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Biomedical subjects

S A McKenzie

Publications and source records attributed to S A McKenzie.

At least 19 recordsLinked to original sources
PubMed2001

Difficult asthma: defining the problems.

A retrospective survey was undertaken of children with difficult asthma, attending a respiratory clinic. The clinical and laboratory profiles of asthmatic children who were poorly controlled on > or = 800 microg of inhaled corticosteroids (ICS) were studied and compared to children well-controlled on > or = 800 microg ICS. Assessments were made of atopy, growth, lung function, treatment adherence, home environment, and responsiveness to corticosteroids (CS). Fiftyseven "difficult" and 23 well-controlled children were studied. Significant differences in the home environment were identified. Smoking was significantly more common in the difficult-to-control group. Nine children had alternative diagnoses. Poor CS responsiveness was present in 10 children. Adverse home environments, poor treatment supervision, alternative diagnoses, and unresponsiveness to CS were the most important factors in difficult asthma. A full assessment, including bronchoscopy, is indicated to avoid unnecessary increases in CS to doses that could cause side-effects.

Administration, Inhalation↗
PubMed2001

Parents' interpretations of children's respiratory symptoms on video.

AIMS: To investigate how parents report children's respiratory sounds on video compared to a clinical "gold standard". METHODS: Five clinicians agreed on 10 video clips of children with audible breathing. These responses were the "gold standard". The clips were shown to parents of children: (a) with asthma/wheeze; (b) with other respiratory complaints; (c) without respiratory complaints. Parents were asked what they called the sounds, where they originated, and whether their own child made similar sounds. RESULTS: A total of 190 parents took part. The "correct" labelling of wheeze was 59% (95% confidence interval 52 to 66%) and 47% (95% confidence interval 40 to 54%) for other sounds (stridor, snoring, stertor). Parents were better at locating both sounds than labelling. There were no differences between subject groups. There were more false positive responses to labelling and locating other sounds than for wheeze (27% v 8% and 33% v 10%). CONCLUSION: Parents locate sounds better than describing them. At least 30% of all parents use other words for wheeze and 30% labelled other sounds as "wheeze". This could have important clinical implications.

Adult↗
PubMed2001

Safety and ethics of bronchoscopy and endobronchial biopsy in difficult asthma.

AIM: To investigate the safety of bronchoscopy and endobronchial biopsy in children with difficult asthma, and discuss the ethical issues associated with the procedure. METHODS: A three year prospective observational study was performed in two tertiary paediatric respiratory centres specialising in the management of children with difficult asthma. A total of 48 children with difficult asthma and 35 non-asthmatic children were studied. RESULTS: Flexible bronchoscopy was performed under general anaesthesia in 38 children with difficult asthma, and rigid bronchoscopy was performed in 10, following a two week course of prednisolone. Endobronchial biopsy was performed in 47 patients. Perioperative complications occurred in one asthmatic undergoing flexible bronchoscopy (desaturation) and in two undergoing rigid bronchoscopy (desaturation in one, and bronchospasm and desaturation in one). There were no cases of significant bleeding or pneumothorax among the asthmatics. Flexible bronchoscopy was performed in 35 non-asthmatic patients with a variety of clinical indications. The total number of perioperative complications was greater in the non-asthmatics undergoing flexible bronchoscopy than in the asthmatics (17 complications in 35 children versus one in 38). Fever requiring hospital admission was documented in two asthmatics following bronchoscopy. Four asthmatics reported an increase in symptoms in the week following bronchoscopy. CONCLUSIONS: Bronchoscopy and endobronchial biopsy under general anaesthesia can be performed safely in children with difficult asthma, when the bronchoscopist and anaesthetist are suitably trained. The procedure is acceptable to the families involved.

Adolescent↗
PubMed2001

Airway resistance measured by the interrupter technique: expiration or inspiration, mean or median?

The measurement of airway resistance by the interrupter technique (Rint) needs standardization. Should measurements be made be during the expiratory or inspiratory phase of tidal breathing? In reported studies, the measurement of Rint has been calculated as the median or mean of a small number of values, is there an important difference? Subjects were 2.5-5.0 yrs (median 4.0 yrs) who had previous respiratory symptoms. The Rint in expiration (RintE) and inspiration (RintI) pre and postsalbutamol, the coefficient of variation (CV) of values contributing to measurements, and bronchodilator responsiveness(BDR) in both phases were compared. Measurements using median and mean were compared. RintE was higher than RintI by 4% (p < 0.01). The CV of values making up RintE and RintI, and BDR measured in expiration and inspiration were similar. The median difference between means and medians of values making up measurements was 0.6% (range -6-11%). RintE has been shown to be consistently greater then RintI but the difference in this study is small. It is suggested that one or the other is chosen as the standard. In the present data the mean of a set of values contributing to a measurement was not significantly different from the median. However, the use of the median has been recommended since it is less affected by possible outlying values such as might be included by fully automated equipment.

Airway Resistance↗
PubMed2000

Airway resistance and atopy in preschool children with wheeze and cough.

The extent to which the measurement of airways resistance by the interrupter technique (Rint) distinguishes preschool children with previous wheeze from those with no respiratory symptoms and helps to classify subjects with persistent cough, was investigated. Rint was measured before and after salbutamol treatment in 82 children with recurrent wheeze, 58 with isolated cough and 48 with no symptoms (control subjects). Their mean age (range) was 3.7 yrs (2-<5 yrs). Median baseline Rint was higher (p<0.0001) in wheezers than in either coughers or control subjects (1.16, 0.94 and 0.88 kPa x L(-1) x s(-1) respectively); coughers did not differ significantly from control subjects (p=0.14). The median ratios of baseline to post-salbutamol measurements (bronchodilator response (BDR)) in the groups differed significantly (1.40, 1.27 and 1.07, p< or =0.01 for all), suggesting that coughers occupy an intermediate position. A BDR ratio of >1.22 had a specificity and sensitivity for wheeze of 80% and 76% respectively. Twenty-eight coughers had a BDR ratio >1.22. Wheezers' immunoglobulin E was inversely related to baseline Rint. It is concluded that measurements of airway resistance by the interrupter technique are useful for classifying preschool children with respiratory symptoms and could be used to monitor the effect of interventions. The relation between atopy and airways resistance suggests that they have separate roles in preschool wheezing. Coughers with a high bronchodilator response could represent "cough-variant" asthma in children who have baseline airway resistance by the interrupter technique measurements similar to control subjects. Whether these children develop classical asthma will only be known at follow-up later in childhood.

Airway Resistance↗
PubMed2000

What do parents of wheezy children understand by "wheeze"?

BACKGROUND: Reported wheeze is the cornerstone of asthma diagnosis. AIMS: To determine what parents understand by wheeze. METHODS: Two studies were undertaken: (1) Parents of clinic attendees with reported wheeze (n=160) were asked by questionnaire what they understood by "wheeze" and how they knew their child was wheezy. Responses were compared to definitions of wheeze in 12 epidemiology studies and their response options. (2) The extent of agreement of parents' reports (n=139) of acute wheezing in their children and clinicians' findings of "wheeze" and "asthma" was examined. RESULTS: (1) "Sound" and "difficulty in breathing" were perceived central to "wheeze". "What you hear" was not selected by 23% (95% confidence interval (CI) 16-30%). "Whistling" was mentioned by 11% (CI 6-15%) but featured in 11 of 12 epidemiology questionnaires. (2) There was les than 50% agreement between parents' and clinicians' reports of wheeze and asthma. CONCLUSIONS: Conceptual understandings of "wheeze" for parents of children with reported wheeze are different from epidemiology definitions. Parents' reports of acute wheeze and clinicians' findings also differ.

Asthma↗
PubMed1999

Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting.

This study describes the feasibility, repeatability, and interrater reliability of the measurement of airway resistance by the interrupter technique (Rint) in children 2-5 yrs of age, and examines whether reversibility to bronchodilator can be demonstrated in wheezy children. The mean of six Rint values was taken as a measurement. If subjects could complete one measurement and then a second 15 min after bronchodilator, baseline testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy children was measured after bronchodilator. Fifty-six per cent of 2-3-yr-olds (n=79), 81% of 3-4-yr-olds (n=104) and 95% of 4-5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% completed reversibility testing. Baseline measurements were 0.47-2.56 kPa x L(-1) x s. Repeatabilities (2 SD of the mean differences between measurements) at 30 s in the three age bands were 0.21, 0.17 and 0.15 kPa x L(-1) x s and 0.19 kPa x L(-1) x s after placebo. Using 0.21 kPa x L(-1) x s as the threshold for reversibility, reversibility was demonstrated in most wheezy children. Interrater reliability was 0.15 kPa x L(-1) x s. Preschool children can undertake measurements of airway resistance by the interrupter technique in ambulatory settings and reversibility to bronchodilator in wheezy children can be demonstrated. This technique promises to be a useful clinical and research tool.

Airway Resistance↗
PubMed1999

Persistent nocturnal cough: randomised controlled trial of high dose inhaled corticosteroid.

OBJECTIVE: To investigate the effect of a short course of inhaled corticosteroid in the treatment of isolated and persistent nocturnal cough in children. DESIGN: Randomised double blind placebo controlled study. SETTING: Subjects' homes in east London, England. SUBJECTS: Consecutively referred children, 1-10 years old, with persistent nocturnal cough. INTERVENTIONS: Placebo or fluticasone propionate 1 mg twice daily for three nights and 500 microg twice daily for 11 nights. Videotaping of children at night: two nights' baseline, nights 3 and 4 after three days of inhaled corticosteroid, and nights 15 and 16. MAIN OUTCOME MEASURE: A fall in 75% of coughs from baseline. RESULTS: 50 subjects were recruited. The median number of coughs in the baseline period for the inhaled corticosteroid group and placebo group were 92 and 71, respectively (p = 0.43) and, on nights 15 and 16, 8 and 36, respectively (p < 0. 01). Compared to baseline, both groups of subjects improved significantly by nights 15 and 16 (p < 0.01; p < 0.01). Comparing the inhaled corticosteroid and placebo groups, coughs fell to a median of 22% and 57% of baseline totals on nights 3 and 4, respectively (p = 0.38), and 8% and 35% on nights 15 and 16, respectively (p = 0.02). 17 of 24 subjects on inhaled corticosteroid who completed the study and 8 of 23 on placebo improved by 75% after two weeks (p = 0.03). CONCLUSIONS: Children with persistent nocturnal cough improve in two weeks after referral on placebo. There is a modest benefit from a two week course of high dose inhaled corticosteroid.

Administration, Topical↗
PubMed1998

Prescribing for persistent cough in children.

To identify the medications general practitioners consider for the treatment of persistent isolated cough, we undertook a postal questionnaire survey of a sample of general practitioners in east London. Fewer than 10% indicated that they never prescribed for such cough. About 70% sometimes considered antibiotics and/or bronchodilators in all age groups. Inhaled steroids and cromoglycate were considered by about 30% of prescribers for infants compared with over 60% for older age groups. As yet there is no evidence that medication is beneficial for persistent isolated cough. The role of asthma drugs for children with this symptom needs to be evaluated so that we can better identify those who are likely to benefit.

Age Factors↗
PubMed1998

Cough and sleep in inner-city children.

This study aimed to determine whether cough at night keeps children awake, to describe the relationship between children's cough and sleep and to report parents' perceptions of their children's cough and sleep. Thirty-nine children with reported persistent cough at night (>3 weeks) were recruited and studied for 6 nights by video-recording. Coughs were counted and sleep state was coded for awake, restless sleep and quiet sleep. The relationships between cough and sleep state between subjects and within subjects were examined by correlation and regression. After night 2 the parents were asked whether their child had coughed or had disturbed sleep and after night 6 they were asked whether there had been any change. There was a weak relationship between log percentage of the night awake and log number of coughs (r=0.13, SE 0.036), and log (percentage of the night awake plus restless sleep) and log number of coughs (r=0.016, SE 0.0071). If the relationship between cough and sleep state is causal, halving the number of coughs will reduce the percentage of the night awake by 9% (95% confidence interval (CI) 4-15%) and percentage awake and restless by 1% (95% CI 0-2%). All but one parent correctly identified coughing and 82% detected change. Most could not comment on their child's sleep. Improvement in cough would result in little reduction in either the percentage of the night awake or awake and restless in the average child in the population studied. Parents could detect whether their children were coughing but not whether their sleep was disturbed.

Asthma↗