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Biomedical subjects

J R Britton

Publications and source records attributed to J R Britton.

At least 19 recordsLinked to original sources
PubMed2003

Mechanical simulation of muscle loading on the proximal femur: analysis of cemented femoral component migration with and without muscle loading.

OBJECTIVE: This study examines the effect of including muscle forces in fatigue tests of cemented total hip arthroplasty reconstructions. DESIGN: An experimental device capable of applying the joint reaction force, the abductor force, the vastus lateralis force, and the tensor fasciae latae force to the implanted femur is described. BACKGROUND: Current in vitro fatigue tests of cemented total hip arthroplasty reconstructions do not apply physiological muscle loads. Experimental and numerical studies report significant differences in stresses obtained in the cement mantle depending on the loads applied. The differing stresses may alter the outcome of an in vitro test. METHODS: Ten femoral components were reproducibly implanted into proximal composite femurs. Five of these femoral components were tested using a loadprofile which included muscle loading, five were tested without muscle loading. The migration of each femoral component was monitored continuously during dynamic fatigue tests. RESULTS: Clinically comparable migration amounts were found for both sets of femoral components, with the femoral components tested with muscle loading experiencing lower mean migration, lower mean inducible displacement, and less experimental scatter. CONCLUSIONS: The inclusion of muscle forces seems to stabilise the femoral component during the test. In vitro fatigue tests of cemented total hip arthroplasty reconstructions should include muscle loading to provide increased confidence in the results obtained. RELEVANCE: This study examines how the migration of cemented femoral hip prostheses is influenced by muscle forces. Hip prostheses are one of the few medical devices for which pre-clinical testing protocols have emerged, and this study ascertains whether or not the inclusion of muscle forces is necessary for pre-clinical tests. The conclusion that muscle loading should be included, and that it is important for the development of a new generation of standardised tests to provide enhanced patient protection against functionally poor prostheses.

Arthroplasty, Replacement, Hip↗
PubMed2003

Respiratory symptoms in patients with treated hypothyroidism and inflammatory bowel disease.

BACKGROUND: Patients with idiopathic chronic cough and unexplained airflow obstruction in non-smokers have been shown to have an increased prevalence of hypothyroidism and other organ specific autoimmune disorders. Whether patients with hypothyroidism have an increased prevalence of respiratory symptoms is unknown. METHODS: The prevalence of respiratory symptoms was assessed in 124 patients with treated hypothyroidism recruited from primary and secondary care, 64 outpatients with inflammatory bowel disease, and 1346 control adults recruited randomly from the electoral register in a case-control study. Respiratory symptoms and smoking history were assessed by a respiratory symptom questionnaire. RESULTS: After adjustment for age, sex and smoking, symptoms of breathlessness and sputum production were more prevalent in both patient populations than in controls (odds ratios for hypothyroidism and inflammatory bowel disease; breathlessness: 3.1 (95% CI 2.1 to 4.6) and 3.4 (95% CI 2.0 to 6.0), respectively; sputum production: 2.7 (95% CI 1.6 to 4.5) and 2.5 (95% CI 1.2 to 5.0), respectively). Cough during the day and night was significantly more prevalent in patients with hypothyroidism (1.8 (95% CI 1.2 to 2.9)) and approached significance in those with inflammatory bowel disease (1.8 (95% CI 1.0 to 3.4)). Wheeze and nocturnal cough were no more prevalent in either disease population than in controls. CONCLUSION: There is a significantly increased prevalence of respiratory symptoms in patients with hypothyroidism or inflammatory bowel disease compared with controls recruited from the general population. Further work is required to determine whether similar differences are seen in comparison with hospital based controls. These findings support the hypothesis that there is a link between autoimmune hypothyroidism and respiratory disease.

Airway Obstruction↗
PubMed2002

Asthma.

Asthma is one of the commonest chronic diseases of affluent societies. The striking increase in prevalence of asthma over recent decades and the rarity of this disease in less affluent populations confirms the importance of environmental factors in the cause of asthma--although which environmental factors are responsible is still not clear. Family studies show that genetic factors are also important in determining individual susceptibility to asthma, with results of genetic studies suggesting that there are many genes with moderate effects rather than a few major genes. Asthmatic airways show inflammation and remodelling, with CD4+ helper cells, mast cells, and eosinophils characterising the inflammatory response. Inhaled corticosteroids remain the cornerstone of treatment with the addition of long-acting beta agonists as the next step if symptoms continue. Leukotriene antagonists, the only new drugs to reach the market in the past decade, have modest effects. However, a better understanding of the mechanisms underlying asthma and the genetic and environmental factors that predispose individuals to asthma should lead to better preventative strategies and new therapeutic approaches.

Asthma↗
PubMed2001

Maternal postpartum behaviors and mother-infant relationship during the first year of life.

OBJECTIVE: To assess the hypothesis that maternal postpartum behaviors toward the newborn may predict the quality of the maternal-infant relationship during the first year. DESIGN: Prospective, non-randomized, longitudinal cohort study of 174 maternal-infant dyads. METHODS: A Postpartum Parenting Behavior Scale (PPBS) was formulated to measure clearly defined observed maternal behaviors toward the infant shortly after birth. The quality of the maternal-infant relationship was assessed at 6 months after birth with the Nursing Child Assessment Satellite Training (NCAST) Feeding Scale and at 12 months after birth with the NCAST Teaching Scale and Ainsworth Strange Situation. RESULTS: The PPBS score correlated significantly with the Feeding Scale score (r =.27, P <.005) and with the Teaching Scale score (r =.23, P <.01). Mothers whose infants were later classified as securely attached in the Ainsworth Strange Situation had higher PPBS scores than mothers of infants classified as insecurely attached (mean +/- SD: 5.18 +/- 1.51 vs 4.63 +/- 1.69, respectively, P <.05). In regression models adjusting for social and demographic factors, the PPBS remained a significant predictor of the Feeding Scale score, the Teaching Scale score, and security of attachment. CONCLUSIONS: Maternal behaviors in the immediate postpartum period may aid in predicting quality of the maternal-infant relationship during the subsequent 12 months, suggesting the potential for early identification of suboptimal parenting.

Adolescent↗
PubMed2001

Airway responsiveness and peak flow variability in the diagnosis of asthma for epidemiological studies.

Airway responsiveness and variability in peak expiratory flow (PEF) are widely used as objective diagnostic measures of asthma, but it is not clear how these variables should be calculated or adjusted to obtain the highest diagnostic validity for physician-diagnosed asthma in the community. Data from a community-based sample of 1,513 adults has been used. Airway responsiveness to methacholine and 7-day PEF data were obtained in 1991, asthma and respiratory symptoms were diagnosed by questionnaires in 1991 and 1999. Airway responsiveness was expressed as the provocative dose causing a 20% fall in forced expiratory volume in one second (PD20), two-point and least-squares regression slopes. PEF variability was expressed as daily amplitude, weekly standard deviation and mean of the two lowest readings. Continuous measures were adjusted for measures of baseline airway calibre by linear regression. Measures of airway responsiveness had greater sensitivity for specificity for self-reported diagnosed asthma than expressions of PEF variability, before and after adjustment for airway calibre. Diagnostic validity was substantially better in adults aged <50 yrs; PD20 provided the best sensitivity for specificity (61% for 95% at 8.3 micromol). In those aged > or =50 yrs, no measure was closely related to diagnosed asthma. In younger age groups, provocative dose causing a 20% fall in forced expiratory volume in one second provides a valuable objective measure of asthma for epidemiological studies, but is unable to distinguish between asthma and chronic obstructive pulmonary disease in older people.

Adult↗
PubMed2001

The relation between peripheral blood leukocyte counts and respiratory symptoms, atopy, lung function, and airway responsiveness in adults.

STUDY OBJECTIVES: Eosinophils and neutrophils play major roles, respectively, in the pathogenesis of asthma and COPD, and it is well recognized that levels of these cells in peripheral blood are increased in relation to their pulmonary involvement. However, the relation between peripheral blood cell counts of the other major leukocyte groups and these lung diseases or markers of allergy or airflow obstruction is less clear. We have therefore investigated the association between peripheral blood levels of eosinophils, neutrophils, basophils, monocytes, and lymphocytes and the occurrence of chronic respiratory symptoms, atopy, lung function, and bronchial hyperresponsiveness, and the modifying effect of age, in adults. DESIGN: A cross-sectional general population study. SETTING: Data on > 2,000 British adults, who originally participated in a study of diet and lung health, were analyzed using multiple linear and logistic regression to adjust for potential confounders, including age, sex, and smoking history. RESULTS: We found that, like eosinophils, the peripheral basophil count was increased in relation to asthma and associated symptoms, and to airway hyperreactivity and increased total IgE, but differed from eosinophils in that basophils were unrelated to atopy. Monocytes were predominantly associated with symptoms indicative of obstructive airway disease, in similar relation to neutrophils, but both of these leukocyte counts were also increased in asthma patients in older age groups. Lymphocyte counts were unrelated to any objective or subjective marker of disease. CONCLUSIONS: If peripheral blood cell counts reflect pulmonary involvement of these leukocyte groups, basophils and monocytes may play a distinct role in the pathogenesis of allergic and nonallergic respiratory disease.

Adolescent↗
PubMed1999

Prospective audit of a respiratory sleep disorders service at District General Hospital level.

This study was designed to examine the organisation and outcomes of a District General Hospital respiratory sleep service, since data are lacking on the management of sleep-disordered breathing at this level. Questionnaires and case-notes review were used to assess the management of 119 consecutive patients referred with suspected sleep-disordered breathing. Patients diagnosed with sleep-disordered breathing were assigned nasal continuous positive airway pressure (nCPAP), ear/nose/throat (ENT) surgery or simple measures (e.g., weight loss). There were six non-attenders. At 12 months follow-up, 33 patients had been assigned to nCPAP, 25 to ENT surgery, and 37 to simple measures. Of the remainder, nine had alternative diagnoses, two were still being assessed and seven were lost to follow-up. Patients prescribed nCPAP (81% compliance) had significant symptomatic improvements with low dissatisfaction rates (20%); patients on simple measures did not improve (33% dissatisfied); only half assigned surgery had it performed, with 42% awaiting surgery and dissatisfied. Interspecialty referral resulted in major delays (mean 16 weeks). Referral letters were generally unhelpful in deciding on the appropriateness of initial referral (respiratory physician vs ENT). nCPAP was generally effective in improving symptoms, with a high level of patient satisfaction, while simple measures did not improve symptoms and were associated with lower satisfaction levels. Waiting times to ENT surgery can be long and patients express significant dissatisfaction. Referral letters are not useful in directing initial referral. Services should be co-ordinated between respiratory and ENT specialties to reduce waiting times and improve patient satisfaction.

Adult↗
PubMed1999

Early perinatal hospital discharge and parenting during infancy.

OBJECTIVE: To evaluate the relationship between early perinatal hospital discharge and several parenting outcomes during infancy, including breastfeeding, mother-infant interaction, and mother-infant attachment. STUDY DESIGN: A prospective, longitudinal, nonrandomized study of mother-infant dyads discharged </=36 hours after birth (early discharge), compared with those discharged >36 hours after birth (late discharge). METHODS: Demographic, perinatal, and psychosocial factors were determined from medical record review and maternal questionnaires. Questionnaires also assessed maternal perceptions of the hospital stay and breastfeeding rates. Mother-infant interaction was assessed at 3 months after birth using the NCAST Feeding Scale and at 9 months after birth using the NCAST Teaching Scale. Security of attachment was measured in the Ainsworth Strange Situation at 12 months after birth. RESULTS: Early and late discharge groups were similar with respect to major demographic, perinatal, and psychosocial characteristics and perceptions of the hospital stay. Even after adjusting for these factors in regression analyses, no significant association was found between early discharge and breastfeeding at 3 months, NCAST scores at 3 and 9 months, and security of attachment at 12 months. CONCLUSION: Parenting outcomes, such as breastfeeding, mother-infant interaction, and attachment, are not influenced by early perinatal hospital discharge.

Adult↗
PubMed1998

Consistent effects of high socioeconomic status and low birth order, and the modifying effect of maternal smoking on the risk of allergic disease during childhood.

Birth order, maternal age, gestational age, birth weight, maternal smoking, and social class have all been associated with allergic rhinitis, eczema and asthma in childhood, but the consistency of independent effects of these exposures in relation to all of these allergic conditions has not been investigated. We have compared and contrasted the independent effects of these putative risk factors on parent-reported hayfever, eczema and wheeze by age 16 years and in the past 12 months at age 16 using data from the 1970 British birth cohort. The 1970 British birth cohort comprised all children born in England, Scotland and Wales in one week of April 1970, and follow-up surveys at birth, 5, 10 and 16 years of age involved a cumulative total of 17,427 children. We have used data on over 6000 children with complete data at every stage. Social advantage was a risk factor common to each of wheeze at, and hayfever and eczema at and by age 16. Low birth order was an independent risk factor for eczema and hayfever at age 16, but not for wheeze. However, wheeze at age 16 was significantly increased in relation to maternal smoking, with a significant interaction such that the effect of smoking was greatest in those of high birth order and, in the absence of maternal smoking, low birth order was a risk factor for wheeze at age 16. Social advantage and low birth order appear to be the independently consistent determinants of atopic disease. Maternal smoking is an additional risk factor for wheeze, which applies primarily in low socioeconomic groups.

Adolescent↗
PubMed1998

Measles infection, measles vaccination and the effect of birth order in the aetiology of hay fever.

BACKGROUND: It has recently been suggested that measles infection may reduce the risk of atopy. OBJECTIVE: To study the independent effect of measles infection and measles vaccination on the occurrence of hay fever in a British national birth cohort. METHODS: In over 6000 children born in 1970, details of immunizations and childhood diseases were collected by parental interviews at ages 5, 10 and 16 years, and hay fever within the past year at age 16 years. RESULTS: In univariate analysis, hay fever was less common in those contracting measles infection than in those not infected (OR 0.86, 95% CI 0.76-0.96), and more common in those given measles vaccination than in those not vaccinated (OR 1.16, 95% Cl 1.03-1.31). However, these effects were strongly confounded by birth order, which was closely associated with the likelihood of receiving measles vaccination and with the risk of hay fever. A strong interaction between the effects of measles vaccination and infection, and birth order was found, such that in those with many older sibling contacts, hay fever was significantly and independently reduced in relation to both measles infection and measles vaccination relative to those who were neither infected nor vaccinated. CONCLUSIONS: Both measles infection and measles vaccination in childhood appear to reduce the risk of hay fever in children with multiple older sibling contacts. Differential exposure or response to the measles virus may explain the effect of birth order on the occurrence of allergic disease.

Adult↗
PubMed1998

Postpartum early hospital discharge and follow-up practices in Canada and the United States.

BACKGROUND: Although official guidelines and recent legislation have addressed early postpartum hospital discharge and follow-up, little is known about the practices of obstetricians in Canada and the United States on this issue. METHODS: Questionnaires were mailed to two separate random samples of 2000 Fellows of the American College of Obstetricians and Gynecologists (ACOG) in the United States and all Canadian Fellows. Practices and perceptions were compared with those recommended in the literature, recent legislation, and guidelines of ACOG and American Academy of Pediatrics (AAP). RESULTS: In contrast to concerns expressed in the medical literature and official AAP/ACOG guidelines, many physicians considered potential psychosocial and demographic risk factors relatively unimportant in making early discharge decisions, preferring to emphasize aspects of the patient's medical condition, hospital course, and social support. Although the official guidelines encourage follow-up for all patients discharged early, additional visits are routinely advised by only 39 percent of obstetricians after vaginal delivery and by 68 percent after cesarean section. After vaginal delivery 39 percent of obstetricians used telephone follow-up and 37 percent after cesarean delivery. Moreover, although the official guidelines recommend follow-up within 48 hours of discharge, only one-half of the obstetricians surveyed advised follow-up at this time. In contrast to the guidelines, most obstetricians defined early discharge as that occurring within 24 hours after vaginal delivery and 72 hours after cesarean delivery; most defined optimal lengths of stay within the 48-hour (after vaginal delivery) and 96-hour (after cesarean delivery) periods considered short by the guidelines. CONCLUSIONS: Current postpartum early discharge and follow-up practices emphasize the physical health of the mother and place little emphasis on social risk. They appear to be influenced by perceptions of the appropriateness of the length of stay and are not in agreement with professional guidelines.

Aftercare↗
PubMed1998

The transition to extrauterine life and disorders of transition.

With shorter postnatal hospital stays, concern has arisen that many infants may be discharged prior to completion of the transition to extrauterine life, a time of dynamic physiologic change when many neonatal problems may present. This article reviews the physiology of the neonatal transition together with common transitional disorders. Most disorders of transition present at typical postnatal time periods, permitting their timely anticipation and treatment. Moreover, many are associated with factors that may further aid the clinician in defining those infants at highest risk.

Humans↗
PubMed1998

The perinatal assessment of psychosocial risk.

Although evaluation of psychosocial risk factors prior to perinatal hospital discharge has been advocated, the means for accomplishing such an evaluation are not well established. This article reviews several major psychosocial risk factors together with instruments that have been utilized to assess them during the perinatal period. Formal constructs reviewed include anxiety, depression, self-concept, general attitudes, life events, stress, adaptation, social support, marital and family functioning, and the home environment. Ongoing assessment of psychosocial status using formal instruments during routine perinatal care may provide a more complete picture of the psychosocial needs of the individual mother and her family, allowing for more appropriate, timely intervention and utilization of social and health care resources.

Adaptation, Psychological↗
PubMed1996

Neonatal mortality and length of newborn hospital stay.

OBJECTIVE: To investigate the effect of hospital discharge time on neonatal mortality of term newborns. DESIGN: Infants who were discharged home at 5 days of age of younger and who subsequently died were compared with control infants using a retrospective case-control design. Descriptive information was collected from records of infants who were not discharged home from the hospital of birth (because of death or transfer to a tertiary care hospital) to determine the age at which their illnesses presented. METHODS: We reviewed death certificates for all infants with birth weights of 2500 g or greater born at 37 weeks' gestational age or greater who died in the first 28 days of life and who were born in one of four Utah counties (1985 through 1989). Of the 109,256 eligible births, 115 infants were found who had died in the neonatal period. Eighty-four infants had not been discharged home from the hospital of birth, 5 infants had had hospital stays of more than 5 days, 9 records could not be located, 17 presumed healthy infants were discharged from the hospital at 5 days of age or younger. These 17 infants were each matched with 3 control infants. Newborn nursery charts were reviewed to determine hospital discharge times for case and control infants. Descriptive information regarding the time of presentation of illness was collected for the other 89 infants. RESULTS: The mean age of hospital discharge was 43 +/- 21 hours for the 17 case infants and 47 +/- 25 hours for the 51 control infants. The odds ratio for neonatal mortality for discharge at less than 24 hours was 1.65 (95% confidence interval, 0.42 to 3.34) and for discharge at less than 48 hours was 1.16 (95% confidence interval, 0.4 to 3.34). Of the 84 infants who were not discharged home from the hospital of birth, 93% had been symptomatic by 12 hours of age, and 99% were symptomatic by 18 hours. CONCLUSIONS: Most full-term infants who die in the neonatal period are symptomatic within the first 18 hours after birth. We could not demonstrate an association between early hospital discharge and neonatal mortality in those infants who died after discharge home.

Age of Onset↗
PubMed1995

Geographical and social class effects on asthma mortality in England and Wales.

To determine whether asthma mortality is influenced by geographical or social factors, a retrospective analysis of deaths from asthma in England and Wales between 1979-1987 was performed. Death rates in the 15 Regional Health Authority areas of England and Wales were stratified by sex, age group (0-4, 5-34, 35-64, and > 64 years), and occupational social class. Detailed analysis was restricted to subjects aged 5-64 years because adequate social class data was only available over this age range. Death rates were higher in manual occupational groups (social class IIIb-V) than in non-manual occupations (social class I-IIIa), but on further analysis this effect was confined to males aged 35-64 years. In younger subjects (5-34 years), mortality was higher in the south of the country, and this difference was significant in males (P < 0.05). In older subjects (35-64 years), mortality in both sexes was significantly higher in the north of the country. This study demonstrates that mortality is not evenly distributed between social classes or regions of the country.

Adolescent↗
PubMed1995

Dietary antioxidant vitamin intake and lung function in the general population.

We have investigated the relation between lung function and dietary intake of the antioxidant vitamins C and E in the general population in a cross-sectional survey of a random sample of adults from the electoral register of an administrative area of Nottingham. In 2,633 subjects 18 to 70 yr of age, we measured FEV1 and FVC, allergen skin sensitivity to grass pollen, cat fur, and Dermatophagoides pteronyssinus, pack-years smoking exposure by personal recall, and usual dietary intake of vitamins C and E by semiquantitative food frequency questionnaire. After adjustment for the effects of age, sex, height, mean allergen skin wheal diameter, and pack-years smoking history, both FEV1 and FVC were significantly and independently related to mean daily intake of vitamin C, such that a standard deviation (40 mg/d) higher vitamin C intake was associated with a 25.0 (95% CI, 5.2 to 44.8; p = 0.01) ml higher FEV1 and a 23.3 (0.94 to 45.7, p = 0.04) ml higher FVC. There was also an association between vitamin E intake and lung function, such that a standard deviation (2.2 mg) higher intake of vitamin E was associated with a 20.1 (1.3 to 40.4, p = 0.04) ml higher FEV1 and a 23.1 (1.0 to 45, p = 0.04) ml higher FVC. However, vitamin C and vitamin E intakes were significantly correlated (r = 0.29, p < 0.001), and after allowing for the effects of vitamin C there was no additional independent effect of vitamin E on either FEV1 or FVC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗