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Biomedical subjects

A D Milner

Publications and source records attributed to A D Milner.

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

The effect of ribavirin to treat previously healthy infants admitted with acute bronchiolitis on acute and chronic respiratory morbidity.

The role of ribavirin in the treatment of acute bronchiolitis is controversial. It has been suggested that the use of ribavirin may be of benefit during the acute illness and may reduce subsequent recurrent respiratory morbidity. This randomized, double-blind, placebo-controlled study was designed to determine whether ribavirin administered during the acute illness would have an influence on respiratory morbidity during both the acute illness and during the following year. Bronchial reactivity 6 months after the acute illness was also assessed. Forty previously well infants with moderately severe acute bronchiolitis were recruited during three winter epidemics. Subjects received study medication for 18 h a day. Management was otherwise unaltered. Subjects were evaluated daily by the investigator and subsequently assessed at 6 weeks, 6 months and 1 year following the acute illness. Assessment of bronchial hyper-responsiveness was assessed at 6 months of age using total body plethysmography and an established ultra-sonically nebulized distilled water challenge. A total of 40 patients (21 ribavirin, 19 placebo) were entered into the study. The two groups did not differ with respect to age, gender or clinical severity on entry to the trial. No significant differences were identified in the rate of clinical improvement over the first 24 h, the time to discharge, bronchial responsiveness at 6 months of age, frequency of significant respiratory symptoms over the first year of life and the frequency of prescribed bronchodilators and inhaled steroids during the year of follow-up. This study was unable to demonstrate any clinical benefit from the use of ribavirin in the acute illness or during subsequent follow-up for 1 year.

Antiviral Agents↗
PubMed2001

Visual and tactile size distortion in a patient with right neglect.

One typical feature of the neglect syndrome in patients with right hemisphere damage is that they bisect horizontal lines to the right of centre. It has been argued that to a large extent these bisection errors can be attributed to a perceptual change whereby the patient experiences the left half of a line as shorter than the right half, causing them to set the midpoint of the line towards the right. We describe here a patient with a left hemisphere lesion and rightward neglect, who consequently makes bisection errors in a leftward direction. We carried out a series of tests which confirmed that he shows a subjective visual distortion in the converse direction, i.e. a perception of horizontal extents on the right as shorter than extents on the left. We also found that he shows a similar distortion in his tactile perception. The association of visual and tactile distortions in this patient is compatible with the view that the distortion effects have a rather high-level origin. Multiple single-case studies will, however, be required to establish whether this association of deficits is typical, or whether visual and tactile size distortions are separable symptoms associated with neglect.

Attention↗
PubMed2001

Volume of activation of the Hering-Breuer inflation reflex in the newborn infant.

Although the Hering-Breuer inflation reflex (HBIR) is active within tidal breathing range in the neonatal period, there is no information regarding whether a critical volume has to be exceeded before any effect can be observed. To explore this, effects of multiple airway occlusions on inspiratory and expiratory timing were measured throughout tidal breathing range using a face mask and shutter system. In 20 of the 22 healthy infants studied, there was significant shortening of inspiration because the volume at which occlusion occurred rose from functional residual capacity (FRC) to end-inspiratory volume [14.9% reduction in inspiratory time (per ml/kg increase in lung volume at occlusion)]. All infants showed a significant increase in expiratory time [17.1% increase (per ml/kg increase in lung volume at occlusion)]. Polynomial regression analyses revealed a progressive increase in strength of HBIR from FRC to approximately 4 ml/kg above FRC. Eighteen infants showed no further shortening of inspiratory time and 10 infants no further lengthening of expiratory time with increasing occlusion volumes, indicating maximal stimulation of the reflex had been achieved. There was a significant relationship between strength of HBIR and respiratory rate, suggesting that HBIR modifies the breathing pattern in the neonatal period.

Humans↗
PubMed2000

Synchronized mechanical ventilation for respiratory support in newborn infants.

BACKGROUND: During synchronous ventilation, positive pressure ventilation and spontaneous inspiration coincide. Thus, if synchronous ventilation is provoked, it is likely that adequate gas exchange should be achieved at lower peak pressures, reducing barotrauma and hence airleak and chronic lung disease. Synchronous ventilation can be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient assisted ventilation. OBJECTIVES: To compare (i) the efficacy of synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation or triggered ventilation (patient triggered ventilation (PTV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (ii) different types of triggered ventilation SEARCH STRATEGY: Searches were made of the Oxford Database of Perinatal Trials, Medline (MESH terms: mechanical ventilation; triggered ventilation; newborn infant); previous reviews, abstracts, symposia proceedings, hand searching of journals in the English language and contacting expert informants. SELECTION CRITERIA: Randomized or quasi randomized clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (PTV/SIMV) to conventional ventilation (CMV) in neonates. Randomized trials comparing different triggered ventilation modes (PTV and SIMV) in neonates. DATA COLLECTION AND ANALYSIS: Data regarding clinical outcomes including mortality, airleaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intracerebral haemorrhage (grades 3 and 4), chronic lung disease (oxygen dependency beyond 28 days) and duration of weaning/ventilation. Data subdivided into three groups: (i) HFPPV vs CMV; (ii) PTV/SIMV vs CMV; (iii) PTV vs SIMV. Data analysis was conducted according to the standards of the Neonatal Cochrane Review Group. MAIN RESULTS: The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of airleak (typical relative risk 0.68, 95% CI 0.55, 0.68). PTV/SIMV compared to CMV was associated with a shorter duration of ventilation (Weighted mean difference -45.2 hours, 95% CI -78.3, -12.1). PTV compared to SIMV was associated with a trend to a shorter duration of weaning (Weighted mean difference 42.4 hours, 95% CI -9.6,94.4). No disadvantage to HFPPV or triggered ventilation was noted regarding other outcomes. REVIEWER'S CONCLUSIONS: Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in airleak and a shorter duration of ventilation respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with a reduction in chronic oxygen dependency.

Humans↗
PubMed2000

Lateralized word recognition: assessing the role of hemispheric specialization, modes of lexical access, and perceptual asymmetry.

The processing advantage for words in the right visual field (RVF) has often been assigned to parallel orthographic analysis by the left hemisphere and sequential by the right. The authors investigated this notion using the Reicher-Wheeler task to suppress influences of guesswork and an eye-tracker to ensure central fixation. RVF advantages obtained for all serial positions and identical U-shaped serial-position curves obtained for both visual fields (Experiments 1-4). These findings were not influenced by lexical constraint (Experiment 2) and were obtained with masked and nonmasked displays (Experiment 3). Moreover, words and nonwords produced similar serial-position effects in each field, but only RVF stimuli produced a word-nonword effect (Experiment 4). These findings support the notion that left-hemisphere function underlies the RVF advantage but not the notion that each hemisphere uses a different mode of orthographic analysis.

Brain↗
PubMed2000

Lung volume measurements in childhood.

Although less commonly used in clinical practice than spirometry, lung volume measurements are helpful in assessing progress and response to therapy in situations where lung volume is likely to be increased, as in asthma or cystic fibrosis, or reduced secondary to pulmonary hypoplasia, pulmonary fibrosis, or musculoskeletal abnormalities. Their contribution to research has been considerable. The techniques most commonly used are those of inert gas dilution on rebreathing, applicable to children of all ages but tending to under-record in the presence of gas trapping. The gold standard is body plethysmography. This is relatively expensive and requires more technical skill, but will measure all the gas within the chest. Computer programmes have been developed to obtain a reasonable estimate of lung volume from chest X-rays alone. More accurate results are obtained by echo-planar imaging but this is only available in highly specialized units. Information on fetal lung volumes can be obtained using digitized ultrasound images and position sensors attached to the ultrasound probe.

Child↗
PubMed2000

Resonance frequency in respiratory distress syndrome.

AIM: To observe how the resonance frequency changes with the course of respiratory distress syndrome (RDS), by examining the effect of changing static compliance on the resonance frequency in premature infants. METHODS: In 12 ventilated premature infants with RDS (mean gestational age 26.6 weeks, mean birth weight 0.84 kg), resonance frequency and static compliance were determined serially using phase analysis and single breath mechanics technique respectively in the first seven days of life. RESULTS: The minimum number of measurements done in any one baby was three and maximum was five in this seven day study period. The first measurement in each baby was done within the first 72 hours of life. The increase in compliance in this period varied from 27% to 179%. The variation in the corresponding resonance frequency was within 2 Hz in eight babies and within 6 Hz in all recruited babies. CONCLUSIONS: The resonance frequency of the respiratory system in preterm infants with RDS remains remarkably constant in the early stages of the illness, despite relatively large changes in static compliance.

Female↗
PubMed1999

A paradoxical improvement of misreaching in optic ataxia: new evidence for two separate neural systems for visual localization.

We tested a patient (A. T.) with bilateral brain damage to the parietal lobes, whose resulting 'optic ataxia' causes her to make large pointing errors when asked to locate single light emitting diodes presented in her visual field. We report here that, unlike normal individuals, A. T.'s pointing accuracy improved when she was required to wait for 5 s before responding. This counter-intuitive result is interpreted as reflecting the very brief time-scale on which visuomotor control systems in the superior parietal lobe operate. When an immediate response was required, A. T.'s damaged visuomotor system caused her to make large errors; but when a delay was required, a different, more flexible, visuospatial coding system--presumably relatively intact in her brain--came into play, resulting in much more accurate responses. The data are consistent with a dual processing theory whereby motor responses made directly to visual stimuli are guided by a dedicated system in the superior parietal and premotor cortices, while responses to remembered stimuli depend on perceptual processing and may thus crucially involve processing within the temporal neocortex.

Adult↗
PubMed1999

Effects of different modes of delivery on lung volumes of newborn infants.

The aim of our study was to examine the effect of labor and birth canal compression on the rate of clearance of lung fluid. We recruited 10 babies born by vaginal delivery and 10 born by elective cesarean section (ECS). Thoracic gas volume (TGV) was measured using total body plethysmography, and functional residual capacity (FRC) by argon dilution, at ages 4-6 h and 24 h. Additional measurements were obtained at age 48 h in the infants born by ECS. Our results showed significant increases in mean TGV (from 23.1 mL/kg to 27.4 mL/kg, P = 0.002) and FRC (from 21.2 mL/kg to 24.1 mL/kg, P = 0.04) between 4-6 h and 24 h of age after ECS delivery. Lung volumes did not change significantly over the next 24 h (TGV, 27.4 mL/kg, P = 0.97; FRC, 25.5 mL/kg, P = 0.42). In those infants born by vaginal delivery, the mean TGV at 4-6 h and 24 h were 26.7 and 28.7 mL/kg, respectively (P = 0.09), and the mean FRC results were 23.1 and 24.9 mL/kg, respectively, P = 0.08). The TGV tended to be lower at 4-6 h in those born by ECS than in infants born vaginally (23.1 vs. 26.7 mL/kg, P = 0.05). We conclude that there is a delay of up to 24 h in the establishment of final lung volumes in babies born without exposure to labor or passage through the birth canal, and that this may explain the increased respiratory morbidity associated with delivery by ECS.

Birth Weight↗
PubMed1999

Comparison of two inspiratory: expiratory ratios during high frequency oscillation.

UNLABELLED: The aim of this study was to compare gas exchange and volume delivery during high frequency oscillation at two frequently used inspiratory:expiratory (I:E) ratios: 1:2 and 1:1, other oscillatory settings being kept constant. A group of 13 infants with respiratory distress syndrome, median gestational age 28 weeks (range 23-36) and postnatal age 1 day (range 1-8) were studied. At the I:E ratio of 1:1 compared to 1:2 the median paCO(2) was lower, P < 0.05 (30 mmHg, range 22-47 vs 34 mmHg, range 27-46) and the volume delivered higher, P < 0.01 (2.6 ml/kg, range 1.2-5.6 vs 2.0 ml/kg, range 1.0-3.9). There was no significant difference in oxygenation levels at the two I:E ratios. In a related in vitro study, changing the I:E ratio from 1:2 to 1:1 increased the mean airway pressure by a median of 8.6% (range 2.9-28.1%). CONCLUSION: Routinely maintained longer expiratory than inspiratory times during high frequency oscillation should be discouraged.

Carbon Dioxide↗
PubMed1999

Residual perceptual distortion in 'recovered' hemispatial neglect.

In most neglect patients, line bisection errors become smaller on repeated tests over the months following the lesion. We have tried to determine in two typical patients whether this is because of a real reduction in the perceptual distortions that appear to underlie line bisection errors in neglect, or whether it reflects a learned behavioural strategy to counteract those perceptual biases. We tested the patients on two occasions (2 and 12 months post-stroke), on line bisection and also on the 'Landmark' task. The data indicated that at the first testing session both patients showed strong 'perceptual' neglect, making large rightward errors in the standard bisection task and uniformly leftward pointing in the Landmark task. On the second occasion, as expected, both patients showed a marked recovery when tested with the line bisection task, making only very small errors. In contrast, their landmark performance was still markedly biased in the same direction as before. These findings suggest that despite their apparent recovery on the bisection task, both patients still experience some form of perceptual distortion of horizontal lines. It is suggested that the Landmark task may provide a sensitive means for identifying real recovery of the underlying perceptual deficit.

Adaptation, Psychological↗
PubMed1999

Motion parallax enables depth processing for action in a visual form agnosic when binocular vision is unavailable.

Visual-form agnosic patient DF, who has severe difficulties in using visual information about size, shape and orientation for perceptual report, can nevertheless--under normal viewing conditions--use the same information to accurately guide her hand movements. However, her performance of prehension tasks requiring the analysis of visual depth is severely disrupted when binocular vision is prevented. We have suggested that this deterioration in visuomotor control is due to an inability to use pictorial depth cues to compensate for the removal of binocular vision. In the current study we investigated whether DF was able to use motion parallax as an alternative to binocular cues. We asked her to grasp a square plaque slanted at different orientations in depth, under two monocular testing conditions. In one condition her head remained stationary on a chin rest, and in the other condition she made large lateral head movements just prior to each prehension movement. The results confirmed that DF is impaired in adjusting her hand orientation to the orientation of the target object when reaching monocularly with her head stationary. In contrast, when she made head movements, her manual performance was restored to almost normal levels. Our results are consistent with the idea that the processing of pictorial depth cues depends on the cortical ventral stream, which is known to be disrupted by DF's lesion. They further indicate that orientation in depth can be computed from motion parallax just as well as from binocular cues in the absence of a normally functioning ventral stream.

Adult↗
PubMed1999

Randomised controlled trial of budesonide for the prevention of post-bronchiolitis wheezing.

BACKGROUND: Previous studies suggest that recurrent episodes of coughing and wheezing occur in up to 75% of infants after acute viral bronchiolitis. AIM: To assess the efficacy of budesonide given by means of a metered dose inhaler, spacer, and face mask in reducing the incidence of coughing and wheezing episodes up to 12 months after acute viral bronchiolitis. METHODS: Children under the age of 12 months admitted to hospital with acute viral bronchiolitis were randomised to receive either budesonide or placebo (200 microg or one puff twice daily) for the next eight weeks. Parents kept a diary card record of all episodes of coughing and wheezing over the next 12 months. RESULTS: Full follow up data were collected for 49 infants. There were no significant differences between the two study groups for the number of infants with symptom episodes up to six months after hospital discharge. At 12 months, 21 infants in the budesonide group had symptom episodes compared with 12 of 24 in the placebo group. The median number of symptom episodes was 2 (range, 0-13) in those who received budesonide and 1 (range, 0-11) in those who received placebo. Because there is no pharmacological explanation for these results, they are likely to be caused by a type 1 error, possibly exacerbated by there being more boys in the treatment group. CONCLUSION: Routine administration of budesonide by means of a metered dose inhaler, spacer, and face mask system immediately after acute viral bronchiolitis cannot be recommended.

Acute Disease↗
PubMed1999

Effects of smoking in pregnancy on neonatal lung function.

AIMS: To assess the effects of smoking during pregnancy on lung mechanics and lung volumes in the immediate neonatal period, before infants are exposed to passive smoking. METHODS: Lung function tests were carried out within 72 hours of delivery in infants born to 100 non-smoking and 189 smoking mothers. Lung growth was assessed by plethysmography and lung mechanics using the single breath occlusion technique and oesophageal balloon/pneumotachography. Antenatal maternal serum cotinine values were obtained from 133 mothers. RESULTS: Smoking was associated with a significant reduction in birthweight (mean 256 g, 95% CI 0.164 to 0.392), and length (mean 1.26 cm, 95% CI 0.48 to 2.00). Lung volume was not reduced when related to weight. Smoking was associated with a highly significant reduction in static compliance (Crs). This effect remained significant after relating Crs to weight and lung volume. Regression analyses showed that the Crs association was limited to the boys. Smoking was associated with a small but significant reduction in respiratory system conductance (Grs) (single breath occlusion technique) and total pulmonary conductance (Gp). These associations were limited to girls. CONCLUSIONS: Smoking in pregnancy reduces static compliance in boys and conductance in girls. There was no evidence that maternal smoking adversely affected fetal lung growth.

Adult↗
PubMed1999

Determination of resonance frequency of the respiratory system in respiratory distress syndrome.

AIM: To measure tidal volume delivery produced by high frequency oscillation (HFO) at a range of frequencies including the resonance frequency. METHODS: Eighteen infants with respiratory distress syndrome were recruited (median gestation 28.7 weeks). Each was ventilated at frequencies between 8 and 30 Hertz. Phase analysis was performed at various points of the respiratory cycle. HFO was provided by a variable speed piston device. Resonance frequency was determined from the phase relation between the cyclical movements of the piston and pressure changes at the airway opening. Tidal volume was measured using a jacket plethysmograph. RESULTS: The results were most reproducible when analysis was performed at the end of inspiration (within 1 Hz in nine out of 10 cases). Comparison between tidal volume delivery at 10 Hz and resonance frequency was made in 10 subjects. Delivery was significantly higher at resonance than at 10 Hertz (mean percentage increase 92%, range 9-222%). CONCLUSIONS: These preliminary findings suggest that there is improved volume delivery at resonance frequency.

Airway Resistance↗
PubMed1999

Assessment of effect of nasal continuous positive pressure on laryngeal opening using fibre optic laryngoscopy.

AIM: To assess the effect of nasal continuous positive airways pressure (CPAP) on the dimensions of the laryngeal opening. METHODS: Nine preterm infants who had previously received ventilatory support for respiratory distress syndrome (RDS) were studied. All were receiving nasal CPAP. The laryngeal opening was visualised using a fibre optic video camera system. The ratio of width to length of the opening was measured on and off CPAP. RESULTS: In eight of the infants the width: length ratio increased on CPAP; mean change for group +24.4% (95% CI +11.9 to +37.9). CONCLUSIONS: Nasal CPAP seems to dilate the larynx. This may explain the selective beneficial effects of CPAP on mixed and obstructive apnoea.

Apnea↗
PubMed1998

Neuropsychological studies of perception and visuomotor control.

According to recent conceptualizations, there are two separate cortical visual systems--each with its own distinctive cortical and subcortical links--and these two systems respectively serve the functions of perception and of motor control. These ideas have been arrived at through a confluence of neuroanatomical, electrophysiological, behavioural, and neuropsychological research. It is proposed that this distinction between two broad purposes of vision and their neural bases can provide useful working procedures for analysing both: (i) the nature of visuomotor processing in the normal brain; and also (ii) the abnormal patterns of visual processing that are seen in certain neurological conditions.

Brain↗