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PubMed1993

Effects of adjacent surfaces of different shapes on regurgitant jet sizes: an in vitro study using color Doppler imaging and laser-illuminated dye visualization.

OBJECTIVES: The present study was designed to estimate the influence of different-shaped adjacent surfaces on regurgitant jets as assessed by color Doppler imaging and laser-illuminated dye optical visualization. BACKGROUND: Because color Doppler techniques provide real-time two-dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has been widely used in clinical studies. However, recent studies have demonstrated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interaction between jets and adjacent wall surfaces. In clinical conditions, jets may interact with adjacent walls of variable shapes that might have different effects on the jet size. METHODS: An in vitro model was constructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5, 2.3 and 3.1 mm2 inflow orifices into the chamber. The surfaces were flat or smoothly and equally curved, convex and concave aluminum positioned at 0, 2 and 4 mm from and to the side of the inflow orifices. The pump was run with stroke volumes from 0.5 to 3.0 ml and with a pulse frequency of 70 beats/min. The echocardiographic and laser beams were aimed at the inflow orifice imaging jets perpendicular to the surfaces (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-illuminated dye visualization. RESULTS: Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were variable. All the surface jet areas at a jet-surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both flat and convex surfaces (p < 0.001). Flow constraint by the concave surface resulted in the smallest jet areas (p < 0.001). The color Doppler jet areas on the curved surfaces were significantly smaller than the laser-illuminated dye visualization jet areas (p < 0.01 to 0.0001). However, at intermediate jet-surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the flat and especially with the convex surface resulted in larger jets. This effect was most pronounced on dye fluorescence studies because flow around these jets consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. CONCLUSIONS: Our study suggests that the different-shaped adjacent surfaces with different degrees of flow alterations resulted in variable decreases in jet size and that color Doppler imaging could not encode and image the angled and low velocity swirling events well when jets flowed along the curved surfaces. These effects need to be taken into account when interpreting color Doppler images.

Analysis of Variance↗
PubMed1990

Sensitivity of effect variables in rheumatoid arthritis: a meta-analysis of 130 placebo controlled NSAID trials.

In a meta-analysis of placebo controlled NSAID trials, the sensitivity of the effect variables was calculated as the correlation coefficient and as the difference between drug and placebo, divided by the placebo group standard deviation. The patient's global evaluation was the most sensitive variable overall. Pain was more sensitive than Ritchie's index. Several variables may be omitted from clinical trials, especially if two active drugs are being compared. For example, the best maximum estimate for the difference in ESR between NSAIDs and placebo was 1.0 mm/hr (95% confidence interval -1.5 to 3.4 mm/hr), and for joint size 0.44% (-1.0 to 1.9%), corresponding to a quarter of a millimeter for each of the 10 joints usually measured. It is suggested to record only the patient's global evaluation, pain, and morning stiffness.

Anthropometry↗
PubMed1992

Cholesterol and coronary artery disease: age as an effect modifier.

An elevation of serum cholesterol has been one of the more frequently cited risk factors for coronary heart disease, found in both case-control and cohort studies. As a result, this country has undertaken massive screening of adults older than 20 years of age in an attempt to identify those persons with cholesterol levels greater than 200 mg/dl, and follow up with an active approach for intervention. The suggested cutpoints for borderline (200-240 mg/dl), and definite (> or = 240 mg/dl) hypercholesterolemia have been applied to all age groups despite suggestions of a diminution of risk conferred by cholesterol in the elderly. This study of 2544 white men undergoing coronary angiography shows that for all men, aged 25-84 years, plasma cholesterol levels were associated with an increase in coronary artery occlusion (rs = 0.15, p < 0.01). However, when stratified by age, this association held only for the younger men, the association diminishing to near zero in the oldest age group. The negative interaction between cholesterol levels and age in predicting coronary artery disease proved highly significant (p < 0.001) in multivariable linear regression analysis, suggesting that cholesterol levels are much less predictive of coronary artery disease in the elderly as compared to the young. These results point to the need for a more finely tuned set of criteria for the evaluation of hypercholesterolemia, one that takes into account the age of the screenee.

Adult↗
PubMed1993

Change in self-reported functioning in older persons entering a residential care facility.

We evaluated the responsiveness of measures of function in admissions to a long-term care facility. Between baseline and follow-up assessment, one-fifth or more of the subjects either worsened or improved in most aspects of reported function. We compared two measures of self-reported function (COOP charts and a short-form survey). Convergent validity was observed for changes in pain, social health, and mental health (r = 0.39-0.74), but not for physical functioning. Although the short-form physical function measure discriminated worsening on several performance-based external criteria of physical functioning (area under ROC curves up to 0.82), the COOP and other measures of physical functioning were less likely to do so. All physical function measures were less responsive for detecting improvement. Clinicians and investigators intending to monitor change in function must consider the responsiveness of their measures.

Activities of Daily Living↗
PubMed1993

Interviewer versus self-administered questionnaires in developing a disease-specific, health-related quality of life instrument for asthma.

We wished to determine the extent to which respondents provided the same answers to a health-related quality of life (HRQL) questionnaire in self- and interviewer-administered forms. One hundred and fifty patients with asthma who were symptomatic or required treatment at least once a week, and had airway hyperresponsiveness to methacholine aerosol (PC20 < 8.0 mg/ml) participated. Patients completed a 152-item HRQL questionnaire in both interviewer and self-administered forms, separated by a 2-week interval, the order determined by random allocation. The percentage of items endorsed by the self-administered approach was significantly higher than that of the interviewer-administered approach overall (46.9 vs 35.8%) (p < 0.0001). The difference was consistent across all six domains; the absolute difference in the proportion of items endorsed varied from 8.9 to 12.3%. The intraclass correlations for the proportion of subjects endorsing an item was 0.84. Self- and interviewer-administered questionnaires yield very similar results in discriminating between subjects, but the self-administered version shows systematically greater HRQL impairment.

Adult↗
PubMed1996

The evaluation of changes in functional health status in patients with abdominal complaints.

Measuring functional status changes in various patient subgroups is important in stratifying risk, assessing disease severity, and predicting and defining clinically relevant outcomes. Data from a multi-centered study of 980 primary care patients presenting with nonspecific abdominal complaints were studied to demonstrate the importance of such an assessment procedure. Patients were prospectively followed for 6 months. Five diagnostic categories based on illness duration and seriousness were derived from the clinical course of these patients. The functional status of each patient was determined at baseline, 1 month, and 6 months using the Sickness Impact Profile (SIP). Intraclass correlation coefficients accounted for two aspects of the reliability of the SIP regarding the measurement of change over time: differences between patients which are stable over time (reproducibility) and different effects of treatment between subsets (responsiveness). A priori formulated expectations about the degree of health status change in patient subgroups were evaluated with the help of effect-size calculations. Patient impairment only partially depended on the final diagnosis and was also influenced by the presence of co-morbidity, psycho-social determinants, and other complaints. The health status change in the patient subgroups agreed with a priori formulated expectations. Standardized effect-size calculations revealed that the degree of change over time in SIP scores was in accordance with these expectations. We conclude: (a) the SIP appeared to be a reliable clinimetric instrument in detecting change over time resulting from different clinical courses, (b) clinical studies that use clinimetric instruments to assess the effects of clinical interventions must adequately control for the influence of baseline "functional status" as well as traditional demographic features such as gender and age, and (c) evaluating a priori formulated clinical expectations concerning functional change with statistics such as intraclass correlation and effect sizes can lead to a clearer understanding of the clinical relevance of statistically significant changes.

Abdominal Pain↗
PubMed1995

Hawthorne effect: implications for prehospital research.

STUDY OBJECTIVE: The phenomenon of altered behavior or performance resulting from awareness of being a part of an experimental study has been termed the "Hawthorne effect." Prehospital studies generally involve paramedics or are designed to use data collected by paramedics. Our objective was to determine whether paramedic performance, as measured by frequency of documentation, can be modified by (1) written notification of the importance of documentation, (2) written notification of a research project involving paramedic documentation, or (3) written notification of a quality-improvement audit of paramedic documentation. DESIGN: Prospective, sequential intervention study with five study phases. SETTING: Urban, all-advanced life support public utility model emergency medical services system with 55,000 emergency calls per year. PARTICIPANTS: One hundred forty-five paramedics who completed all ambulance run reports from August 1992 to May 1993. RESULTS: A total of 30,828 run reports was entered into the study. Baseline undocumented parameters ranged from 3.7% to 6.5%. Compared with baseline, a memo to heighten awareness (phase 2) did not alter documentation (P > or = .08). A medication study memo (phase 3) improved medication documentation (P = .0005) and allergies documentation (P = .037). A quality-improvement audit memo (phase 4) improved documentation of all parameters (P < or = .001). CONCLUSION: The Hawthorne effect occurs in prehospital research. It does not require direct observation, nor does it require direct feedback. However, it may require a perceived demand for performance. The Hawthorne effect must be considered in the design of prehospital studies and interpretation of data collected by paramedics.

Data Collection↗
PubMed1995

Defibrillation by basic emergency medical technicians: effect on survival.

Several studies have examined the effect of early defibrillation by basic EMTs on patient survival. Although the studies have a common theme of early basic EMT defibrillation, they are diverse in locations, devices, control groups, caregivers, and protocols. They provide a confusing array of information that is difficult to review, synthesize, and interpret. Metaanalysis allows data pooling of these primary studies to combine results and statistically compare the observed variation in study outcomes. The purpose of this metaanalysis was to examine the published studies of early basic EMT defibrillation to learn whether this treatment has an effect on survival of out-of-hospital cardiac arrest. Analysis of the 10 studies that met inclusion criteria showed that despite variations in design, the overall effect size for all the studies was .092, indicating a 9.2% increase in survival over what would have been expected had the EMT-Ds not intervened.

Effect Modifier, Epidemiologic↗
PubMed1992

Memory improvements and pharmacological treatment: a method to distinguish direct effects on memory from secondary effects due to attention improvement.

Chronic cerebrovascular disturbances of the aged are characterized by a decline of attention. When these patients undergo pharmacological treatment, it is very difficult to distinguish between a direct benefit and/or a secondary effect on memory resulting from attention improvement. In our study we have proposed and evaluated a new method for identifying the different components of therapeutic efficacy on memory and attention in chronic cerebrovascular patients. This method is based on the use of the Randt Memory Test, traditional scores of memory efficiency (Acquisition, Recall, and a combined index), and the RMT three-factor scores derived from a structural model of memory functioning. The three scores have been called Encoding and Organization, Cognitive Efficiency, and Attention Efficiency. Participants were 96 selected chronic cerebrovascular patients treated in a double-blind study for 12 weeks with dihydroergocristine versus placebo. While changes in both acquisition and recall scores were related to the treatment, only changes of the Encoding and Organization factor scores were systematically related to therapy. Changes in Attention Efficiency were positively related to therapy only in proportion to the degree of cerebrovascular impairment.

Attention↗
PubMed1995

The effectiveness of the cervical halo: open versus closed ring. A preliminary report.

The halo cervical orthosis has proven extremely effective in stabilizing the spine, both non-operatively and as a supplement to operative procedures. Current designs of the available halo utilize either a closed or an open stabilizing ring. Twenty-four patients with various indications for halo application are reviewed. Eleven were treated with a closed ring apparatus (Ace Medical, Los Angeles, California), and thirteen with an open ring device (Bremer, Inc, Jacksonville, Florida). X-rays of the treated patients were compared by group, and patients were interviewed regarding their complaints while wearing the halo. Rates of complication were compared. Results showed no significant differences between radiographs (kyphosis or translation) throughout the follow-up period. Patients experienced a significantly higher incidence of halo-associated pain in the open group. Otherwise, there were no statistical differences in the complication rates of either device. Whether or not the higher incidence of pain in the open group is related to decreased device rigidity is unknown. The open design may theoretically permit bending and opening of the ring to occur, the so-called 'wishbone' effect. Based on these data, it cannot be determined whether the advantages of the open ring--ease of application--are offset by this potential disadvantage. Clearly, a larger, randomized prospective study is required to investigate this.

Adolescent↗
PubMed1995

Interobserver variability of sonographically determined second-trimester nuchal skinfold thickness measurements.

Twenty physicians experienced in fetal sonographic evaluation obtained fetal nuchal skinfold thickness measurements in each of five pregnant women between 16 and 18 weeks' gestation. A random effects analysis of variance model was used to explore the sources of variation in the set of measurements, to determine the interobserver variability of sonographically measured second-trimester nuchal skinfold thickness. It was possible to obtain 96 measurements. Four measurements (all in the same patient) were deemed unobtainable due to fetal position. All recorded measurements were between 1.7 and 4.5 mm. The means (and ranges) for the five patients were 2.7 (1.7-3.6), 2.9 (2.0-4.5), 2.7 (2.0-4.0), 3.3 (2.2-4.0), and 2.7 (1.8-4.0) mm. The standard deviation for interobserver variability, caused by the combined effect of physician and machine imprecision, was 0.56 mm and the overall coefficient of variation was 19.8%. Interpatient differences were statistically significant (p = 0.004). Interphysician differences were not (p = 0.11). We conclude that experienced physician sonographers using high-resolution ultrasound equipment are able to obtain second-trimester nuchal skinfold thickness measurements within 1.1 mm of the estimated true value with 95% probability.

Analysis of Variance↗
PubMedDate not supplied

Associations of London, England, daily mortality with particulate matter, sulfur dioxide, and acidic aerosol pollution.

During the extreme pollution episodes of 1952 and 1962 in London, England, excesses in daily mortality were clearly evident. In this study, we examined daily British Smoke, sulfur dioxide, acid aerosols, and weather variables for their short-term associations with daily mortality in the more typical (nonepisodic) winters of 1965-1972. Consideration of the acid aerosol data was of special interest because this chemical component has been suspected as a causal agent in past episodes. Temporal lag structures between the variables were examined after removal of long-term components from each series in order to obtain "rational" cross-correlations. Significant associations between same-day and lagged pollution variables and mortality were found. Alternative regression models with pollution and weather variables were also developed. The coefficients obtained were applied to the 1962 pollution episode to examine the continuity of the estimated slopes. The pollution-predicted deaths fit the observed deaths well, which supports the applicability of such deviation-derived coefficients to the absolute scale. These models were also employed to estimate mean excess daily deaths attributed hypothetically to air pollution. On average, mean effect ranged from 2-7% of all deaths during the nonepisodic winters in Greater London, but the 95% confidence intervals of these estimates overlapped for all model specifications examined. This estimated pollutant mixture "effect" cannot be attributed to a particular pollutant because of a lack of quantitative information on the relative downward biases caused by both analytical errors and errors in the spatial representativeness of each respective pollution index.

Acids↗
PubMed1993

Misinformation and warnings in eyewitness testimony: a new testing procedure to differentiate explanations.

Although psychologists agree that the presentation of misleading post-event information often results in errant recollections, there is disagreement about the explanation as to why this occurs. Some (cf. Loftus, Donders, Hoffman, & Schooler, 1989) believe this misinformation alters the memory trace created by the original information, whereas others (cf. McCloskey & Zaragoza, 1985) have argued that the data do not necessitate this explanation. An experiment, designed to differentiate the various explanations, was conducted. Its critical elements were: (1) a condition with a specific warning presented immediately after the misleading information; and (2) a ranking procedure used at testing. The results suggest multiple traces may exist for a limited period, but not indefinitely.

Chi-Square Distribution↗
PubMed1994

Why are there sometimes concreteness effects in memory for prose?

Four experiments explored on-line encoding strategies and memory for high imagery and low imagery texts. Results consistently indicated that concreteness effects in memory for text depend on how materials are presented in several different respects. Most importantly, the experiments clarified apparently contradictory results of previous studies by indicating that concreteness effects generally do not occur in memory for prose when imageability is manipulated between-subjects, and that their occurrence when imageability is manipulated within-subjects depends on the order occurrence when imageability is manipulated within-subjects depends on the order of presentation. In addition, moving window analyses of text processing strategies indicated that differential strategies observed in previous studies when subjects listened to high vs low imagery text do not generalize to reading of the same materials. Potential explanations for the pattern of results are evaluated, and implications for theories of mental imagery and memory are considered.

Analysis of Variance↗
PubMed1994

Assessment of long-term verbal memory in children.

This study was designed to evaluate the use of a Paired Associate Learning Test (PALT) and a Story Recall test with children aged from 8 to 12 years. 46 normal control children and 19 children of low ability were given the PALT from the Wechsler Memory Scale, and a story recall task, based on Wechsler's Logical Memory subtest, but using stories designed to be suitable for children. Performance on PALT approached ceiling levels for the control children. Both PALT and story recall were more strongly correlated with measures of verbal ability than with digit span. Reliable measures of immediate story recall can be obtained using two or three stories. Many children who are unable to recall a story after a 45 minute delay show dramatic improvement when given a single cue, and it is argued that cued delayed recall gives a better index of long-term memory than uncued recall. Correlations between immediate recall and cued delayed recall are high, and the data presented here may be used to compute a forgetting score which takes into account the level of immediate recall. In the sample seen here, rate of forgetting was remarkably constant across individuals, in both normal and low ability individuals. It is concluded that memory deficits affecting rate of forgetting are rare, but that the test materials described here could be useful for identifying such disorders in children with neurological impairments.

Case-Control Studies↗
PubMed1991

Extrapolating from toxicity data to occupational exposure limits: some considerations.

This paper evaluates procedures relevant to extrapolating from toxicity data in man and animals to Occupational Exposure Limits. It examines effects at or around the "No Observed Adverse Effect Level' (NOAEL) and the magnitude of safety factors which can be applied in developing occupational exposure limits for non-stochastic effects. The relationship between incidence of stochastic effect and occupational exposure limit is also discussed.

Clinical Protocols↗