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D Dawson

Publications and source records attributed to D Dawson.

At least 37 records · Page 2Linked to original sources
PubMed2001

A quantitative model of work-related fatigue: background and definition.

Fatigue has been identified as a major risk factor for shiftworkers. However, few organizations or governments currently manage work-related fatigue in any systematic or quantitative manner. This paper outlines an approach to managing fatigue that could improve shiftwork management. Using shift start and finish times as an input, the outlined model quantifies work-related fatigue on the basis of its known determinants; that is shift timing and duration, work history and the biological limits on sleep length at specific times of day. Evaluations suggest that work-related fatigue scores correlate very highly with sleep-onset latency, neurobehavioural impairment and subjective sleepiness. The model is useful in that it allows comparisons to be made between rosters independent of shift length and timing or the total number of work hours. Furthermore, unlike many models of sleepiness and fatigue, individual's sleep times are not required as hours of work are used as the input. It is believed the model provides the potential quantitatively to link the effects of shiftwork to specific organizational health and safety outcomes. This simple approach may be especially critical at a time when many organizations view longer and more flexible hours from their employees as an immediate productivity gain.

Fatigue↗
PubMed2001

Improving performance in public hospitals: a role for comparative costs?

In order to encourage performance improvements, the English government has set targets for acute hospitals to reduce their unit costs. Targets are based on analysis of costs across all acute hospitals. This policy has parallels with that of 'yardstick competition', advocated as a means to encourage efficiency in industries that lack competitive pressures. However, the prospect of cost improvements may not be realised in England. Firstly, there are insufficient incentives to respond appropriately to the provision of comparative cost information. Secondly, there is more than one index purporting to measure relative hospital costs. As comparison of unit costs is highly dependent on the measurement technique adopted, caution should be exercised when setting performance targets.

Benchmarking↗
PubMed2001

The effects of day-time exogenous melatonin administration on cardiac autonomic activity.

Melatonin has a functional role in the nocturnal regulation of sleep and thermoregulation. In addition to its action on peripheral receptors, melatonin may act by altering autonomic activity. To determine the effect of melatonin on cardiac autonomic activity, 5 mg of melatonin or placebo was orally administered to 12 young subjects at 14:00 hr, in a repeated measures design. Melatonin decreased sleep onset latency to Stage 2 sleep by 4.92+/-1.81 min (measured by Multiple Sleep Latency Tests), rectal temperature by 0.19+/-0.05 degrees C, and increased foot temperature by 0.74+/-0.45 degrees C (all P<0.05). Melatonin decreased heart rate by 3.66+/-1.68 beats/min (P<0.05) and pre-ejection period (measure of cardiac sympathetic activity) by 16.48+/-4.28 ms (P<0.05), but had no effect on respiratory sinus arrhythmia (measure of cardiac parasympathetic activity) (P>0.05). As the decrease in pre-ejection period is likely to have resulted from a decrease in blood pressure, these results do not confirm an effect of melatonin on cardiac sympathetic activity. However, the results do clearly indicate that melatonin is unlikely to drive the previously observed presleep increase in cardiac parasympathetic activity.

Administration, Oral↗
PubMed2001

Perceptions of labour pain by mothers and their attending midwives.

AIMS: The aim of the current study was to examine the perception of pain by labouring women and their attendant midwife, from the onset of labour to delivery. RATIONALE: Accurate measurement and appropriate management of pain is a significant problem for attendant medical and nursing personnel. Both the experience and perception of pain are regarded as subjective and are therefore difficult to measure objectively. Indeed, much of the literature reports that pain is often under- or over-estimated by nursing staff who as a consequence consistently fail to administer adequate analgesia. Few studies have specifically examined the ability of midwives to assess the pain of labouring women. DESIGN: The short form McGill Pain Questionnaire (SF-MPQ), routinely used to assess pain in obstetric environments, was used to determine pain perception. Thirteen labouring women and nine midwives completed the SF-MPQ every 15 minutes beginning at the time of admittance to the delivery suite. Peak pain ratings for the preceding 15 minutes were obtained without reference to prior ratings or each other's scores. Further, midwives in the maternity unit of The Queen Elizabeth Hospital (TQEH), Adelaide, South Australia completed a survey investigating the cues they use to assess pain during labour. RESULTS: On each measure of pain on the SF-MPQ, the midwives scores correlated with the mothers' scores across the entire pain range. Further analysis showed that mothers' and midwives' pain scores were similar at mild-moderate pain levels, but midwives significantly underestimated pain intensity at levels that mothers described as severe. The survey responses indicated that midwives rely on both verbal and nonverbal cues to assess pain levels. CONCLUSIONS: The cues used by midwives to differentiate pain intensities and qualities are similar to those used in other clinical settings, but may have limited discriminatory value as pain levels become severe.

Adult↗
PubMed2001

Carving an identity for allied health.

This paper outlines the development, growth and performance of the Division of Allied Health at Lottie Stewart Hospital, Sydney. It discusses the choice of a suitable organisational model, the findings from three evaluations conducted and a summary of the significant outcomes of the Division. An early version of this paper was presented at the 4th National Allied Health Conference in March 2001.

Aged↗
PubMed2001

Analysis of whole-body doses received by occupationally exposed workers in Ireland (1996-1999).

The work described in this paper is based on the results of routine whole-body measurements carried out by the Radiological Protection Institute of Ireland Dosimetry Service from 1996 to 1999. Data on the occupational radiation exposures of monitored personnel are examined and have been found to follow the skewed distribution reported by UNSCEAR. The annual average effective dose for each major work practice over the 4 years is given and compared with the UNSCEAR reference value of 1.1 mSv per year for all occupations. Evidence suggests that improvements in procedures and the use of better equipment have resulted in a reduction in the numbers of workers receiving measurable doses.

Air Pollutants, Radioactive↗
PubMed2001

Comparing performance on a simulated 12 hour shift rotation in young and older subjects.

OBJECTIVES: To simulate a 12 hour shift rotation and measure the difference in performance if any, between older and younger subjects. Significant reductions in neurobehavioural performance during shift work and particularly night work have long been recognised. There are conflicting reports of the effects of 12 hour shifts on performance, alertness, and safety. Furthermore, research suggests that older shift workers have more sleep disruption and maladaption to shift work. When this is combined with longer hours at work there may be considerable reductions in performance for older compared with younger workers. METHODS: Thirty two subjects were allocated to groups according to age. Group one had 16 subjects with a mean (SD) age of 21.2 (2.7) years, and group two had 16 subjects with a mean (SD) age of 43.9 (6.8) years. Subjects came to the laboratory for six consecutive days and completed a simulated 12 hour shift rotation consisting of two 12 hour day shifts (0700-1900), followed by two 12 hour night shifts (1900-0700). During the work period subjects completed a computer administered neurobehavioural performance task every hour. RESULTS: Performance for the older subjects was consistently lower than for the younger subjects. There was a significant difference in performance across the shift between older and younger subjects. There was a significant change in performance across the shifts in the older subjects, such that performance significantly increased across the day shifts and decreased across the night shifts. By contrast, the younger subjects were able to maintain performance across both day shifts and the second night shift. CONCLUSIONS: There are significant differences in performance of older and younger subjects during a simulated 12 hour shift rotation. Future studies both in the field and the laboratory would be useful in determining whether this is typical and if there are any important consequences for the older worker on 12 hour shifts.

Adolescent↗
PubMed2001

Effects of bright light and melatonin on sleep propensity, temperature, and cardiac activity at night.

Melatonin increases sleepiness, decreases core temperature, and increases peripheral temperature in humans. Melatonin may produce these effects by activating peripheral receptors or altering autonomic activity. The latter hypothesis was investigated in 16 supine subjects. Three conditions were created by using bright light and exogenous melatonin: normal endogenous, suppressed, and pharmacological melatonin levels. Data during wakefulness from 1.5 h before to 2.5 h after each subject's estimated melatonin onset (wake time + 14 h) were analyzed. Respiratory sinus arrhythmia (cardiac parasympathetic activity) and preejection period (cardiac sympathetic activity) did not vary among conditions. Pharmacological melatonin levels significantly decreased systolic blood pressure [5.75 +/- 1.65 (SE) mmHg] but did not significantly change heart rate. Suppressed melatonin significantly increased rectal temperature (0.27 +/- 0.06 degrees C), decreased foot temperature (1.98 +/- 0.70 degrees C), and increased sleep onset latency (5.53 +/- 1.87 min). Thus melatonin does not significantly alter cardiac autonomic activity and instead may bind to peripheral receptors in the vasculature and heart. Furthermore, increases in cardiac parasympathetic activity before normal nighttime sleep cannot be attributed to the concomitant increase in endogenous melatonin.

Adult↗
PubMed2001

Utility of echocardiography in assessment of pulmonary hypertension secondary to COPD.

Studies have confirmed the close correlation of echocardiographically estimated pulmonary arterial pressure with invasive measurements in patients with chronic obstructive pulmonary disease (COPD), but there are few data on utility of echocardiographic measurement in assessing pulmonary arterial hypertension (PH) in COPD and correlation with pulmonary function tests. Presence or absence of tricuspid regurgitation (TR) was determined by Doppler echocardiography in 73 consecutive COPD patients attending a hospital outpatient clinic. Transtricuspid pressure gradient (TTPG) was calculated. PH was defined as TTPG > or =30 mmHg. Patients also underwent spirometry, forced expiratory volume in one second (FEV1), single breath gas transfer (carbon monoxide transfer coefficient; (K(CO)) and carbon monoxide diffusing capacity of the lung; D(L,CO)) and arterial blood gas measurement. Measurable TR was observed in 56/73 patients (77%). There were no differences between the group in which TR was observed compared to that in which it was absent, with regard to age, smoking history nor pulmonary function variables. PH was seen in 31/56 cases (55%), with good reproducibility. There were statistically significant correlations of TTPG with FEV1 (r=-0.26, p=0.05), Kco (r=-0.31, p=0.04) and D(L,CO) (r = -0.42, p = 0.006) expressed as % pred. Stepwise regression analysis showed that age and K(CO) combined provide a multivariate model for prediction of TTPG. It is concluded the presence and degree of pulmonary arterial hypertension is readily and reliably determined by echocardiography in the majority of chronic obstructive pulmonary disease patients. Pulmonary arterial hypertension is common in severe chronic obstructive pulmonary disease and transtricuspid pressure gradient correlates with spirometry and indices of gas transfer, similar to previous invasive studies. In view of the adverse effects of pulmonary arterial hypertension on morbiditv and mortality routine echocardiography in patients with severe chronic obstructive pulmonary disease may be warranted.

Aged↗
PubMed2001

Tuberculosis in Australia: bacteriologically confirmed cases and drug resistance, 1998-1999: report of the Australian Mycobacterium Reference Laboratory Network.

The Australian Mycobacterium Reference Laboratory Network collected and analysed laboratory data on new diagnoses of infection with Mycobacterium tuberculosis complex in 1998 and 1999. Totals of 700 and 760 cases were identified, representing annual reporting rates of 3.7 and 4.0 cases of laboratory confirmed tuberculosis (TB) per 100,000 population in the years 1998 and 1999 respectively. Australia's TB reporting rates have varied little in the past decade, ranging from 3.7 to 4.1 cases per 100,000 population. Reporting rates vary between States, reflecting differences in the distribution of persons in 'high-risk' categories for TB. The male:female ratio decreased to almost 1:1. The median age for males with culture-confirmed TB is in the 45-49 age group; for females, the median is in the 35-39 age group. Pulmonary disease was diagnosed in 63 per cent of cases whereas disease of lymph nodes accounted for 21 per cent of all cases. Children have the lowest rates of culture-confirmed TB; males in the older age groups have the highest rates. Microscopy was positive for 60 per cent of culture-positive sputa, and for approximately 45 per cent of bronchoscopy specimens. The frequency of multi-drug resistance (less than 1%) was slightly lower than in previous years.

AIDS-Related Opportunistic Infections↗
PubMed2001

Ultrasound evaluation of the magnitude of pneumothorax: a new concept.

Pneumothorax is commonly seen in trauma patients; the diagnosis is confirmed by radiography. The use of ultrasound where radiographic capabilities are absent, is being investigated by the National Aeronautics and Space Administration. We investigated the ability of ultrasound to assess the magnitude of pneumothorax in a porcine model. Sonography was performed on anesthetized pigs in both ground-based laboratory (n = 5) and microgravity conditions (0 x g) aboard the KC-135 aircraft during parabolic flight (n = 4). Aliquots of air (50-100 cm3) were introduced into the chest to simulate pneumothorax. Results were videorecorded and digitized for later interpretation. Several distinct sonographic patterns of partial lung sliding were noted including the combination of a sliding zone with a still zone and a "segmented" sliding zone. These "partial lung sliding" patterns exclude massive pneumothorax manifested by a complete separation of the lung from the parietal pleura. In 0 x g, the sonographic picture is more diverse; one x g differences between posterior and anterior aspects are diminished. Modest pneumothorax can be inferred by the ultrasound sign of "partial lung sliding." This finding, which increases the negative predictive value of thoracic ultrasound, may be attributed to intermittent pleural contact, small air spaces, or alterations in pleural lubricant. Further studies of these phenomena are warranted.

Animals↗
PubMed2001

Comparing the effects of fatigue and alcohol consumption on locomotive engineers' performance in a rail simulator.

Laboratory studies have established that the performance impairments due to fatigue and alcohol consumption are quantitatively similar. However, the generalisability of this phenomenon is not clear because comparisons have not been made in realistic work settings with experienced shiftworkers. The aim of the current study was to quantify the effects of fatigue on performance in a simulated work environment (i.e. rail simulator) and compare them with the effects of alcohol consumption. It was hypothesised that fatigue would significantly impair driving performance, and that this impairment would be quantitatively similar to that associated with moderate levels of alcohol consumption. Twenty locomotive engineers participated in the study with a randomised cross-over design and three conditions: baseline, fatigue, and alcohol. During each 8-hour condition, participants completed four driving sessions in the rail simulator. The results indicate that fatigue caused participants to disengage from operating the simulator such that safety was traded off, not necessarily deliberately, against efficiency. The impairment in safety due to fatigue was in a range similar to the impairment associated with moderate levels of alcohol consumption. In summary, the study demonstrated that the effects of fatigue in a simulated work environment can be quantified and may be considerable.

Adult↗
PubMed2001

Performance, sleep and circadian phase during a week of simulated night work.

The current study investigated changes in night-time performance, daytime sleep, and circadian phase during a week of simulated shift work. Fifteen young subjects participated in an adaptation and baseline night sleep, directly followed by seven night shifts. Subjects slept from approximately 0800 hr until they naturally awoke. Polysomnographic data was collected for each sleep period. Saliva samples were collected at half hourly intervals, from 2000 hr to bedtime. Each night, performance was tested at hourly intervals. Analysis indicated that there was a significant increase in mean performance across the week. In general, sleep was not negatively affected. Rather, sleep quality appeared to improve across the week. However, total sleep time (TST) for each day sleep was slightly reduced from baseline, resulting in a small cumulative sleep debt of 3.53 (SD = 5.62) hours. Finally, the melatonin profile shifted across the week, resulting in a mean phase delay of 5.5 hours. These findings indicate that when sleep loss is minimized and a circadian phase shift occurs, adaptation of performance can occur during several consecutive night shifts.

Adolescent↗
PubMed2001

Daytime cardiac autonomic activity during one week of continuous night shift.

Shift workers encounter an increased risk of cardiovascular disease compared to their day working counterparts. To explore this phenomenon, the effects of one week of simulated night shift on cardiac sympathetic (SNS) and parasympathetic (PNS) activity were assessed. Ten (5m; 5f) healthy subjects aged 18-29 years attended an adaptation and baseline night before commencing one week of night shift (2300-0700 h). Sleep was recorded using a standard polysomnogram and circadian phase was tracked using salivary melatonin data. During sleep, heart rate (HR), cardiac PNS activity (RMSSD) and cardiac SNS activity (pre-ejection period) were recorded. Night shift did not influence seep quality, but reduced sleep duration by a mean of 52 +/- 29 min. One week of night shift evoked a small chronic sleep debt of 5 h 14 +/- 56 min and a cumulative circadian phase delay of 5 h +/- 14 min. Night shift had no significant effect on mean HR, but mean cardiac SNS activity during sleep was consistently higher and mean cardiac PNS activity during sleep declined gradually across the week. These results suggest that shiftwork has direct and unfavourable effects on cardiac autonomic activity and that this might be one mechanism via which shiftwork increases the risk of cardiovascular disease. It is postulated that sleep loss could be one mediator of the association between shiftwork and cardiovascular health.

Adolescent↗
PubMed2001

A week of simulated night work delays salivary melatonin onset.

In most studies, the magnitude and rate of adaptation to various night work schedules is assessed using core body temperature as the marker of circadian phase. The aim of the current study was to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as an alternative circadian phase marker. It was hypothesised that the night work schedule would result in a phase delay, manifest in relatively later DLMO, but that this delay would be somewhat inhibited by exposure to natural light. Participants worked seven consecutive simulated 8-hour night shifts (23:00-07:00 h). By night 7, there was a mean cumulative phase delay of 5.5 hours, equivalent to an average delay of 0.8 hours per day. This indicates that partial circadian adaptation occurred in response to the simulated night work schedule. The radioimmunoassay used in the current study provides a sensitive assessment of melatonin concentration in saliva that can be used to determine DLMO, and thus provides an alternative phase marker to core body temperature, at least in laboratory studies.

Adaptation, Physiological↗