Single and serial measurements of cardiac troponin I in asymptomatic patients on chronic hemodialysis.

AIMS: Coronary artery disease is the major cause of death in patients with end-stage renal failure on dialysis. This study aimed to assess the predictive value of a single cardiac troponin I (cTnI), and also the kinetics of serial values. METHODS: Since cTnI is a potential biomarker of cardiac outcome, the present study examined single cTnI measurements (n = 88 patients) and its predictive value for future cardiac events, and a kinetic substudy of serial weekly cTnI measured for 8 weeks (n = 57) in a group of patients on hemodialysis. RESULTS: Single cTnI measurements: 9 patients (10.2%) had a detectable cTnI at baseline and 79 patients (89.8%) had a negative baseline cTnI. There were no significant differences in age, sex, history of ischemic heart disease, diabetes, smoking or dyslipidemia between patients with detectable and negative cTnI. At the end of 9 months, the rate of combined primary endpoints, which included myocardial infarction, cardiac death and cardiac revascularization, was significantly higher in the patients with a detectable baseline cTnI (55.6%), compared to patients with a negative cTnI (6.3%) (p = 0.0007). Serial weekly cTnI measurements: significant fluctuations in cTnI were noted over time; 27% of patients with an undetectable cTnI measured at baseline had subsequent detectable levels in the serial follow-up. CONCLUSION: A single detectable cTnI in asymptomatic patients on hemodialysis defines patients at high risk of future cardiac events. However, the incidence of detectable cTnI levels is markedly increased when serial weekly measurements are performed. The clinical significance of detectable serial measurements of cTnI is the focus of ongoing studies.

Claude's syndrome in association with posterior cerebral artery stenosis.

BACKGROUND: We report a case of a 61 year old man with midbrain infarction causing Claude's syndrome attributable to stenosis of the posterior cerebral artery. CASE DESCRIPTION: The patient presented with a pupil-sparing left third nerve palsy and contralateral ataxia. A background history of treated hypertension and cigarette smoking was obtained. Magnetic resonance imaging revealed an area of infarction involving the left medial midbrain. Magnetic resonance angiography revealed significant stenosis of the left posterior cerebral artery. Antiplatelet therapy was instituted and the patient made a satisfactory recovery. CONCLUSIONS: This is the first reported case of Claude's syndrome arising in association with stenosis of the posterior cerebral artery. Intracranial large vessel disease should be considered as a potential aetiologic factor in patients with similar midbrain ischaemia.

Integrality of nasalization and F1. II. Basic sensitivity and phonetic labeling measure distinct sensory and decision-rule interactions.

In vowel perception, nasalization and height (the inverse of the first formant, F1) interact. This paper asks whether the interaction results from a sensory process, decision mechanism, or both. Two experiments used vowels varying in height, degree of nasalization, and three other stimulus parameters: the frequency region of F1, the location of the nasal pole/zero complex relative to F1, and whether a consonant following the vowel was oral or nasal. A fixed-classification experiment, designed to estimate basic sensitivity between stimuli, measured accuracy for discriminating stimuli differing in F1, in nasalization, and on both dimensions. A configuration derived by a multidimensional scaling analysis revealed a perceptual interaction that was stronger for stimuli in which the nasal pole/zero complex was below rather than above the oral pole, and that was present before both nasal and oral consonants. Phonetic identification experiments, designed to measure trading relations between the two dimensions, required listeners to identify height and nasalization in vowels varying in both. Judgments of nasalization depended on F1 as well as on nasalization, whereas judgments of height depended primarily on F1, and on nasalization more when the nasal complex was below than above the oral pole. This pattern was interpreted as a decision-rule interaction that is distinct from the interaction in basic sensitivity. Final consonant nasality had little effect in the classification experiment; in the identification experiment, nasal judgments were more likely when the following consonant was nasal.

The mean-integral representation of rectangles.

To assess perceptual interaction between the height and width of rectangles, we used an accuracy variant of the Garner paradigm. We measured the discriminability of height and width (baseline tasks) and size and shape (correlated tasks). From the d' values in these conditions, we estimated perceptual distances and inferred a mean-integral representation in which height and width corresponded to non-independent dimensions in a perceptual space. This model accounted well for performance in these two-stimulus conditions, and it also explained 70%-80% of the decline in performance in selective and divided attention. In a second experiment, conducted for purposes of comparison with the rectangle discrimination Experiment, we studied the discrimination of horizontal and vertical line segments connected in an L-shape. In size discrimination, observers were equally good with line pairs and rectangles, suggesting holistic perception; but in shape discrimination, they appeared to combine information from the two line-pair components of the rectangle independently. The mean-integral model was again successful in relating performance in the Garner tasks quantitatively.

Integrality in the perception of tongue root position and voice quality in vowels.

In English and a large number of African and Southeast Asian languages, voice quality along a tense-lax dimension covaries with advancement of the tongue root in vowels: a laxer voice quality co-occurs with a more advanced tongue root. As laxing the voice increases energy in the first harmonic relative to higher ones and advancing the tongue root lowers F1, the acoustic consequences of these two articulations may integrate perceptually into a higher-level perceptual property, here called spectral "flatness." Two Garner-paradigm experiments evaluated this interaction across nearly the entire range of tense-lax voice qualities and a narrow range of F1 values. The acoustic consequences of laxness and advanced tongue root integrated into spectral flatness for tenser and laxer but not for intermediate voice qualities. Detection-theoretic models developed in earlier work proved highly successful in representing the perceptual interaction between these dimensions.

d'plus: A program to calculate accuracy and bias measures from detection and discrimination data.

The program d'plus calculates accuracy (sensitivity) and response-bias parameters using Signal Detection Theory. Choice Theory, and 'nonparametric' models. is is appropriate for data from one-interval, two- and three-interval forced-choice, same different, ABX, and oddity experimental paradigms.

Rising to the information challenge.

PIP: Since 1990, the lack of information at the community level had already become clear to the Center for Social Development (CDS) in Quito. It is a country where not even politicians have enough access to good information on a lot of topics, whether it is Public Health or Shining Path. Rising to this information challenge, CDS established a network of community bookstores located within organizations committed to nonformal education. Supported by the International Development Research Center (IDRC), the network, known as ¿Jatarishun¿, became a major distributor of publications throughout Ecuador. The publications cover topics related to health, economic and political issues, agricultural and community development. Another project supported by IDRC focused on using information technology to facilitate information management and computer-based communication within the network and with partners in the region. Meanwhile, the National Federation of Peasant and Indigenous Organizations, a second participant in the pilot project, recognizes the crucial importance of recording and systematizing information now stored in the heads of the people and in documents, particularly on agrarian reform issues. On the other end, is the third network member, the Telmo Hidalgo Cultural Institute for popular Education (ICEP). Library is the main function of ICEP, which also offers audiovisual resources, organizes cultural events, gives courses, prints educational materials, and sells books. Once these 3 organizations have developed their own pilot databases, the goal is to connect them via electronic mail.^ieng

Triangles in ROC space: History and theory of "nonparametric" measures of sensitivity and response bias.

Can accuracy and response bias in two-stimulus, two-response recognition or detection experiments be measured nonparametrically? Pollack and Norman (1964) answered this question affirmatively for sensitivity, Hodos (1970) for bias: Both proposed measures based on triangular areas in receiver-operating characteristic space. Their papers, and especially a paper by Grier (1971) that provided computing formulas for the measures, continue to be heavily cited in a wide range of content areas. In our sample of articles, most authors described triangle-based measures as making fewer assumptions than measures associated with detection theory. However, we show that statistics based on products or ratios of right triangle areas, including a recently proposed bias index and a not-yetproposed but apparently plausible sensitivity index, are consistent with a decision process based on logistic distributions. Even the Pollack and Norman measure, which is based on non-right triangles, is approximately logistic for low values of sensitivity. Simple geometric models for sensitivity and bias are not nonparametric, even if their implications are not acknowledged in the defining publications.

Integrality of nasalization and F1 in vowels in isolation and before oral and nasal consonants: a detection-theoretic application of the Garner paradigm.

In vowel height contrasts, tongue height and soft palate height covary. A series of vowel classification experiments examined the perceptual interactions between F1 and nasalization, the principal acoustic correlates of these articulations. Listeners classified imperfectly discriminable stimuli in the set of tasks that compose the Garner paradigm. Detection-theoretic models applied to the data led to the conclusion that vowels, whether in isolation, before oral consonants, or before nasal consonants, display integrality of F1 and nasalization. The contrary conclusion reached by Krakow et al. [J. Acoust. Soc. Am. 83, 1146-1158 (1988)] on the basis of data from a trading relations experiment reflect a limitation of that design for studying perceptual interaction. A second experiment used an array "rotated" in the stimulus space to determine whether F1 and nasalization are privileged, perceptually primary dimensions. A new method for predicting classification performance for the rotated array without the assumption of primacy showed that they are not.

Sound localization precision under conditions of the precedence effect: effects of azimuth and standard stimuli.

Minimum audible angles (MAAs) were estimated for single noise bursts, and for burst pairs that satisfied the conditions of the precedence effect (that is, produced fused images). In one burst-pair condition, the bursts to be discriminated differed in lead location; in the other, they differed in lag location. Sounds were presented over loudspeakers. MAAs were lowest for single bursts, slightly higher for lead discrimination, and much higher for lag discrimination. Presence of a standard reference burst had no reliable effect on performance. The data are interpreted using a model of Shinn-Cunningham et al. [J. Acoust. Soc. Am. 93, 2923-2932 (1993)] in which discrimination of precedence-effect burst pairs is based on the lateral position of the auditory image, which is a weighted average of the positions of the leading and lagging bursts.

Closed versus open endotracheal suctioning: costs and physiologic consequences.

OBJECTIVE: To examine the physiologic consequences and costs associated with two methods of endotracheal suctioning: closed vs. open. DESIGN: A prospective, randomized, controlled study. SETTING: An eight-bed trauma intensive care unit (ICU) in a 460-bed level I trauma center. PATIENTS: The study included 35 trauma/general surgery patients (16 in the open suction group, 19 in the closed suction group) who were treated with a total of 276 suctioning procedures (127 open, 149 closed). MEASUREMENTS AND MAIN RESULTS: Physiologic data collected after hyperoxygenation, immediately after suctioning, and 30 secs after suctioning, were compared with baseline values. Open endotracheal suctioning resulted in significant increases in mean arterial pressure throughout the suctioning procedure. Both methods resulted in increased mean heart rates. However, 30 secs after the procedure, the open-suction method was associated with a significantly higher mean heart rate than was the closed method. Closed suctioning was associated with significantly fewer dysrhythmias. Arterial oxygen saturation and systemic venous oxygen saturation decreased with open suctioning. In contrast, arterial oxygen saturation and systemic venous oxygen saturation increased with the closed suction method. There was no difference between the two methods in the occurrence of nosocomial pneumonia. Open endotracheal suctioning cost $1.88 more per patient per day and required more nursing time. CONCLUSIONS: The closed suction method resulted in significantly fewer physiologic disturbances. Closed suctioning appears to be an effective and cost-efficient method of endotracheal suctioning that is associated with fewer suction-induced complications.

Helmet promotion in the emergency room following a bicycle injury: a randomized trial.

Head injury is the leading cause of serious morbidity and mortality in bicycle accidents. There is good evidence to recommend helmets, yet few children wear them. Following a survey of children presenting to the emergency room with a bicycle injury, helmet promotion was evaluated in a randomized trial. The intervention consisted of physician counseling and take-home pamphlets. The study involved 334 children: 161 in the intervention group and 173 in the control group. In a follow-up telephone call, 2 to 3 weeks later, only 9.3% of the intervention group had purchased helmets, compared with 8.0% of the control group. Families in the intervention group received further counseling during the telephone contact, resulting in one additional purchase at 6-week follow-up. Evidence that a bike injury motivates cyclists to purchase helmets, and the influence of the self-administered questionnaire most likely account for the high purchase rate in the control group. Surprisingly, the helmet promotion intervention, including follow-up phone counseling, made no further impact. The results probably are best explained by a "double threshold" effect. Certain families were easily encouraged to buy a helmet, whereas others were far from ready to adapt this fairly recent innovation as routine cycling equipment. The findings suggest that physicians interested in helmet promotion would do better to participate in the design and implementation of multidisciplinary community campaigns.

Bicycle-related injuries: a survey in a pediatric emergency department.

The number of bicycle-related injuries has risen significantly with the increased popularity of bicycle riding in Canada. The risk of injury is highest among children. To assess the magnitude of the problem and to identify the contributing factors we used a questionnaire, injury reports and patient charts to survey bicycle-related injuries among children brought to the emergency department of the Children's Hospital of Eastern Ontario, Ottawa, between May 1 and Sept. 30, 1988. The questionnaire was completed for 517 (91%) of the 568 children; 70% were boys, and the mean age was 9.4 years. Only 2% of the patients had been wearing a helmet at the time of injury, although 13% claimed to own one for cycling. Over 60% of the accidents were attributable to carelessness or poor bicycle control; mechanical failure and environmental hazards were minor factors. Over 80% of the injuries occurred within a kilometre of the child's home. Of the 97 children admitted to hospital 49% had head and skull injuries and 40% had limb fractures. Bicycle-related injuries represented 14.8% of all nonwinter (Apr. 1 to Oct. 31) trauma admissions among children 5 years or older. Our results further document bicycle-related injuries as an important childhood problem and underscore the need for improved safety measures.

Bicycle helmet use in Ottawa.

A survey of cyclists was conducted in Ottawa in September 1988 to determine the use of protective helmets. The survey observed 1963 cyclists, of whom 211 (10.7%) wore helmets. The highest level of helmet use was found among older, commuting cyclists (17.9%), followed by recreational cyclists (14.3%). Overall helmet use among students was found to be very low (1.9%), and differed significantly (p < 0.0001) from the other two groups, which consisted almost entirely of adults. When the student population was subdivided, helmet use was found to be 3% among university and college students, 1.9% among high school students, and 0.8% among elementary school students. The authors conclude that children and young adults are the least likely groups to wear helmets while cycling. The five to 19 age group, however, suffer the most cycling injuries, particularly head injuries.