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Biomedical subjects

S Parks

Publications and source records attributed to S Parks.

At least 19 recordsLinked to original sources
PubMed2006

Microbial aerosol generation during laboratory accidents and subsequent risk assessment.

AIM: To quantify microbial aerosols generated by a series of laboratory accidents and to use these data in risk assessment. METHODS AND RESULTS: A series of laboratory accident scenarios have been devised and the microbial aerosol generated by them has been measured using a range of microbial air samplers. The accident scenarios generating the highest aerosol concentrations were, dropping a fungal plate, dropping a large bottle, centrifuge rotor leaks and a blocked syringe filter. Many of these accidents generated low particle size aerosols, which would be inhaled into the lungs of any exposed laboratory staff. Spray factors (SFs) have been calculated using the results of these experiments as an indicator of the potential for accidents to generate microbial aerosols. Model risk assessments have been described using the SF data. CONCLUSIONS: Quantitative risk assessment of laboratory accidents can provide data that can aid the design of containment laboratories and the response to laboratory accidents. SIGNIFICANCE AND IMPACT OF THE STUDY: A methodology has been described and supporting data provided to allow microbiological safety officers to carry out quantitative risk assessment of laboratory accidents.

Accidents, Occupational↗
PubMed2005

Determining the performance of a commercial air purification system for reducing airborne contamination using model micro-organisms: a new test methodology.

The performance of a duct-mounted air disinfection system, designed to reduce airborne pathogens in the hospital environment, was determined using a new testing methodology. The methodology places the equipment in a test duct, a microbial aerosol is generated and then sampled simultaneously before and after the test system. This allows a percentage efficiency value to be calculated. The air disinfection system is a novel chemical-coated filter and ultraviolet (UV) radiation air purification system, operating at a flow rate of 500 m(3)/h, against aerosols of MS2 phage and Mycobacterium vaccae (surrogates of viral and mycobactericidal pathogens). A three UV lamp system was effective against airborne phages, removing an average of 97.34% of the aerosolized challenge. With the UV component switched off, the average efficiency dropped to 61.46%. This demonstrates that the chemical-coated filter component plays a more significant role than the UV radiation in destroying phages. When six UV lamps were used, the system was able to remove mycobacteria with an efficiency exceeding 99.99%. This test methodology can be used to assess manufacturers' claims of efficacy of equipment against airborne micro-organisms in the hospital environment.

Air Microbiology↗
PubMed2005

Retinal toxicity during pegylated alpha-interferon therapy for chronic hepatitis C: a multifocal electroretinogram investigation.

BACKGROUND: Ocular side-effects in the form of retinal ischaemia and haemorrhages have been reported in patients undergoing standard alpha-interferon therapy. AIM: To assess the ocular impact of therapy with sustained release pegylated alpha-2a interferon (Pegasys) for chronic hepatitis C. METHODS: Ten patients receiving Pegasys and ribavirin and 10 healthy volunteers were recruited. Patients underwent full ophthalmic investigations and multifocal electroretinogram testing at baseline, at regular intervals during treatment and post-treatment. The multifocal electroretinogram maps retinal function. Responses were compared with sequential recordings from healthy volunteers. RESULTS: All patients had normal clinical ophthalmic investigations at baseline. During therapy a single patient experienced central visual disturbance lasting 24 h with no prolonged ill effect. No other patient was aware of any change in vision. Fundal abnormalities appeared in five patients during treatment. The multifocal electroretinogram showed reductions in retinal function in five patients. Nine of 10 patients exhibited abnormalities on at least one multifocal electroretinogram or fundoscopic investigation. CONCLUSIONS: Subclinical retinal toxicity during anti-viral therapy with pegylated alpha-interferon and ribavirin was frequent in this study and it suggests that patients should be warned of this risk and monitored during therapy.

Adult↗
PubMed2004

The effects of pupil size on the multifocal electroretinogram.

This is an investigation of the effect of changing the pupil diameter on the P1 amplitude and latency of the multifocal electroretinogram (mfERG). MfERGs were recorded using a custom built wide field electrophysiological system. An array of 61 empirically scaled hexagons was used to stimulate the visual field. The duration of overall recording period was 8 min, segmented into 16 intervals each lasting 30 s. A combination of mydriatics and miotics were used to pharmacologically alter the pupil size and diameters between 1 and 10 mm were measured. There was a reduction in mfERG P1 amplitude in some cases greater than 50% (mfERG P1 amplitude 53 nV at 8 mm to 25 nV at 1 mm), with a change in pupil diameter of 7 mm. The mfERG P1 latency increased in some cases by as much as 8 ms in the central 40 degrees (mfERG P1 latency 39 ms at 8 mm to 47 ms at 1 mm). These results suggest that pupil size has significant effects on mfERG P1 amplitude and latency.

Electroretinography↗
PubMed2004

Secondary retinal changes associated with choroidal naevi and melanomas documented by optical coherence tomography.

AIMS: To establish the characteristics of secondary retinal changes associated with the presence of choroidal melanomas and choroidal naevi as documented by optical coherence tomography (OCT). METHODS: Twenty patients with untreated choroidal melanoma and 40 patients with presumed choroidal naevi managed by regular observation were included in the study. OCT scans across the surface of the tumour and surrounding tissue were acquired for all participants. The appearance of retinal tissue on the OCT scans was considered to be abnormal if it did not display the well defined band structure characteristic of normal tissue on OCT scans. RESULTS: Serous retinal detachments were observed in all patients with choroidal melanoma and 18 out of 20 also had abnormal retinal structure or intra-retinal splitting in the tissue overlying the tumour. Out of the 40 patients with presumed choroidal naevi, 12 had serous detachments and three had either abnormal retinal structure or intra-retinal splitting overlying the lesion. CONCLUSIONS: Secondary retinal changes associated with choroidal lesions can be documented by OCT. These changes were observed in most patients with choroidal melanoma included in the study group but were far less prevalent in the patients with presumed choroidal naevi. OCT is also able to identify the presence of small serous detachments before they become clinically visible. Follow up of these patients is required to determine whether the OCT results may be of use in the differential diagnosis of small choroidal lesions.

Adult↗
PubMed2003

Peripheral retinal dysfunction in patients taking vigabatrin.

OBJECTIVE: To assess the wide-field multifocal electroretinogram (WF-mfERG) for assessment of retinal function in vigabatrin-treated patients. METHODS: Thirty-two adults who had taken vigabatrin for at least 3 years for localization-related epilepsy underwent WF-mfERG, ERG, logMar visual acuity and color vision evaluation, Humphrey visual field analysis (static perimetry), and funduscopy. The group was matched with a cohort of patients who had never received vigabatrin. Results were compared with a normative data set (120 drug-free controls) with respect to potential bilateral abnormalities in response timing. RESULTS: There were no significant differences between groups in visual acuity or color vision testing. Of the vigabatrin patients, 19 (59%) had bilateral visual field defects compared to none of the controls. Using WF-mfERG, all patients on vigabatrin with visual field defects showed abnormalities (100% sensitivity) and only 2 of the 13 patients without a field defect showed retinal abnormalities (86% specificity). CONCLUSIONS: WF-mfERG may be useful for detecting retinal pathology in patients taking vigabatrin. The majority of previous reports based on subjective testing may have underestimated the prevalence of peripheral retinal toxicity related to the drug.

Adult↗
PubMed2002

Identification of appropriate primitive polynomials to avoid cross-contamination in multifocal electroretinogram responses.

Abstract-The basis of the multifocal/electroretinogram is the use of a decimated m-sequence for simultaneous and independent stimulation of many areas of the visual pathway. The purpose of this study was to investigate the effects of cross-contamination from higher orders of the response. A series of primitive polynomials were found by construction of finite fields. The first-order ERG response was formed by cross-correlation of m-sequence with the physiological response. A second-order response was formed by investigation of particular flash sequences of the stimulation sequence and cross-correlation of a second-order m-sequence with the physiological response. Zech logarithms were used to identify cross-contamination between the various first and second-order sequences. Tables of good and bad primitive polynomials were constructed for degrees 12-16, and the effects of window length and decimation length were examined. When the sequence was decimated into 128 areas, and a window of length 16 was examined, cross-contamination occurred in all sequences generated from primitive polynomials of degree less than or equal to 12, but in only 26% of degree 14, and 5.6% of degree 16. A photodiode (artificial eye) was used in an experiment to construct trace arrays showing responses from 61 individual areas. Additional waveforms were present on the trace array when the experiment was carried out with a bad primitive polynomial. The use of finite field theory to generate primitive polynomials and Zech logarithm analysis allowed prediction of which primitive polynomials were suitable for m-sequence generation for multifocal electroretinography. Practical investigations supported the theoretical analysis. This has important implications for developers of multifocal electrophysiology systems.

Artifacts↗
PubMed2001

A comparison of CRT and digital stimulus delivery methods in the multifocal ERG.

The purpose of this paper is to compare and evaluate the multifocal ERG response from raster based CRT and Digital Projection (LCD) stimulus delivery systems. A custom built p.c. based multifocal system was used to generate a 61 hexagonal element stimulus array. The stimulus was presented on a high luminance CRT display and on a back projected screen using a Digital polysilicon projection system. A fast response photodiode was used to analyse the stimulus pulse characteristics of both systems. A number of recordings were performed to assess the effect of stimulus delivery on a standard m-sequence response, inserted full-field filler response and on separation of onset and offset components. The pulse width for a CRT system is dependant on the type of phosphor and is typically 2 msec whereas the Digital Projection system produces a 13.3 msec pulse equivalent to the frame rate for the system. Slowing down the m-sequence by a factor of eight results in a pulse width of 106 msec which should enable the recovery of true offset responses. The CRT stimulus consists of a series of eight pulses of 2 msec duration each separated by 11.3 msec. First order responses are larger from the CRT system and second order responses larger from the Digital system. In conclusion, there are fundamental differences in the two delivery systems. The CRT system may have more potential in examining non-linear aspects of the multifocal response. Although both systems may be able to record offset responses, the Digital system will generate true offset responses whereas the CRT system may not allow true separation of these components.

Adult↗
PubMed2001

The impact of fixation on the multifocal electroretinogram.

There are a number of variables which can influence the quality of multifocal ERG waveforms. In common with visual field measurements, fixation quality may be an important parameter on the integrity of the acquired data. A low cost, fixation-monitoring device was used to assess fixation quality on a group of normal volunteers. Data was successfully acquired while five subjects viewed a fixation target for a period of time equal to that of a single multifocal recording segment. The target was presented on a stationary grey background and as the central fixation mark on a 61-element multifocal flicker stimulus. The results show no significant difference with or without the flickering pattern. The percentage of samples falling within 1.2 degrees of the point of fixation was 51%. This suggests that fixation quality is adequate for scaled stimuli where the central element subtends 2.4 degrees. High resolution stimuli of less than 2.4 degrees may be more susceptible to fixation fluctuations during the recording process.

Adult↗
PubMed2001

Spatial localization after different types of retinal detachment surgery.

PURPOSE: To compare the effect on spatial localization of two different forms of surgery for primary rhegmatogenous retinal detachment. METHODS: Two groups of 30 patients (one group undergoing conventional external scleral-buckling procedures, the other undergoing vitrectomy procedures) were recruited. They pointed at targets appearing on a computer touchscreen without being able to see their hands, while viewing targets with the non-surgically treated eye. The sizes of the horizontal pointing errors were recorded on three separate occasions: before surgery, on the first postoperative day, and approximately 10 days later. RESULTS: On the first postoperative day a significant change in localization of 2.9 +/- 0.9 degrees [SD]) was observed in the scleral-buckling group, compared with 1.3 +/- 0.6 degrees in the vitrectomy group. These changes resolved by the second postoperative assessment. CONCLUSIONS: These results, particularly in patients in the scleral-buckling group in whom greater manipulation of the extraocular muscles inevitably occurs, are consistent with an alteration in the extraretinal eye position information that is used in spatial localization. This is likely to be a consequence of modified efference copy and/or extraocular muscle proprioception.

Adult↗
PubMed2000

Technical aspects of multifocal ERG recording.

There are a wide range of variables which can influence the quality of the multifocal response. It is possible to place these variables into one of four categories. First, the method of stimulus delivery will determine the field of view, interference levels and the duration of on-state stimulation. Second, data acquisition variables such as electrode type and placement, amplifier specifications and filter bandwidth settings will have a direct impact on waveform shape and on the topographic distribution of signal amplitudes. Third, patient variables such as fixation, pupil dilation and refractive error will also contribute to the multifocal response. Fourth, there are many measurements that can be taken from multifocal recordings. In addition to standard amplitude and implicit time measures (the implicit time measure in the multifocal response is becoming increasingly important particularly in early stages of disease processes), the scalar product measure provides information on waveform shape. The conventional impulse and higher order responses will be different for different modes of stimulation such as Cathode Ray Tube (CRT) and Liquid Crystal Display (LCD) systems and latency shifts will be introduced if not corrected in software. Procedures which could lead to misleading interpretation include artefact rejection, averaging with neighbours and summing of responses. These procedures should be handled with caution.

Electroretinography↗
PubMed2000

Ozone exposure: a case report and discussion.

A 45-year-old man working with ozone presents with evidence of sinusitis, mucus membrane irritation, sleep disturbance and shortness of breath. Naturally occurring or manmade, ozone may damage pulmonary alveolar type I cells at significant exposure levels. EPA and OSHA regulate exposure concentrations. Studies show dose responses with exposures. Supporting epidemiological studies are reviewed briefly. Limiting potential for excess exposure is key to prevention. Recognition of ozone as a potential exposure in the Oklahoma workplace is key to symptom management.

Bicycling↗
PubMed2000

Use of complementary medicine by adult patients participating in cancer clinical trials.

PURPOSE/OBJECTIVES: To document the prevalence, demographic correlates, patterns of use, and beliefs about complementary and alternative medicine (CAM) therapies of adult patients enrolled in National Cancer Institute (NCI) clinical trials. DESIGN: Prospective, cross-sectional, descriptive survey. SETTING: W.G. Magnuson Clinical Center of the National Institutes of Health in Bethesda, MD. SAMPLE: Convenience sample of 100 English-speaking, adult patients with cancer admitted to intramural clinical trials. METHODS: A standardized, 99-item questionnaire assessing use of CAM therapies pre- and postcancer diagnosis was administered by face-to-face interview. MAIN RESEARCH VARIABLES: Use of CAM therapies, beliefs, communication with physician. FINDINGS: 63% used at least one CAM therapy, with an average use of two therapies per patient. Men were significantly less likely to use a therapy than women; women were more likely to use numerous therapies. Cancer diagnosis seems to have had no influence overall on the frequency of use of CAM therapies. The major reasons stated for CAM use were for treatment-related medical conditions as well as depression, anxiety, and insomnia. The most frequently reported therapies were spiritual, relaxation, imagery, exercise, lifestyle diet (e.g., macrobiotic, vegetarian), and nutritional supplementation. Patients unanimously believed that these complementary therapies helped to improve their quality of life through more effective coping with stress, decreasing the discomforts of treatment and illness, and giving them a sense of control. CONCLUSIONS: Patients with cancer use various complementary therapies to cope with their disease and the rigors of clinical trials. Women and those with higher educational backgrounds were more frequent users. IMPLICATIONS FOR NURSING PRACTICE: Nurses who provide care to subjects of biomedical research have an opportunity and responsibility regarding their patients' use of CAM therapies. Nurses may use in-house resources to help evaluate subjects' use of a CAM modality or to provide quality-of-life therapies such as relaxation, imagery, or healing touch. Discussing these health practices in a nonjudgmental manner adds to the assessment of patients' coping skills and ability to make decisions about their health care.

Adaptation, Psychological↗