Biomedical subjects
A D Milner
Publications and source records attributed to A D Milner.
Bronchodilator drugs in childhood asthma.
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Ketotifen in the prophylaxis of childhood asthma.
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Bronchodilator effects of clemastine, ipratropium, bromide, and salbutamol in preschool children with asthma.
The bronchodilator activity in nebulised salbutamol, ipratropium bromide, clemastine, and a placebo was studied in 14 asthmatic children aged between 3 and 5 years. Changes in lung function were monitored by measuring peak expiratory flow rate and total respiratory resistance using a modification of the forced oscillation technique. Ipratropium bromide produced a degree of bronchodilation similar to that of salbutamol, but the bronchodilatory activity of clemastine was not appreciably better than for the placebo.
Bradycardia and associated respiratory changes in neonates.
Electrocardiogram and patterns of respiration were recorded continuously in 9 newborn infants having episodes of bradycardia. The episodes were not associated with demonstrable apnoea, either by using an apnoea mattress or by visual observation. The 'non-apnoea' associated bradycardia was always associated with changes in respiratory pattern, of which three different forms could be identified. These were prolonged apnoea if the apnoea alarm failed to trigger, short episodes of respiratory abnormalities associated with body movement (possibly in rapid eye movement sleep), and minor changes in respiratory pattern. It may be appropriate to incorporate a period of delay in heart rate monitoring systems before the alarm sounds, in a similar manner to apnoea alarm systems. We should rely more on heart rate in conjunction with apnoea alarms to detect problems, or produce better systems which detect respiratory flow.
Bronchodilator effect of inhaled ipratropium bromide in wheezy toddlers.
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Measurement of work of breathing in infancy.
Assessment of lung function in young children is extremely difficult unless sedation is given. If tidal exchange and intrathoracic pressure swings can be recorded, the severity of the respiratory problem can be measured by construction pressure-volume loops and calculating the work of breathing. The system we have used to measure tidal thoracic volumes is that of a soft, rubber, inflatable jacket with pressure-volume characteristics linear from inflation pressure of 2.5 to 7 cm H2O. Oesophageal (intrathoracic) pressures are measured using water-filled nasogastric tubes (FG6). Frequency responses showed that 63% rise times for the jacket and water-filled nasogastric tube assessed together to be 10.5 msec. Recordings were traced onto a computer digitizing tablet and print-outs were obtained with the following information: respiratory rate, tidal thoracic volume, minute thoracic volume, oesophageal pressure, resistive work per min, elastic work per min, and total work per min. Comparisons were made between volumes measured using the respiratory jacket (VJ) and by pneumotachograph and integrator (VInt) in six infants. Hysteresis arising from the jacket produces some change in resistive work of breathing, but the total work of breathing is only increased by a maximum of 10.5%. Studies on healthy newborn babies showed that the jacket system tends to underrecord the resistive work of breathing, but that total work of breathing values are very similar. Reproducibility of analysis showed the following coefficients of variation from the mean: tidal thoracic volume, 1.6%; minute thoracic volume, 1.7%; resistive work, 5%; elastic work, 2%; and total work, 2.5%. The extent of breath-to-breath variation is much larger. This system makes it possible to obtain serial measurements of work of breathing without the need for sedation in infants who may be acutely ill and in respiratory failure.
Response to bronchodilator drugs in the first years of life.
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Upper airways obstruction and apnoea in preterm babies.
Measurements of tidal flow, volume, and oesophageal pressure were recorded on a group of 8 severely preterm infants with periodic respiration. Analysis of the flow trace for evidence of cardiac artefact, and the tidal volume trace to identify at what point of the tidal cycle apnoea starts, indicated that upper airways obstruction was associated with about half these attacks. It is surmised that this is produced by glottic closure.
Efficacy of orally administered salbutamol and theophylline in pre-schoolchildren with asthma.
Oral administration of salbutamol and theophylline has been shown to be effective in relieving bronchoconstriction in asthmatic children aged between 3 and 5 years. Changes in respiratory function were monitored using a Wright's low range peak flow meter and a modification of the forced oscillation technique. A combination of both drugs in half doses was as effective as either alone. Nebulised salbutamol produced considerable further improvement in lung function.
Bronchopulmonary dysplasia.
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Lung expansion, tidal exchange, and formation of the functional residual capacity during resuscitation of asphyxiated neonates.
Ventilatory exchange and endotracheal and esophageal pressures were measured during resuscitation of asphyxiated neonates born by cesarean section. In contrast to spontaneously breathing, vaginally born babies, an opening pressure had to be exceeded before lung expansion occurred. Subsequently there was usually a gradual increase in gaseous exchange over the first few lung inflations. A further rise in lung compliance occurred with the baby's inspiratory efforts. The functional residual capacity was formed with or without active inspiratory efforts by the baby, although gaseous retention occurred more rapidly as a result of the infant's inspiration.
Visual sampling after lesions of the superior colliculus in rats.
In two separate experiments, rats with bilateral lesions of the superior colliculus showed significantly poorer relearning of a horizontal/vertical stripe discrimination than control animals. In Experiment 1, all animals showed disruption of performance when a stimulus--response (S--R) separation was introduced by raising the stimuli above the site of responding. However, the colliculectomized rats were much more disturbed by the S--R separation than were animals in the control group. In Experiment 2, all animals showed lower performance levels when conflicting patterns were introduced into the upper portion of the stimulus doors, but this time the rats with collicular lesions were less disturbed than the control animals. It is suggested (a) that when the stimulus and response sites are discontiguous, animals must make an appropriate orienting response in order to effectively sample the visual stimuli and (b) that lesions of the superior colliculus alter performance by interfering with this orienting behavior. The impairment in relearning is tentatively attributed to the absence of preoperative overtraining on the discrimination task.
Recent advances in respiratory medicine.
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Physiological responses of the newborn infant to resuscitation.
Lung ventilation, endotracheal, and intraoesophageal pressures were measured during standard resuscitation of 20 asphyxiated babies born by caesarean section. The most common response to resuscitation was the production of a large positive intraoesphageal pressure. An opening pressure greater than 2.0 kPa was required to expand the lungs of most of these babies. The need for resuscitation was associated with prolonged maternal anaesthesia before delivery.
Continuous and intermittent salbutamol tablet administration in asthmatic children.
We studied 22 asthmatic children aged seven years two months to thirteen years eight months over a four-month period. Each child received two months continuous and two months intermittent salbutamol tablets using a double-blind cross-over technique. No significant clinical differences were found between the two treatment regimens as judged by daily diary card scores. Daily PEFRs (both a.m. and p.m.) were significantly higher (P < 0.05) when the children were receiving continuous salbutamol and this was more obvious in the eleven children under ten years old. Lung function tests performed monthly in hospital showed no significant differences between the two treatment regimens.
The bronchodilator effects of chlorpheniramine in childhood asthma.
Significant improvement in lung function has been demonstrated following the inhalation of chlorpheniramine. The doses which were used caused local irritation and are probably unsuitable for routine clinical use. Nevertheless, we believe that antihistamines deserve further investigation in the treatment of childhood asthma.
Visual orientation in the rat: a dissociation of deficits following cortical and collicular lesions.
Rats with either bilateral ablations of superior colliculus, bilateral ablations of visual cortex, or sham operations were trained to run across a large arena towards a small illuminated target which varied in location from trial to trial. An impairment in this visually-guided running was apparent in the cortical group, but not in the collicular group. When, in a second experiment, the spatial relationships within the apparatus were changed by extending the entry-tunnel some distance into the arena, the running of the cortical group became even more impaired, while the collicular animals continued to run towards the targets under efficient visual control. In a third experiment, the effect of introducing a novel flashing light in various locations around the perimeter of the arena was investigated. It was found that unlike the other two groups, the collicular animals showed no orienting reflex to the novel stimulus when it was presented outside a broad central area of the visual field.