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Biomedical subjects

I B Masters

Publications and source records attributed to I B Masters.

At least 19 recordsLinked to original sources
PubMed1999

Clinical versus polysomnographic profiles in children with obstructive sleep apnoea.

OBJECTIVE: To examine the clinical and polysomnographic (PSG) profiles of neurologically normal and abnormal children with obstructive sleep apnoea (OSA) and explore the relationship between these profiles. METHODOLOGY: We enrolled 56 children with persistent snoring and OSA for the study, 16 of whom were neurologically abnormal. All children were examined clinically and attended an overnight PSG study. Total clinical scores, PSG scores, and mild/moderate or severe ratings were derived for each child. RESULTS: Comparison of individual PSG parameters with neurological status demonstrated that the abnormal children had significantly increased obstructive apnoea indices, increased desaturation events and lower mean arousal indices compared to their neurologically normal OSA peers. For the neurologically abnormal children, there was a significant correlation between severity ratings of disease according to clinical and PSG profiles (r = 0.56, P = 0.03, sensitivity 82%) using the clinical summary as the gold standard, although the association was less marked in the neurologically normal children (r = -0.08, P = NS, sensitivity 69%). CONCLUSION: Neurologically abnormal children are likely to have more severe abnormalities in selected polysomnographic indices and overall scores. However, the clinical assessment is only likely to reflect this at the severe end of the spectrum. These relationships are not seen in the neurologically normal child, where little or no reliance can be placed upon predicting the severity of the polysomnographic findings from the clinical data. Decisions regarding the severity of disease and treatment should be based on the combined findings of the clinical and PSG data rather than overall clinical and polysomnographic scores or selected clinical and polysomnographic parameters.

Arousal↗
PubMed1998

Educating young children about asthma: comparing the effectiveness of a developmentally appropriate asthma education video tape and picture book.

Asthma self-management programmes have been shown to increase children's knowledge about asthma and improve their management practices and health status. However, existing programmes have rarely addressed the unique learning needs of very young children. This study aimed to develop and assess the effectiveness of a video tape and picture book designed to teach children about the prevention and management of acute episodes of asthma. The information content of the educational resources was determined by analysis of relevant medical information and asthma management skills. Social Learning Theory and consideration of the developmental stage of the target population informed the format and style of presentation of the resources. Eighty children aged between 2 and 5 years who had been diagnosed with asthma by their medical practitioner and who required daily asthma medication participated in a controlled experimental study. The study evaluated the impact of the asthma education resources on children's knowledge about asthma, compliance with medication regimens and health status. Children were randomly allocated to one of three experimental groups. Children in these groups were exposed to either the video tape alone, the book alone or both the video tape and book, or to a control group who viewed materials unrelated to asthma. The results for the three experimental groups were compared with the control group who did not receive exposure to any of the asthma education resources. The results showed that children in each experimental group had significantly greater gains in asthma-related knowledge than children in the control group and children exposed to both resources showed the greatest increases in knowledge. Children in each of the three experimental groups also had better compliance and health than children in the control group. These findings indicate that carefully designed asthma education resources are useful for providing even the youngest children with information about asthma and its management.

Asthma↗
PubMed1998

Measuring tidal volume and functional residual capacity change in sleeping infants using a volume displacement plethysmograph.

The noninvasive measurement of infant lung function during unsedated sleep in infants has been a long-standing objective in paediatric respiratory medicine. This note reports on the design and performance of a head-out volume-displacement plethysmograph (VDP) that overcomes some of the limitations of traditional lung function apparatus. The VDP comprises a rigid acrylic box with an integral water-sealed spirometer and a novel neck seal. The bilayer neck seal is of variable compliance and is comfortable and simple to use. The spirometer permits volume resolution of 1.5 mL and a dynamic range in excess of 100 mL. The frequency response extends from 0-7 Hz. Spirometer inertance was measured as 0.0015 kPa.L(-1).s(-2), resistance 0.021 kPa.L(-1).s(-1) and box capacitance 0.18L.kPa(-1). Tidal volume, respiratory rate and changes in functional residual capacity can be recorded during unsedated rapid eye movement and nonrapid eye movement whilst monitoring with conventional polysomnographic methods. The head-out configuration allows additional instrumentation to be implemented with ease, avoids facial stimulation and allows unimpeded access to the upper airway. A polysomnograph illustrating the limitations of respiratory inductance plethysmography signals and typical changes in functional residual capacity are shown.

Functional Residual Capacity↗
PubMed1997

Abnormalities in surfactant in sudden infant death syndrome as a postmortem marker and possible test of risk.

OBJECTIVE: To determine whether physical abnormalities in lung surfactant, particularly inversion of the hysteresis between surface tension and surface area, are an effective postmortem marker for sudden infant death syndrome (SIDS). METHODOLOGY: Bronchoalveolar lavage (BAL) was employed to obtain lung rinsings from 55 infants under 24 months of age at autopsy, comprising 34 index cases and 21 controls. Folch reagent was used to extract the lipoid content which was then applied at two surface concentrations, fixed and BAL-determined (BALD), to the pool of a Langmuir trough in which surface tension (gamma) was measured continuously by the Wilhelmy method as surface area (A) was cycled. RESULTS: The gamma:A loops from SIDS samples were inverted relative to controls (i.e. they were hysteresis reversed, this inversion being quantified by an empirical surface tension: area reversal (STAR) score). There was a wide scatter of STAR scores, but a critical value was found which offered a significant (P = 0.017) separation of SIDS cases from controls for a fixed surface concentration and a highly significant separation (P = 1.0 x 10(-4)) for BALD surface concentrations. Differences in the yields of phospholipid and proteolipid, or their correlation to STAR scores, did not reach statistical significance. CONCLUSIONS: Inversion of the gamma :A loops (i.e. hysteresis inversion) would appear to offer a better postmortem marker of SIDS than any reported previously, the procedure having potential for development as a prospective test indicating the risk of this disease.

Autopsy↗
PubMed1997

Raised bile acid concentrations in SIDS lungs at necropsy.

Previous studies of the abnormal physical properties of lung surfactant derived from infants experiencing prolonged expiratory apnoea, or who have died of sudden infant death syndrome (SIDS), have led to a search for the agent responsible. Bronchoalveolar lavage (BAL) has been performed upon 12 infants under 12 months at necropsy and the rinsings analysed for up to 26 bile acids using high performance liquid chromatography, which requires nanomolar quantities. They were also analysed for simultaneously retrieved phospholipid and proteolipid-a minor component of lung surfactant-as markers of lavage efficiency. Total bile acid (TBA) was found to be higher in six SIDS cases, reaching a mean (SE) 8.54 (2.24) mumol/l in the BAL fluid compared with 4.66 (1.47) mumol/l in the six controls of similar age. When related to the concomitant surfactant yield, the TBA/ proteolipid and TBA/phospholipid ratios both showed highly significant differences between index lungs and controls, providing another postmortem marker of SIDS with potential for development as a test of risk. Since the bile:phospholipid ratio determines whether phospholipase A2 synthesises or hydrolyses phospholipid, the raised TBA/phospholipid ratio could be highly significant, causing this enzyme to function more like its role in the gut than in the lung.

Autopsy↗
PubMed1995

A novel role for surfactant in the lung with implications for the sudden infant death syndrome.

Feedback from mechanoreceptors in the lungs to the brainstem has long been known to be vital for control of rhythmogenesis during normal breathing. Action potentials transmitted via the vagi are shown to display an irreversible relationship with respect to lung area (A), i.e. hysteresis, which closely resembles the hysteresis in surface tension (gamma) versus A for normal surfactant which coats that surface. Since lung recoil is largely determined by surface tension for resting tidal volumes, this will dominate the stretch of mechanoreceptors. Hence, it is postulated that, through the Hering-Breuer reflex, surfactant largely determines afferent neural feedback, explaining the above similarity in clockwise hysteresis loops. Thus the ability of normal surfactant to impart normal clockwise gamma: A hysteresis is seen as a desirable property enabling the brainstem to differentiate between the inspiratory and expiratory phases of the breathing cycle at the same lung volume. It is further hypothesized that the very abnormal surfactant found recently in some infants with prolonged expiratory apnoea by displaying anti-clockwise gamma: A loops would render afferent neural feedback to the brainstem highly confusing and could cause prolonged expiratory apnoea. This concept is discussed as a possible cause of sleep apnoea, recurrent cyanotic episodes and the Sudden Infant Death Syndrome (SIDS).

Brain Stem↗
PubMed1994

Age-related changes in oxygen saturation over the first year of life: a longitudinal study.

Stability of oxygen saturation depends on maturation and function of individual components of the respiratory system. The aim of this study was to record and analyse comprehensive oxygen saturation data in a longitudinal study over the first year of life. Detailed sleep studies were performed on 15 normal infants eight times in the first year of life. The accrued oxygen saturation data were analysed on a computerized oximetry data analysis system. Results show the mean sleep saturation levels trending upwards and stabilizing by 185 days. There was an inverse curvilinear relationship between mean age and median desaturation time and the median number of desaturations at < or = 95, < or = 92 and < or = 90% saturation. The mean cumulative desaturation time < or = 90% in the first 4 months was 11.08 min (range 2.5-36.57 min). This study demonstrates monotonic patterns of increasing saturation and decreasing number and time of desaturations < or = 95% and < or = 90% but a random pattern of desaturations < or = 85% occurs across the first 6 months of life. Cumulative desaturation times over the first 4 months of life were high and could be important to the development of maturity of the respiratory system. After 6 months, all indices of saturation and desaturation point to a stable and mature respiratory system.

Aging↗
PubMed1994

Surfactant abnormalities in ALTE and SIDS.

Abnormalities in the relative concentrations of the components of surfactant have been implicated in prolonged expiratory apnoea (PEA) and sudden infant death syndrome (SIDS). Controversy has, however, surrounded these findings, as they may be secondary to terminal life events. In this study the physical properties of surfactant were measured in children with recurrent apparent life threatening events (ALTEs), PEA, and SIDS. Bronchial lavage samples were obtained from 21 children with recurrent ALTEs, two SIDS victims, and 26 control patients. Lipid components were immediately elutriated from these samples with liquid chloroform. The physical properties of the extracted surfactant were studied on a Langmuir trough in which the area (A) of the monolayer was cycled continuously as the surface tension (gamma) was measured by the Wilhelmy method using a platinum 'flag'. The investigators performing these tests were unaware of the clinical diagnosis. Twenty one of 23 patients displayed abnormal physical properties while seven of 26 controls displayed similar abnormalities. These abnormalities were partially inverted hysteresis (figure of eight) loops and inverted (anticlockwise) loops that also generally exhibited less hysteresis. Of the 26 controls 20 exhibited a wide hysteresis pattern that cycled in a normal (clockwise) direction. These differences were significantly different. It is concluded that children with recurrent ALTEs have definable abnormalities in the physical properties of surfactant and that these findings may provide a sensitive means of identifying those at risk of recurrent ALTEs and SIDS.

Apnea↗
PubMed1992

Abnormalities of surfactant in children with recurrent cyanotic episodes.

The mechanism of recurrent cyanotic episodes in infants and children is not known, but a deficiency of surfactant is a possible cause. We have measured the amount of surfactant collected by bronchoalveolar lavage from two children with recurrent cyanotic episodes and from two controls with anatomical airway obstructions. We also assessed the physical properties of the surfactant by changing the surface area (A) of a monolayer and measuring its surface tension (gamma). The cases had lower amounts of surfactant extracted, which could explain some of the abnormalities of the gamma/A loops. However, the finding that the cases had reversed loops (ie, the surface tension is higher during monolayer compression than during expansion) shows that there is also a qualitative abnormality. These features suggest a possible diagnostic test if not a mechanism for this disorder.

Airway Obstruction↗
PubMed1992

Single daily dose ceftriaxone therapy in epiglottitis.

Ceftriaxone as a single daily intravenous dose for 5 days was used to treat seven patients with proven Haemophilus influenzae epiglottitis. All children responded favourably. The serum levels achieved exceeded the MIC by up to 1500 times at the trough level during and for up to 24 h after the completion of the treatment. Side effects were mild and transient and did not disrupt the continuity of the treatment. Ceftriaxone potentially offers a number of clinical and economic advantages in the management of epiglottitis.

Ceftriaxone↗
PubMed1990

Single breath versus panting technique in salbutamol delivery through a 750 mL spacing device.

Spacing devices have been widely advocated for asthmatic patients having difficulty actuating metered aerosols and co-ordinating inspiration. Studies have generally supported the slow inspiration/breath hold technique. This requires conscious respiratory control. Such control is often not possible in young children; consequently panting techniques are widely recommended. The panting technique has not been studied. The aim of this study was to compare the bronchodilator effectiveness of panting and the single breath maneuver, each followed by a breath hold, and each at functional residual capacity (FRC), using a Volumatic Space. The study design was a randomly allocated cross-over assessment of bronchodilator response for each technique. The drug dosage was controlled by limiting the inspired volumes of gas (single and cumulative) to the pretested inspiratory capacity. Two hundred micrograms of salbutamol was delivered into the spacer. Twenty-one patients were entered in the study and 15 (mean age +/- SD = 10.9 +/- 3.3 years) completed the protocol. There was no significant difference in bronchodilator response between the two groups. We conclude that the panting and the single breath techniques are equally effective in children of this age group.

Adolescent↗
PubMed1989

Errors in low flow oxygen delivery systems.

Accurate delivery of low flow oxygen is essential for the management of infants with chronic respiratory failure. Twenty-seven examples of one low flow oxygen meter were tested. Measured flows were found to differ greatly from indicated settings, particularly at 250 mL/min settings. Knowledge of such errors as well as improved quality control are essential for appropriate management of oxygen therapy.

Oxygen Inhalation Therapy↗
PubMed1989

Disturbance in respiratory mechanics in infants with bronchiolitis.

The passive flow-volume and partial forced expiratory flow-volume techniques were used to assess pulmonary function in 14 spontaneously breathing infants with acute respiratory syncytial virus bronchiolitis. Two additional infants were studied while paralysed and ventilated. During the acute stage of the illness there was a significant reduction in forced expiratory flow rates and an increase in respiratory resistance. Although the mean thoracic gas volume for the group was increased, five infants did not compensate for their airways obstruction by hyperinflation. Curvilinear passive flow-volume curves were seen in three of the 14 non-ventilated infants and in both ventilated infants. At follow up three to four months later all passive flow-volume curves were linear. There was a significant reduction in hyperinflation and an increase in forced expiratory flow rates, but values still differed significantly from those in normal infants.

Bronchiolitis↗