Search PubMed⌕ Search

Biomedical subjects

D C Wilson

Publications and source records attributed to D C Wilson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Digital analysis of myocardial contrast echocardiography: a clinical study using an air-filled agent in normal subjects.

The purpose of the present study was to determine whether direct digital image analysis would allow improved detection of myocardial contrast. Eighteen normal subjects were recruited and separated into two groups. In group 1, the time-brightness curves of the left ventricular cavity and three myocardial perfusion beds were formed from digitized video tape, with output power and imaging time as secondary variables. In group 2, curves constructed from direct polar digital data were compared, with fundamental and second harmonic image formation as variables. In group 1 subjects, using fundamental imaging, the area under the curve in the left ventricular cavity increased slightly with intermittent imaging. No consistent myocardial opacification was identified. In group 2 subjects, using intermittent imaging, the area under the myocardial curve and peak intensity increased with high output, second harmonic imaging in the left anterior descending and right coronary artery regions. Intermittent, second harmonic imaging and digital processing can demonstrate myocardial contrast even with an air-filled agent.

Adult↗
PubMed2000

Neurodevelopmental and functional outcomes of extremely low birth weight infants in the National Institute of Child Health and Human Development Neonatal Research Network, 1993-1994.

OBJECTIVES: The purposes of this study were to report the neurodevelopmental, neurosensory, and functional outcomes of 1151 extremely low birth weight (401-1000 g) survivors cared for in the 12 participating centers of the National Institute of Child Health and Human Development Neonatal Research Network, and to identify medical, social, and environmental factors associated with these outcomes. STUDY DESIGN: A multicenter cohort study in which surviving extremely low birth weight infants born in 1993 and 1994 underwent neurodevelopmental, neurosensory, and functional assessment at 18 to 22 months' corrected age. Data regarding pregnancy and neonatal outcome were collected prospectively. Socioeconomic status and a detailed interim medical history were obtained at the time of the assessment. Logistic regression models were used to identify maternal and neonatal risk factors for poor neurodevelopmental outcome. RESULTS: Of the 1480 infants alive at 18 months of age, 1151 (78%) were evaluated. Study characteristics included a mean birth weight of 796 +/- 135 g, mean gestation (best obstetric dates) 26 +/- 2 weeks, and 47% male. Birth weight distributions of infants included 15 infants at 401 to 500 g; 94 at 501 to 600 g; 208 at 601 to 700 g; 237 at 701 to 800 g; 290 at 801 to 900 g; and 307 at 901 to 1000 g. Twenty-five percent of the children had an abnormal neurologic examination, 37% had a Bayley II Mental Developmental Index <70, 29% had a Psychomotor Developmental Index <70, 9% had vision impairment, and 11% had hearing impairment. Neurologic, developmental, neurosensory, and functional morbidities increased with decreasing birth weight. Factors significantly associated with increased neurodevelopmental morbidity included chronic lung disease, grades 3 to 4 intraventricular hemorrhage/periventricular leukomalacia, steroids for chronic lung disease, necrotizing enterocolitis, and male gender. Factors significantly associated with decreased morbidity included increased birth weight, female gender, higher maternal education, and white race. CONCLUSION: ELBW infants are at significant risk of neurologic abnormalities, developmental delays, and functional delays at 18 to 22 months' corrected age.

Birth Weight↗
PubMed1999

Spectral fitting of NMR spectra using an alternating optimization method with a priori knowledge.

As alternatives to the fast Fourier transform, advanced parametric methods based on the damped sinusoidal data model have been devised to better quantify the nuclear magnetic resonance (NMR) spectroscopy time-domain data. Previously, linear prediction (LP) fitting methods using Householder triangularization and singular value decomposition (SVD) techniques have been applied to the NMR spectroscopy data analysis. In this paper, we propose an alternating optimization method to quantify the time-domain NMR spectroscopy data. The proposed algorithm uses the a priori knowledge of the possible frequency intervals of the damped sinusoids to obtain more accurate parameter estimates when the NMR spectroscopy data are obtained under low signal-to-noise ratio conditions and the peaks are close together. None of the LP and SVD type of methods can use such approximate a priori knowledge. We have shown with measured NMR spectroscopy data that the proposed algorithm can be used to obtain accurate parameter estimates of frequencies, amplitudes, and damping ratios of the damped sinusoids and therefore the ultimate fit of the spectrum by using the a priori knowledge about the possible frequency intervals of the damped sinusoids.

Algorithms↗
PubMed1999

Reassessment of the suction blister model of wound healing: introduction of a new higher pressure device.

BACKGROUND: Negative pressure suction blisters have been used as a reproducible and minimally invasive in vivo model of wound healing in human subjects. Despite advantages over other available methods, this technology has not been employed widely in wound healing research. OBJECTIVE: To evaluate the efficacy of a higher pressure suction blister system as an in vivo human model for wound healing and to demonstrate the superiority of this method over previously used suction blister models of wound healing. METHODS: Four 5-mm-diameter suction blisters were induced on the medial upper arm of 18 healthy men and women using a negative pressure of 508 mmHg. Blister roofs were removed, exposing the underlying dermis. The time required for blister formation, the uniformity of wounds, and the degree of patient tolerance were assessed. The ability to monitor clinical re-epithelialization over 7 days was also evaluated by a team of investigators. RESULTS: Four partial-thickness wounds were produced on each subject in 25-45 min. Wound diameter and morphology were uniform in all subjects. Volunteers tolerated the procedure without complaints of pain or discomfort. Progressive, re-epithelialization was observed daily starting 24 h post-wounding. CONCLUSIONS: This higher pressure suction blister system is an effective model for wound healing. Compared to reported methods, it is a better tolerated, more reliable, and more efficient approach to studying in vivo wound repair in human subjects. It is especially well suited for screening the wound healing potential of new pharmacologic agents.

Adult↗
PubMed1998

Uncertainty in the diagnosis of cystic fibrosis: possible role of in vivo nasal potential difference measurements.

The diagnosis of cystic fibrosis (CF) is not always certain, despite extensive clinical evaluation, multiple sweat chloride tests, and genotype analysis. We hypothesized that nasal transepithelial potential difference measurements have a useful role in this situation. In 11 patients without an established diagnosis of CF, results of simultaneous nasal potential difference (PD) and sweat chloride measurements were compared with those from control subjects, obligate CF heterozygotes, and patients with a confirmed diagnosis of CF. Two patients conformed to the PD profile for CF patients, whereas nine had values corresponding to those of the healthy control subjects. Subsequently the 5-thymidine (IVS8-5T) CF gene variant was identified in the two patients with abnormal PD measurements.

Adolescent↗
PubMed1998

Autonomous epicardial and endocardial boundary detection in echocardiographic short-axis images.

An autonomous endocardial and epicardial boundary detection (ABD) method is reported. One hundred ten cycles from 55 clinical studies were selected retrospectively. Image sequences were digitized at 512 x 480 pixel resolution. The point-by-point boundary positions of the ABD and the areas enclosed were compared with positions and enclosed areas drawn by three independent observers. Correlation coefficients for epicardial end-diastolic (ED) and end-systolic (ES) areas, endocardial ED and ES areas, muscle area, and fractional area change were 0.970, 0.976, 0.951, 0.985, 0.887, and 0.878, respectively. Bland-Altman analysis showed negligible biases with standard deviations comparable to those of the observers. The mean difference between the ABD border and the consensus observer border positions in 64 directions falls within the mean range of interobserver border positions, suggesting that shape is also well defined by the ABD.

Echocardiography↗
PubMed1998

Nutrition and cystic fibrosis.

Cystic fibrosis is commonly associated with energy deficiency in children and adults. Chronic undernutrition will lead to failure to thrive, wasting, and stunting of linear growth; nutrition and survival are intimately related in cystic fibrosis. These problems can simply be considered as energy imbalance, and management centers on restoration of energy balance. Specific nutrient deficiencies, such as fat soluble vitamins, are common in cystic fibrosis. Recent work has highlighted problems with bone density and also the prevalence of vitamin K deficiency. Management of nutritional problems can be complex, and injudicious treatment can further worsen the situation, as the relationship between high daily doses of pancreatic enzymes and the development of fibrosing colonopathy illustrates.

Adolescent↗
PubMed1997

Randomized trial of high nutrient density formula versus standard formula in chronic lung disease.

To test the hypothesis that the nutrient intake and growth of infants with chronic lung disease would be improved by providing nutrients in more concentrated form, and that the lower volume would improve respiratory status, 60 preterm infants requiring supplemental oxygen at 28 days of age were randomly assigned a low-density (24 kcal/oz) formula fed at 180 ml/kg/day, or a high-density (30 kcal/oz) formula at 145 ml/kg/day. There was no difference in growth, respiratory outcome, oedema or diuretic requirement between dietary groups. Infants fed the high nutrient density formula had significantly greater total energy (143 vs 134 kcal/kg/day) and protein (3.9 vs 3.6 g/kg/day) intakes, largely because the low-density formula group did not achieve the designated 180 ml/kg/day. In conclusion, use of a high-density formula in infants with chronic lung disease did not improve growth or respiratory outcome, despite a small increase in total energy and protein intake.

Energy Intake↗
PubMed1997

Randomised controlled trial of an aggressive nutritional regimen in sick very low birthweight infants.

AIMS: To improve energy intake in sick very low birthweight (VLBW) infants; to decrease growth problems, lessen pulmonary morbidity, shorten hospital stay, and avoid possible feeding related morbidity. Morbidity in VLBW infants thought to be associated with parenteral and enteral feeding includes bronchopulmonary dysplasia, necrotising enterocolitis, septicaemia, cholestasis and osteopenia of prematurity. METHODS: A prospective randomised controlled trial (RCT) comparing two types of nutritional intervention was performed involving 125 sick VLBW infants in the setting of a regional neonatal intensive care unit. Babies were randomly allocated to either an aggressive nutritional regimen (group A) or a control group (group B). Babies in group B received a conservative nutritional regimen while group A received a package of more aggressive parenteral and enteral nutrition. Statistical analysis was done using Student's t test, the Mann-Whitney U test, the chi 2 test and logistic regression. RESULTS: There was an excess of sicker babies in group A, as measured by initial disease severity (P < 0.01), but mean total energy intakes were significantly higher (P < 0.001) in group A at days 3 to 42 while receiving total or partial parenteral nutrition. Survival and the incidences of bronchopulmonary dysplasia, septicaemia, cholestasis, osteopenia and necrotising enterocolitis were similar in both groups. Growth in early life and at discharge from hospital was significantly better in babies in group A. There were no decreases in pulmonary morbidity or hospital stay. CONCLUSION: Nutritional intake in sick VLBW infants can be improved without increasing the risk of adverse clinical or metabolic sequelae. Improved nutritional intake resulted in better growth, both in discharge, but did not decrease pulmonary morbidity or shorten hospital stay.

Bacterial Infections↗
PubMed1996

Evidence for a relation between inspired gas mixture and the left ventricular contrast achieved with Albunex in a canine model.

BACKGROUND: In a previous experiment, a marked reduction in the right- and left-sided contrast effect of Albunex was noted in an intubated animal spontaneously breathing isoflurane in 100% oxygen. The theory suggests that the time course of echogenicity of microbubbles in liquid is dependent on the pressure and the gradients of dissolved gases. The present set of experiments tested whether the loss of contrast occurs at commonly used therapeutic concentrations of inspired oxygen. HYPOTHESIS: This research tested the hypothesis that the left ventricular (LV) contrast effect achieved with intravenous injection of the ultrasound contrast agent Albunex is related to the inspired oxygen content. METHODS: Intubated dogs were maintained in a spontaneously respiring anesthetic state on isoflurane and mixtures of oxygen (12-50%) in nitrogen. FIO2 was held steady for 15 min prior to injection of 0.08 ml/kg of Albunex. The contrast effects were recorded from a transthoracic short-axis view. Left and right ventricular brightness curves were generated from digitized sequences of end-diastolic frames. The minimum and maximum brightness and area under the time-brightness curves were determined. RESULTS: The LV maximum brightness and area under the curve showed significant negative correlations (p = < 0.004) with the FIO2, while the minimum brightness showed a significant positive correlation (p = < 0.002). No significant correlations were found for the right ventricular brightness parameters. CONCLUSIONS: These findings show an important relationship between the FIO2 and loss of the contrast effect of Albunex. This loss occurs at oxygen concentrations in the therapeutic range, but could be overcome by increasing the dose of Albunex. The mechanism is likely related to an outward nitrogen gradient causing a loss of echogenicity. The clinical implication is that patients on supplemental oxygen may require higher doses of Albunex to achieve optimal opacification.

Albumins↗
PubMed1996

Long-term follow-up of patients with cutaneous T-cell lymphoma treated with extracorporeal photochemotherapy.

BACKGROUND: Few studies have assessed the long-term outcome of patients with cutaneous T-cell lymphoma (CTCL) treated with extracorporeal photochemotherapy (ECP). OBJECTIVE: Our objective was to assess the efficacy, safety, and survival of a cohort of patients with refractory T-cell lymphoma in various stages of cutaneous involvement who were treated with ECP. METHODS: Twenty patients who had received at least 6 months of ECP between September 1988 and April 1991 were reevaluated and the data analyzed statistically to obtain outcome data through December 1995. RESULTS: A complete response (disappearance of all lesions) was obtained in five patients (25%) and a partial response (disappearance of at least 50% of lesions) in five patients (25%). Of the 10 responders, seven (70%) were weaned from ECP. Two of seven patients had a relapse. Ten patients (50%) showed no response to ECP. No statistically significant differences between responders and nonresponders were found with respect to demographic, clinical, or laboratory variables. Seven patients died of causes directly related to CTCL and two patients died of unrelated causes. Median survival time for the entire cohort was 96 months (range, 16 to 152 months). An assessment of early response after 6 to 8 months of ECP had a sensitivity of 100% and a specificity of 90% for predicting long-term (> 4 years) outcome. Adverse effects were minimal. CONCLUSION: ECP is a safe effective alternative therapy for CTCL that is refractory to other therapies; it can induce a long-term, disease-free remission in a minority of patients. Response in the first 6 to 8 months of treatment predicts long-term outcome.

Adult↗
PubMed1996

Automatic identification of papillary muscles in left-ventricular short-axis echocardiographic images.

An automatic method for identifying the location of the papillary muscles in two-dimensional (2-D) short-axis echocardiographic images is described. The technique uses both spatial and temporal information to identify the presence and track the location of the muscles in the left ventricle from end-diastole to end-systole. The three main steps of the method are spatial preprocessing, spatial processing, and temporal processing. The spatial preprocessing step includes a region of search estimation. The spatial processing step includes a papillary muscle existence test and an initial approximation of the papillary muscle points. The temporal processing includes motion-pattern evaluation and final papillary muscle location. The estimates of existence and position for the automatic method were compared with estimates made by an independent expert observer. Two hundred and ten frames, three taken from each of 70 image sequences, were evaluated. Since two regions of search were processed for each frame (one for the posterior-inferior and one for the anterior-lateral papillary muscle), a total of 420 approximations were made. Of this total, 340 automatic estimates were judged to be in close agreement with estimates made by the expert. Of the remaining 80 approximations, 54 estimates were made by the expert when the computer determined that no papillary muscle was present, 17 estimates provided poor results, and nine estimates were made by the computer when the observer concluded that no papillary muscle was present.

Algorithms↗
PubMed1996

Tolerance of mixed lipid emulsion in neonates: effect of concentration.

AIMS: To compare the effect of concentration of a mixed lipid emulsion (50:50 medium chain triglyceride/long chain triglyceride) (MCT/LCT) on lipid tolerance in neonates. METHODS: A prospective randomised controlled trial of 75 neonates requiring prolonged parenteral nutrition was conducted in the neonatal intensive care units of the Royal Maternity Hospital, Belfast, and the Waveney Hospital, Ballymena. Thirty eight infants received 10% and 37 20% lipid emulsion. Infants were randomly assigned to groups at the start of parenteral nutrition and studied if they required seven or more days of this. Lipid tolerance was assessed by twice weekly measurements of plasma triglyceride and cholesterol concentrations and weekly measurement of non-esterified fatty acids and beta hydroxy butyrate. Anthropometry was carried out weekly. RESULTS: The mean cholesterol in the 10% group was significantly higher within the first seven days of the study compared with the 20% group (3.5 vs 2.87 mmol/l), and continued to rise over the study period in contrast to the 20% group. A similar pattern was observed with the triglyceride concentrations. There was no significant difference in non-esterified fatty acids, beta hydroxy butyrate, or growth between the two groups. CONCLUSION: Sick neonates show better biochemical tolerance to 20% MCT/LCT emulsion than to 10% emulsion.

Cholesterol↗
PubMed1996

Babies born under 1000 g--perinatal outcome.

Improved survival of very pre-term infants is a result of advances in obstetric and neonatal medicine. To provide relevant data for a Northern Ireland population group, we evaluated mortality and morbidity of extremely low birthweight (ELBW; < 1000 g) infants from a tertiary referral neonatal unit. Seventy-seven ELBW infants were admitted on the first day of life during the period April 1990 to April 1992. Mean (SD) gestational age (GA) was 26.2 (2.1) weeks and birthweight (BW) was 781 (132) g. The degree of severity of initial illness was high, with a mean (SD) CRIB (clinical risk index for babies) score of 7.4 (4.2). Fifty (65%) babies survived, being discharged home at a mean (SD) age of 95 (34) days. Survivors were more likely to have received maternal steroid therapy or been born in this hospital. Ten (20%) of the survivors had evidence of severe neonatal brain injury or cranial ultrasonography--Papile grade 3 or 4 intraventricular haemorrhage (IVH) or periventricular leucomalacia (PVL). Survival rate of ELBW infants without severe brain injury was 54% overall; this ranged from 0% in ELBW infants born at 23 weeks GA and 33% at 24 weeks GA to 85% at 27 weeks GA.

Brain Injuries↗
PubMed1995

Percutaneous central venous catheter use in the very low birth weight neonate.

UNLABELLED: A retrospective study was carried out comparing 61 very low birth weight infants (VLBW) with percutaneous central venous catheters with 92 infants managed with peripheral cannulae. Eighteen infants developed one or more episodes of catheter-associated bacteraemia. In 70% of cases the infection was successfully treated with the line in situ. Logistic regression analysis was performed to examine risk factors for bacteraemia. The duration of intravenous fluids and of intermittent positive pressure ventilation were both significant risks for infection (odds ratios and 95% confidence limits 4.4, 2.7-12.0 and 2.5, 1.0-6.1 respectively), but the presence of a silastic catheter was not an independent risk factor (odds ratio 0.6, 95% confidence limits 0.1-3.0). CONCLUSION: Percutaneous central venous catheters provide a satisfactory means of delivering parenteral nutrition with minimal disturbance to ill VLBW infants.

Bacteremia↗