Geolocalization of water-waves origin within water distribution networks using time reversal of first event detection.

Drinking water distribution networks in urban areas are daily subject to fast propagating pressure waves resulting from routine operations. These water-hammer waves lead to structural aging and facility damages, the origin of which is not easy to find but are sometimes of high managerial interest. In this contribution, we demonstrate that using a reasonable number of high-frequency pressure detectors distributed within the network combined with a proper post-processing method permits a close geolocalization of the damaging wave origin. The method is first tested and validated on a real water distribution network having approximately 26000 pipes, whereas considering a known, prescribed waveorigin, so that the sensitivity to sensor number (sensor spatial density), sensor location and signal-to-noise ratio on the geolocalization robustness are analyzed in detail. It is then applied and illustrated over real sensor recordings the result of which are validated on the field from history matching. This paper thus presents the first field-scale geolocalization of water-hammer events origin test as well conditions for which, given sensor density and signal-to-noise ratio, the geolocalization success is to be expected.

A reduced-order modeling for efficient design study of artificial valve in enlarged ventricular outflow tracts.

A computational approach is proposed for efficient design study of a reducer stent to be percutaneously implanted in enlarged right ventricular outflow tracts (RVOT). The need for such a device is driven by the absence of bovine or artificial valves which could be implanted in these RVOT to replace the absent or incompetent native valve, as is often the case over time after Tetralogy of Fallot repair. Hemodynamics are simulated in the stented RVOT via a reduce order model based on proper orthogonal decomposition, while the artificial valve is modeled as a thin resistive surface. The reduced order model is obtained from the numerical solution on a reference device configuration, then varying the geometrical parameters (diameter) for design purposes. To validate the approach, forces exerted on the valve and on the reducer are monitored, varying with geometrical parameters, and compared with the results of full CFD simulations. Such an approach could also be useful for uncertainty quantification.

The effect of brushing time and dentifrice quantity on fluoride delivery in vivo and enamel surface microhardness in situ.

While the clinical anticaries efficacy of fluoride toothpaste is now without question, our understanding of the relation of fluoride efficacy to brushing time and dentifrice quantity is limited. The aim of this in situ study was to determine how differences in brushing time and dentifrice quantity influence (i) fluoride distribution immediately after brushing, (ii) clearance of fluoride in saliva, (iii) enamel fluoride uptake (EFU) and (iv) enamel strengthening, via the increase in surface microhardness. The study compared brushing times of 30, 45, 60, 120 and 180 s with 1.5 g of dentifrice containing 1,100 microg/g fluoride as sodium fluoride. In addition, 60 s of brushing with 0.5 g dentifrice was evaluated. A longer brushing time progressively reduced retention of dentifrice in the brush, thereby increasing the amount delivered into the mouth. A longer brushing time also increased fluoride concentrations in saliva for at least 2 h after the conclusion of brushing, showing that increased contact time promoted fluoride retention in the oral cavity. There was a statistically significant positive linear relationship between brushing time and both enamel strengthening and EFU. Compared to 0.5 g dentifrice, brushing with 1.5 g dentifrice more than doubled the fluoride recovered in saliva after brushing and increased EFU. In conclusion, the results of this preliminary, short-term usage study suggest for the first time that both brushing time and dentifrice quantity may be important determinants both of fluoride retention in the oral cavity and consequent enamel remineralization.

Making decisions about cancer screening when the guidelines are unclear or conflicting.

OBJECTIVE: Our purpose was to determine the factors involved in the cancer screening decisions of family physicians in situations where the clinical practice guidelines are unclear or conflicting as opposed to when they are clear and uncontroversial. STUDY DESIGN: We analyzed discussions with focus groups using a constant comparative approach. POPULATION: A total of 73 family physicians in active practice participated in 10 focus groups (1 urban group and 1 rural group in each of 5 Canadian provinces). OUTCOME MEASURES: Our main outcome measures were participants' perceptions regarding cancer screening when the guidelines were unclear or conflicting. RESULTS: We propose a model of the determinants of cancer screening decision making with regard to unclear and conflicting guidelines. This model is rooted in the physician-patient relationship, and is an interactive process influenced by patient factors (anxiety, expectations, and family history) and physician factors (perception of guidelines, clinical practice experience, influence of colleagues, distinction between the screening styles of specialists and family physicians, and the amount of time and financial costs involved in performing the maneuver). CONCLUSIONS: Our model is unique, because it is embedded in the physician-patient relationship. Ultimately, a modified model could be used to design interventions to assist with the implementation of preventive services guidelines.

Tolerability of antihypertensive drugs in a community-based setting.

BACKGROUND: Outside the experimental environment of clinical trials, the tolerability of angiotensin-converting enzyme inhibitors (ACEIs), calcium channel blockers (CCBs), and the angiotensin II antagonist losartan has not been compared. OBJECTIVES: The purpose of this study was to estimate, in current clinical practice, the 3-month cumulative incidence of side effects among first-time users of losartan, ACEIs, and CCBs for hypertension. METHODS: We conducted a prospective cohort study through a network of 173 pharmacies across Canada to identify patients with hypertension who were newly prescribed monotherapy with losartan, an ACEI, or a CCB. Individuals were interviewed by telephone 3 times over a 3-month period to determine perceived side effects of the antihypertensive medication prescribed. Data were analyzed using a multivariate logistic regression model. RESULTS: Among the 663 eligible individuals, the 3-month cumulative incidence of perceived side effects was 52.5% (42/80), 60.2% (222/369), and 69.6% (149/214) for those treated with losartan, an ACEI, and a CCB, respectively. After adjustment for sex, age, level of education, number of symptoms perceived the week before entering the study, prior use of antihypertensive drugs, current use of any other drug, drug insurance coverage, and duration of hypertension, the odds of reporting a side effect were significantly higher among patients treated with an ACEI (odds ratio [OR] = 1.78: 95% CI, 1.02-3.12) or a CCB (OR = 2.65; 95% CI, 1.47-4.78) compared with patients treated with losartan. CONCLUSIONS: In a community-based setting, we observed that losartan is better tolerated than ACEIs and CCBs. Given that the occurrence of side effects may contribute to lower adherence to drug treatment, the low incidence of side effects associated with losartan makes it an attractive antihypertensive drug choice.

Communication between family physicians and oncologists: qualitative results of an exploratory study.

OBJECTIVE: To study communication between family physicians (FPs) and oncologists, and to look at the factors that may influence FP involvement in cancer care. DESIGN: This survey design uses a qualitative methodology, where the data are analyzed using a modified grounded theory approach. SETTING: This was a multisite study using 14 focus groups of FPs, followed by structured telephone interviews with 116 FPs in 6 different Canadian provinces. MAIN OUTCOME MEASURE: Interview questions were used to explore the actual and desired roles of FPs in cancer care, and the quality of communication with oncologists with reference to a particular cancer patient in the FPs' practice. RESULTS: Physicians providing cancer care must consider complex psychosocial and biomedical factors, more so than with other chronic diseases, and so written communication alone is inadequate. Family physicians require face-to-face and/or telephone communication with the oncologist to negotiate their respective roles, and to discuss the patient's prognosis and the effectiveness of proposed treatments. Family physicians expressed a desire to become more involved in all stages of cancer care in both the biomedical and psychosocial aspects, and to help better define their roles throughout the illness trajectory. CONCLUSION: These results suggest opportunities to improve the communication, coordination and comprehensiveness of shared cancer care provided by family physicians and oncologists in different clinical settings.

The concept mapping method. An alternative to focus group inquiry in general practice.

BACKGROUND: The concept mapping rationale and process are explained step by step. The concept mapping method produces a two dimensional conceptual map of ideas produced by the group which can be analysed at the level of individual statements, clusters of statements, and groups of similar clusters. An example of concept mapping conducted with four general practitioner (GP) groups from different practice types and demographic locations is provided. A total of 51 participating GPs were asked to complete an 'evaluation questionnaire' at the end of each group session. The majority of GP participants (68%) rated the method as highly useful. OBJECTIVE: To describe the concept mapping method and its interpretation for use in general practice research. To report on its perceived usefulness and acceptability by general practitioners. DISCUSSION: Concept mapping is a very useful method combining benefits from qualitative and quantitative approaches for exploring the breadth of a topic in its entirety, especially for abstract concepts. GPs found the concept mapping method to be efficient for group inquiry, rating it high on utility. There is scope to refine the method, reducing time spent in some stages of the session, and substituting more time on final analysis.

What factors determine whether individuals found to have hypercholesterolaemia at mass screening accept advice to visit their physician.

OBJECTIVE: This study aims to identify the determinants of compliance with the recommendation to visit a physician for advice which was given to individuals whose cholesterolemia was > 6.2 mmol/l at mass screening for risk factors of cardiovascular diseases. METHODS: Data were collected from 1144 adults found to be hypercholesterolemic during a screening programme in 54 work sites and 29 public areas and contacted by phone two to six months later. Based on the Health Belief Model, perceived seriousness, perceived self-efficacy, and cues to action were measured. Potential determinants of compliance to the recommendation were examined using multivariate analyses. RESULTS: Mean compliance was 58.6%. For the perceived seriousness dimension of the Health Belief Model, personal history of CVD or risk factors, and prior awareness of cholesterol levels were important determinants. Those already treated for hypercholesterolemia comply twice as much as those who were aware and untreated. Among cues to action, higher cholesterol levels and hypertension are associated with greater compliance; however, smokers were less likely to comply. The dimension of perceived self-efficacy, as measured by ease of access to health services and prior success in eating habit modification, is also associated with compliance to the recommendation. Compliance increases significantly with age. For those previously aware of their elevated cholesterol level, variables representing perceived self-efficacy were no longer determinants. For those previously unaware of their elevated cholesterol level, variables representing CVD perceived threat do not influence compliance. CONCLUSION: The Health Belief Model appears to be an appropriate framework to the determinants of compliance with the recommendation to visit a doctor during mass screening.

Medical conditions and the risk of motor vehicle crashes in men.

OBJECTIVE: To determine whether men aged 45 to 70 years with any medical condition are at an increased risk of involvement as drivers in police-reported motor vehicle crashes. DESIGN: Case-control study. SETTING: Province-wide population-based sampling. PARTICIPANTS: A total of 2504 drivers randomly selected from those involved as a driver in a motor vehicle crash (cases) and 2520 men not involved in a crash (controls) during a 6-month period. DATA COLLECTION: The Societé de l'assurance automobile du Quebec (SAAQ) computerized files provided data on crashes, age, and medical conditions. A mailed questionnaire elicited information on usual mileage and driving conditions. RESULTS: Data from the SAAQ files were obtained for all 5024 drivers. The overall response rate to the mailed survey was 35.5% with no statistically significant differences in the distribution of characteristics between respondents and nonrespondents. There was no increase in crude (odds ratio, 0.99; 95% confidence interval, 0.85-1.17) or age-adjusted risk of crashes for men with a medical condition in the entire sample of subjects (N = 5024). Among respondents to the mailed questionnaire only, men with a medical condition showed no increased crude risk of crashes (odds ratio, 0.99; 95% confidence interval, 0.76-1.27); no difference was observed after adjustment for age, mileage driven, driver behaviors, and sociodemographic characteristics (odds ratio, 0.91; 95% confidence interval, 0.64-1.31). CONCLUSIONS: Unlike previous studies, the risk estimate was derived from a population-based sample of drivers and adjusted for age, mileage driven, driver behaviors, and sociodemographic characteristics in multivariate analyses. The adjusted estimates failed to show an increased risk of motor vehicle crashes for drivers with a medical condition.

Knowledge of and attitude toward patient confidentiality within three family medicine teaching units.

PURPOSE: To describe the knowledge and attitudes about confidentiality issues within family medicine teaching units (FMUs) at McGill University. METHOD: The authors surveyed McGill University FMU staff (physicians, nurses, and support staff) on their knowledge of and attitudes toward confidentiality issues. RESULTS: The response rate was 84%. Only one of nine questions on confidentiality laws was correctly answered by more than 80% of the respondents. Only 55% of the support staff knew that police are not permitted free access to charts, although the majority of those who answered incorrectly held attitudes that were consistent with the law. Only approximately 25% knew that physicians and nurses are not permitted free access to any medical record within the center. There were minimal differences between the professions or between the FMUs. CONCLUSION: These findings suggest that FMU staff do not fully understand their obligations towards patient confidentiality.

Are drivers with CVD more at risk for motor vehicle crashes? Study of men aged 45 to 70.

OBJECTIVE: To examine whether male drivers aged 45 to 70 years suffering from cardiovascular disease (CVD) are more likely to be involved in motor vehicle crashes (MVC) that are reported to the police. DESIGN: Population-based case-control study. SETTING: Data on drivers' ages and medical conditions were compiled from the Societé de l'assurance automobile du Québec's (SAAQ) computerized files. A questionnaire was mailed to all subjects to collect additional information on annual distances driven and various driving behaviours. PARTICIPANTS: Age-stratified population-based random sample. Subjects were 2504 drivers involved in MVCs during a 6-month period; controls were 2520 drivers not involved in crashes. MAIN OUTCOME MEASURES: Proportion of drivers with CVD involved in MVCs. RESULTS: Response rate to the questionnaire was 35.5%. Analysis of the SAAQ files' entire sample of 5024 drivers showed that drivers suffering from CVD were less likely to be involved in MVCs (odds ratio [OR] 0.82, 95% confidence interval [CI] 0.67 to 0.99) than drivers without CVD. Although the estimate of risk remains unchanged when adjusted for age, it becomes statistically insignificant. It also remains unchanged and statistically insignificant when adjusted for yearly distance driven and driver behaviour, as shown by responses to the questionnaire. Drivers suffering from CVD drove significantly less each year (8900 km) than drivers without medical conditions (13,000 km). CONCLUSION: This study shows no increased risk of motor vehicle crashes for drivers suffering from CVD.

Efficacy of diclofenac in lateral epicondylitis of the elbow also treated with immobilization. The University of Montreal Orthopaedic Research Group.

OBJECTIVE: To evaluate the efficacy of an oral nonsteroidal anti-inflammatory drug in the treatment of lateral epicondylitis. DESIGN: Multicenter double-blind randomized controlled trial in which the following hypothesis was tested: whether diclofenac sodium provided a 20% or greater improvement over rest and cast immobilization in the response rate to treatment of lateral epicondylitis beyond and over rest in an experimental group compared with a control group after 4 weeks of treatment. SETTING: Recruitment from urban general practices and referrals to 4 university hospitals. SUBJECTS AND METHODS: During a 1-year period, 206 subjects aged 18 to 60 years with lateral epicondylitis were recruited from the clientele treated by family physicians. Thirty subjects refused to participate and 47 presented with exclusion criteria, leaving 129 subjects who entered the study. One subject withdrew after 21 days. INTERVENTIONS: The experimental group was treated with a daily dose of diclofenac sodium (150 mg) for 28 days, while the control group received a placebo during the same period. In addition, both groups were immobilized in a cast for 14 days and were told not to perform repetitive movements of the involved limb for 21 days. MAIN OUTCOME MEASURES: Measuring instruments consisted of grip strength measurements with a squeeze dynamometer, a visual analog pain scale, a visual analog function scale, and an 8-item pain-free function index. RESULTS: A statistically and clinically significant reduction of pain was associated with treatment with diclofenac, but no clinically significant difference in grip strength or functional improvement could be detected between the 2 groups. Secondary effects (diarrhea and abdominal pain) were significantly more frequent in the diclofenac-treated group. CONCLUSION: Taking into account the limited improvement noted over rest and cast immobilization and the number of associated adverse events, it is difficult to recommend the use of diclofenac in the treatment of lateral epicondylitis at the dosage used in this study.

Attitudes toward obstetrics training. Residents surveyed at McGill University and University of Montreal.

OBJECTIVE: To determine family medicine residents' attitudes toward family practice training in obstetrics and neonatology before and after implementation of a modified obstetrics curriculum at McGill University (MG). DESIGN: Two-group pretest and posttest. Fifty-seven respondents, 31 at MG, 26 at University of Montreal (UM), were case matched as first-year and second-year residents. SETTING: Departments of Family Medicine at MG and UM. PARTICIPANTS: Family medicine residents at MG and UM. INTERVENTION: A modified obstetrics curriculum was introduced at MG (study group); no modifications were introduced at UM (control group). First- and second-year residents' attitudes toward the adequacy of training were assessed through responses to a questionnaire administered in July 1992 and July 1994. MAIN OUTCOME MEASURES: Changes in response scores before and after implementation of the modified curriculum. RESULTS: Repeated multivariate analysis of variance (MANOVA) showed respondents believed family practice obstetrics training was adequate in general, but that family practitioners were inadequately trained in emergency obstetric skills. Scores for items assessing neonatology skills increased significantly in the MG group after the intervention. CONCLUSIONS: Residents' overall confidence in their obstetrics training did not appear to improve, but this might be due to a time lag between curriculum modification and attitudinal change. McGill residents' confidence in neonatology skills improved significantly after curriculum modification.

Choosing a definition of hypertension: impact on epidemiological estimates.

OBJECTIVE: To assess the impact of the use of different definitions on epidemiological estimates of hypertension. METHOD: The four most commonly accepted definitions of hypertension were applied to the 2353 subjects of a hypertension population prevalence survey in Québec. RESULTS: Depending on the definition used, the estimated prevalences of hypertension ranged from 9.6 to 19.9%, from 9.3 to 22.5% for men and from 9.9 to 17.4% for women. Successful control ranged from 15.5 to 68.1%. Regardless of the definition employed, lack of case detection was the main barrier to hypertension control, from 73.2 to 77.1% for men and from 34.6 to 62.0% for women. Lack of appropriate treatment or compliance, or both, was a more important barrier to blood pressure control for women than for men. CONCLUSION: This study shows that the choice of a definition has an important impact on clinically and epidemiologically relevant hypertension estimates for impending clinical and public health decisions.

Cost-effectiveness analysis of lipid-modifying therapy in Canada: comparison of HMG-CoA reductase inhibitors in the primary prevention of coronary heart disease.

This study estimated the cost-effectiveness of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors available in Canada for the primary prevention of coronary heart disease (CHD). A model of the cost-effectiveness of therapy used to modify low-density lipoprotein (LDL) cholesterol and high-density lipoprotein cholesterol levels was developed in the primary prevention of CHD based on risk functions from the Framingham Heart Study and Canadian data on coronary risk factors and the cost of treating the leading manifestations of CHD. Relative to no treatment, discounted gains in life expectancy range from 0.174 year for fluvastatin 40 mg to 0.215 year for simvastatin 10 mg. Costs per year-of-life-saved range from $38,800 for fluvastatin 40 mg to $56,200 for pravastatin 20 mg. In the incremental analysis relative to fluvastatin 40 mg, additional gains in life expectancy range from 0.011 year for pravastatin 20 mg to 0.041 year for simvastatin 10 mg, and incremental cost-effectiveness ratios range from $88,200 for simvastatin, 10 mg to $330,300 for pravastatin 20 mg. Our analysis showed that the cost-effectiveness of cholesterol-lowering therapy is sensitive to pretreatment risk of CHD, as expressed by pretreatment cholesterol levels and the presence of additional risk factors such as hypertension, diabetes, and smoking. The results of the analysis suggest that it is more cost-effective to initiate treatment with fluvastatin than with pravastatin, simvastatin, or lovastatin. Sensitivity analysis showed the results to be stable even if the lipid-lowering effect of fluvastatin is varied by 23% from the original assumption of 25% LDL reduction (ie, from 19.3% to 30.8%). Limitations of the study are recognized and discussed. A head-to-head comparison of these HMG-CoA reductase inhibitors could provide further evidence that therapy initiated with fluvastatin may be the most cost-effective way to treat patients with hypercholesterolemia who are eligible for treatment with HMG-CoA reductase inhibitors.

Hypertension follow-up survey Laval, Quebec, 1988.

In 1988, a follow-up study of a group of hypertensives (n = 278), identified two years earlier in a prevalence survey (1986), was conducted. Blood pressure (BP) levels, treatment and control status and medical follow-up were assessed. Subjects were classified as either known hypertensives or newly identified hypertensives. There was a moderate increase in blood pressure control over the two-year period in known hypertensives. Approximately half of newly identified hypertensives remained untreated, uncontrolled; half became ex-hypertensives. One third of the ex-hypertensives, however, still had high-normal diastolic readings (85-89 mm Hg). Newly identified hypertensives reported less frequent medical visits and fewer non-pharmacological recommendations from their physicians than known hypertensives. The study suggests that follow-up and counselling on modifiable risk factors in borderline and mild hypertensives might not be up to recent Canadian and American guidelines.

Lack of scientific evidence for the treatment of lateral epicondylitis of the elbow. An attempted meta-analysis.

We have reviewed 185 articles published since 1966 to assess the scientific evidence for methods of treatment for lateral epicondylitis of the elbow. Of the 185 articles, 78 discussed treatment, but since the natural history of the syndrome is uncertain we considered only those series with concurrent control groups. Only 18 of these were randomised and controlled studies. We then graded these papers for scientific validity, using the methods of Chalmers et al (1981). The mean score of the 18 articles was only 33%, with a range from 6% to 73%. A minimum of 70% is required for a valid clinical trial, and we therefore concluded that there was insufficient scientific evidence to support any of the current methods of treatment. There were too many methodological differences to allow a quantitative meta-analysis, but our qualitative review established the importance of the natural evolution of the syndrome and of the placebo effect of all treatments. Properly designed, controlled trials are needed.

Medication Compliance in a Family Practice: Testimg a self-report questionnaire in a primary care setting.

For the physician in a primary care setting, a self-report questionnaire on medication compliance can help to determine whether a lack of hypertension control is due to a drug-taking behavior problem or inadequate medication. Such a questionnaire can easily be implemented as a part of routine care and can help clinicians increase the efficiency of medical care dispensed to hypertensive patients.

Could the coronary heart disease mortality rates decline be artefactual?

The recent decline in Coronary Heart Disease (CHD) mortality rates has been attributed to reduction in risk factors and to improved management. In this article, we review whether artefacts of classification could have played a role as well. Knowledge and information on disease, competing causes of death, death certification accuracy and completeness, advancing age of the population with multiple conditions as well as death certificate coding practice could have affected secular trends of CHD mortality rates. However, the lack of noticeable shifts within the cardiovascular category or with another category makes it difficult for the CHD decline to be artefactual.

Decline of acute myocardial infarction death rates not due to cause of death coding.

The recent decline in coronary heart disease (CHD) mortality has been attributed to reduction in risk factors, improved management and the possibility of statistical artifacts. The purpose of this study is to assess the impact of geographic and time variation in the coding of cause of death from death certificates into ICD codes upon CHD mortality rates in Canada. Equal samples of death certificates were recoded for Nova Scotia and Saskatchewan for each of the years 1970 and 1984: 1) a first set of 1,600 death certificates originally coded as acute myocardial infarction (AMI) and 2) a second set of 800 death certificates from all causes of death. The coding error rates increased with age and with the number of contributing and underlying causes of death reported on the death certificates. The net effect of false positive and false negative AMI codes on death certificates did not vary significantly by province or year. Thus, variation of death certificate coding over time and geographic regions do not contribute toward the explanation of the AMI mortality rate decline.