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Biomedical subjects

S Lewis

Publications and source records attributed to S Lewis.

At least 199 records · Page 11Linked to original sources
PubMed1997

Occupational asthma in New Zealanders: a population based study.

OBJECTIVES: To examine the effect of occupation on respiratory symptoms in a randomly selected adult population aged 20-44 years. METHODS: It is based on the phase II sampling of the New Zealand part of the European Community respiratory health survey. 1609 people (63.9% response rate) completed a detailed respiratory questionnaire. Of those responding, 1174 (73%) underwent skin tests and 1126 (70%) attended to undergo methacholine bronchial challenge. Current occupation was recorded and a previous occupation was also recorded if it had led to respiratory problems. 21 occupational groups were used for analysis for the five definitions of asthma wheezing in the previous 12 months; symptoms related to asthma; bronchial hyperresponsiveness (BHR); BHR with wheezing in the previous 12 months; and BHR with symptoms related to asthma. RESULTS: Prevalence odds ratios (ORs) were significantly increased for farmers and farm workers (OR 4.16, 95% confidence interval (95% CI) 1.33 to 13.1 for the combination of wheezing and BHR). Increased risks of prevalence of asthma were also found for laboratory technicians, food processors (other than bakers), chemical workers, and plastic and rubber workers. Workers had also been divided into high and low risk exposure categories according to relevant publications. The prevalence of wheezing was greater in the high risk group (OR 1.57, 95% CI 0.83 to 2.95) than in the low risk group. Atopy was associated with asthma, but the prevalence of atopy did not differ significantly between occupational exposure groups. The attributable risk of wheezing that occurred after the age of 15 years and that was estimated to be due to occupational exposure (based on the defined high risk group) was 1.9%, but this increased to 3.1% when farmers and food processors (other than bakers) were also included in the high risk group. CONCLUSIONS: This population based study has identified certain occupations significantly associated with combinations of asthmatic symptoms and BHR.

Adult↗
PubMed1997

Changes in breathing and ventilatory muscle recruitment patterns induced by lung volume reduction surgery.

Patients with chronic obstructive pulmonary disease have abnormal breathing and ventilatory muscle recruitment patterns at rest and during exercise, and these alterations may contribute to the limited exercise capacity seen in this disease. Lung volume reduction surgery (LVRS), a recently described treatment for emphysema, is reported to improve exercise performance. We studied the breathing and ventilatory muscle recruitment (VMR) patterns in eight patients with severe chronic obstructive lung disease (median FEV1 = 0.79 L, range 0.46 to 1.13 L) by measuring esophageal and gastric pressure measurements as well as tidal volumes (VT), respiratory rates (f), inspiratory (TI) and expiratory (TE) times, and watts at rest and during maximal exercise, before and 3 mo after lung volume reduction surgery. Maximal exercise capacity increased a median of 49% (median increase 17 watts, range 6 to 44 watts, p < 0.05) and maximal minute ventilation (VEmax) increased by a median of 22% (median increase 6.5 L/min, range 3 to 25 L/min, p < 0.05). At isowatt exercise after surgery, VT increased 0.31 L (range 0.07 to 0.69 L) and f decreased four breaths/min (range +0.5 to -15 breaths/min). Dyspnea scores as measured by a visual analog scale (VAS) decreased significantly at rest and at peak exercise after surgery. End-expiratory esophageal (Pes) and gastric (Pga) pressures at rest and at isowatt exercise decreased. A rightward shift in the slope of the Pes versus Pga plot was also observed suggesting increased use of the diaphragm after surgery. Our data indicate that LVRS improves the mechanics of breathing both at rest and during exercise.

Adult↗
PubMed1997

Lung volume reduction surgery improves maximal O2 consumption, maximal minute ventilation, O2 pulse, and dead space-to-tidal volume ratio during leg cycle ergometry.

Early experience suggests that lung volume reduction surgery improves exercise tolerance as measured by the 6-min walk distance in patients with emphysema. To identify the physiologic mechanism(s) by which lung volume reduction surgery improved exercise, we performed progressive cardiopulmonary exercise testing, including rest and peak exercise blood gas determinations, on 21 consecutive patients before and 3 mo after lung volume reduction surgery. Maximal work (median, range, % change) increased 17.5 watts (-13 to +44 watts, 46%, p < 0.05), maximal oxygen consumption increased 0.16 L/min (-0.17 to +0.48, 25%, p < 0.05), maximal ventilation increased 6.6 L/min (-7 to +26 L/min, 27%, p < 0.05), and the dead space/tidal volume ratio at peak exercise decreased 0.07 (-0.22 to +0.09, 12%, p < 0.05), exclusively as a result of an increase in the tidal volume. After lung volume reduction surgery heart rate decreased at the point of isowatt exercise, from 115 to 111 beats/min (p < 0.05). No difference was observed in the other physiologic variables measured at isowatt exercise. In 13 patients exercised while breathing room air, the alveolar-to-arterial O2 difference increased, and the arterial O2 tension decreased from rest to peak exercise both before and after the operation, but significant changes in this response were not observed after surgery. The primary problem limiting exercise performance in these patients was the limited ventilatory capacity as 16 and 13 of the 21 subjects developed acute respiratory acidemia at peak exercise before and after surgery, respectively. Lung volume reduction surgery in patients with severe emphysema improved maximal ventilation, thereby improving maximal exercise performance.

Exercise Test↗
PubMed1997

Comparison of reported prevalences of recent asthma in longitudinal and cross-sectional studies.

A potential source of bias in prevalence rates reported for symptoms and diagnoses of asthma in longitudinal studies could arise if repeated questioning of subjects or previous experience of lung function and airway responsiveness tests increased awareness of respiratory symptoms. We wished to determine the extent of any such bias by comparing reported prevalence rates from a longitudinal and cross-sectional study within similar populations. The prevalences of wheezing in the last year, waking with chest tightness, waking with shortness of breath, waking with coughing, having an attack of asthma in the last year, and current use of medications for asthma were determined using identical questions in two populations. Self-completed questionnaire responses of 946 subjects, 21 yrs of age, participating in the seventh respiratory assessment in the longitudinal Dunedin Multidisciplinary Health and Development Research Study were compared with responses provided by 991 subjects, aged 20-22 yrs, completing a postal questionnaire on one occasion only for the New Zealand section of the European Community Respiratory Health Study. The prevalence rates were not significantly different between the two populations, for all of the reported symptoms and for medication use. Differences in responses between genders were similar in each study, with all responses being more common in females. We conclude that repeated questioning regarding respiratory symptoms and repeated lung function and bronchial challenge testing in a longitudinal study of asthma did not bias prevalence rates compared with those obtained in a similar population of the same age studied on only one occasion.

Adult↗
PubMed1997

Investigation of the effect of short-term change in dietary magnesium intake in asthma.

Epidemiological evidence suggests that a low dietary intake of magnesium is associated with impaired lung function, bronchial hyperreactivity and wheezing. This study was designed to investigate whether short-term alterations of dietary magnesium intake have an effect on the clinical control of asthma. In a randomized, double-blind, placebo-controlled, cross-over study, 17 asthmatic subjects adhered to a low magnesium diet for two periods of 3 weeks, preceded and separated by a 1 week run-in/wash-out, in which they took either placebo or magnesium (400 mg x day(-1)) tablet supplementation. Forced expiratory volume in one second (FEV1) and the provocative dose of methacholine required to cause a 20% fall in FEV1 from baseline (PD20,FEV1) were measured at the beginning and end of each treatment period, and variation in peak expiratory flow (PEF) rate, bronchodilator use and symptom scores recorded throughout. Asthma symptom scores were significantly lower during the magnesium treatment period, the median (95% confidence interval) difference from placebo being 3.8 (0.5-7.0) symptom points per 7 days (p=0.02). However, there was no significant improvement in FEV1, PD20,FEV1, log amplitude percentage mean PEF variation or bronchodilator use during magnesium supplementation. A high magnesium intake was associated with improvement in symptom scores, though not in objective measures of airflow or airway reactivity, in these stable asthmatic subjects.

Adult↗
PubMed1997

Visual organization test performance in an African American population with acute unilateral cerebral lesions.

Controversy abounds as to whether the Hooper Visual Organization Test (VOT) is a measure of hemisphere-specific, region-specific, or non-specific brain damage. The present study examines this issue in a group of African Americans with acute unilateral brain damage and non-brain-injured controls. Consistent with the idea that the VOT is a measure of "organic" cerebral pathology, non-brain damaged controls earned significantly higher VOT scores than brain-damaged patients. While other studies have noted that the VOT is primarily sensitive to damage in the right parietal region of the brain, the present study shows that VOT performance is especially vulnerable to acute lesions in the right anterior quadrant of the brain. This latter finding supports the idea that VOT performance is differentially sensitive to regional cerebral pathology, but challenges the region specific claim of poorer VOT performance among patients with right posterior cerebral damage.

Acute Disease↗
PubMed1997

Studies of the effects of inhaled magnesium on airway reactivity to histamine and adenosine monophosphate in asthmatic subjects.

BACKGROUND: Magnesium is a cation with smooth muscle relaxant and anti-inflammatory effects and may therefore have a role in the therapy of asthma. Several studies have investigated the effects of intravenous magnesium in acute or stable asthma, but little is known about the effects of inhaled magnesium. OBJECTIVE: To measure the effects of a single inhaled nebulized dose of 180 mg magnesium sulphate on airway reactivity to a direct-acting bronchoconstrictor (histamine) and an indirect-acting bronchoconstrictor (adenosine monophosphate [AMP]) in asthmatic subjects. METHODS: Two separate randomized, double-blind, placebo-controlled crossover studies, each involving 10 asthmatic subjects. In the histamine study, airway reactivity to histamine was measured and lung function allowed to recover spontaneously over 50 min before administering nebulized magnesium sulphate or saline placebo. Airway reactivity to histamine was then measured at 5 and 50 min. In the AMP study, a single measurement of airway reactivity was made 5 min after magnesium or placebo. RESULTS: In the histamine study, the provocative dose required to reduce FEV1 by 20% (PD20FEV1) was significantly lower after magnesium than after placebo, by a mean (95% CI) of 1.02 (0.22-1.82) doubling doses at 5 min (P = 0.018), and 1.0 (0.3-1.7) doubling doses at 50 min (P = 0.01). In the AMP study, PD20FEV1 was also significantly lower at 5 min after magnesium than after saline, by 0.64 (0.12-1.16) doubling doses (P = 0.023), though this difference was not statistically significant after adjustment for differences in baseline FEV1 on the two study days. CONCLUSIONS: Inhaled magnesium did not protect against the effects of these direct and indirect bronchoconstrictor stimuli in subjects with asthma, and may have increased airway reactivity to histamine.

Adenosine Monophosphate↗
PubMed1997

Low back pain assessment training of industry-based physicians.

We have developed an educational program to train industry-based physicians in a new low back pain assessment procedure based on the recommendation of The Clinical Practice Guidelines on Acute Low Back Pain Problems in Adults published by the Agency for Health Care Policy and Research, U.S. Department of Health and Human Services. The clinical classification system based on the findings from the Quebec Task Force was used to categorize the subjects. The educational program included group and individual sessions with an extensive period of active follow-up. Protocol compliance was measured through a computer-based surveillance system that monitored evaluation form completion. The results showed significant change (p < 0.001) in physician compliance in completing a standardized examination following an administrative mandate to change. Little change in clinical practice was recorded with an educational training program only. Further research into the factors responsible for the results is suggested.

Adult↗
PubMed1997

The influence of antibiotics and other factors on reconsultation for acute lower respiratory tract illness in primary care.

BACKGROUND: Antibiotics are prescribed to the majority of patients consulting their general practitioner (GP) for lower respiratory tract illness (LRTi). A common reason for prescription is the belief that antibiotics reduce re-attendance; a motive supported by the high reconsultation rates for this largely self-limiting illness. Information about reconsultation following treatment of LRTi, and the factors that influence it, is scarce. AIM: To explore factors associated with reconsultation after initial management of LRTi. METHOD: Analysis of data collected prospectively during presentation of acute LRTi in primary care. RESULTS: Seventy-six per cent of 518 patients were prescribed antibiotics, and 30% reconsulted for similar symptoms within the next 28 days (29% of those who were given antibiotics and 33% of those who were not). Forty-one per cent of patients who had seen their GP 15 or more times in the previous two years reconsulted, compared with 13% of those who had made fewer than five visits. Reconsultation was more common in patients with a history of underlying disease (38.6% versus 24.3%) and in patients who reported dyspnoea (41.5% versus 24.3%). CONCLUSION: Reconsultation is common in acute LRTi and is associated with a heightened consulting habit prior to the index consultation, the presence of previous ill health, and dyspnoea. It appears not to be influenced by prescribing antibiotics.

Acute Disease↗
PubMed1996

Augmentation of the therapeutic activity of lometrexol -(6-R)5,10-dideazatetrahydrofolate- by oral folic acid.

Recent clinical trials with lometrexol [(6R)-5,10-dideazatetrahydrofolate] have revealed a level of toxicity in humans that was not predicted on the basis of previous in vivo preclinical studies. Because standard laboratory animal diets contain high levels of folic acid relative to human folate intake, the toxicity and therapeutic activity of lometrexol was studied in mice under conditions of restricted dietary folate intake. Remarkably, the lethality of this drug increased by three orders of magnitude in mildly folate-deficient mice, mimicking the unexpected toxicity seen in humans. Lometrexol had limited therapeutic activity in folate-deficient mice bearing the C3H mammary adenocarcinoma, compared with the substantial therapeutic index for treatment of this tumor in animals on standard diet. When folic acid was administered p.o. to mice that were mildly folate deficient, antitumor activity was again observed at nontoxic doses of lometrexol, and the range of lometrexol doses that allowed safe therapeutic use of this drug increased at higher dietary folate intake. At a fixed dose of lometrexol, the antitumor effects in animals were dependent on the level of dietary folate and went through a distinct optimum. Excessively high folate intake reversed the antitumor effects of lometrexol. Optimization of the folic acid content in the diet and of the lometrexol dosage are predicted to have substantial impact on the clinical activity of this class of drugs.

Adenocarcinoma↗
PubMed1996

Angiographic and procedural outcome after coronary angioplasty in high-risk subsets using a decremental diameter (tapered) balloon catheter. Tapered Balloon Registry Investigators.

The angiographic and clinical outcomes of 115 patients (129 lesions) treated at 11 clinical centers using a decremental diameter (tapered) balloon catheter were evaluated. The presence of marked tapering of the reference vessel, lesion location involving a bifurcation or anastomosis of a saphenous vein graft, or total coronary occlusion where estimation of the distal vessel size was difficult were indications for this device. The tapered balloon was used as the initial dilatation device in 62 patients (73 narrowings), and as a secondary device in 53 patients (56 narrowings). Lesions selected for tapered balloon angioplasty were generally complex (95% had > or = 1 and 60% had > or = 2 adverse morphologic features). Vessel diameters were larger in the proximal reference segments (3.07 +/- 0.52 mm) than in distal ones (2.48 +/- 0.45 mm) (p<0.001). After tapered balloon angioplasty, the minimal lumen diameter increased from 0.85 +/- 0.34 mm to 2.13 +/- 0.50 mm (p<0.001), and the percent diameter stenosis decreased from 69 +/- 12% to 24 +/- 12% (p<0.001). Coronary dissections occurred in 20% of lesions; they were severe in 4% (National Heart, Lung, and Blood Institute grade C to F). Abrupt closure occurred in 4.3% of patients (2.6% immediate; 1.7% delayed). Procedural success was obtained in 110 patients (96%); major complications (in-hospital death, myocardial infarction, or emergency coronary bypass surgery) occurred in 3 patients (2.7%). Coronary angioplasty using the tapered balloon catheter appears to be a safe and effective technique for the treatment of complex lesion subsets, particularly those involving coronary arteries with marked segmental tapering.

Aged↗
PubMed1996

Occupational exposure to metal or wood dust and aetiology of cryptogenic fibrosing alveolitis.

BACKGROUND: We have previously suggested that cryptogenic fibrosing alveolitis (CFA) may be caused by occupational exposures, particularly to metal or wood dust. We have specifically investigated this hypothesis in a case-control study of patients with CFA. METHODS: We obtained lifetime occupational histories by postal questionnaire from 218 patients with CFA and 569 controls matched for age, sex, and community, living in the Trent region of the UK. Information was subsequently verified by telephone interview in 165 cases and 408 controls. Serum IgE, rheumatoid factor, and antinuclear antibodies and skin sensitivity to common allergens were measured in cases and in one matched control for each. FINDINGS: The relative risk of CFA, after adjustment for smoking, was significantly increased in relation to questionnaire-reported exposure to metal dust (odds ratio 1.68 [95% CI 1.07-2.65], p = 0.024) or to wood dust (1.71 [1.01-2.92], p = 0.048). Similar results were obtained with the telephone interview data. Significant exposure-response effects were found for both metal-dust and wood-dust exposure. CFA was also associated with the presence of rheumatoid factor or antinuclear antibodies, but not with positive allergen skin tests or raised IgE concentrations. There was no evidence of interaction between the effects of rheumatoid factor, antinuclear antibodies, positive skin allergen tests, or IgE concentrations and exposure to metal or wood dust. The combined aetiological fraction attributable to exposure to metal or wood dust was of the order of 20%. INTERPRETATION: Occupational exposures to metal or wood dust are independent risk factors for CFA. Avoidance or limitation of these exposures may provide an opportunity to prevent the disease.

Autoantibodies↗
PubMed1996

Guideline values for sediments contaminated with dioxins and furans.

There is a growing volume of data reporting contamination of aquatic sediments with dioxins and furans. Despite a great deal of research and investigation into the occurrence and effects of these chemicals no standards or reference values currently exist to assist putting these data into an operational pollution control context, or to help decision making in relation to remediation actions. This paper uses information from the literature to propose an approach to deriving sediment guideline values for these substances, which could be used to aid such operational decisions.

Animals↗
PubMed1996

Life events before psychotic episodes: do clinical and social variables affect the relationship?

We have previously used data from the Camberwell Collaborative Psychosis Study to demonstrate a strong relationship between life events and subsequent episodes of schizophrenic, manic and depressive psychoses. In the current paper, we confirmed the robustness of this relationship, which was not vitiated by controlling for clinical and social variables. Thus, the event-onset association was not affected by the type of onset or the number of previous episodes. The influences of social variables, such as social class, ethnicity and marital status, did not seriously diminish the importance of events, although there may be a role for other forms of social disadvantage as reflected in these variables.

Adolescent↗
PubMed1996

Doctor-patient interactions in oncology.

Studies which apply content analysis techniques to the cancer consultation are few. This descriptive study examines the structure and content of the bad news cancer consultations of 117 outpatients newly referred to the Medical Oncology Department of a large London teaching hospital. From previous communication research three main hypotheses are formed: (i) the cancer consultation is clinician-dominated rather than patient-centred; (ii) the level of psychosocial discussion between clinicians and patients is low and (iii) patient characteristics such as sex, age and prognostic category influence clinician behaviours. Each patient had two consultations with one of 5 oncologists. Both these were audiotaped with the patients' consent. The tapes were content coded using the Roter Interaction Analysis System. Results showed that clinicians tended to use closed rather than open questions. Patients asked few questions and were seldom given space to initiate discussion. Thus, the level of patient-centredness was low. Despite the fact that consultations concerned life threatening disease and often contained information regarding toxic treatment which is known to provoke psychological dysfunction, the number of questions relating to patients' psychological health were few. The amount of discussion concerning medical topics from both parties was 2.5 times greater than the amount of psychosocial discussion. Although there was a suggestion in the data that 3 clinicians showed variations in behaviour according to patient age and prognostic group, the number of patients for each doctor was small. Patients were well informed about their diagnosis, prognosis and treatment options, but their emotional well-being was rarely probed.

Adult↗