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Biomedical subjects

A Searle

Publications and source records attributed to A Searle.

At least 19 recordsLinked to original sources
PubMed2007

Alliance and compliance in tuberculosis treatment of older Pakeha people in Auckland, New Zealand.

SETTING: A community-based ethnography of tuberculosis (TB) treatment of 'European' New Zealanders in Auckland was completed in 2003. OBJECTIVE: To document and analyse the nature of the process of care in this population where the majority of patients are older with other health and social complications. DESIGN: Data collection included repeated semi-structured interviews with all patients who were willing and able to give consent, semi-structured interviews on health and TB with matched participants without TB, discussions with health care providers, participant observation with TB patients, readings of patient records and monitoring of TB in the media. Reiterative inductive analyses were made of transcripts, field notes and textual materials. RESULTS: Eight patients from 2003 (out of a possible nine) and one patient from 1997 participated. All were aged 47-75 years. They represent a wide socio-economic range. All completed treatment. The contribution of multidimensional care, from initial acceptance through exigencies of treatment to successful recovery, is evident in the participants' narratives. The public health nurse is a key support and a lynchpin in the patients' support network. CONCLUSION: A model of care including alliances between patients and care givers as part of treatment is clearly successful in this population group. This study has implications for older cohorts in other low-incidence countries.

Aged↗
PubMed2006

The uncertainty of the surgical margin in the treatment of head and neck cancer.

We discuss our surgical philosophy concerning the subtle interplay between the size of the surgical margin taken and the resultant morbidity from ablative oncological procedures, which is ever more evident in the treatment of head and neck malignancy. The extent of tissue resection is determined by the "trade off" between cancer control and the perioperative, functional and aesthetic morbidity and mortality of the surgery. We also discuss our dilemmas concerning recent minimally invasive endoscopic microsurgical techniques for the trans-oral laser removal or co-ablation of aero-digestive tract tumours, which result in a minimal surgical margin of oncological clearance. By a process of inductive argument as to the nature of the surgical margin, we consider whether the risks of taking a lesser margin with adjuvant therapy is justified by the attendant gain in reduced surgical morbidity and the possible costs in tumour control.

Head and Neck Neoplasms↗
PubMed2006

Phenotype of autosomal dominant cone-rod dystrophy due to the R838C mutation of the GUCY2D gene encoding retinal guanylate cyclase-1.

AIMS: To describe the phenotype of members of a large Caucasian British family affected by autosomal dominant cone-rod dystrophy due to an R838C mutation in the guanylate cyclase 2D (GUCY2D) gene encoding retinal guanylate cyclase-1 (RETGC-1). METHODS: Retrospective review of 29 patients from four generations of the same family. RESULTS: Visual symptoms usually commenced in childhood. Only two patients, aged 14 and 25 years, had visual acuity compatible with driving. Of the 12 patients aged over 40 years, eight (66%) had vision of counting fingers or worse and were eligible for blind registration in the UK. Of the 29 patients, 18 (62%) had myopia greater than 5 D in at least one eye. Most had discernible macular changes on biomicroscopy, which varied from subtle RPE change to gross macular atrophy. All patients who underwent computerised perimetry exhibited a central or paracentral scotoma with normal peripheral field of vision. Of the 21 patients who underwent electrodiagnostic testing, all exhibited decreased cone function, but rod function was normal in 12 (57%) patients. CONCLUSION: We believe this report highlights the importance of phenotype-genotype correlation in cone and cone-rod dystrophies. Increased understanding of the varying phenotypes associated with different genetic mutations allows appropriate counselling of patients. In addition, the phenotypic characterisation of the natural history of these conditions may prove valuable in the future should therapeutic interventions become available.

Adolescent↗
PubMed2002

Psychosocial and clinical determinants of compliance with occlusion therapy for amblyopic children.

AIMS: The objective of this study was to determine the extent that psychosocial and clinical variables influence parental compliance with occlusion therapy (eye patching) in children with amblyopia. METHODS: Children (n = 151) receiving occlusion therapy (eye patching) for the treatment of amblyopia were recruited from five orthoptic clinics in Bristol, UK. Parents completed a questionnaire based on Rogers' (1983) Protection Motivation Theory (PMT). The parents (n = 105) were also followed up 2 months later. Clinical data, including measures of visual acuity, were also recorded. Compliance with eye patching was assessed through self-report accounts of parents. Stepwise regression analyses were used to determine the factors predictive of compliance with eye patching. RESULTS: Self-reported compliance with eye patching at study entry revealed that only 54% of parents were achieving orthoptists' recommendations to patch their child. Perceived self-efficacy was positively associated with compliance and perceived prohibition of the child's activities were negatively associated with compliance. At follow-up, past behaviour accounted for the largest proportion of explained variance in patching behaviour followed by response efficacy, and prohibition of the child's activities. CONCLUSION: The present findings may serve to inform interventions aimed at enhancing current orthoptic practice to improve compliance in amblyopic children. The importance of 'self-efficacy' and past behaviour suggests that consultations with parents exhibiting higher levels of success with patching may elicit strategies that could be shared with parents experiencing difficulties with patching their children. In addition, it is possible that the perceived efficacy of the treatment could be enhanced if orthoptists emphasised evidence of improvements in visual acuity which may, in turn, foster the maintenance of eye patching.

Amblyopia↗
PubMed2001

Detection of alpha electro-encephalogram onset following eye closure using four location-based techniques.

Detection of alpha activity in the electro-encephalogram (EEG) has been used extensively in neurophysiological studies. Previously applied alpha parameterisation techniques, which utilise the amplitude information from a pair of differential electrodes, are often susceptible to interference from artifact signals. This is an issue if the purpose of detecting the change in alpha wave synchronisation is the basis of an environmental control system (ECS). An alternative approach to alpha activity detection is proposed that utilises the information from an array of electrodes on the scalp to estimate the apparent location of alpha activity in the brain. Four methods are described that successfully detect the onset of alpha EEG increase following eye closure by monitoring the apparent location of alpha activity in the head. The methods use Bartlett beamforming, a four-sphere anatomical head model, the MUSIC algorithm and a new 'power vector' technique. Of the methods described, the power vector technique is found to be the most successful. The power vector technique detects the alpha increase associated with eye closure in times that are, on average, 33% lower than previously applied alpha detection methods.

Algorithms↗
PubMed2001

Effect of luminance level on electro-encephalogram alpha-wave synchronisation.

A control system for the remote activation of electronic devices, based on alpha-wave synchronisation, must be robust over a wide range of lighting conditions. This study investigates the effect that low light levels have on the increase in amplitude of the occipital alpha-wave component of the human electro-encephalogram spectrum in response to eye closure. Measurements of the time required for the amplitude of the occipital alpha wave to increase above a predetermined threshold, upon eye closure, were taken from 21 subjects and at four illuminances, ranging from 2 x 10(-1) lx to 2 x 10(-5) lx. The light source used to provide these illuminances was a featureless, uniformly illuminated white paper that subtended 30 degrees of the visual field. Statistical analysis showed that the time to exceed threshold (TTET) upon eye closure was not independent (p< 0.001) of illuminance, and that the main source of this lack of independence occurred at the lowest illuminance, 2 x 10(-5) lx. At this luminance, the median TTET value was 15.0s. However, at 2 x 10(-4) lx, the median value of the TTET was 4.2s. This is a sufficiently short time for device activation, and therefore a control system based on alpha-wave synchronisation is functional at very low light levels.

Adolescent↗
PubMed2000

The effectiveness of activating electrical devices using alpha wave synchronisation contingent with eye closure.

Increases in alpha wave amplitude occur with eye closure (EC) and decreases occur when the eyes are opened (EO). The research reports in this paper emphasise effectiveness of people using these alpha wave changes to activate electrical devices. Effectiveness was measured in terms of time taken and errors made when selecting the correct device. Ten non-disabled subjects significantly decreased the time taken and errors made to activate correctly a device using a six-option environmental control system (ECS) in the laboratory. In addition, a severely disabled person was shown to use the ECS successfully to control her television in her home environment. This research demonstrates that alpha wave manipulation contingent with EC and EO can be the basis for a reliable and quick switching system for controlling electrical devices. Applications to disability are discussed.

Adult↗
PubMed2000

A direct comparison of wet, dry and insulating bioelectric recording electrodes.

Alternatives to conventional wet electrode types are keenly sought for biomedical use and physiological research, especially when prolonged recording of biosignals is demanded. This paper describes a quantitative comparison of three types of bioelectrode (wet, dry and insulating) based on tests involving electrode impedance, static interference and motion artefact induced by various means. Data were collected simultaneously, and in the same physical environment for all electrode types. Results indicate that in many situations the performance of dry and insulating electrodes compares favourably with wet electrodes. The influence of non-stationary electric fields on shielded dry and insulating electrode types was compared to wet types. It was observed that interference experienced by dry and insulating electrode types was 40 dB and 34 dB less than that experienced by wet electrode types. Similarly, the effect of motion artefact on dry and insulating electrodes was compared to wet types. Artefact levels for dry and insulating electrodes were significantly higher than those for wet types at the beginning of trials conducted. By the end of the trial periods artefact levels for dry and insulating types were lower than wet electrodes by an average of 8.2 dB and 6.8 dB respectively. The reservations expressed in other studies regarding the viability of dry and insulating electrodes for reliable sensing of biosignals are not supported by the work described here.

Artifacts↗
PubMed1999

Real time impedance plots with arbitrary frequency components.

Temporal changes in the impedance spectra of bioelectrodes in contact with skin provide useful data for comparisons between differing electrode materials and skin preparation methods. Traditional impedance measuring systems employ swept frequency methods which will distort results in the impedance spectra of a sample which has nonstationary electrical characteristics. The system reported here obtains impedance spectra by applying a digitally constructed waveform consisting of many frequency components. This allows impedance values to be measured at a number of frequencies simultaneously. Sample data are provided and compared with data obtained using similar square wave techniques.

Calibration↗
PubMed1998

Three methods compared for detecting the onset of alpha wave synchronization following eye closure.

Recent work indicates that the variation in the occipital alpha wave component of the EEG spectrum, controlled through eye closure, can be used by an untrained person to effect reliable activation of electrical devices. Here we describe and compare three real-time strategies, based on analogue and digital signal processing methods, of detecting the onset of alpha wave synchronization during eye closure. The goal of this work is to establish a method which satisfies the condition of rapid detection of alpha wave enhancement, thereby allowing for the efficient activation of devices, while simultaneously registering few or no false positives due to the natural variation in the alpha signal with eyes open. This work, based on measurements on 15 subjects in the age range 12 to 40 years, indicates that renal-time analysis of the EEG power spectrum provides for rapid detection of the onset of alpha wave synchronization while maintaining low counts of false positives.

Alpha Rhythm↗
PubMed1998

Improving the donor site cosmesis of the latissimus dorsi flap.

A modification in the design of the pedicled latissimus dorsi musculocutaneous flap is described that aims to minimize the cosmetic morbidity of its donor site. The implications of this variation are discussed with particular reference to use of the flap in postmastectomy reconstruction.

Back↗
PubMed1997

EEG-based system for rapid on-off switching without prior learning.

Details are reported of an EEG-based system that permits a person rapidly and reliably to switch on and off electrical devices without prior learning. The system detects and utilises increases in the amplitude of the alpha component of the EEG spectrum that occur when people close their eyes for more than 1 s. In addition to conventional signal-processing elements, the system incorporates a module for suppressing switching at the output of the system when predetermined noise threshold levels (such as those due to sources of EMG) are exceeded. This work indicates that a majority, perhaps in excess of 90%, of the adult population can demonstrate the control necessary to operate an electrical device or appliance using this system. It is indicated that multi-level switching and quasi-continuous control options are feasible with further development of the system. This work has implications for the design of a system that could be used, for example, to assist the infirm or severely physically disabled to effect greater control over their environment.

Adult↗
PubMed1990

Measles appendicitis.

Measles is a common disorder in the United Kingdom, due partly to the decreasing incidence of vaccination in children of a susceptible age. We report a case of abdominal pain in a child caused by the measles virus.

Appendicitis↗