Long term effects of antenatal betamethasone on lung function: 30 year follow up of a randomised controlled trial.

BACKGROUND: Antenatal betamethasone is routinely used for the prevention of neonatal respiratory distress syndrome in preterm infants. However, little is known of the long term effects of exposure to antenatal betamethasone on lung function in adulthood. METHODS: Five hundred and thirty four 30 year olds whose mothers had participated in the first and largest randomised controlled trial of antenatal betamethasone were followed. Lung function was assessed by portable spirometric testing. The prevalence of asthma symptoms was assessed using the European Community Respiratory Health Survey questionnaire. RESULTS: Fifty (20%) betamethasone exposed and 53 (19%) placebo exposed participants met the criteria for current asthma (relative risk 0.98 (95% CI 0.74 to 1.30), p = 0.89). 181 betamethasone exposed and 202 placebo exposed participants had acceptable spirometric data. There were no differences in lung function between betamethasone and placebo exposed groups (mean (SD) forced vital capacity in the betamethasone and placebo groups 105.9 (12.0) v 106.6 (12.6)% predicted, difference = -0.7 (95% CI -3.2 to 1.8), p = 0.59; mean (SD) forced expiratory volume in 1 second in the betamethasone and placebo groups 98.9 (13.4) v 98.5 (13.6)% predicted, difference = 0.3 (95% CI -2.4 to 3.1, p = 0.80)). CONCLUSIONS: Antenatal exposure to a single course of betamethasone does not alter lung function or the prevalence of wheeze and asthma at age 30.

Spirometry in primary care practice: the importance of quality assurance and the impact of spirometry workshops.

OBJECTIVE: To determine the quality of spirometry performed in primary care practice and to assess the impact of formal training. DESIGN: Randomized, controlled prospective interventional study. SETTING: Primary care practice, Auckland City, New Zealand. PARTICIPANTS: Thirty randomly selected primary care practices randomized to "trained" or "usual" groups. One doctor and one practice nurse were nominated to participate from each practice. INTERVENTIONS: "Trained" was defined as participation in an "initial" spirometry workshop at week 0 and a "maintenance of standards" workshop at week 12. "Usual" was defined as no formal training until week 12, when participants they attended the same "initial" workshop provided for the trained group. The study duration was 16 weeks. Each practice was provided with a spirometer to be used at their clinical discretion. MEASUREMENTS AND RESULTS: Spirometry data were uploaded weekly and analyzed using American Thoracic Society (ATS) criteria for acceptability and reproducibility. The workshops were assessed objectively with practical and written assessments, confirming a significant training effect. However, analysis of spirometry performed in clinical practice by the trained practitioners revealed three acceptable blows in only 18.9% of patient tests. In comparison, 5.1% of patient tests performed by the usual practitioners had three acceptable blows (p<0.0001). Only 13.5% of patient tests in the trained group and 3.4% in the usual group (p<0.0001) satisfied full acceptability and reproducibility criteria. However, 33.1% and 12.5% of patient tests in the trained and usual groups, respectively (p<0.0001), achieved at least two acceptable blows, the minimum requirement. Nonacceptability was largely ascribable to failure to satisfy end-of-test criteria; a blow of at least 6 s. Visual inspection of the results of these blows as registered on the spirometer for the presence of a plateau on the volume-time curve suggests that < 15% were acceptable. CONCLUSIONS: Although a significant training effect was demonstrated, the quality of the spirometry performed in clinical practice did not generally satisfy full ATS criteria for acceptability and reproducibility. Further study would be required to determine the clinical impact. However, the ATS guidelines allow for the use of data from unacceptable or nonreproducible maneuvers at the discretion of the interpreter. Since most of the failures were end-of-test related, the FEV1 levels are likely to be valid. Our results serve to emphasize the importance of effective training and quality assurance programs to the provision of successful spirometry in primary care practice.

Measuring morbidity from asthma in children.

AIMS: To develop new measures of asthma morbidity which would be applicable to children with asthma of all grades of severity. METHODS: This study used a cross sectional sample of asthmatic children. Traditional asthma morbidity measures (admission to hospital, use of Emergency Room, general practitioner, after hours deputising service and ambulance) were compared with new measures (school attendance, teacher assessment, parental perception of morbidity and parents emotional response to child's asthma). RESULTS: Data was obtained for 381 children with asthma. Children with poor school attendance were found in the severe group as judged by a composite score using traditional measures (r = 0.30, p < 0.0001). A new composite morbidity score based on two questions about parental perception of severity (how often has asthma prevented participation in activities and rating of severity of asthma in general over the last year) and two questions about parent emotional response to the child's asthma (how often has your child's asthma (a) made you feel frightened and (b) stopped family activities) was developed. This new measure of asthma morbidity was correlated with the composite score using traditional morbidity measures (r = 0.43, p < 0.0001) and with school attendance (r = 0.28, p < 0.0001). CONCLUSION: These new morbidity measures are quick and easy to use, and provide an opportunity to measure asthma severity at the moderate to mild end of the severity spectrum. We recommend their use for both clinical assessment and research.

The association between asthma drugs and severe life-threatening attacks.

OBJECTIVES: To measure the association between asthma drugs and death or ICU admission due to asthma (severe life-threatening attack of asthma [SLTA]), and to assess the possibility that these associations may not be causal but due to the prescription of these drugs to patients with more severe disease (confounding). DESIGN: Retrospective cohort study of 655 asthmatics who attended an emergency department in 1986 to 1987 followed till death or May 1989. METHODS: Outcome events were death or ICU admission due to asthma (SLTA). All hospital attendances were identified and patients classified at each according to drug exposure and a wide variety of measures of asthma severity. Incidence rates were computed as total outcome events divided by person-time contributed for each subject classified according to drug use and asthma severity. Rate ratio (RR) estimates for severe asthma outcomes associated with use as compared to nonuse of asthma drugs were calculated. Severity markers were identified and used to adjust the crude RR estimates. RESULTS: One hundred five SLTAs (15 deaths, 90 ICU admissions) occurred in 66 patients. Like inhaled fenoterol, oral beta-agonists, theophylline, cromolyn, inhaled steroids, and oral steroids were all associated with an increased risk of SLTA. When adjusted progressively for measures of severity, these increased risks became insignificant except for cromolyn. CONCLUSION: Unadjusted RR estimates for severe asthma events comparing exposure to a particular drug with nonuse are overestimates due to confounding. Control with two severity markers (hospital admission in the last year, use of oral corticosteroid at the time of previous admission) removes some confounding but control for additional severity markers not available in previous studies reduces the effect estimates further. These results suggest that the problem of confounding is substantial in nonrandomized epidemiologic studies of asthma drugs. Previous studies reporting RR estimates are likely to be confounded.

Risk of severe life threatening asthma and beta agonist type: an example of confounding by severity.

BACKGROUND: A study was undertaken to test the hypothesis that a particular inhaled beta agonist, fenoterol, increases the incidence of severe life threatening asthma. METHODS: A retrospective cohort was assembled comprising 655 patients with asthma aged 15-55 years who attended a single Auckland hospital for acute asthma between 1 January 1986 and 31 December 1987 (the "index event"). Patients were followed for the occurrence of death from asthma or admission to the intensive care unit for asthma, until death or 31 May 1989. Data on asthma medications and asthma severity were obtained from forms used specifically for managing patients with acute asthma in the emergency department and maintained as part of the hospital record and/or from the hospital record (when patients were admitted). RESULTS: Following the index event 90 admissions to the intensive care unit (ICU) and 15 asthma deaths were identified. Before adjusting for asthma severity, patients using inhaled fenoterol had a greater incidence of severe life threatening asthma than patients using inhaled salbutamol (RR = 2.1, 95% CI 1.4 to 3.1). After controlling for two markers of severe asthma used in previous studies-a hospital admission in the previous year and prescribed oral corticosteroids-the relative risk estimate declined to 1.5 (95% CI 1.0 to 2.3). After controlling further for the number of hospital admissions during the study period, continuous oral corticosteroid use rather than short courses of treatment, severity of the previous attack requiring a hospital visit, and race, fenoterol was not associated with severe life threatening asthma at the time of attendance for a previous hospital visit (RR = 1.0, 95% CI 0.6 to 1.7). CONCLUSION: Fenoterol is used more often by patients with severe asthma and, after adjusting for differences in baseline risk, it does not increase the risk of severe life threatening asthma.

Demographic characteristics of patients with severe life threatening asthma: comparison with asthma deaths.

BACKGROUND: Studies of mortality from asthma have suggested that a very severe asthma attack identifies a group at greatly increased risk of subsequent death from the disease. This study compares the demographic characteristics of asthmatic patients who required management in an intensive care unit for a severe life threatening attack between 1981 and 1987 with a group who died of asthma between 1980 and 1986. The outcome of the group admitted to an intensive care unit is described. METHODS: The groups comprised all cases aged between 15 and 49 years arising from the Auckland Area Health Board (AAHB) population who required admission to an intensive care unit for asthma between 1981 and 1987 (n = 413) and all deaths from asthma in those aged 15 to 49 years arising from the New Zealand population between 1980 and 1986 (n = 466). Details of age, sex, and information on the day and month of the attack were collected. For the group requiring admission to an intensive care unit, outcome in terms of mortality and readmission to intensive care was determined. RESULTS: The age distributions of the two groups were dissimilar, with the severe life threatening attack group having an excess of asthmatic patients under 30 years old. The distribution of events by calendar month was uniform in both groups, but there was an unexpected increase in frequency of attacks on Sundays in both groups. Over the study period, mortality fell from 5.3 per 100,000 to 3.5 per 100,000 but the admission rate to intensive care increased from 10.8 per 100,000 to 17.9 per 100,000. At least 24% of asthma deaths occurring in the AAHB region during the study period had previously experienced a severe life threatening attack. CONCLUSIONS: The similarities between the groups suggest that asthmatic patients who experience severe life threatening attacks are likely to come from the same subgroup of the asthma population as those who die. The group who experience severe life threatening attacks are at high risk of subsequent morbidity and mortality and further studies may produce information relevant to reducing mortality from asthma.

Effects of a physical conditioning programme on asthmatic patients.

AIMS: to determine whether moderate/severe asthmatics can improve their physical fitness using standard commercial gymnasium fitness programmes and to examine the effect on their asthma. METHODS: eight moderate to severe asthmatics and seven nonasthmatic controls were tested before and after 12 weeks indoor circuit training at a commercial gymnasium. The aerobic fitness of both groups was assessed before, during and after the conditioning period. Measures of asthma severity, habitual activity levels and psychological status were also assessed. RESULTS: peak oxygen uptakes increased significantly in both asthmatics and controls, mean and 95% confidence interval (95% CI) values rising from 27.5 (21.9-33.0) to 31.3 (23.5-39.1) and 29.2 (25.9-32.5) to 32.2 (28.5-35.9) mL.min-1.kg-1 respectively. Following training, minute ventilation at high workloads was significantly reduced in the asthmatic subjects. In all participants subjective ratings of the ability to perform physical tasks was significantly increased as was the amount of habitual physical activity reported. Although the asthmatics' bronchial responsiveness to histamine, medication usage and symptom scores did not change, the daily recorded peak expiratory flow (PEFR) increased slightly, and its variability declined. CONCLUSIONS: these findings demonstrate that with proper management severe asthmatics can engage in vigorous circuit training and enjoy the health benefits of regular exercise.

Emergency room care of asthmatics: a comparison between Auckland and Toronto.

We compared emergency room visits for the treatment of asthma in two large downtown teaching hospitals: one in Auckland, New Zealand and one in Toronto, Canada. We wished to determine whether the differences in asthma mortality between New Zealand and Canada were reflected in different patterns of emergency room use or physician management. Emergency room use during the past decade was enumerated in both hospitals, and charts containing the sole diagnosis of asthma were reviewed in detail for a defined study period in 1986. In both Toronto and Auckland, the number of emergency visits for asthma had increased significantly in the past decade (P less than .015 but the rate of rise was significantly higher in Auckland (P less than .05). In Auckland, 27% of asthmatics were admitted whereas in Toronto significantly fewer (16%) were admitted (P less than .0005). Objective measures of pulmonary function were documented more frequently by emergency room physicians in New Zealand than in Canada (90% versus 48%; P less than .0005). Pulmonary function measurement was primarily by peak flow meter in Auckland and most commonly by spirometer in Toronto so that pulmonary function measurements could not be compared directly between centers. In both centers, however, admitted patients had significantly lower pulmonary function indices than discharged patients. In New Zealand, mean peak flow was 38% of the predicted value among all asthmatics assessed; in Toronto, mean FEV1 was 47% of predicted. In Toronto, pulmonary function measurements were most likely to be missing among presumably healthier discharged patients. Pulse rate, respiratory rate, and pulsus paradoxus were documented more consistently in Auckland than in Toronto.(ABSTRACT TRUNCATED AT 250 WORDS)

A tool for measuring the asthma self-management competency of families.

A tool for measuring a family's asthma self-management behaviour has been developed for a study examining the relationships of asthma self-management behaviour, knowledge, and psychosocial factors with various indices of morbidity in children with asthma. The tool involves a structured interview which includes three typical situations of asthma self-management (scenarios). Each of the scenarios is divided into graded challenges. A scoring schedule was developed according to the critical incidents of self-management inherent in each situation. This schedule was then applied to the verbatim transcripts of the subjects' responses. These were presented to 380 asthmatic children aged 5-11 yr and their primary caregivers. Inter-rater reliability, inter-rater agreement and test-retest reliability coefficients indicate that the scores obtained are stable across raters and time. Correlations between scores on different scenarios suggest there is a common factor of self-management competency across all scenarios, but families are better at some aspects of self-management than others. The distribution of scores for each scenario is presented. The place of this tool as a means of assessing self-management behaviour is discussed.

The interrelationship among bronchial hyperresponsiveness, the diagnosis of asthma, and asthma symptoms.

Bronchial hyperresponsiveness (BHR) to inhaled histamine has often been cited as the gold standard in asthma diagnosis, but recently this has been questioned. This report assesses the relationship of BHR to asthma symptoms and asthma diagnosis in a large community-based sample of children. A total of 2,053 children 7 to 10 yr of age were randomly sampled from Auckland primary schools and assessed by a questionnaire and histamine inhalation challenge. In all, 14.3% had had asthma diagnosed, 29.6% reported having had one of the four respiratory symptoms in in the previous 12 months, and 15.9% had BHR (PD20 less than or equal to 7.8 mumol histamine). After a cumulative dose of 3.9 mumol histamine, the percent change in FEV1 from postsaline FEV1 was unimodally distributed, with those in whom asthma had been diagnosed dominating the severe end of the spectrum. However, 53% of those with BHR had no asthma diagnosis, and 41% had no current asthma symptoms. On the other hand, 48% of all subjects with diagnosed asthma and 42% of children with diagnosed asthma and current symptoms did not have BHR. Although severity of BHR tended to increase with wheezing frequency, all grades of severity (including no BHR) were found for any given frequency of wheeze. An existing diagnosis of asthma identified symptomatic children more accurately than did BHR, regardless of the criteria used for BHR or for "symptomatic" and irrespective of ethnic group. In conclusion, BHR is related to, but not identical to, clinical asthma. Bronchial challenge testing is an important tool of respiratory research, but cannot reliably or precisely separate asthmatics from nonasthmatics in the general community.

Socioeconomic status in childhood asthma.

This study examines the relationship between socioeconomic status (SES) and asthma prevalence and the use of asthma medication. One thousand and fifty European children aged eight and nine years were studied by parent completed questionnaire and histamine inhalation challenge. After controlling for sex of the child and for smokers in the house there were significantly higher lifetime (P = 0.029) and current (P = 0.046) prevalence rates of wheeze in children in low SES groups. There was no relationship between SES and asthma diagnosis, bronchial hyperresponsiveness (BHR: PD20 less than 7.8 mumol), or any combination of BHR with symptoms or diagnosis. The use of bronchodilators and asthma prophylactic drugs was less frequent in the low SES groups of children with wheeze in the last 12 months both with concurrent BHR or irrespective of BHR than in those in high SES groups.

Ethnic differences in prevalence of asthma symptoms and bronchial hyperresponsiveness in New Zealand schoolchildren.

Maoris and Pacific Islanders in New Zealand have a higher asthma mortality and hospital admission rates than Europeans. To determine whether difference in asthma prevalence is the major factor underlying these differences in mortality, 2053 Auckland children aged 7-10 years (European 1084, Maori 509, Pacific Islander 460) were randomly sampled from school classes in the Auckland Urban Area, and studied by questionnaire (completed by parents) and histamine inhalation challenge to assess the provocative dose of histamine causing a 20% fall in FEV1 (PD20). Maoris had the highest prevalence rates of respiratory symptoms, and Europeans had rates similar to Pacific Islanders. For "any current wheeze" for example, the prevalence in Maoris was 22.2% compared with 16.1% and 16.3% in the Europeans and Pacific Islanders. The prevalence of diagnosed asthma was similar in the three groups. When bronchial hyperresponsiveness (defined as a PD20 less than or equal to 7.8 mumol histamine) was considered, Europeans had the highest rates (20%), followed by Maoris (13%), and then Pacific Islanders (8.7%). These differences were not accounted for by differences in socioeconomic status, rates of smoking in the home, age, gender, or height. It is concluded that differences in asthma prevalence do not satisfactorily explain the mortality and admission rate differences, although the higher symptom prevalence in the Maoris could be relevant to the higher mortality rate. Maori and Pacific Island children with symptoms of asthma were less likely to be taking prophylactic medication than European children. It is proposed that differences in management are important factors relevant to the increased mortality and morbidity from asthma in Polynesians.