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Biomedical subjects

G J Gibson

Publications and source records attributed to G J Gibson.

At least 19 recordsLinked to original sources
PubMed2006

Umbilical cord plasma concentrations of free morphine following single-dose diamorphine analgesia and their relationship to dose-delivery time interval, Apgar scores and neonatal respiration.

OBJECTIVE: To find the effect of dose-delivery interval on cord-blood levels of diamorphine metabolites and its effect on Apgar sores and neonatal respiration. STUDY DESIGN: Pilot study conducted in labour ward of a district general hospital. One hundred women who had normal delivery and received single dose of 7.5mg of intramuscular injection of diamorphine in labour were recruited in the study. A 2.0 ml sample of umbilical venous blood was collected from the placenta after delivery of the baby. The sample was analysed using RIA method to measure free morphine. Details about the labour and baby's condition at birth were recorded. RESULTS: The concentration of free morphine in the umbilical venous blood was significantly associated with the dose-delivery interval (coefficient (95% CI)=1.08(0.99-1.18), p<0.001). Twenty neonates had low Apgar score (< or =7) at 1 min. The odds of such a low score were raised with higher log free morphine in the cord venous plasma, but not statistically significantly (OR (95% CI)=5.3 (0.84-34), p=0.08). Fourteen neonates required resuscitation. The odds of requiring resuscitation were significantly raised with higher log free morphine: OR (95% CI)=9.3 (1.0-86), p=0.05. CONCLUSION: Concentration of free morphine in the umbilical venous blood after delivery was significantly associated with the dose-delivery interval and this had significant effect on the need for resuscitation.

Analgesics, Opioid↗
PubMed2006

Bayesian inference of hospital-acquired infectious diseases and control measures given imperfect surveillance data.

This paper describes a stochastic epidemic model developed to infer transmission rates of asymptomatic communicable pathogens within a hospital ward. Inference is complicated by partial observation of the epidemic process and dependencies within the data. The epidemic process of nosocomial communicable pathogens can be partially observed by routine swabs testing for the presence of the pathogen. False-negative swab results must be accounted for and make it difficult to ascertain the number of patients who were colonized. Reversible jump Markov chain Monte Carlo methods are used within a Bayesian framework to make inferences about the colonization rates and unknown colonization times. The methods are applied to routinely collected data concerning methicillin-resistant Staphylococcus Aureus in an intensive care unit to estimate the effectiveness of isolation on reducing transmission of the bacterium.

Bayes Theorem↗
PubMed2006

Evaluation of a transcutaneous carbon dioxide monitor ("TOSCA") in adult patients in routine respiratory practice.

BACKGROUND: Non-invasive measurement of oxygenation is routine in adult clinical practice but transcutaneous monitoring of PCO(2) (PtcCO(2)) is used much less due to technical difficulties with earlier transcutaneous electrodes. OBJECTIVE: Our aim was to determine the reliability of estimating arterial PCO(2) (PaCO(2)) using a recently introduced combined SaO(2)/PtcCO(2) monitor ("TOSCA", Linde Medical Systems) in adult patients in routine clinical respiratory practice. METHODS: PtcCO(2) was measured in patients requiring arterial blood gases for clinical reasons. Ten minutes after the probe had been attached to an earlobe PtcCO(2) was recorded, immediately before arterial blood sampling. The PCO(2) values obtained were compared by Bland-Altman analysis. RESULTS: Samples were taken from 48 unselected patients with varied pathology. There were no technical problems. Median age was 56 years (range 20-86 years). The mean difference between PaCO(2) and PtcCO(2) was -0.04kPa, sd of the difference 0.67kPa. Bland-Altman analysis showed generally good agreement between the two measurements across the range of PaCO(2) values (4-10.9kPa). Four of 48 measurements showed a PCO(2) difference >1kPa with no technical or clinical explanations apparent. CONCLUSIONS: The accuracy of estimation of PaCO(2) by the TOSCA transcutaneous electrode was generally good and the device appears promising for use in routine clinical respiratory practice.

Adult↗
PubMed2006

Silencing the snorers: no gain without pain?

OBJECTIVE: To compare the estimated effects of conservative surgery to those of a mandibular advancement splint (MAS) in the treatment of habitual snoring. METHOD: Prospective, observational, non-randomized cohort study. RESULTS: Adequate follow-up data were available for 88 participants (23 following coblation, 65 after provision of an MAS). The mean reduction in snoring symptoms inventory (SSI) score for the 23 subjects undergoing coblation was 9.83 (+/-standard deviation 11.43). Reported pain duration was greatest with uvula amputation, but uvula coblation did not always adequately reduce its bulk. Of the 65 MAS patients, 39 (60 per cent) used the device regularly, with a mean fall in SSI of 12 (+/-16.4, p=0.001). Approximately one in four patients in both groups achieved a significant fall in SSI (>15 points), and the measured effect sizes were close to 0.75 for both treatments. CONCLUSIONS: Mandibular advancement splints and coblation have similar efficacies. However, their efficacy does not match that of radical surgery.

Humans↗
PubMed2005

Matrix concentration of insulin-like growth factor I (IGF-I) is negatively associated with biomechanical properties of human tibial cancellous bone within individual subjects.

Insulin-like growth factor-I (IGF-I), abundant in bone matrix, is believed to play an important role during bone development and remodeling. To our knowledge, however, few studies have addressed the relationship between the concentration of IGF-I in bone matrix and the biomechanical properties of bone tissue. In this study, forty-five cylindrical specimens of cancellous bone were harvested from six human tibiae and scanned using micro-computed tomography (microCT). The bone volume fraction (BV/TV) was calculated from three-dimensional (3D) microCT images. Mechanical tests were then performed on a servohydraulic testing system to determine the strength and stiffness of cancellous bone. Following mechanical testing, the concentration of IGF-I in bone matrix was measured by using an enzyme-linked immunoabsorbent assay (ELISA). Within each subject, the concentration of IGF-I in bone matrix had significant (P<0.01) negative correlations with the bone volume fraction, strength, and stiffness of cancellous bone. In particular, the anterior quadrant of the proximal tibia was significantly (P<0.02) greater in IGF-I matrix concentration and marginally significantly lower in strength (P=0.053) and stiffness (P=0.059) than the posterior quadrant. The negative correlations between the cancellous bone matrix concentration of IGF-I and cancellous bone biomechanical properties within subjects found in this study may help us understand the variation of the biomechanical properties of cancellous bone in proximal human tibiae.

Biomechanical Phenomena↗
PubMed2005

Obstructive sleep apnoea syndrome: underestimated and undertreated.

The obstructive sleep apnoea syndrome (OSAS) was first identified only 40 years ago and its clinical importance is increasingly recognized. Although now acknowledged as a worldwide problem, which in Western countries affects 2-4% of middle-aged men and 1-2% of middle-aged women, the majority of affected individuals remain undiagnosed. OSAS is strongly associated with obesity but is also increasingly identified in the less obese, in whom a particular craniofacial structure is an important contributory factor. The prevalence of OSAS is likely to be increasing in parallel with the epidemic of obesity currently occurring in many countries. The common presenting complaints are excessive daytime sleepiness and loud snoring. The sleepiness impairs social functioning, work performance and driving ability, and accounts for a large socio-economic burden on the community. Hypertension is an important independent association. The treatment of choice is nocturnal continuous positive airway pressure which is highly effective and is also cost effective.

Continuous Positive Airway Pressure↗
PubMed2004

Bayesian analysis of botanical epidemics using stochastic compartmental models.

A stochastic model for an epidemic, incorporating susceptible, latent, and infectious states, is developed. The model represents primary and secondary infection rates and a time-varying host susceptibility with applications to a wide range of epidemiological systems. A Markov chain Monte Carlo algorithm is presented that allows the model to be fitted to experimental observations within a Bayesian framework. The approach allows the uncertainty in unobserved aspects of the process to be represented in the parameter posterior densities. The methods are applied to experimental observations of damping-off of radish (Raphanus sativus) caused by the fungal pathogen Rhizoctonia solani, in the presence and absence of the antagonistic fungus Trichoderma viride, a biological control agent that has previously been shown to affect the rate of primary infection by using a maximum-likelihood estimate for a simpler model with no allowance for a latent period. Using the Bayesian analysis, we are able to estimate the latent period from population data, even when there is uncertainty in discriminating infectious from latently infected individuals in data collection. We also show that the inference that T. viride can control primary, but not secondary, infection is robust to inclusion of the latent period in the model, although the absolute values of the parameters change. Some refinements and potential difficulties with the Bayesian approach in this context, when prior information on parameters is lacking, are discussed along with broader applications of the methods to a wide range of epidemiological systems.

Algorithms↗
PubMed2004

Inferring the dynamics of a spatial epidemic from time-series data.

Spatial interactions are key determinants in the dynamics of many epidemiological and ecological systems; therefore it is important to use spatio-temporal models to estimate essential parameters. However, spatially-explicit data sets are rarely available; moreover, fitting spatially-explicit models to such data can be technically demanding and computationally intensive. Thus non-spatial models are often used to estimate parameters from temporal data. We introduce a method for fitting models to temporal data in order to estimate parameters which characterise spatial epidemics. The method uses semi-spatial models and pair approximation to take explicit account of spatial clustering of disease without requiring spatial data. The approach is demonstrated for data from experiments with plant populations invaded by a common soilborne fungus, Rhizoctonia solani. Model inferences concerning the number of sources of disease and primary and secondary infections are tested against independent measures from spatio-temporal data. The applicability of the method to a wide range of host-pathogen systems is discussed.

Disease Outbreaks↗
PubMed2004

Validation of quality of life instruments in ALS.

BACKGROUND: Non-invasive ventilation (NIV) probably improves survival in ALS, but its effect on quality of life (QoL) is less clear. Most potentially useful QoL instruments have not been validated in this context. METHODS: We assessed the validity (multi-trait multi-method analysis), internal consistency (Cronbach's alpha), test-retest stability (intra-class correlations) and response to disease severity and NIV (effect size) of two generic instruments, the Short Form 36 (SF-36) and the General Well-being Schedule; two specific instruments, the Chronic Respiratory Disease Questionnaire (CRQ) and the Sleep Apnoea QoL Index (SAQLI), and a scale of daytime sleepiness, the Epworth Sleepiness Scale (ESS) in 23 subjects with ALS. Functional status, limb and axial muscle strength, and maximum inspiratory pressure were assessed, together with the QoL measurements, every two months. RESULTS: All instruments showed good or excellent validity, internal consistency and test-retest stability overall. Subjects without symptomatic respiratory compromise had difficulty identifying activities for the CRQ dyspnoea domain and symptoms for the SAQLI symptoms domain. Marked floor effects were observed in the physical function and role domains of the SF-36. Domains assessing sleep-related problems and mental health showed greater effect of differences in respiratory function than functional status, and the greatest response to NIV. CONCLUSIONS: Of the generic instruments the SF-36 was most useful, but limited by floor effects. Of the specific instruments, the SAQLI symptoms domain was most responsive to NIV, but this instrument took longer to complete, and several items were inappropriate. The CRQ and ESS are valid and responsive alternatives.

Adult↗
PubMed2003

White matter disease and sleep-disordered breathing after acute stroke.

OBJECTIVE: To assess sleep-disordered breathing (SDB) in patients with acute stroke and its relationship to prestroke cerebrovascular disease, particularly leukoariosis. METHODS: The authors studied SDB and CT evidence of prestroke cerebrovascular disease, nonacute brain infarction, and white matter disease (WMD) in 78 previously independent patients with acute stroke. Subjects underwent respiratory sleep studies to determine the Apnea-Hypopnea Index (AHI) and Desaturation Index (DI) 7 to 14 days following stroke. CT scans were evaluated for severity of acute prestroke cerebrovascular disease and WMD severity. RESULTS: Prestroke cerebrovascular disease was present in 49 (63%) patients and was associated with worse SDB (mean AHI 35 vs 23, p < 0.01; mean DI 28 vs 18, p < 0.05), particularly in men (mean AHI 43 vs 27, p < 0.01). WMD severity correlated with AHI (r = 0.26, p < 0.05) and age (r = 0.56, p < 0.01). WMD severity in frontal and basal ganglia areas showed the strongest association. On multivariate analysis, WMD severity correlated independently with AHI (R(2) = 0.07, p < 0.05). CONCLUSIONS: The presence of prestroke cerebrovascular disease and severity of WMD are associated with worse SDB. These findings suggest that either white matter is particularly vulnerable to the hypoxia and blood pressure variability associated with SDB or that WMD is a major factor exacerbating SDB following stroke.

Acute Disease↗
PubMed2003

Noninvasive ventilation in ALS: indications and effect on quality of life.

BACKGROUND: Noninvasive ventilation (NIV) probably improves survival in ALS, but the magnitude and duration of any improvement in quality of life (QoL) and the optimal criteria for initiating treatment are unclear. METHODS: QoL (Short Form-36 [SF-36], Chronic Respiratory Disease Questionnaire, Sleep Apnea Quality of Life Index) and respiratory function were assessed every 2 months and polysomnography every 4 months in 22 subjects with ALS. A trial of NIV was offered when subjects met one or more predefined criteria: orthopnea, daytime sleepiness, unrefreshing sleep, daytime hypercapnia, nocturnal desaturation, or an apnea-hypopnea index (AHI) of >10. Seventeen subjects were offered a trial of NIV; 15 accepted, and 10 continued treatment subsequently. Outcome was assessed by changes in QoL and NIV compliance (h/day). Subjects were followed to death or for at least 26 months. RESULTS: QoL domains assessing sleep-related problems and mental health improved (effect sizes 0.88 to 1.77, p < 0.05) and were maintained for 252 to 458 days. Median survival following successful initiation of NIV was 512 days, and survival and duration of QoL benefit were strongly related to NIV compliance. Vital capacity declined more slowly following initiation of NIV. Orthopnea was the best predictor of benefit from, and compliance with, NIV. Daytime hypercapnia and nocturnal desaturation also predicted benefit but were less sensitive. Sleep-related symptoms were less specific, and AHI > 10 was unhelpful. Moderate or severe bulbar weakness was associated with lower compliance and less improvement in QoL. CONCLUSIONS: NIV use was associated with improved QoL and survival. Subjects with orthopnea and preserved bulbar function showed the largest benefit.

Adult↗
PubMed2003

Snoring, daytime sleepiness and stroke: a case-control study of first-ever stroke.

Previous reports have shown an association between snoring and stroke but it is not clear whether this reflects confounding factors nor whether the association is attributable to obstructive sleep apnoea (OSA). We performed a case-control study of 181 patients admitted to hospital with first-ever stroke and community control subjects matched individually for age, sex and general practitioner. Subjects were interviewed with a structured questionnaire to identify snoring, daytime sleepiness and stroke risk factors. The association between snoring alone and stroke was not statistically significant: odds ratio (95% CI) 1.44 (0.88, 2.41). Daytime sleepiness was, however, significantly associated with stroke: odds ratio 3.07 (1.65, 6.08). Multiple logistic regression showed that hypertension, current smoking, taking alcohol regularly (negatively) and a higher Epworth sleepiness score were independently associated with stroke. The results suggest that the previously reported association between 'simple' snoring and stroke might have been due to poor controlling for confounding variables. Our study suggests an association with greater sleepiness prestroke, the cause of which is unclear, although OSA is a possible candidate.

Adult↗