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Biomedical subjects

J Bamford

Publications and source records attributed to J Bamford.

At least 19 recordsLinked to original sources
PubMed2003

Very early risk of stroke after a first transient ischemic attack.

BACKGROUND AND PURPOSE: The commonly quoted early risks of stroke after a first transient ischemic attack (TIA)-1% to 2% at 7 days and 2% to 4% at 1 month-are likely to be underestimates because of the delay before inclusion into previous studies and the exclusion of patients who had a stroke during this time. Therefore, it is uncertain how urgently TIA patients should be assessed. We used data from the Oxford Community Stroke Project (OCSP) to estimate the very early stroke risk after a TIA and investigated the potential effects of the delays before specialist assessment. METHODS: All OCSP patients who had a first-ever definite TIA during the study period (n=209) were included. Three analyses were used to estimate the early stroke risk after a first TIA starting from 3 different dates: assessment by a neurologist, referral to the TIA service, and onset of first TIA. RESULTS: The stroke risk from assessment by a neurologist was 1.9% [95% confidence interval (CI), 0.1 to 3.8] at 7 days and 4.4% (95% CI, 1.6 to 7.2) at 30 days. The 7- and 30-day stroke risks from referral were 2.4% (95% CI, 0.3 to 4.5) and 4.9% (95% CI, 1.9 to 7.8), respectively, and from onset of first-ever TIA were 8.6% (95% CI, 4.8 to 12.4) and 12.0% (95% CI, 7.6 to 16.4), respectively. CONCLUSIONS: The early risk of stroke from date of first-ever TIA is likely to be higher than commonly quoted. Public education about the symptoms of TIA is needed so that medical attention is sought more urgently and stroke prevention strategies are implemented sooner.

Aged↗
PubMed2003

Effects of incremental levels of continuous positive airway pressure on cerebral blood flow velocity in healthy adult humans.

Sleep disordered breathing is common in patients with cerebrovascular disease, and could exacerbate the cerebral damage in acute stroke. Data about the effects of continuous positive airway pressure (CPAP) upon cerebral perfusion are conflicting. We investigated whether increasing levels of CPAP may affect cerebral haemodynamics, assessed by transcranial Doppler (TCD) in normal humans. A group of 25 healthy young volunteers were evaluated before (CPAP0-pre), during (CPAP5, CPAP10 and CPAP15, denoting CPAP at 5, 10 and 15 cmH(2)O respectively) and after (CPAP0-post) application of incremental levels of CPAP delivered through a mouthpiece. The mean cerebral blood flow velocity (CBFV) and the pulsatility index (PI; an indirect measure of cerebrovascular resistance) in the middle cerebral artery were measured with TCD. Respiratory rate, heart rate, end-tidal carbon dioxide pressure (PETCO(2)), transcutaneous haemoglobin oxygen saturation (SpO(2)), mean arterial blood pressure and anxiety score were also recorded. Compared with CPAP0-pre, CBFV was significantly decreased as higher levels of CPAP were applied (P <0.0001). CPAP15 increased PI (P <0.05), ETCO(2) was reduced by CPAP10 and CPAP15 (P <0.0001), and anxiety score and SpO(2) increased at all levels of CPAP (P <0.05). Heart rate, respiratory rate and mean arterial pressure did not change. The decrease in CBFV was correlated with the fall in P ETCO(2) (CPAP15) and the increase in PI (CPAP10, CPAP15) (P <0.05). In conclusion, even low levels of CPAP delivered through a mouthpiece in awake, young volunteers led to a decrease in CBFV, measured by TCD. This fall in CBFV was associated with hypocapnia and with an increase in both cerebrovascular resistance and anxiety due to breathing against positive pressure. As the negative consequences of a fall in CBFV may outweigh the therapeutic effects of CPAP in the post-stroke setting, further studies of the cerebrovascular effects of CPAP with different interfaces in elderly patients with and without stroke are needed before intervention trials can be performed safely.

Adolescent↗
PubMed2002

Prevalence and predictors of upper airway obstruction in the first 24 hours after acute stroke.

BACKGROUND AND PURPOSE: The prevalence of sleep-disordered breathing after stroke has been reported to be between 32% and 71%. However, the first 24-hour period, when upper airway obstruction may have a critical effect on the cerebral circulation because of hemodynamic fluctuations and repetitive hypoxia, has not been studied. Furthermore, data on prediction of upper airway obstruction after stroke are limited. This study sought to assess the prevalence of upper airway obstruction in the first 24 hours of stroke and to ascertain whether its occurrence could be predicted. METHODS: One hundred twenty patients with acute stroke underwent a respiratory variable-only sleep study, started within 24 hours of onset of neurological symptoms. Sleep history and stroke characteristics were recorded on admission. RESULTS: We found that 79%, 61%, and 45% of the patients had a respiratory disturbance index greater than 5, 10, and 15 events per hour, respectively. Patients had a significantly higher respiratory disturbance index when nursed in the supine (29 events per hour), supine left (29 events per hour), and supine right (24 events per hour) positions than in any other position (P<0.0001). On logistic regression analysis, BMI (P=0.025), neck circumference (P=0.026), and limb weakness (P=0.025) independently predicted the occurrence of upper airway obstruction in the first 24 hours after acute stroke. CONCLUSIONS: Upper airway obstruction is common in the first 24 hours after stroke, especially if patients are nursed in the supine position, and typical obstructive sleep apnea risk factors (body mass index and neck circumference) appear to be the best predictors of its occurrence. Stroke characteristics (severity, clinical subtype, and clinically assessed pharyngeal function) are not independently associated with upper airway obstruction after stroke.

Acute Disease↗
PubMed2001

Decreased fibrinolytic potential in South Asian women with ischaemic cerebrovascular disease.

To investigate gender differences in conventional, coagulation and fibrinolytic factors in South Asian ischaemic stroke patients, we compared these variables in 50 South Asian females (SAFP) with 90 South Asian males (SAMP) with ischaemic stroke and in 52 females (SAFC) and 38 males (SAMC) without stroke. Plasminogen activator inhibitor-1 (PAI-1) antigen levels were significantly higher in SAFP compared with SAMP (18.2 vs. 13.3 U/ml, P = 0.04) even after adjustment for known covariates, but there was no difference in PAI-1 antigen levels between males and females in the control group. South Asian females exhibited higher levels of factor VII antigen and FVII:C activity in both stroke patients (114 vs. 99% in males, P = 0.01; 116 versus 104% in males, P = 0.04) and controls (116 vs. 97% in males, P = 0.004; 115 vs. 93% in males, P = 0.01). There were no significant differences in the levels of fibrinogen (3.8 vs. 3.7 g/l), FXIIa (2.2 vs. 2.4 ng/ml), von Willebrand factor (1.8 vs. 1.9 IU/ml) and tissue plasminogen activator (11.4 vs. 12.0 ng/ml) in SAMP and SAFP respectively. These results suggest that South Asian females have increased FVII levels and that females with a history of ischaemic stroke have a decreased fibrinolytic potential in comparison with males.

Adult↗
PubMed2001

Assessing service quality in paediatric audiology and early deaf education.

Quality monitoring and assurance is a key aspect of evidence-based service provision in health and education. Part I of the present paper summarizes the results from a survey in which performance of health-based paediatric audiology services in the UK was assessed against existing good practice guidelines (NDCS, 1994, 1996). The results of the survey indicated varied levels of provision, with guidelines commonly not followed. Part II of the paper reports the detailed development of two short questionnaires designed to provide scores (out of 100) reflecting aspects of service quality in paediatric audiology services and in early deaf education services. The results from the use of the two indices (the Paediatric Audiology Service Index (PASI) and the Deaf Education Early Service Index (DEESI)) are presented along with data from some component questions. Although some services are functioning close to guideline levels of service, the overall distribution of scores is such as to raise serious concerns about the variability of quality and the consequent inequity of provision for children with permanent hearing loss and their families in both health and education services.

Age Factors↗
PubMed2001

Performance of neonatal and infant hearing screens: sensitivity and specificity.

The terms 'sensitivity' and 'specificity' are defined and some of the factors that determine their values are discussed in the context of screening for permanent childhood hearing loss. There is a need to distinguish between the values observed in 'simple experiments' and those that may be obtained under more realistic 'field' conditions. It is not feasible to give a meta-analytic overview of published data because of the variety of methods and objectives used in those studies published in the literature. However, a qualitative synthesis of the data is possible. This suggests that most proposed neonatal hearing screening tests, when implemented in accordance with a programme of quality assurance, can be reasonably accurate at a modest cost. However, the optimal combination of tests and test parameters for given populations has not yet been fully researched. The infant distraction test screen has a lower sensitivity than neonatal hearing screening tests, particularly for moderate impairments, accompanied by a fairly low specificity.

Child Health Services↗
PubMed2001

Mortality at 12 and 24 months after stroke may be associated with depressive symptoms at 1 month.

BACKGROUND AND PURPOSE: Previous studies have reported mood symptoms after stroke to be a risk factor for later mortality. The purpose of the study was to examine whether mood symptoms at 1 month after stroke may be a risk factor for mortality at 12 and 24 months. METHODS: As a cohort within a randomized controlled trial, 448 hospital patients were seen at 1 month after stroke and were randomized into a trial of psychological therapy. Follow-up was at 12 and 24 months. Mood symptoms were assessed by the Present State Examination and the General Health Questionnaire (GHQ)-28. Measures of disability before and after stroke and of cognitive impairment after stroke were also taken at 1 month. Mortality was determined at 12 and 24 months after stroke. RESULTS: In logistic regression analyses, mortality at 12 months was associated unifactorally with scoring on the GHQ-D subscale (odds ratio [OR] 2.4, 95% CI 1.3 to 4.5) and scoring in the highest quartile of the GHQ (OR 3.1, 95% CI 1.1 to 8.8). In multiple logistic regression analyses, only GHQ-D remained a significant predictor after controlling for other known predictors. At 24 months, scoring on GHQ-D (OR 2.4, 95% CI 1.4 to 4.1) and in the highest GHQ quartile (OR 2.2, 95% CI 1.0 to 4.8) was significantly associated with mortality in unifactoral analyses. Scoring on the GHQ-D remained a predictor of mortality after controlling for other variables. Psychiatric disorder, such as major depression (according to International Classification of Diseases, 10th Revision), was not statistically significantly associated with increased mortality at 12 or 24 months. CONCLUSIONS: Mood symptoms on a self-reported rating scale were associated with 12- and 24-month mortality after stroke, after adjustment for factors associated with stroke severity. The result is in keeping with other evidence that depressive symptoms are a risk factor for death from vascular disease.

Aged↗
PubMed2001

Insulin resistance and elevated levels of tissue plasminogen activator in first-degree relatives of South Asian patients with ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: South Asians in the United Kingdom suffer from an increased mortality from cerebrovascular disease compared with whites. Evidence suggests that the relatives of white stroke patients are at increased risk of vascular disease. The aim of this study was to investigate atherothrombotic risk factors in the first-degree relatives of South Asian patients suffering from ischemic cerebrovascular disease and to compare them with South Asian subjects free from clinically detectable cerebrovascular disease. METHODS: We compared 143 relatives of South Asians with ischemic stroke (South Asian relatives group) with 146 South Asian control subjects from West Yorkshire, UK. RESULTS: The ages and ethnic and sex distributions of South Asian relatives and South Asian controls were similar. There were no significant differences in body mass index, waist-hip ratio, number of current smokers, and past medical history of hypertension, diabetes mellitus, or myocardial infarction between the 2 groups. Fasting blood glucose, glycosylated hemoglobin (HbA(1c)), total cholesterol, triglycerides, and HDL cholesterol were similar in the 2 groups. Fasting insulin (South Asian relatives, 12.0; South Asian controls, 8.5 mU/L; P<0.0001) (independent of tissue plasminogen activator) and insulin resistance (derived by Homeostasis Model Assessment) (South Asian relatives, 2.7; South Asian controls, 1.9; P=0.001) were significantly raised in stroke relatives. Stroke relatives showed elevated levels of tissue plasminogen activator (South Asian relatives, 11.6; South Asian controls, 8.4 ng/mL; P<0.0001), which was independent of plasma insulin. There were no differences in plasminogen activator inhibitor antigen or activity between the groups. CONCLUSIONS: South Asians stroke relatives exhibit hyperinsulinemia, increased insulin resistance, and increased tissue plasminogen activator levels. These observations might account for increased susceptibility to atherothrombotic disease in this ethnic group.

Adolescent↗
PubMed2000

Computational models of blood flow in the circle of Willis.

A two-dimensional, steady state model of the circle of Willis has been developed. To simulate the peripheral resistance of the cerebrovascular tree, blocks of porous media were used. Their effective resistance was kept constant, disregarding the effects of arterial auto-regulation. The model was then used to simulate different common abnormalities of the circle of Willis while a range of varying boundary conditions was imposed to the right internal carotid artery (ICA). The total flux was tabulated and compared favourably with both clinical measurements and other models of the circle of Willis. Relevant fluid dynamics effects were also observed and analysed. The present model demonstrates that the use of CFD can produce physiological results if the appropriate boundary conditions are used. We can provide clinicians with a priority list of the severity of the flux reduction for the considered abnormalities for different degrees of stenosis of the right ICA. From this study it is apparent that the redistribution of blood via the circle of Willis is mainly driven by changes in the vascular resistance of the brain rather than in the local arterial geometry. The use of valid peripheral resistances allows for a more realistic model of the circle of Willis but also highlights the need for more accurate means to estimate the vascular resistance of a patient.

Animals↗
PubMed2000

Evidence on the efficacy of insert earphone and sound field VRA with young infants.

Visual reinforcement audiometry (VRA) with insert-earphone stimulus delivery provides a means of obtaining early ear-specific information on the auditory status of infants. The aim of this study was to investigate the efficacy of VRA in young infants, and to compare the use of sound field and insert-earphone stimulus presentation. VRA was performed on 41 normally developing infants aged between 20 and 42 weeks. Infants were tested in the sound field (n=22) and with insert earphones (n=19). Results showed significantly more minimum response levels (MRLs) obtained with sound field testing, and with older children. Nevertheless, in the insert-earphone group, 36% of those aged 32 weeks or more gave two or more MRLs, and 25% of the infants aged 25 weeks or less gave one or more MRLs. This study provides data from developmentally normal infants which confirms the efficacy of insert-earphones as well as sound field VRA with 32-42-week-olds, with reasonable expectation of success. The data in this study also suggest that VRA could be usefully employed for younger infants aged approximately 20-26 weeks where information, although less easily obtained, may be of particular value to early diagnosis and habilitation.

Audiometry↗
PubMed1999

Trial of a two-channel hearing aid (low-frequency compression-high-frequency linear amplification) with school age children.

OBJECTIVE: The study was designed to investigate the efficacy of a 2-channel hearing aid with low-frequency compression and high-frequency linear amplification on a group of school-age hearing aid wearers. DESIGN: The study was a single-center, 2-way crossover design in which 25 children (age 6 to 15 yr) were fitted with 2-channel hearing aids for 12 wk and with their own (single-channel) hearing aids for 12 wk, refitted according to published protocols. Speech perception in quiet and in noise was measured at the end of each 12 wk period; in addition, questionnaires were given to teachers, parents, and children. RESULTS: Two-channel hearing aids showed significantly higher mean scores for speech perception in noise and significantly higher composite questionnaire scores (reflecting aspects of satisfaction and benefit). Final choice of hearing aids at the end of the study by parents and children also favored the 2-channel device. CONCLUSIONS: The 2-channel hearing aids appear to be an acceptable management option for audiometrically suitable children. The results provide support for the 2-channel design rationale and suggest the need for further trials.

Adolescent↗
PubMed1997

Epileptic seizures after a first stroke: the Oxfordshire Community Stroke Project.

OBJECTIVE: To describe the immediate and long term risk of epileptic seizures after a first ever stroke. DESIGN: Cohort study following up stroke survivors for 2 to 6.5 years; comparison with age specific incidence rates of epileptic seizures in the general population. SETTING: Community based stroke register. SUBJECTS: 675 patients with a first stroke, followed up for a minimum of 2 years. MAIN OUTCOME MEASURES: Occurrence of single and recurrent seizures. RESULTS: 52 patients had one or more post stroke seizures; in 25 the seizures were recurrent. The 5 year actuarial risk of a post stroke seizure in survivors (excluding 19 patients with a history of epilepsy and 3 patients in whom the seizure occurred shortly before death from another cause) was 11.5% (95% confidence interval 4.8% to 18.2%). The relative risk of seizures, in comparison with the general population, was estimated at 35.2 in the first year after stroke and 19.0 in year 2. The risk of seizures was increased in survivors of subarachnoid and intracerebral haemorrhage (hazard ratio for intracranial haemorrhage v cerebral infarction 10.2 (3.7 to 27.9)). The risk of seizures after ischaemic stroke was substantial only in patients presenting with severe strokes due to total anterior circulation infarction. Only 9 of 295 patients (3%) independent one month after stroke suffered a seizure between 1 month and 5 years (actuarial risk 4.2% (0.1% to 8.3%)). CONCLUSION: Stroke patients have about an 11.5% risk of single or recurrent seizures in the first 5 years after a stroke. Patients with more severe strokes or haemorrhagic strokes are at higher risk.

Adolescent↗