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Biomedical subjects

D Dawson

Publications and source records attributed to D Dawson.

At least 19 recordsLinked to original sources
PubMed2006

Prediction of long-term occupational performance outcomes for adults after moderate to severe traumatic brain injury.

PURPOSE: To examine predictors of long-term occupational performance outcomes for adults after moderate to severe traumatic brain injury (TBI). METHOD: This study involved analysis of data from a retrospective cohort of adults (N = 306) with moderate to severe TBI discharged from a Pennsylvania rehabilitation treatment facility. Extensive pre-injury sociodemographic, injury-severity, post-injury personal (cognitive, physical, affective), post-injury environmental (social, institutional, physical), and post-injury occupational performance (participation in self-care, productivity, leisure activities) data were gathered from hospital records and using in-person interviews. Interviews occurred at a mean time of 14 (range, 7-24) years post-injury. Hierarchical multiple regression analysis was used to investigate determinants of long-term occupational performance outcomes. RESULTS: Pre-injury behavioural problems, male gender, post-injury cognitive and physical deficits, and lack of access to transportation were significant independent predictors of worse occupational performance outcomes. CONCLUSIONS: The study supports the use of a comprehensive model for long-term outcomes after TBI where pre-injury characteristics and post-injury cognitive and physical characteristics account for the greatest proportion of explained variance.

Adolescent↗
PubMed2006

Investigating pulmonary embolism in the emergency department with lower limb plethysmography: the Manchester Investigation of Pulmonary Embolism Diagnosis (MIOPED) study.

OBJECTIVES: To measure the diagnostic accuracy of computerised strain gauge plethysmography in the diagnosis of pulmonary embolism (PE). METHODS: Two researchers prospectively recruited 425 patients with pleuritic chest pain presenting to the emergency department (ED). Lower limb computerised strain gauge plethysmography was performed in the ED. All patients underwent an independent reference standard diagnostic algorithm to establish the presence or absence of PE. A low modified Wells' clinical probability combined with a normal D-dimer excluded PE. All others required diagnostic imaging with PIOPED interpreted ventilation perfusion scanning and/or computerised tomography (CT) pulmonary angiography. Patients with a nondiagnostic CT had digital subtraction pulmonary angiography. All patients were followed up clinically for 3 months. RESULTS: The sensitivity of computerised strain gauge plethysmography was 33.3% (95% confidence interval (CI) 16.3 to 56.2%) and specificity 64.1% (95% CI 59.0 to 68.8%). The negative likelihood ratio was 1.04 (95% CI 0.68 to 1.33) and positive likelihood ratio 0.93 (95% CI 0.45 to 1.60). CONCLUSIONS: Lower limb computerised strain gauge plethysmography does not aid in the diagnosis of PE.

Adult↗
PubMed2006

Outpatient diagnosis of pulmonary embolism: the MIOPED (Manchester Investigation Of Pulmonary Embolism Diagnosis) study.

BACKGROUND AND OBJECTIVES: Pleuritic chest pain, a symptom of pulmonary embolism, is a common presenting symptom in the emergency department. The aim of this study was to validate an algorithm for the diagnosis of pulmonary embolism in emergency department patients with pleuritic chest pain. METHODS: This was a prospective, diagnostic cohort study conducted in a large UK city centre emergency department. A total of 425 patients with pleuritic chest pain presenting to the emergency department between February 2002 and June 2003 were recruited. Patients scoring a low modified Wells clinical probability of pulmonary embolism, who had a normal latex agglutination D-dimer, were discharged. All others followed a diagnostic imaging protocol to exclude and diagnose pulmonary embolism using PIOPED interpreted ventilation-perfusion scanning, CT pulmonary angiography, and digital subtraction pulmonary angiography. All patients were followed up for three months for evidence of pulmonary embolism or deep vein thrombosis. An independent adjudication committee reviewed all deaths. RESULTS: A total of 408 patients completed the diagnostic algorithm; 86.5% (353/408) were investigated as outpatients, 5.4% (22/408) were diagnosed as having pulmonary embolism, and 98.8% (403/408) were followed up for three months. Of the 381 patients without pulmonary embolism who completed follow up, the incidence of thromboembolic disease was 0.8% (95% CI 0.3% to 2.3%): two patients had pulmonary embolism and one had a deep vein thrombosis. CONCLUSIONS: The MIOPED (Manchester Investigation Of Pulmonary Embolism Diagnosis) diagnostic protocol can safely exclude pulmonary embolism in outpatients with pleuritic chest pain.

Adult↗
PubMed2006

Omega-3 fatty acid effect on alveolar bone loss in rats.

Gingival inflammation and alveolar bone resorption are hallmarks of adult periodontitis, elicited in response to oral micro-organisms such as Porphyromonas gingivalis. We hypothesized that omega (omega)-3 fatty acids (FA) dietary supplementation would modulate inflammatory reactions leading to periodontal disease in infected rats. Rats were fed fish oil (omega-3 FA) or corn oil (n-6 FA) diets for 22 weeks and were infected with P. gingivalis. Rats on the omega-3 FA diet exhibited elevated serum levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), documenting diet-induced changes. PCR analyses demonstrated that rats were orally colonized by P. gingivalis; increased IgG antibody levels substantiated this infection. P. gingivalis-infected rats treated with omega-3 FA had significantly less alveolar bone resorption. These results demonstrated the effectiveness of an omega-3 FA-supplemented diet in modulating alveolar bone resorption following P. gingivalis infection, and supported that omega-3 FA may be a useful adjunct in the treatment of periodontal disease.

Alveolar Bone Loss↗
PubMed2005

Development and validation of a scale to measure work-related fatigue and recovery: the Occupational Fatigue Exhaustion/Recovery Scale (OFER).

OBJECTIVE: Various empirical studies link persistent failure to recover from acute fatigue to the evolution of chronic fatigue. However, existing fatigue measurement scales do not tend to distinguish between acute and chronic fatigue elements well, and none include a measure of effective recovery from fatigue. METHODS: The 15 item Occupational Fatigue Exhaustion Recovery (OFER) scale has been developed and validated in three study populations specifically to measure work-related fatigue. RESULTS: The OFER scale possesses robust, gender-bias free psychometric characteristics. Its three subscales identify and distinguish between chronic work-related fatigue traits, acute end-of-shift states and effective fatigue recovery between shifts. CONCLUSION: These studies confirm the mediating role of intershift-shift recovery in the evolution of adaptive end-of-shift fatigue states to maladaptive persistent fatigue traits. The OFER scale is suggested as a potentially valuable new tool for use in work-related fatigue research.

Adult↗
PubMed2005

Countermeasures to driver fatigue: a review of public awareness campaigns and legal approaches.

OBJECTIVE: Driver fatigue accounts for 10-40% of road crashes and is a critical area for public health. As other major road safety issues are more successfully managed, driver fatigue becomes proportionately more important. Both public awareness and legal developments have been slow to reach the same levels as for other road safety risks. The aim of this article is to review countermeasures for non-commercial drivers that are designed to reduce the likelihood of fatigue-related crashes through education and legislation. METHODS: This review outlines information from a wide variety of sources including governments, road safety groups and the scientific literature. Educational and legislative approaches are discussed in terms of both their effectiveness and the associated implications for public health. CONCLUSIONS: Areas for improvement in education include personalising the risk to drivers and developing simple metrics for the self-assessment of fatigue. Legal implications should be more clearly defined and specific laws are needed to more effectively prosecute fatigued drivers who cause crashes. Additional research is needed to further investigate the efficacy of available countermeasures. IMPLICATIONS: Increasingly, road traffic injury is being discussed more broadly as a public health issue. However, the specific issue of driver fatigue still receives less attention than other main causes of road crashes, despite making a significant and comparable contribution to crash rates. Countries such as Australia and New Zealand have a responsibility to counter driver fatigue, as well as other causes of road crashes, and to further pursue improvements for the benefit of public health.

Accidents, Traffic↗
PubMed2004

Gill histopathology of wild marine fish in Tasmania: potential interactions with gill health of cultured Atlantic salmon, Salmo salar L.

This study surveyed conditions in the gills of wild marine fish in Tasmania to determine potential interactions between wild and cultured fish. Wild marine fish of 12 species were captured from three Atlantic salmon farm sites and three reference sites around Tasmania. The survey concentrated on three species, red cod, Pseudophycis bachus, sand flathead, Platycephalus bassensis, and jack mackerel, Trachurus declivus. Seventy-six per cent of salmon pens contained wild fish species. The number of species found in a pen ranged from one to nine and the number of individuals ranged from one to 23. Trichodinids were prevalent and occurred on seven of the 13 species examined. Trichodina occurred on the gills of all but one specimen of red cod. Monogenean gill flukes were observed on all three major species sampled and were abundant on sand flathead. Other parasites and conditions observed in the survey included metacercariae of digenean trematodes, epitheliocystis and cysts of unknown origin. Infestations of trichodinids on red cod and monogenean gill flukes on sand flathead were significantly more intense at farm sites than at reference sites. Atlantic salmon sampled at the same time from the farms were only affected by amoebic gill disease and isopods.

Analysis of Variance↗
PubMed2004

Lipomatous hypertrophy of the interatrial septum: a commonly misdiagnosed mass often leading to unnecessary cardiac surgery.

Lipomatous hypertrophy of the interatrial septum is a benign cardiac mass that should be considered as part of the differential diagnosis for any atrial cardiac tumour. In the reported case, this lesion was initially suspected to be malignant and the patient was thus referred directly to cardiac surgeons for surgical removal. Unnecessary surgical intervention was swiftly averted because the cardiac surgeon promptly referred the patient for an expert echocardiogram that confirmed the diagnosis of lipomatous hypertrophy. The authors discuss the characteristic features of this lesion and how the diagnosis may be made based on several non-invasive imaging modalities without the need for a tissue biopsy. This condition is more common than initially thought and remains under-recognised by most clinicians. In such cases an increased awareness of this lesion along with the opinion of a specialist echocardiologist would help to avoid a misdiagnosis and unnecessary intervention.

Aged↗
PubMed2003

The impact of a week of simulated night work on sleep, circadian phase, and performance.

AIMS: To investigate factors that may contribute to performance adaptation during permanent night work. METHODS: Fifteen healthy subjects participated in an adaptation and baseline night sleep, directly followed by seven simulated eight-hour night shifts (2300 to 0700 hours). At the end of each shift they were taken outside and exposed to natural light for 20 minutes. They then slept from approximately 0800 hours until they naturally awoke. RESULTS: There was a significant increase in mean performance on a visual psychomotor vigilance task across the week. Daytime sleep quality and quantity were not negatively affected. Total sleep time (TST) for each of the daytime sleeps was reduced, resulting in an average cumulative sleep debt of 3.53 hours prior to the final night shift. TST for each of the daytime sleep periods did not significantly differ from the baseline night, nor did TST significantly vary across the week. There was a significant decrease in wake time after sleep onset and sleep onset latency across the week; sleep efficiency showed a trend towards greater efficiency across the consecutive daytime sleeps. Hours of wakefulness prior to each simulated night shift significantly varied across the week. The melatonin profile significantly shifted across the week. CONCLUSIONS: Results suggest that under optimal conditions, the sleep debt that accumulates during consecutive night shifts is relatively small and does not exacerbate decrements in night-time performance resulting from other factors. When sleep loss is minimised, adaptation of performance during consecutive night shifts can occur in conjunction with circadian adaptation.

Adaptation, Physiological↗
PubMed2003

The amount of sleep obtained by locomotive engineers: effects of break duration and time of break onset.

AIMS: To determine the effects of break duration and time of break onset on the amount of sleep that locomotive engineers obtain between consecutive work periods. METHODS: A total of 253 locomotive engineers (249 male, 4 female, mean age 39.7 years) participated. Data were collected at 14 rail depots, where participants drove electric or diesel locomotives; worked with another engineer or drove alone; carried passengers, freight, or coal; and operated in rural or urban areas. Participants completed sleep diaries and work diaries for a two week period while working their normal roster patterns. RESULTS: For breaks that began at similar times of day, total sleep time (TST) increased with break duration. For breaks of similar duration, TST was greater for those that occurred during the night-time than for those that occurred during the daytime. An average of 3.1-7.9 hours sleep was obtained in 12 hour breaks (minimum break requirement in the Australian rail industry), depending on when the break began. CONCLUSIONS: The duration and timing of breaks are both important factors in determining the amount of sleep that locomotive engineers obtain between consecutive work periods. Consequently, minimum length break requirements that do not include a time of day component may not provide locomotive engineers with the opportunity to obtain a sufficient amount of sleep prior to resuming work.

Adult↗
PubMed2002

Costing hospital activity: the experience with healthcare resource groups in England.

Development of an English measure of hospital casemix can be traced back to the early 1980s and has resulted in the creation of healthcare resource groups (HRGs). Despite the availability of this casemix classification system, less use has been made of HRG costs than might be expected, primarily because hospitals are not funded on the basis of their casemix adjusted activity. Instead, the main use of casemix information has been in benchmarking exercises, such as the recent example of the government's use of HRG costs to set hospital efficiency targets. This paper outlines the historical context in which HRGs were developed, the data used for classification purposes and the calculation of HRG costs. The responses of hospitals to efficiency targets based on HRG costs are considered, including the options of improving data quality, reducing costs, and ignoring the targets. It is argued that the latter strategy is most evident in England.

Journal Article↗
PubMed2002

Extraocular light exposure does not phase shift saliva melatonin rhythms in sleeping subjects.

Preliminary work in humans suggests that extraocular light can shift circadian phase. If confirmed, extraocular light may be of therapeutic benefit in the treatment of circadian-related sleep disorders with the advantage over ocular exposure that it can be administered while subjects are asleep. In sleeping subjects, however, the effect of extraocular light exposure on circadian phase has yet to be fully tested. Likewise, there is limited data on the acute effects of extraocular light on sleep and body temperature that may influence its clinical utility Thirteen subjects [3F, 10M; mean (SD) age = 22.1 (3.0)y] participated in a protocol that totaled 7 nights in the laboratory consisting of a screening phase measurement night followed 1 week later by two counterbalanced experimental sessions each of 3 consecutive nights (habituation, treatment, and posttreatment phase measurement night) separated by 4 days. Saliva was collected for melatonin measurement every half hour from 1800 to 0300 h on the screening night and both the posttreatment phase measurement nights. On the treatment nights, continuous measures of rectal temperature and polysomnographic sleep were collected and overnight urine for measurement of total nocturnal urinary 6-sulphatoxymelatonin excretion. To test for the phase-delaying effects of extraocular light, subjects received either placebo or extraocular light (11,000 lux) behind the right knee from 0100 to 0400 h. Treatment had no significant effect on the onset of saliva melatonin secretion, phase of nocturnal core body temperature, or urinary 6-sulfatoxymelatonin excretion, but a small increase was observed in wakefulness over the light administration period. In summary, extraocular light was not shown to delay circadian phase but was shown to increase wakefulness. The authors suggest that the present protocol has limited application as a treatment for circadian-related sleep disorders.

Adult↗
PubMed2002

Skeletal muscle microvascular recruitment by physiological hyperinsulinemia precedes increases in total blood flow.

Supraphysiological doses of insulin enhance total limb blood flow and recruit capillaries in skeletal muscle. Whether these processes change in response to physiological hyperinsulinemia is uncertain. To examine this, we infused either saline (n = 6) or insulin (euglycemic clamp, 3.0 mU x min(-1) x kg(-1), n = 9) into anesthetized rats for 120 min. Femoral artery flow was monitored continuously using a Doppler flow probe, and muscle microvascular recruitment was assessed by metabolism of infused 1-methylxanthine (1-MX) and by contrast-enhanced ultrasound (CEU). Insulin infusion raised plasma insulin concentrations by approximately 10-fold. Compared with saline, physiological hyperinsulinemia increased femoral artery flow (1.02 +/- 0.10 vs. 0.68 +/- 0.09 ml/min; P < 0.05), microvascular recruitment (measured by 1-MX metabolism [6.6 +/- 0.5 vs. 4.5 +/- 0.48 nmol/min; P < 0.05] as well as by CEU [167.0 +/- 39.8 vs. 28.2 +/- 13.8%; P < 0.01]), and microvascular flow velocity (beta, 0.14 +/- 0.02 vs. 0.09 +/- 0.02 s(-1)). Subsequently, we studied the time dependency of insulin's vascular action in a second group (n = 5) of animals. Using CEU, microvascular volume was measured at 0, 30, and 90 min of insulin infusion. Insulin augmented microvascular perfusion within 30 min (52.8 +/- 14.8%), and this persisted at 90 min (64.6 +/- 9.9%). Microvascular recruitment occurred without changes to femoral artery flow or beta. We conclude that insulin increases tissue perfusion by recruiting microvascular beds, and at physiological concentrations this precedes increases in total muscle blood flow by 60-90 min.

Animals↗
PubMed2001

The relationship between slow-wave activity, body temperature, and cardiac activity during nighttime sleep.

STUDY OBJECTIVES: Recent work indicates that cardiac sympathetic activity is not influenced by the circadian system and instead decreases after sleep onset. However, little is known about the pattern of change in cardiac sympathetic activity during NREM/REM sleep cycles and whether this is associated with alterations in slow-wave activity (SWA). To address these questions, we examined SWA, cardiac sympathetic activity, heart rate and rectal and foot temperatures during the first three NREM/REM sleep cycles and during transitions between NREM and REM sleep. DESIGN: Subjects were required to maintain a constant sleep-wake cycle for at least a week and have at least one adaptation night, before their night of recording. SETTING: Individual temperature controlled bedrooms. PARTICIPANTS: 10 young healthy males and females. INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: All variables showed the greatest change in the first NREM cycle. Specifically, SWA, sympathetic activity, heart rate and foot temperature increased while rectal temperature decreased. After the initial increase, cardiac sympathetic activity decreased across the sleep phase, in association with a decrease in heart rate. Cardiac sympathetic activity did not significantly alter across NREM-REM cycles. CONCLUSIONS: The results suggest that increases in heart rate and cardiac sympathetic activity early in the sleep period are, in part, a compensatory reaction to the concomitant thermoregulatory changes observed. These results also indicate that the effect of time asleep on cardiac sympathetic activity may be greater than the influence of sleep cycles. These results are discussed with reference to the recuperative value of naps.

Adult↗
PubMed2001

A quantitative model of work-related fatigue: empirical evaluations.

Systematic and quantitative management of work-related fatigue within workplaces has been a challenging task due to a lack of useful tools. A previous paper provided background and development of a work-related fatigue modelling approach. The current paper outlines model evaluations using sleep deprivation experiments and recommendations of work scheduling. Previous studies have reported cumulative effects of sleep restriction (4-5 h per night) on a number of measures. Model predictions were correlated against psychomotor vigilance task lapses (r = 0.92) and reaction time responses (slowest 10%, r = 0.91) as well as sleep latency (r = -0.97). Further correlations were performed on four measures from a 64 h continuous sleep deprivation study; that is objective vigilance (r = -0.75) as well as subjective performance (r = -0.75), sleepiness (r = 0.82) and tiredness (r = 0.79). Evaluation against current scheduling recommendations illustrated consistency with the literature with the exception that forward rotation did not provide benefits over backward rotation. The results indicate that model predictions correlate well across a range of objective and subjective measures. This relationship also appears to hold for cumulative and continuous sleep deprivation protocols. Future studies will also focus on field-based evaluation.

Ergonomics↗