considered in this approach are frequency-, time-, and time-frequency-domain indices. The frequency-domain indices detect changes in the harmonic and subharmonic energy content of the pump flow signal when a suction event is occurring. The time-domain indices detect changes in pump flow pulsatility based on a beat-to-beat analysis of the pump flow and first derivative of pump flow. The time-frequency index can track variations in the standard deviation of the instantaneous frequency of the pump flow signal. These indices are combined in a DA decision system to generate a suction alarm. The proposed system has been tested in simulations and in-vivo experimental tests and produced satisfactory results.

Identification of speech transients using variable frame rate analysis and wavelet packets.

Speech transients are important cues for identifying and discriminating speech sounds. Yoo et al. and Tantibundhit et al. were successful in identifying speech transients and, emphasizing them, improving the intelligibility of speech in noise. However, their methods are computationally intensive and unsuitable for real-time applications. This paper presents a method to identify and emphasize speech transients that combines subband decomposition by the wavelet packet transform with variable frame rate (VFR) analysis and unvoiced consonant detection. The VFR analysis is applied to each wavelet packet to define a transitivity function that describes the extent to which the wavelet coefficients of that packet are changing. Unvoiced consonant detection is used to identify unvoiced consonant intervals and the transitivity function is amplified during these intervals. The wavelet coefficients are multiplied by the transitivity function for that packet, amplifying the coefficients localized at times when they are changing and attenuating coefficients at times when they are steady. Inverse transform of the modified wavelet packet coefficients produces a signal corresponding to speech transients similar to the transients identified by Yoo et al. and Tantibundhit et al. A preliminary implementation of the algorithm runs more efficiently.

The use of splines to calculate jerk for a lifting task involving chronic lower back pain patients.

Motion differences in a repetitive lifting task have been described previously using differences in the timing of body angle changes during the lift. These timing changes relied on small differences of motion and are difficult to measure. The purpose of this study was to evaluate shoulder jerk (rate of change of acceleration) in a repetitive lifting task as an alternative parameter to detect differences of motion between controls and chronic lower back pain (CLBP) patients and to measure the impact of a rehabilitation program on jerk. The jerk calculation was a noisy measure, since jerk is the third derivative of position; consequently a simulation was performed to evaluate smoothing methods. Woltring's generalized cross-validation spline produced the best estimates of the third derivative and was fit to subject data. The root mean square (rms) amplitude of jerk was used for comparison. Significant group differences were found. CLBP patients performed lifts with lower jerk values than controls and, as the task progressed, both groups increased jerk. After completion of a rehabilitation program, CLBP patients performed lifts with greater rms jerk. In general, patients performed lifts with lower jerk values than controls, suggesting that pain impacts lifting style.