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Biomedical subjects

R E Dales

Publications and source records attributed to R E Dales.

At least 19 recordsLinked to original sources
PubMed1992

Does forced air heating exacerbate asthma?

Asthma morbidity increases in the Canadian autumn coincident with the beginning of home heating. To test the hypothesis that forced air heating exacerbates asthma, 51 subjects were randomly assigned to one of two groups: the intervention (off1-on2) group was instructed to keep their home forced air heating off from September 9 to 17 and then to set the thermostat to 22 degrees C from 8 PM to 8 AM between September 18 and 25. The concurrent control (off1-off2) group was instructed to keep their forced air heating off during the entire study period. Forty-eight of the 51 subjects randomized recorded morning peak flows, asthma symptoms, and bronchodilator use during the study period. For the intervention group, results before compared with during home heating, respectively, were as follows: mean nocturnal awakenings 0.36 versus 0.36; any breathing difficulties an awakening 82% versus 73%; mean morning peak flows 406 lpm versus 409 lpm, a difference of 3.3% +/- 6.7% (SEM), p = 0.6. There was a 95% probability that the true change in peak flows with forced air was less than 2%. For the control group, the comparable results were as follows: mean nocturnal awakening 0.40 versus 0.47; breathing difficulties on awakening 40% versus 47%; mean morning peak flows 400 lpm versus 399 lpm (p = 0.9). The commencement of forced air heating did not exacerbate asthma in this clinical population and is therefore unlikely to be an important problem for most people suffering from asthma.

Adolescent↗
PubMed1992

Asthma management preceding an emergency department visit.

BACKGROUND: The burden of illness from asthma in North America has not decreased despite advancements in understanding disease pathogenesis and improved pharmacotherapeutics. This study examined the adequacy of preventive measures applied to asthma. METHODS: Using a standardized self-administered questionnaire, 111 consecutive patients presenting to the emergency department because of asthma were surveyed about their "usual" level of disability from asthma, usual medications, self-management plans to deal with an asthma attack, and environmental control measures. RESULTS: Twenty-five percent of subjects suffered sleep disturbance more than 15 days per month, had work/school attendance affected more than 14 days per year, and previously visited an emergency department twice in the past year. Thirty-seven percent had no effective plans to deal with an attack and another 32% had plans that were never discussed with a physician. Although 78% reported that cigarette smoke aggravated their asthma, one third of these were exposed at home. CONCLUSIONS: For a significant proportion of adults requiring emergency health services for asthma, preexisting management was poor by current standards. We recommend that patients be screened by emergency physicians and those with identifiable inadequacies in usual care be referred to physicians with expertise in asthma management.

Adult↗
PubMed1992

Chronic cough responsive to ibuprofen.

A 57-year-old woman believed that ibuprofen, prescribed for back pain, improved her idiopathic chronic cough that had been resistant to inhaled and oral corticosteroids. To confirm this observation, we performed an n-of-1 clinical trial with four treatment periods, each separated by a 4-day washout. Ibuprofen 1800 mg/day for 6 days or placebo was randomly allocated in a double-blind fashion with a block size of 4. The number of coughs during the first 30 minutes after awakening were counted daily throughout the study using a tape recorder. Sixty-two coughs/hour occurred while taking ibuprofen, compared with 164 with placebo. We conclude that ibuprofen may be effective in idiopathic chronic cough, and suggest that prostaglandins may be pathogenic factors in some patients.

Chronic Disease↗
PubMed1991

Respiratory health effects of home dampness and molds among Canadian children.

In 1988, the authors conducted a questionnaire-based study on the health effects of the indoor environment in 30 Canadian communities. This paper focuses on the association between the respiratory health of young children and home dampness and molds. A total of 17,962 parents or guardians of schoolchildren received a questionnaire, and 14,948 (83.2%) questionnaires were returned. Children living in mobile homes, tents, and boats were excluded as were those with cystic fibrosis, leaving 13,495 children included in the study group. The housing stock was distributed as follows: 81% were one-family detached homes, 6% were one-family attached homes, and 13% were buildings for two or more families. Molds were reported in 32.4%, flooding in 24.1%, and moisture in 14.1% of the homes. Prevalences of all respiratory symptoms were consistently higher in homes with reported molds or dampness; i.e., adjusted odds ratios ranged from 1.32 (95% confidence interval 1.06-1.39) for bronchitis to 1.89 (95% confidence interval 1.58-2.26) for cough. The prevalence of home dampness or molds, 37.8%, indicates that it is an important public health issue. Further studies are required to elucidate the pathogenesis.

Canada↗
PubMed1991

Adverse health effects among adults exposed to home dampness and molds.

To investigate the association between home dampness and mold and health, questionnaires were administered through the primary school system to parents of school-aged children in six regions of Canada. The present report focuses on the symptoms of the 14,799 adults at least 21 yr of age. The overall response rate was 83%, and missing values for individual variables ranged from 3 to 8%. The presence of home dampness and/or molds (that is, damp spots, visible mold or mildew, water damage, and flooding) was reported by 38% of respondents. The prevalence of lower respiratory symptoms (any cough, phlegm, wheeze, or wheeze with dyspnea) was increased among those reporting dampness or mold compared with those not reporting dampness or mold as follows: 38 versus 27% among current smokers, 21 versus 14% among exsmokers, and 19 versus 11% among nonsmokers (all p values less than 0.001). This association persisted after adjusting for several sociodemographic variables (including age, sex, and region) and several other exposure variables (including active and passive cigarette smoke, natural gas heating, and wood stoves). The odds ratio between symptoms and dampness was 1.62 (95% confidence interval, 1.48 to 1.78) in the final model chosen. This association persisted despite stratification by the presence of allergies or asthma. Exposure to home dampness and mold may be a risk factor for respiratory disease in the Canadian population.

Adult↗
PubMed1990

Computed tomography to stage lung cancer. Approaching a controversy using meta-analysis.

The ability of computed tomography (CT) to detect mediastinal lymph node metastases from nonsmall cell bronchogenic lung cancer is highly controversial, as evidenced by reported accuracies ranging from 0.35 to 0.95 over the past eight years. We examined all studies on this matter published between January 1980 and April 1988, both to describe the overall experience and to identify characteristics (study design and methodology and CT scan techniques) that influenced reported accuracy. Of 79 relevant publications, 37 were excluded because they were review reports, assessed small cell lung cancer, or contained insufficient evidence to construct a contingency table (CT result versus node histology). The pooled, unweighted (weighted) results based on the remaining 42 studies were as follows: sensitivity, 0.79 (0.83); specificity, 0.78 (0.81); accuracy, 0.79 (0.81). Using a node size greater than 1.0 cm to define a "positive" CT result, as compared to a smaller diameter, was associated with significantly higher specificity, 0.89 versus 0.76, and accuracy, 0.86 versus 0.75 (p less than or equal to 0.005), but not sensitivity, 0.79 versus 0.75. The observed differences in accuracy between a fourth generation CT (0.83) and either a third or a second generation CT, (0.77 and 0.78, respectively) were not significant at p less than 0.05. No characteristics, either singly or in combination, resulted in accuracies exceeding 0.86. There exists random variation of individual study results around an overall mean accuracy of only 0.79, which is marginally improved by advances in CT technology and methods. Significant advances in the noninvasive detection of lymph node metastases must await an approach fundamentally different from CT-determined node size.

Carcinoma, Non-Small-Cell Lung↗
PubMed1990

Severe exacerbations of COPD and asthma. Incremental benefit of adding ipratropium to usual therapy.

Single dose studies have assessed the utility of ipratropium bromide alone or with beta agonists in the short- and long-term management of chronic obstructive lung disease and asthma. We performed a randomized, double-blind trial to assess the incremental benefit over 24 hours of adding ipratropium vs placebo to a standardized regimen of medications commonly used in the acute and subsequent hospital management of COPD and asthma. Sixty-eight subjects received nebulized salbutamol, intravenous methylprednisolone, intravenous aminophylline, and antibiotics and were randomized to receive either 80 micrograms of ipratropium or placebo via metered dose inhaler and spacing device with each salbutamol treatment (6 to 8 times per day). Among the 50 patients who completed the study, there were no significant differences between ipratropium and placebo groups with respect to baseline FEV1, FVC, and PaCO2. The improvement of FEV1 from baseline to 24 hours was 294 (SD = 568) ml in the ipratropium group vs 393 (SD = 622) ml in placebo group. Adjusting FEV1 by age, gender, and smoking did not significantly alter the findings. Those with an admission diagnosis of asthma showed larger 24 hour FEV1 responses (487 ml in ipratropium vs 801 ml in placebo) than those with COPD (149 ml ipratropium vs 102 ml in placebo). However, within these two strata, there were no significant differences in FEV1 improvement between ipratropium and placebo groups. This study suggests that if ipratropium is used in the initial emergency treatment of COPD or asthma, it could safely be discontinued by 24 hours in order to reduce the cost and complexity of therapy.

Administration, Inhalation↗
PubMed1989

Chronic exposure to sour gas emissions: meeting a community concern with epidemiologic evidence.

For 25 years residents of a rural area in southwestern Alberta have complained of health problems attributed to sour gas emissions from nearby natural gas refineries. We undertook a large epidemiologic study of the current health status and the selected morbidity rates among 2152 people in the exposed area. We established two comparison groups: one was a demographically similar unexposed population and the other a demographically different group also exposed to sour gas emissions in another region. The methods included a cross-sectional survey of current residents and separate historical cohort studies involving registry linkage to investigate cancer incidence and all-cause mortality. The cross-sectional survey involved a comprehensive health questionnaire, standardized clinical examinations by physicians blinded to the subjects' symptoms and concerns, and several laboratory tests. We were able to contact just under 60% of the people who we knew had moved from each area since 1958 and found no evidence of selective migration for health reasons. Although the residents of the exposed area reported an excess number of symptoms and health problems there were no significant differences in the mortality rate, incidence of cancer, reproductive problems, major ailments, hair levels of arsenic and certain metals or respiratory function between the groups.

Adolescent↗
PubMed1989

Relation of airway responsiveness to duration of work in a dusty environment.

Health selection within a workforce has been found in several industries and appears to be more pronounced in dustier occupations. In this study of airway disease among workers exposed to asbestos and man made mineral fibres, 215 of 246 construction insulators 50 years old or less and currently working in the Montreal area were examined. Spirometry was completed successfully in 214 workers without known asbestosis and 207 underwent methacholine bronchoprovocation testing. Airway responsiveness was expressed as PC15, the concentration of methacholine causing a 15% fall in the forced expiratory volume in one second (FEV1). Exposure to asbestos and synthetic mineral fibre dust was estimated from the total hours of work in the trade since first employment. After the effect of age, height, and pack years of smoking had been taken into account, no relation was found between hours of work and any indices obtained from the forced expiratory manoeuvre (FEV1/FVC, MMF). After the effect of airway calibre (FEV1/FVC), age, and pack years of cigarette consumption had been taken into account, airway responsiveness decreased as the total hours of work in the trade increased. These findings suggest that workers with greater levels of airway responsiveness are more sensitive to exposure in a dusty workplace and in consequence are less likely to continue. In studies of workforces a survivor effect of this nature will tend to weaken the relation between lung function abnormality and occupational exposure.

Adult↗
PubMed1989

Respiratory health of a population living downwind from natural gas refineries.

Since 1958 there has been a perception of excess illness in a rural Canadian population living downwind from two natural gas refineries, the emissions of which contain mostly sulfur dioxide but also hydrogen sulfide. To determine if there was an excess of adverse health outcomes in the population exposed (defined by place of residence), a health survey was undertaken in 1985 in this area and in one unexposed to emissions but demographically similar. Participation was 92% from both the exposed population (n = 2,157) and a representative sample (n = 839) of the main reference population. More respiratory symptoms were reported in the exposed group than in the non-exposed group among those 5 to 13 yrs of age (28% versus 18%) and among never-smokers greater than or equal to 14 yrs of age (35% versus 24%). FEV1, FVC, and FEV1/FVC were similar in both areas. Dichotomizing the level of exposure (high, low) within the exposed area revealed a trend in the high exposure area toward increased respiratory symptoms in the younger age group (39% versus 24%), but decreased symptoms in the older age group (33% versus 36% among never-smokers). FEV1 was similar between the two areas. The excess of respiratory symptoms in the exposed area unassociated with impaired spirometric values would be compatible with increased awareness of health or a small biologic environmental effect.

Child↗
PubMed1989

The influence of psychological status on respiratory symptom reporting.

The American Thoracic Society respiratory symptom questionnaire (ATS-Q) is widely used and has provided valuable information in epidemiologic studies. To determine the influence of psychological status on respiratory symptoms, we compared subjects' ATS-Q responses to their Ilfeld Psychiatric Symptom Index (PSI) scores. To minimize the potential confounding effect of respiratory disease on the association between respiratory and psychological status, from a population-based survey of 3,628 subjects, we studied only the 600 "healthy" subjects, defined by the following characteristics: between 14 and 55 yr of age; never-smokers; no diagnoses of respiratory, heart, kidney, thyroid disease, or anemia; and normal spirometry (defined as an FEV1 and FVC greater than 80% of predicted). Associations were found between respiratory symptoms (cough, phlegm, wheeze, dyspnea) and PSI subscales (anxiety, anger, depression, and cognitive disturbance). Adjusted odds ratios for respiratory symptoms ranged from 1.13 to 2.15 for every 10% increase in PSI score. Psychological status is an important determinant of respiratory symptoms and therefore must be taken into consideration when interpreting results of epidemiologic studies using questionnaire information.

Adolescent↗
PubMed1989

Cancer downwind from sour gas refineries: the perception and the reality of an epidemic.

A rural population in southwestern Alberta, Canada, living downwind from natural gas refineries, has expressed concerns about an excess of adverse health outcomes over the last 25 years. This has escalated to the point of causing a prominent sociopolitical controversy within the province. As part of a large field epidemiologic study undertaken during the summer of 1985 to investigate possible health effects, a residential cohort study was carried out to study cancer incidence. The cohort was defined as all those individuals who resided in the area in 1970. A total of 30,175 person-years of risk within Alberta were experienced by this cohort from 1970 to 1984. The incident cancers during this period were enumerated by computerized record linkage with the Alberta Cancer Registry. Age- and sex-standardized incidence ratios, based on expected rates from three prespecified demographically similar, nonmetropolitan Southern Alberta populations, were 1.05, 1.09, and 1.03, respectively, none of which was significantly different from unity. Although they do not address the issue of etiologic association, these data can provide considerable reassurance to a community that was convinced it had experienced an epidemic of cancer.

Acid Rain↗
PubMed1988

Evaluation of the effect of norfloxacin on the pharmacokinetics of theophylline.

To investigate a possible interaction between norfloxacin and theophylline, eight healthy nonsmoking volunteers (mean age 27 +/- 5.3 years) were administered aminophylline, 5 mg/kg, before and after a 6-day course of norfloxacin, 400 mg every 12 hours, and changes in pharmacokinetic parameters were measured and compared. Norfloxacin induced significant decreases in theophylline clearance (14.9%; p less than 0.01) and the terminal phase slope (13.3%; p less than 0.02) and increased the AUC (16.6%; p less than 0.01). The apparent volume of distribution at steady state was unchanged. The greatest norfloxacin-induced individual change in theophylline clearance was a reduction of 28.6%. Given these findings, we advise that, for patients who are treated with theophylline and are subsequently treated with norfloxacin, adjustment of the theophylline dosage may be necessary in some patients to minimize the risk of theophylline toxicity.

Adult↗
PubMed1988

Does seasonal employment in grain elevators increase nonspecific airways responsiveness?

Grain handling and increased airways responsiveness (AR) have been independently associated with an accelerated decline in forced expiratory volume in 1 sec. We performed methacholine inhalation bronchial challenge tests in 45 river port grain handlers during layoff and again during employment to determine whether short-term exposure increased AR. To assess bias, due to seasonal/temporal influences, AR was also measured in 56 nonexposed men of similar age and socioeconomic status. AR, slightly higher among laid-off grain handlers than the comparison group, fell more among grain handlers during employment than among the comparison group during the same time period. Our results do not support the hypothesis that seasonal exposure to grain dust increases AR.

Adult↗
PubMed1988

Clinical interpretation of airway response to a bronchodilator. Epidemiologic considerations.

Airways responsiveness to a bronchodilator is frequently measured to assist in determining the cause of respiratory symptoms. Clinically, a greater than 15% improvement in the FEV1 is often used to define the "increased" response indicative of asthma. However, unlike other tests of lung function, reference standards derived from "healthy" members of a general population sample have never been reported. As part of a health survey carried out in Alberta, Canada, 2,609 subjects completed a standardized respiratory symptom questionnaire and had FEV1 measured before and 20 min after inhaling terbutaline sulfate via a 750-ml spacer device. Among asymptomatic never-smoking subjects with a FEV1 greater than 80% of predicted, the upper 95th percentile of bronchodilator response (BDR), when expressed as 100 x (FEV1 postBDR - FEV1 preBDR)/predicted baseline FEV1 averaged 9%. This value remained remarkably stable across gender, age (7 to 75 yr), and height groups, and deviated to 6% only when baseline FEV1 was greater than 120% of predicted. Consistent with other respiratory function variables, in which the upper limit of normal is often defined as the upper 95th percentile, our population-derived reference values provide a conceptual definition of BDR that can easily be applied to define "increased" response in the clinical setting.

Adolescent↗
PubMed1988

Clinical prediction of airways hyperresponsiveness.

We tested the ability of chest physicians to detect increased airways responsiveness (IAR) in patients presenting with symptoms suggestive of asthma. Physicians ordering bronchial provocation tests for diagnostic purposes were asked to predict the clinical probability (based on the patient's history, examination, and spirometry) of IAR (defined by a PC20 for FEV1 less than or equal to 8 mg/ml of histamine). Presenting symptoms in the 38 subjects aged 16 to 78 years included cough, wheeze, dyspnea, chest tightness, and recurrent colds. There was no association between IAR and clinical probability dichotomized as less than or equal to 50 percent or greater than 50 percent (p = .16, Fisher test). The association was no stronger using only subjects in whom the clinical prediction was greater than 67 percent or less than 33 percent. If knowledge of the level of airway reactivity would influence subsequent patient management (eg, prescription of antiasthmatic therapy), then its clinical prediction should not be relied upon.

Adult↗
PubMed1987

Computer modelling of measurement error in longitudinal lung function data.

The effect of measurement error on the accuracy of results in two epidemiological study designs involving longitudinal lung function data was assessed using computer modelling. Five realistic data sets (cohorts) were created, each of 400 subjects, half of whom were exposed to an agent whose effects approximated in magnitude that of cigarette smoking. In each cohort, FEV1 decline was modelled after 6, 4 and 2 years of observation with and without error in the measurement of level of FEV1. For each length of observation the effect of exposure on decline was estimated using a follow-up design comparing the FEV1 decline between exposure groups, and a case-control design comparing risk of exposure in subjects in the top 20th percentile of FEV1 decline (cases) to exposure in those in the bottom 20th percentile (controls). For both study designs an exposure effect at p less than or equal to 0.01 could only be consistently detected after 6 years of observation.

Computer Simulation↗