Margaret R. Becklake

Concepts of normality applied to the measurement of lung function

Lung function testing has become an integral part of the clinical assessment of pulmonary disease. However, increasing application of such testing in research into the origins of disease as well as in the assessment of health raises the issue of what is meant by normal respiratory function. In essence, this depends on the sources of variation in lung function measurements that are of interest (the signal) and those that are not (the noise). For instance, clinicians are primarily interested in variation due to disease, all other sources of variation being considered noise. Physiologists are concerned with sources of variation other than disease, and the interest of epidemiologists (and their definition of normality) varies according to the specific objectives of each particular study, report or program. Consideration of the sources of variation in lung function (within a subject, between subjects, and between populations) not only is useful in clarifying the concepts of normality for clinical application, physiologic studies, and epidemiologic purposes, but also is mandatory for an understanding of lung function in the transition between health and disease, a major thrust in all three areas of endeavour.

Childhood predictors of smoking in adolescence: a follow-up study of Montréal schoolchildren

Background: The factors that cause children to become smokers in adolescence remain unclear. Although parental smoking and peer pressure may play a role, physiological factors such as lung volume have also been identified. Methods: To investigate these and other possible childhood predictors of teenage smoking, we gathered follow-up data on 191 Montréal schoolchildren, aged 5–12 years (average 9.2 yr) when first examined. At an average age of 13.0 years, they answered further questions on their health and smoking behaviour and provided a second set of spirometric measurements. Results: At the second survey, 80% of the children had entered high school and 44% had become smokers. Reaching puberty between the surveys was the most significant determinant of becoming a smoker: 56.4% of the 124 children postpubertal at the second survey had taken up smoking, versus 17.9% of the 67 who were still prepubertal (p = 0.001). We found salivary cotinine level, a measure of uptake of environmental tobacco smoke, to be an independent predictor of becoming a teenage smoker; even after adjustment for sex, socioeconomic status of parents, a crowding index, and the numbers at home of siblings, adult smokers and cigarettes smoked, it remained significant for both groups: postpubertal (odds ratio [OR] 1.2, 95% confidence interval [CI] 1.2–3.0) and prepubertal (OR 2.1, 95% CI 1.0– 4.5). The influence of forced vital capacity was marginally significant only in the postpubertal group (OR 5.0, 95% CI 0.88–28.3). Interpretation: The proportion of nicotine absorbed from that available in environmental tobacco smoke during childhood is associated with subsequent smoking in adolescence. The more efficient absorption of nicotine seen in some children may be related to physiological factors such as lung capacity.

The health of chrysotile asbestos mine and mill workers of Quebec.

The results of studies of respiratory symptoms and function, roentgenographic changes, and mortality in relation to dust exposure in the Quebec chrysotile industry, which has employed some 28,000 workers, are brought together and their implications for control examined. Breathlessness on exercise, diminished inspiratory capacity, parenchymal and pleural changes, and respiratory disease mortality were related to dust exposure and to each other. Respiratory cancer was also related to dust exposure. The overall excess of deaths from respiratory cancers, including five with malignant mesothelioma, was at most 50% above expectation, based on age-specific rates for Quebec and the mining region. If safety standards are set, they should be based on epidemiological evidence. From these data for the chrysotile producing industry of Quebec, a resonable figure, based on a 1% risk of acquiring clinically significant disease, would lie between 2 to 4 million particles per cubic foot, calculated for a working life of 50...

Lung Function in Chrysotile Asbestos Mine and Mill Workers of Quebec

Lung function tests were carried out on art age-stratified random sample of 1,015 Quebec asbestos workers whose dust exposure had been estimated from their work history and available dust levels in the industry in nonsmokers, several function tests distinguished the lower two dust-exposure groups. These were inspiratory capacity, forced vital capacity, and forced expiratory volume in 0.75 second and in 1.0 second. In smokers the same tests were somewhat less sensitive. Any of the tests mentioned appear to be suitable for health surveillance of asbestos-exposed workers, whatever their smoking habits.

Risk factors for bronchial hyperresponsiveness in late childhood and early adolescence

The prevalence of asthma and bronchial hyperresponsiveness (BHR) tends to decrease in male children but increase in female children in the transition from childhood to adolescence. Hormonal factors may be involved in the natural history of asthma during this period. In a prospective study of Montreal school children, the authors examined the determinants of BHR according to the childs pubertal status; 156 male children and 168 female children without a prior diagnosis of asthma were followed for an average of 4.6 yrs. Average age at follow-up was 13.4 yrs and 59% had reached puberty. The prevalence of BHR at follow-up was similar among pre- and postpubertal male children (25.0% versus 29.2%),while BHR was more common among post- compared with prepubertal female children (33.1% versus 14.2%). There were no differences in the determinants (measured in childhood) of BHR at follow-up according to pubertal status. The major determinant of BHR was a positive skin test to dust-mite antigen. BHR was also linked to exposure to gas cooking and the presence of exercise-induced bronchospasm. In conclusion, the results of this study do not support a change in asthma phenotype with the onset of puberty. Pre- and postpuberty, the major determinant of bronchial hyperresponsiveness was skin sensitivity to mite allergen.

The cardio-respiratory effects of thoracic epidural anaesthesia.

SummaryThe cardio-respiratory effects of an epidural anaesthetic given to 13 subjects pre-operatively are reported. They were fasting, unpremedicated and supine. A sensory block up to the 4th thoracic segment was not followed by any significant change in frc, fev1, vc, A-aDo2, Qs/Qt or cardiac output.RésuméLes auteurs rapportent leurs observations sur les effets cardio-respiratoires lore d’une anesthésie péridurale thoracique haute (au niveau du t4), Leur rapport est surtout concentré sur la capacité résiduelle fonctionnelle (crf) et le gradient alvéolo-artériel de PO2 (A-aDo2), ces paramétres n’étant pas rapportés dans la litérature à date. Les cas étudiés étaient 13 candidats à la chirurgie abdominale haute. Ils rapportent des changements sans importance clinique ou statistique dans la capacité vitale (cv), crf, fev i.o de même que dans le A-aDo2, le shunt (Qs/QT) et débit cardiaque (Qc) ainsi que dans le rapport vd/vt. Ces observations suivirent une hydratation adéquate (10 ml/kg de dextrose à 5 pour cent dans sérum physiologique), Temploie de lidocaine 1.5 pour cent et un dosage qs pour atteindre une analgésie à la piqûre et à la glace de t4 seulement.En conclusion ils soulignent l’importance des précautions à prendre vis-à-vis le dosage et l’iydration pour en arriver à un résultat clinique satisfaisant de cette technique.

Effect of cigarette smoking on evolution of ventilatory lung function in young adults: an eight year longitudinal study.

BACKGROUND: There are few data on the quantitative effects of cigarette smoking on lung function in young adults. These effects are important in the understanding of the early stages of chronic airflow obstruction. METHODS: A longitudinal study over eight years was carried out to estimate quantitatively the effect of cigarette smoking on ventilatory lung function in young adults and to examine the possibility that the effect is modified by other factors. The study population were 15 to 40 years of age at initial examination, when they underwent spirometry and completed an interviewer administered questionnaire on respiratory health. Eight years later 391 of the subjects were re-examined (38% response rate). The quantitative effect of cigarette smoking during the study period on the average change of forced expiratory volume in one second (FEV1) over time (delta FEV1) was estimated in two linear regression models that included potential confounders and other determinants of outcome. RESULTS: The first model showed a significant dose-response relation between the average rate of smoking during the study period and delta FEV1, giving an estimate of annual change in FEV1 of -0.42 ml for each cigarette smoked per day (-8.4 ml for each pack) (p = 0.04). In the second model, which took smoking before the study period as a potential confounder, the effect of smoking during the study period was slightly smaller (-0.33 ml/year for each cigarette smoked per day). This indicated that smoking before the study period had a marginal latent effect on delta FEV1 during the study. However, neither the effect of smoking before the study nor that of smoking during the study was significant, presumably because of collinearity. Interactions between cigarette smoking and gender, wheezing, atopy, and exposure to environmental tobacco smoke during the growth period were not significant with respect to their effect on the relation between cigarette smoking and delta FEV1. CONCLUSION: Cigarette smoking has a dose related adverse effect on the evolution of ventilatory lung function in young adulthood.

Reliability of Hospital Data for Population-based Studies of Air Pollution

The use of hospital databases for research into the respiratory effects of air pollution has been questioned. In an attempt to address that issue, reabstracts of 1,279 discharge records from 14 Montreal hospitals were compared with the universal health insurance database of Quebec. Agreement levels on discharge diagnoses were 94.9% for asthma; 75.5% for all other respiratory diagnoses combined, including upper airway infections, pneumonia, and coronary obstructive pulmonary disease (COPD) (90% after ignoring disagreements between closely related respiratory diagnoses); and 93.1% for a nonrespiratory comparison group. Factors associated with misclassification included use of nonurgent admissions; delays in hospital admission from emergency rooms; and differences in levels of diagnostic agreement between hospitals, age groups, and outcome groups. These should be taken into account in air pollution epidemiologic research in which databases of the kind commonly maintained in North American health care systems are used.

Passive smoking and evolution of lung function in young adults. An 8-year longitudinal study.

The objective of the study was to examine the relation between exposure to environmental tobacco smoke (ETS) and the rate of change in ventilatory lung function in young adults during a study period of 8 years, with an additional aim to recognize susceptible subgroups. The study population consisted of 117 never smokers, who were 15-40 years of age at the time of an initial examination when they underwent spirometry and a standardized interviewer-administered questionnaire on respiratory health, and were re-examined 8 years later. Lifetime exposure to ETS at home and at work before the start of the study was ascertained at an early stage of the study, and exposure during the study period was recorded at the 8-year examination. The relations between home and work ETS exposure before and during the study period and the rate of change in forced expiratory volume in one second (delta FEV1 in ml/yr) and in mean forced expiratory flow during the middle half of the forced vital capacity (delta FEF25-75 in 1/sec/yr) were studied in linear regression models including potential confounders and other determinants of the outcome. There was no statistically significant relation between ETS exposure during or before the study period and evolution of FEV1 or FEF25-75. The 95% confidence intervals of the estimates indicated that ETS exposure was unlikely to have a physiologically relevant effect. A statistically significant but physiologically unimportant relation was observed between cumulative home ETS exposure before the study and delta FEV1 in the subgroup of subjects 25 years of age or younger. There was no evidence of modification by atopy, wheezing or gender. The results suggest that exposure to environmental tobacco smoke in young adulthood at home and in office work environment does not lead to a clinically important ventilatory impairment in such exposure levels as experienced in Canadian housing conditions. This does not refute the possibility that higher exposure due to more frequent smoking in smaller indoor spaces with lower rates of ventilation may be harmful.

Prevalence of vitamin A deficiency in children aged 6-9 years in Wukro, northern Ethiopia

OBJECTIVE To determine the prevalence of vitamin A deficiency in children aged 6-9 years in northern Ethiopia. METHODS A cross-sectional study was carried out and the data were analysed for 824 (61.5%) of 1339 eligible children for whom there was complete information on biochemical vitamin A status, dietary vitamin A intake, ocular examination for xerophthalmia, and anthropometry. FINDINGS The prevalence of xerophthalmia was 5.8%; serum retinol levels were below 0.35 mumol/l and between 0.35 and 0.70 mumol/l in 8.4% and 51.1% of the children respectively. The liver vitamin A reserve (modified relative dose response ratio > or = 0.06) was low in 41.0% of the children. CONCLUSION The high prevalence of severe vitamin A deficiency in children aged 6-9 years indicates the need to reevaluate the practice of targeting vitamin A supplementation programmes on children under 6 years of age in areas where vitamin A deficiency is endemic.