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The auditory brainstem response in pediatrics.

When properly recorded and interpreted, the auditory brainstem response (ABR) serves as a powerful, noninvasive tool for the diagnosis of pediatric auditory disorders. The detection of eighth cranial nerve and brainstem dysfunction relies primarily on the comparison of wave latencies to normative data and between ears of the same patient. The description of peripheral hearing sensitivity thresholds by ABR relies primarily on the determination of the weakest stimulus intensity at which the ABR can be elicited. Differential diagnosis of sensorineural versus conductive loss is assisted by analysis of latency-intensity relationships and by bone-conducted ABR findings, whereas description of the frequency contour of the audiogram is possible using band-limited tone burst stimuli as well as other methods. From the caveats and case examples reported here, it should be clear that the ABR cannot be measured or interpreted from a patient in a "black box" fashion. Suprathreshold ABR recordings for neurotologic analysis are influenced by cochlear dysfunction, which can affect both absolute and interpeak wave latencies, and by conductive hearing loss, which affects absolute wave latencies, in such a way that the patient's audiogram must be known for proper test administration and interpretation. Interpretation of suprathreshold ABR data to infer hearing threshold sensitivity has extremely limited utility and can "clear" a child who indeed has substantial hearing loss. Threshold ABR recordings represent the most accurate means available to estimate the audiogram in the very young infant or difficult-to-test child, yet can be influenced by retrocochlear dysfunction, and require concurrent knowledge of outer and middle ear status as well as careful interpretive statements of the actual frequency range for which the audiogram has been estimated. The diagnosis of hearing impairment by ABR in a child is accomplished best when it is performed in the context of concurrent audiologic and otologic workups, with availability (on site or by referral) of a team of hearing health care professionals to evaluate and support the whole child and family. In the case of a newly diagnosed significant hearing impairment in an infant or toddler, input is needed from various professionals including those involved in education of the hearing-impaired, speech-language pathology, developmental psychology, social service, genetics, and ophthalmology, as well as the primary care pediatrician.(ABSTRACT TRUNCATED AT 400 WORDS)

Audiometry, Evoked Response↗

Local lymph node assay: use in hazard and risk assessment.

The murine local lymph node assay (LLNA) was developed as an alternative method for the identification of chemicals that have the ability to cause skin sensitization and allergic contact dermatitis. The assay now has been evaluated extensively in the context of both national and international inter-laboratory collaborative trials and has been the subject of detailed comparisons with guinea pig test methods and human skin sensitization data. On the basis of these evaluations the LLNA has been endorsed recently by the US Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) as a stand-alone method for skin sensitization testing. The assay offers a number of important benefits compared with conventional guinea pig test methods, among these being provision of an objective and quantitative endpoint. Moreover, the LLNA provides advantages in the context of animal welfare; compared with guinea pig tests, fewer animals are required and these animals are subject to less trauma. It is important now that the validation status of the LLNA is recognized and the method applied widely so that these advantages may be realized. Hazard identification represents only the first step in the risk assessment process. A full toxicological evaluation of skin sensitization activity requires an understanding of relative potency. Guinea pig methods do not lend themselves readily to assessment of potency, and interest recently has focused on the utility of the LLNA for this purpose. Contained within this review article are brief descriptions of the history of the LLNA and the immunobiological basis for the method, together with detailed accounts of the conduct and interpretation of the assay. Procedural modifications to, and alternative endpoints for, the LLNA are considered also. Finally, the current regulatory status of the LLNA is summarized and the application of the method for the purposes of defining relative potency and developing risk assessments is reviewed.

Allergens↗

Methods for using narrative text from injury reports to identify factors contributing to construction injury.

BACKGROUND: Several methods exist for classifying injuries from written text, thereby identifying possible points of intervention. We describe an innovative method for such classification. METHODS: Using Haddon's matrix as a framework, two independent reviewers coded text from over 4,000 injury reports into a qualitative software package to identify factors contributing to injuries sustained during construction of Denver International Airport (DIA). We compared our classification scheme with three others. RESULTS: This process created a coded data set, an expanded version of Haddon's matrix adapted for construction injury, and coding rules for interpreting narrative text. Haddon's matrix provides a flexible theoretical framework for coding information about a spectrum of contributing factors. CONCLUSIONS: Narrative descriptions from injury reports can provide detail on circumstances surrounding injuries and identify factors contributing to injury. Forms guiding investigators to explicitly consider human, organizational, and environmental factors could foster more complete descriptions of factors contributing to construction injury.

Accidents, Occupational↗

Breeding biology of muscovy duck (Cairina moschata) under natural incubation: the use of the weibull function and a beta-binomial model to predict nest hatchability

In this paper we tested the Weibull function and beta-binomial distribution to analyse and predict nest hatchability, using empirical data on hatchability in Muscovy duck (Cairina moschata) eggs under natural incubation (932 successfully incubated nests and 11 822 eggs). The estimated parameters of the Weibull function and beta-binomial model were compared with the logistic regression analysis. The maximum likelihood estimation of the parameters was used to quantify simultaneously the influence of the nesting behaviour and the duration of the reproduction cycle on hatchability. The estimated parameters showed that the hatchability was not affected in natural dump nests, but in artificial dump nests and in nests with non-term eggs the hatchability was reduced by 10 and 25%, respectively. Similar results were obtained using logistic regression. Both models provided a satisfactory description of the observed data set, but the beta-binomial model proved to have more parameters with practical and biological meaningful interpretations, because this model is able to quantify and incorporate the unexplained variation in a single parameter theta (which is a variance measure). Copyright 1999 Academic Press.

Journal Article↗

Blood flow in major blood vessels-modeling and experiments.

Although primarily motivated by an interest in atherosclerosis, modeling of arterial blood flow is also important to an understanding of congenital effects and to improvements in therapeutics. A variety of methods are available to estimate the flow field in living arteries, each with its own advantages and limitations. Tradeoffs must be made among the realism of the technique, spatial resolution, geometric fidelity, and the reliability of assumed wall mechanical properties. Once the velocity field is obtained, each differentiation, to obtain wall shear or its spatial or temporal derivatives, adds additional uncertainty into the results, demanding cautious interpretation. A distinction is made between "macro" and "micro" levels of flow structure detail: macro level structure is relatively coarse and more descriptive of the flow field, pressure, and shear distribution than the cellular response; the micro approach tries to relate a more local hemodynamic description to vascular pathology. The applications of each, and the interactions between them, are described. Issues related to these approaches, including the use of clinical data, animal experimentation, the role of cell and organ culture, and in vivo flow measurement, are briefly discussed. The summary closes with a list of recommendations for future developments in this area.

Animals↗

Removing the assumption of conditional independence from Bayesian decision models by using artificial neural networks: some practical techniques and a case study.

The article describes how artificial neural networks with special designs can be applied to approximate a subjective Bayesian decision model without the assumption of conditional independence. New techniques are proposed to resolve some of the practical difficulties during the processes of problem structuring, knowledge elicitation, quantitative modeling, and model interpretation. A Bayesian model considering the conditional dependencies to predict a teenager's marijuana use was constructed by experts using these techniques, and compared to another conventional Bayesian model which assumed conditional independence. The new approach without the assumption of conditional independence had predictive power (r = 0.7) in the test of linearity compared to the conventional approach (r = 0.58) on a data set (n = 129). Its receiver operating characteristic curve dominated the alternative approach within the range (true positive fraction > 0.7) that we were interested in. The interpretations of the possible conditional dependencies provided by the artificial neural network after the training process were consistent with the expert's descriptions.

Adolescent↗

Local understanding, perceptions and reported practices of mothers/guardians and health workers on childhood malaria in a Tanzanian district--implications for malaria control.

Knowledge on local understanding, perceptions and practices of care providers regarding management of childhood malaria are needed for better malaria control in urban, peri-urban and rural communities. Mothers of under five children attending five purposively selected public health facilities in the Kibaha district, Tanzania, were invited to participate in 10 focus group discussions (FGDs). The health workers of these facilities were included in six other FGDs to elicit their professional views. Analysis was done using interpretative and qualitative approaches. Both health workers and all mothers were clear about the signs and symptoms of homa ya malaria, a description consistent with the biomedical definition of mild malaria. Although most of the mothers related this to mosquito bites, some did not. Mothers also described a severe childhood illness called degedege, consistent with convulsions. Most of the mothers failed to associate this condition with malaria, believing it is caused by evil spirits. Urinating on or fuming the child suffering from degedege with elephant dung were perceived to be effective remedies while injections were considered fatal for such condition. Traditional healers were seen as the primary source of treatment outside homes for this condition and grandmothers and mother in-laws are the key decision makers in the management. Our findings revealed major gaps in managing severe malaria in the study communities. Interventions addressing these gaps and targeting mothers/guardians, mother in-laws, grandmothers and traditional healers are needed.

Adult↗

Jumping to conclusions: "language loss" versus "language impairment".

This paper discusses the impact of different metaphors of language dysfunction, with particular notice taken of the contribution of Marshall's work. This is especially the case regarding the notable paper on semantic error patterns (Marshall and Newcombe, 1973), and his later commentary on Chomsky's Rules and Representations (1980) with his elaboration of the conceptual commitments of The New Organology (1980). Examples of language performance provided by two sets of studies are used to illustrate the view that talk of language "loss" is hard to differentiate from the effects of concomitant processing mechanisms such as working memory. These examples are taken from studies of English and Turkish dementia of the Alzheimer type (DAT) patients (March, 2004), and temporal lobe epilepsy (TLE) patients (Field, 2001). Much contemporary neuropsychological research seems focussed on issues which assume that we already know how to describe the behaviours and processes we are interested in, and thus we can now concentrate on how and where in the brain these processes are handled. This perspective is examined from the points of view both that we do not yet have a sufficiently precise application of descriptions which utilise Linguistic constructs, and also that the available models of such processes as memory do not yet allow us to interpret task effects independently of the theoretician's intuitions.

Dementia↗

Cluster formation in a symmetrical network: a dynamical system for the description of the suppression among non-immune T lymphocytes and its application to the effects of immunization.

A mathematical model has been developed for the description of the suppressive regulation between polyclonally activated normal and immune T cells. The model assumes reversible cell-cell interactions to interpret results from limiting dilution experiments performed to determine the frequencies of precursor cells for antigen-specific T effector lymphocytes and to analyse mechanisms regulating the maturation of precursor into effector T cells. In particular, the model deals with the changes induced in the T lymphocytes population following immunization with antigens. In these limiting dilution experiments, T cells are placed in cultures at varying cell numbers with all other essential culture constituents kept in excess. After polyclonal activation of the T cells in culture they are supplied with growth and maturation factors so that they form daughter clones of functionally active T effector cells. The typical result observed was that effector T cells develop in cultures at low cell input but that this development is totally suppressed at high cell numbers. This result suggested that, at high cell numbers, the effector T cells are exposed to a sufficient number of other T cells of appropriate specificity to permit suppressive interactions. Whereas this is the case for non-immune T cells, T cells after immunization develop into effector cells both at high as well as at low cell concentrations, though with efficiencies less than proportional to their number of precursors. Our mathematical model is made up of a set of first order autonomous ordinary differential equations in many variables permitting the calculations of numbers of free cells and of cells engaged in cellular clusters of varying sizes. Free cells can develop into effector cells whereas cells engaged in clusters cannot. We calculate the consequences of several reasonable hypotheses concerning the effects of immunization. We consider the possibility that immunization modifies the growth behavior of the antigen-specific cells to permit an increased or accelerated clonal expansion in culture. Alternatively, we consider the possibility that immunization changes the interaction strength between cells specific for the immunizing antigen and other cells. Thirdly, we have connected both behaviors by calculating the case of an inverse relationship between growth rates and intensities of interaction between cells. Our model has been inspired by the symmetrical network model and can be interpreted in this framework. It proposes that immune regulation is a consequence of idiotype-anti-idiotype interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Carbon dioxide angiography in lower limbs: a prospective comparative study with selective iodinated contrast angiography.

This was a prospective comparison of the accuracy and image quality of carbon dioxide digital subtraction angiography (CO2 DSA) and iodinated contrast digital subtraction angiography (ICDSA) in evaluating lower extremity arteries and patient tolerance of the procedures. Selective DSA was performed in 14 Taiwanese patients who were diagnosed with peripheral artery occlusive disease (PAOD). Both contrast materials were administered through mechanical injectors. Post-processing of the image used pixel shifting. Images of vessels were divided into 22 anatomic segments and evaluated by two experienced radiologists. A four-point scale was used to classify diseased vessels. Two interpreters rated the CO2 DSA image against the ICDSA image on a three-point scale. Patient tolerance was assessed from verbal descriptions. Cohen's kappa was used to determine interobserver agreement and descriptive statistics were used to summarize patient experience. Interobserver agreement ranged from fair to excellent, with most being good or excellent. Three patients (21.4%) could not tolerate the whole procedure and nine patients (64.3%) reported discomfort during the CO2 DSA procedure. CO2 DSA image quality was better for the thigh than the distal runoff and pelvic regions. Our results showed that selective CO2 DSA cannot replace ICDSA as a routine diagnostic tool for PAOD because it does not give images of comparative quality.

Aged↗

Methodological and statistical techniques: what do residents really need to know about statistics?

The purpose of this study was to catalog the statistical methods used in six journals two each from the fields of Family Practice, Emergency Medicine, and Obstetrics and Gynecology. We reviewed the quantitative articles from January 1998 through December 2000 from the Journal of Family Practice, the Journal of Family Medicine, the Annals of Emergency Medicine, the Journal of Academic Emergency Medicine. Articles from January 2000 through December 2000 of Obstetrics and Gynecology and the American Journal of Obstetrics and Gynecology were also included. Case reports and editorials were not included in this analysis. There were a total of 1828 articles reviewed (666 from Emergency Medicine articles, 380 from Family Practice, and 782 from Obstetrics and Gynecology). The distribution of study types (cross-sectional or survey, retrospective, or prospective) did not differ between the selected journals within Emergency Medicine, Family Practice, or Obstetrics and Gynecology. Pearson's chi-square/Fisher's Exact test was the statistic of choice overall (47.5%) followed by Student's t-test (33.1%). Analysis-of-variance was used in 23.3% of the studies, nonparametric methods (8.1%), linear regression (17.6%), and odds ratios/logistic regression (17.4%). Other statistical procedures were used less than 10% of the time. These results show that a physician who comfortably comprehends the appropriate use of descriptive statistics Student's t-test, Pearson's chi-square/Fisher's Exact test will be able to read and interpret at least 70% of the published medical literature. Educational efforts should focus on appropriate study design and analysis.

Clinical Competence↗

Comparison of a direct and indirect population pharmacodynamic model: application to recombinant human erythropoietin in athletes.

Basic physiologic indirect response models have been proposed to account for the pharmacodynamics of drugs that act by way of inhibition or stimulation of the production or loss of endogenous substances or mediators. In this work, these models were applied to account for the effects of recombinant human erythropoietin (rHuEpo) in man. Indeed, rHuEpo induces a delayed increase of serum soluble transferrin receptors (sTfr) and a delayed decrease in ferritin (fr) concentrations. The purpose of the present study was to compare two pharmacodynamic approaches to relate serum erythropoietin (Epo) concentrations to the effect of rHuEpo on sTfr, and fr, the "indirect effect" and the "effect compartment" models. However, due to the average lag time of about 50 hr between the first intake of rHuEpo and the onset of the measurable effects, a delay function was incorporated into the "indirect response models" to describe the relationship between the Epo plasma concentrations and the endogenous receptors or mediators affected by the drug and responsible for the effects on sTfr and fr. There are no real differences in the descriptive features of the two models used. For these reasons, the indirect model seems more appropriate because it supplies a possible mechanistic interpretation of the physiological process.

Adult↗

Quantification of X-chromosome inactivation patterns using RT-PCR of the polymorphic iduronate-2-sulphatase gene and correlation of the results obtained with DNA-based techniques.

Most studies using X-chromosome inactivation patterns (XCIPs) to determine clonality in females have used polymorphic DNA loci, but interpretation may be complicated by the complexity of the differential methylation patterns necessary to distinguish active and inactive X-chromosomes. Recent description of polymorphisms within the transcribed region of three X-chromosome genes has enabled XCIP analysis of allele expression at the RNA level, which should circumvent this problem. We report here a quantitative RT-PCR assay for one of these loci, the iduronate-2-sulphatase (IDS) gene, using a mismatch primer to introduce a Bc/l cutting site in one of the alleles. DNA samples from 150 females were screened and 61 (41%) were found to be informative for the polymorphism. Reproducible results were obtained from clonal analysis of 56 RNA samples covering the complete spectrum of XCIP ratios. The values correlated closely with those obtained from the corresponding DNA samples analyzed using either PGK or HUMARA (r=0.98) provided that the number of amplification cycles was limited to 25 to reduce heteroduplex formation. However, sample purity is of greater importance than in the DNA-based assays as contaminating red cells and platelets will still contain the relevant transcripts and could influence the result.

Base Sequence↗

Speech timing of phonologically disordered children: voicing contrast of initial and final stop consonants.

Speech timing of nine phonologically disordered and nine normally developing children was investigated for the voicing contrasts of word-initial and word-final stop consonants. Measurements of voice onset time, vowel duration, consonant closure duration, and voicing during consonant closure were made from spectrograms. In addition, listener transcriptions were employed for perceptual analysis. Results indicated that some phonologically disordered subjects failed to differentiate VOT in word-initial voiced and voiceless stops, whereas others produced much longer VOTs for voiceless stops than did control subjects. In the word-final voicing contrast, the phonologically disordered children evidenced longer consonant closure durations and less voicing during consonant closure than did normal subjects. However, like normal subjects, they demonstrated differential vowel and consonant closure durations in voiced and voiceless contexts. Perceptual analysis indicated significantly more voicing errors in the initial final stops of phonologically disordered children. These various results are interpreted to mean that some phonologically disordered children may have less mature speech timing control. The implications of these data for the description of voicing errors also are discussed.

Articulation Disorders↗

Rethinking ethnography: reconstructing nursing relationships.

AIMS OF THE STUDY: Critical ethnography is being adopted increasingly by nurses as a legitimate form of research methodology. This paper explores the research practices and dilemmas that emerge from this methodology using a recently completed ethnographic study of nurse-nurse and nurse-doctor interactions in a critical care hospital setting. BACKGROUND: Critical ethnography provides a useful methodology that facilitates mutual dialogue among participants. It may be limited, however, by the central role of researchers and by a tendency to negotiate participants' realities according to a particular 'truth'. These concerns have been strongly critiqued by poststructuralists using concepts such as discourse, subjectivity and power. By incorporating the notion of a poststructural analysis into critical ethnography, researchers are in a position to examine critically the tensions in their own practices, and their struggles with documenting and analysing ethnographic accounts. DESIGN: Six registered nurses comprised the participants of the research group. Through the method of professional journalling, the first author of this paper explored her professional interactions with doctors and other nurses in her role as a nurse in the critical care setting under investigation. Other methods included participant observation, and individual and focus group interviews with nurse participants. ISSUES OF METHODOLOGICAL CONCERN: This paper considers three issues of methodological concern: researcher/participant subjectivity; the movement from empowerment to reflexivity and the construction of one form of ethnographic 'truth'. These issues are discussed in reference to the research relationships with the nurse participants and the process of analysing ethnographic accounts. CONCLUSIONS: In working with critical ethnography using a poststructural analysis, we were able to generate valuable insights about previously hidden areas of relationships among nurse participants in a research group during all stages of the research process. It also provided a means of informing the analysis of ethnographic texts.

Anthropology, Cultural↗

Using a management perspective to define and measure changes in nursing technology.

AIMS: The aims of this paper are to discuss the uses of the concept of technology from the medical science and the management perspectives; to propose a clear definition of nursing technology; and to present a study applying the use of the concept of nursing technology on nursing units. BACKGROUND: Nurse managers must use management terms correctly and the term technology may be misleading for some. A review of the nursing literature shows varied uses of the concept of technology. Thus a discussion of the dimensions, attributes, consequences, and definitions of nursing technology from the management perspective are given. DESIGN: A longitudinal study to measure the dimensions of nursing technology on nursing units 10 years apart. RESULTS: The findings suggest that the dimensions of nursing technology change over time and support the need for nurse managers to periodically assess nursing technology before making management changes at the level of the nursing unit. CONCLUSIONS: This study helps health care providers understand the unique role of nurses as healthcare professionals by identifying and measuring nursing technology on the nursing unit.

Data Interpretation, Statistical↗

Differential effects of isoflurane and halothane on aortic input impedance quantified using a three-element Windkessel model.

BACKGROUND: Systemic vascular resistance (the ratio of mean aortic pressure [AP] and mean aortic blood flow [AQ]) does not completely describe left ventricular (LV) afterload because of the phasic nature of pressure and blood flow. Aortic input impedance (Zin) is an established experimental description of LV afterload that incorporates the frequency-dependent characteristics and viscoelastic properties of the arterial system. Zin is most often interpreted through an analytical model known as the three-element Windkessel. This investigation examined the effects of isoflurane, halothane, and sodium nitroprusside (SNP) on Zin. Changes in Zin were quantified using three variables derived from the Windkessel: characteristic aortic impedance (Zc), total arterial compliance (C), and total arterial resistance (R). METHODS: Sixteen experiments were conducted in eight dogs chronically instrumented for measurement of AP, LV pressure, maximum rate of change in left ventricular pressure, subendocardial segment length, and AQ. AP and AQ waveforms were recorded in the conscious state and after 30 min equilibration at 1.25, 1.5, and 1.75 minimum alveolar concentration (MAC) isoflurane and halothane. Zin spectra were obtained by power spectral analysis of AP and AQ waveforms and corrected for the phase responses of the transducers. Zc and R were calculated as the mean of Zin between 2 and 15 Hz and the difference between Zin at zero frequency and Zc, respectively. C was determined using the formula C = (Ad.MAP).[MAQ.(Pes-Ped)]-1, where Ad = diastolic AP area; MAP and MAQ = mean AP and mean AQ, respectively; and Pes and Ped = end-systolic and end-diastolic AP, respectively. Parameters describing the net site and magnitude of arterial wave reflection were also calculated from Zin. Eight additional dogs were studied in the conscious state before and after 15 min equilibration at three equihypotensive infusions of SNP. RESULTS: Isoflurane decreased R (3,205 +/- 315 during control to 2,340 +/- 2.19 dyn.s.cm-5 during 1.75 MAC) and increased C(0.55 +/- 0.02 during control to 0.73 +/- 0.06 ml.mmHg-1 during 1.75 MAC) in a dose-related manner. Isoflurane also increased Zc at the highest dose. Halothane increased C and Zc but did not change R. Equihypotensive doses of SNP decreased R and produced marked increases in C without changing Zc. No changes in the net site or the magnitude of arterial wave reflection were observed with isoflurane and halothane, in contrast to the findings with SNP. CONCLUSIONS: The major difference between the effects of isoflurane and halothane on LV afterload derived from the Windkessel model of Zin was related to R, a property of arteriolar resistance vessels, and not to Zc or C, the mechanical characteristics of the aorta. No changes in arterial wave reflection patterns determined from Zin spectra occurred with isoflurane and halothane. These results indicate that isoflurane and halothane have no effect on frequency-dependent arterial properties.

Animals↗

Adolescents with cancer: experience of life and how it could be made easier.

This study is about what adolescents with cancer think about their life situation, the support they get, and the information they receive about their illness. The data for this qualitative and descriptive study were collected in 3 focus group interviews with 20 adolescents aged 13 to 18 years attending a cancer adjustment camp. Interpretation was based on the method of inductive content analysis. The adolescents' experiences of their current situation were analyzed into 5 categories: views on life here and now, negative experiences of self because of the illness, resources recognized in self, difficulties caused by the illness in relation to life around them, and resources identified in the world around. They made very little, if any, conscious effort to plan ahead for the future. The information received by the adolescents concerned their illness and its treatment here and now, various practical matters, as well as the future impacts of the illness and its treatments. Most of this information focused on the here and now, whereas the adolescents' information needs were mainly oriented to the future. As for the adolescents' chances to take part in making decisions about their care and life, the analysis yielded 6 categories: joint decision making, inadequate chances for decision making, independent decision making, illusion of decision making, reluctant to make decisions, and excluded from decision making. Finally, the adolescents' hopes for improvement were focused on staff activities, physical care facilities, chances to discuss and work through their experiences of the illness, and the support received from society.

Adaptation, Psychological↗