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Biomedical subjects

M Stokes

Publications and source records attributed to M Stokes.

At least 19 recordsLinked to original sources
PubMed2006

A survey of the use of 2D ultrasound guidance for insertion of central venous catheters by UK consultant paediatric anaesthetists.

BACKGROUND AND OBJECTIVE: National Institute for Clinical Excellence guidance states that 2D imaging ultrasound guidance should be used when inserting internal jugular venous lines in adults and children in the elective situation and should be considered in most clinical circumstances requiring central venous catheter insertion. This survey explored the availability, training and use of ultrasound devices by consultant paediatric anaesthetists in the UK. METHODS: A questionnaire was distributed to UK members of the Association of Paediatric Anaesthetists of Great Britain and Ireland. RESULTS: There was a response rate of 63% and of those responding, 212 (81%) inserted paediatric central venous catheters. Ultrasound devices were available in the workplace of 216 (82%) and the average number of devices available per department was two. For elective paediatric theatre cases, 26% of paediatric anaesthetists with access to an ultrasound device always used it when inserting an internal jugular central venous line. The majority (74%) of respondents had received training in the use of 2D ultrasound. CONCLUSIONS: National Institute for Clinical Excellence guidance on the use of ultrasound locating devices for placing central venous catheters is not universally adhered to. Among the reasons for this are problems with availability of equipment, lack of training in the use of ultrasound and non-acceptance of the guidelines.

Anesthesiology↗
PubMed2005

Size and shape of the posterior neck muscles measured by ultrasound imaging: normal values in males and females of different ages.

Measurements of muscle strength or size are valuable indicators of muscle status in health and disease. When force cannot be measured directly, due to a particular muscle being one of a functional group or because of pain, size measurements may be the only option. For such data to be useful, normal values for age and gender are necessary. Procedures for scanning and measuring semispinalis capitis and the deep posterior neck muscles (semispinalis cervicis, multifidus and rotatores) using ultrasound imaging are described and normal data provided on size, shape and symmetry of these muscles from a sample of 99 healthy subjects (46 males aged 20-72 years and 53 females aged 18-70 years). Significant gender differences were found (P<0.001) but muscle size did not alter significantly with age. Between-side symmetry can be used to assess abnormality of the deep neck muscle group but not semispinalis capitis. A regression equation is provided for predicting the cross-sectional area (CSA) of the deep neck muscles from spinous process length in males. Clinically, linear measurements can be used to predict the neck muscle CSAs (r=0.66-0.84, P<0.001). The method described for assessing the neck muscles is a potentially valuable tool in clinical practice.

Adaptation, Physiological↗
PubMed2005

Spontaneous rupture of the liver following a normal pregnancy and delivery.

Liver haematoma and rupture is a rare but potentially devastating complication of pregnancy. The majority of cases are associated with severe preeclampsia. We report a case of spontaneous hepatic rupture in a 39-year old woman following a normal pregnancy and delivery. Shoulder tip pain and serum haemoglobin of 6.8 prompted immediate imaging with computed tomography. A large subcapsular haematoma involving the right lobe of the liver was identified and managed conservatively. This diagnosis should be considered in the patient who presents with pain in the upper part of the abdomen and signs of haemorrhagic shock, even in the case of an uncomplicated pregnancy.

Adult↗
PubMed2004

Ultrasound imaging of lumbar multifidus muscle: normal reference ranges for measurements and practical guidance on the technique.

This cross-sectional, prospective study aimed to produce normal reference data for measurements of the lumbar multifidus muscle. A total of 120 subjects, 68 females (aged 20-64 years) and 52 males (20-69 years) were studied. Bilateral transverse ultrasound images were made of multifidus at the fourth and fifth lumbar vertebrae (L4 & L5). Cross-sectional area (CSA, cm(2)) and linear dimensions (AP, anteroposterior; Lat, lateral) were measured and the latter expressed as a ratio (AP/Lat) to reflect shape. Relationships between CSA and anthropometric measures were examined. Multifidus CSA was larger in males (P<0.001) and age had no effect. The CSA was larger at L5 than L4 (P<0.001) and highly correlated between the two levels (males r=0.82, females 0.80). Differences in muscle shape were observed for gender, age and vertebral level. Between-side symmetry was high for size but not shape (CSA <10% difference). Linear measurements multiplied (APxLat) correlated highly with CSA (all groups r0.94, P<0.0001). The AP dimension was also acceptably predictive of CSA at L4 (r0.79). There were no clinically useful correlations between CSA and anthropometric measures. These findings provide normal references ranges for objective assessment of lumbar multifidus. This paper also addresses specific practical issues when scanning multifidus.

Adult↗
PubMed2004

Injury prevention during physical activity in the Australian Defence Force.

INTRODUCTION: Injuries sustained by Australian Defence Force (ADF) personnel during non-combat military training and sports activity are associated with increasing costs due to work days lost, medical treatment, compensation, and early retirement. In 2001, the ADF commissioned a systematic review of the evidence-base for reducing injuries associated with physical activity, while at the same time improving physical activity participation rates to sustain a trained, fit and deployable workforce. METHOD: Literature from on-line library databases, relevant unclassified military reports, and material from previously published sport-specific injury countermeasure reviews were systematically and critically analysed to address the study aims. RESULTS: Modification of intensity, frequency and duration of basic military training activities and improved equipment is likely to reduce injury occurrence. Sports injury countermeasures used for the civilian population have merit for the ADF physical activity program. Injury countermeasures should be designed to minimise any possible deterrent effect on the motivation to participate in regular physical activity. Increasing the participation of ADF personnel in physical activity in the presence of evidence-based injury prevention strategies has the potential to increase health, fitness and deployability with minimal impact on injury frequency. CONCLUSION: Recommendations arising from the review include injury intervention trials in basic military training and sports. These and other interventions should be supported by refinement to ADF injury surveillance systems. Research should focus on interventions with the greatest gain for fitness, deployability, and cost effectiveness.

Athletic Injuries↗
PubMed2003

Lumbar multifidus muscle size does not differ whether ultrasound imaging is performed in prone or side lying.

This methodological study examined the influence of body position when measuring multifidus muscle size using real-time ultrasound imaging. Previous studies examined multifidus with the subject prone but people with certain conditions cannot be studied in this position, so side lying was investigated as an alternative posture. In 20 normal females (aged 19-45 years), the cross-sectional area (CSA) of lumbar multifidus was measured at the level of the fifth lumbar vertebra (L5) on both the right and left sides, with the subject in prone and in side lying. Multifidus CSA was highly correlated between the two positions on both the right (r=0.90) and left (r=0.91) sides. Paired t-tests found no significant differences between the measurements made in the two scanning postures (right P=0.77; left P=0.16). Bland and Altman plots showed good agreement between the two positions, with no systematic difference. These findings demonstrate that measurements of lumbar multifidus at L5 can be made in either prone or side lying and a valid comparison of the results obtained in both positions can be made.

Adult↗
PubMed2003

The beta fibrinogen gene G-455-A polymorphism is a risk factor for Legg-Perthes disease.

Legg-Perthes disease is a pediatric hip disorder characterized by avascular necrosis of the femoral head. The etiology of Legg-Perthes disease may involve repeated interruptions of the blood supply to the proximal femur. Thus, the role of thrombosis in Legg-Perthes disease is of interest. The focus of this analysis is an evaluation of the relationship between Legg-Perthes disease and the beta fibrinogen gene G-455-A polymorphism in 55 cases of Legg-Perthes disease and 56 age, race, and gender-matched healthy controls. Parents of subjects completed a questionnaire about their child's lifestyle and medical history. Blood was obtained for plasma and DNA analysis. Study subjects were predominantly white (93%), male (77%) and under age 16 (70%). Cases were more likely to be exposed to passive smoke than were controls (odds ratio 5.6, 95% confidence interval 2.0-12.0). Assuming a dominant genetic model, individuals who possessed either the G/A or A/A genotype were over three times more likely to have Legg-Perthes disease compared to those without the polymorphism (odds ratio 3.4, 95% confidence interval 1.5-7.8). Separate analyzes by smoke exposure revealed that the excess risk of the G-455-A polymorphism occurred in those exposed (odds ratio 7.0) as opposed to those unexposed to passive smoke (odds ratio 1.9). Although this difference in the odds ratios is not statistically significant (P=0.2), it suggests a possible interactive effect of cigarette smoke and the b fibrinogen gene G-455-A polymorphism in the risk of developing Legg-Perthes disease.

Adolescent↗
PubMed2003

Probabilistic methods in BCI research.

This paper suggests a probabilistic treatment of the signal processing part of a brain-computer interface (BCI). We suggest two improvements for BCIs that cannot be obtained easily with other data driven approaches. Simply by using one large joint distribution as a model of the entire signal processing part of the BCI, we can obtain predictions that implicitly weight information according to its certainty. Offline experiments reveal that this results in statistically significant higher bit rates. Probabilistic methods are also very useful to obtain adaptive learning algorithms that can cope with nonstationary problems. An experimental evaluation shows that an adaptive BCI outperforms the equivalent static implementations, even when using only a moderate number of trials. This suggests that adaptive translation algorithms might help in cases where brain dynamics change due to learning effects or fatigue.

Algorithms↗
PubMed2000

Sigmoid volvulus after laparoscopic cholecystectomy. An unusual complication.

Laparoscopic cholecystectomy has become the standard surgical technique for treating symptomatic gallbladder disease. Intestinal obstruction after laparoscopic cholecystectomy is unusual. We present the case of a 37-year-old man who underwent routine laparoscopic cholecystectomy for cholelithiasis using an American four-port technique. He was well 24 h postoperatively and was discharged. He presented 36 h later with clinical features of bowel obstruction. A sigmoid loop was seen on a plain abdominal radiograph. Laparotomy revealed distension of the large and small bowel to the level of the rectosigmoid junction and a sigmoid volvulus. This was reduced by releasing adhesions to lengthen the sigmoid mesentery. A primary sigmoid resection and anastomosis was not attempted due to luminal discrepancy and lack of bowel preparation. The patient underwent interval sigmoid colectomy 2 weeks later. A sigmoid volvulus following laparoscopic cholecystectomy has not been previously reported. It may be related to the induction of the pneumoperitoneum, combined with the lateral tilt of the table and a long redundant sigmoid colon. This case expands the range of potential complications associated with laparoscopic cholecystectomy and illustrates the need for continued vigilance after apparently routine procedures.

Adult↗
PubMed2000

Verification of lung dose in an anthropomorphic phantom calculated by the collapsed cone convolution method.

Verification of calculated lung dose in an anthropomorphic phantom is performed using two dosimetry media. Dosimetry is complicated by factors such as variations in density at slice interfaces and appropriate position on CT scanning slice to accommodate these factors. Dose in lung for a 6 MV and 10 MV anterior-posterior field was calculated with a collapsed cone convolution method using an ADAC Pinnacle, 3D planning system. Up to 5% variations between doses calculated at the centre and near the edge of the 2 cm phantom slice positioned at the beam central axis were seen, due to the composition of each phantom slice. Validation of dose was performed with LiF thermoluminescent dosimeters (TLDs) and X-Omat V radiographic film. Both dosimetry media produced dose results which agreed closely with calculated results nearest their physical positioning in the phantom. The collapsed cone convolution method accurately calculates dose within inhomogeneous lung regions at 6 MV and 10 MV x-ray energy.

Algorithms↗
PubMed2000

Auditory evoked potentials to spectro-temporal modulation of complex tones in normal subjects and patients with severe brain injury.

In order to assess higher auditory processing capabilities, long-latency auditory evoked potentials (AEPs) were recorded to synthesized musical instrument tones in 22 post-comatose patients with severe brain injury causing variably attenuated behavioural responsiveness. On the basis of normative studies, three different types of spectro-temporal modulation were employed. When a continuous 'clarinet' tone changes pitch once every few seconds, N1/P2 potentials are evoked at latencies of approximately 90 and 180 ms, respectively. Their distribution in the fronto-central region is consistent with generators in the supratemporal cortex of both hemispheres. When the pitch is modulated at a much faster rate ( approximately 16 changes/s), responses to each change are virtually abolished but potentials with similar distribution are still elicited by changing the timbre (e.g. 'clarinet' to 'oboe') every few seconds. These responses appear to represent the cortical processes concerned with spectral pattern analysis and the grouping of frequency components to form sound 'objects'. Following a period of 16/s oscillation between two pitches, a more anteriorly distributed negativity is evoked on resumption of a steady pitch. Various lines of evidence suggest that this is probably equivalent to the 'mismatch negativity' (MMN), reflecting a pre-perceptual, memory-based process for detection of change in spectro-temporal sound patterns. This method requires no off-line subtraction of AEPs evoked by the onset of a tone, and the MMN is produced rapidly and robustly with considerably larger amplitude (usually >5 microV) than that to discontinuous pure tones. In the brain-injured patients, the presence of AEPs to two or more complex tone stimuli (in the combined assessment of two authors who were 'blind' to the clinical and behavioural data) was significantly associated with the demonstrable possession of discriminative hearing (the ability to respond differentially to verbal commands, in the assessment of a further author who was blind to the AEP findings). Behavioural and electrophysiological findings were in accordance in 18/22 patients, but no AEPs could be recorded in two patients who had clear behavioural evidence of discriminative hearing. The absence of long-latency AEPs should not, therefore, be considered indicative of complete functional deafness. Conversely, AEPs were substantially preserved in two patients without behavioural evidence of discriminative hearing. Although not necessarily indicative of conscious 'awareness', such AEP preservation might help to identify sentient patients who are prevented by severe motor disability from communicating their perception.

Acoustic Stimulation↗
PubMed1998

A prospective study of the length of stay of 150 children following tonsillectomy and/or adenoidectomy.

This is a prospective study of the length of stay in 150 children who underwent adenoidectomy, tonsillectomy and adenotonsillectomy with and without grommets. Seventeen children were unsuitable for same-day discharge because of coexisting medical conditions and 39 because of social factors, which meant that 94 children were potentially suitable for same-day discharge. All patients received a standardized surgical and anaesthetic technique. Twenty-eight of the 94 children were kept in for postoperative complications thus 66 (70%) were treated as day cases. Haemorrhage occurred in one (1%); nausea and vomiting prevented discharge of 11 cases; and a further seven were kept overnight since the children were reluctant to eat and drink. Pain control was a problem with nine children (two had nausea and vomiting as well). Two patients had other complications. These results are compared to those found in the literature. Children who have adenoidectomy without tonsillectomy are more suitable for day surgery (P < 0.001). Because of the high risk of minor complications, the authors recommend that children who have tonsillectomy as part of the procedure should be treated from inpatient beds even when discharged on the same day.

Adenoidectomy↗
PubMed1998

Improvement of intraoperative somatosensory evoked potentials by ketamine.

Many anaesthetics effect the latency and amplitude of somatosensory evoked potentials (SSEP). We present a patient who underwent two anterior/posterior spine fusions (A/PSF) at age 11 and 12 years old after resection of a spinal astrocytoma. She did have residual neurologic deficits of her lower extremities. SSEPs were unobtainable during the first surgery using an opioid-based anaesthetic. A ketamine-based anaesthetic was used for the second surgery and SSEPs were easily monitored. No other factors seem to have changed between the two surgeries. The anaesthetic management during each procedure is reviewed and the contributions of other factors to SSEP monitoring discussed.

Anesthetics, Dissociative↗
PubMed1998

Reliability of assessment tools in rehabilitation: an illustration of appropriate statistical analyses.

OBJECTIVE: To provide a practical guide to appropriate statistical analysis of a reliability study using real-time ultrasound for measuring muscle size as an example. DESIGN: Inter-rater and intra-rater (between-scans and between-days) reliability. SUBJECTS: Ten normal subjects (five male) aged 22-58 years. METHOD: The cross-sectional area (CSA) of the anterior tibial muscle group was measured using real-time ultrasonography. MAIN OUTCOME MEASURES: Intraclass correlation coefficients (ICCs) and the 95% confidence interval (CI) for the ICCs, and Bland and Altman method for assessing agreement, which includes calculation of the mean difference between measures (d), the 95% CI for d, the standard deviation of the differences (SDdiff), the 95% limits of agreement and a reliability coefficient. RESULTS: Inter-rater reliability was high, ICC (3,1) was 0.92 with a 95% CI of 0.72 --> 0.98. There was reasonable agreement between measures on the Bland and Altman test, as d was -0.63 cm2, the 95% CI for d was -1.4 --> 0.14 cm2, the SDdiff was 1.08 cm2, the 95% limits of agreement -2.73 --> 1.53 cm2 and the reliability coefficient was 2.4. Between-scans repeatability was high, ICCs (1,1) were 0.94 and 0.93 with 95% CIs of 0.8 --> 0.99 and 0.75 --> 0.98, for days 1 and 2 respectively. Measures showed good agreement on the Bland and Altman test: d for day 1 was 0.15 cm2 and for day 2 it was -0.32 cm2, the 95% CIs for d were -0.51 --> 0.81 cm2 for day 1 and -0.98 --> 0.34 cm2 for day 2; SDdiff was 0.93 cm2 for both days, the 95% imits of agreement were -1.71 --> 2.01 cm2 for day 1 and -2.18 --> 1.54 cm2 for day 2; the reliability coefficient was 1.80 for day 1 and 1.88 for day 2. The between-days ICC (1,2) was 0.92 and the 95% CI 0.69 --> 0.98. The d was -0.98 cm2, the SDdiff was 1.25 cm2 with 95% limits of agreement of -3.48 --> 1.52 cm2 and the reliability coefficient 2.8. The 95% CI for d (-1.88 --> -0.08 cm2) and the distribution graph showed a bias towards a larger measurement on day 2. CONCLUSIONS: The ICC and Bland and Altman tests are appropriate for analysis of reliability studies of similar design to that described, but neither test alone provides sufficient information and it is recommended that both are used.

Adult↗
PubMed1997

Larval locomotion of the lancelet

The ontogeny of locomotion in the Florida lancelet (Branchiostoma floridae) is described for the early developmental stages through to metamorphosis. Recently hatched larvae swam at speeds up to 1 mm s-1 using their epidermal cilia; this speed decreased to approximately 0.2 mm s-1 by 60 h after fertilization. Changes in cilia-powered fluid flow could be related to changes in the distribution and density of the epidermal cilia during development. Cilia-powered hovering was the dominant behaviour until metamorphosis. The amount of energy expended by ciliating larvae ranged from 10(-9) to 10(-11) W depending upon the age of the larvae and the model used for estimating the power output. The majority of the energy expended was in the ciliary sublayer next to the body. The first muscular movements were seen in larvae 16 h old. These simple flexions increased in complexity during the first 72 h until a complete undulatory (approximately sinusoidal) wave was propagated down the body in the adult manner. The frequency of undulatory beating increased to approximately 10 Hz during the first 48 h, and the larval head showed a large degree of yaw. Lancelet larvae were also capable of high-speed undulations 5&shy;10 times faster than regular swimming motions. In contrast to ciliating larvae, the energy expended during undulation was at least an order of magnitude greater (10(-8) to 10(-6) W) and radiated beyond the ciliary sublayer.

Journal Article↗