Prediction values for the ventilatory capacity in male West Pakistani workers in the United Kingdom

Spirometric reference values for healthy nonsmoking Saudi adults

OBJECTIVES

To derive prediction equations of spirometric values of healthy Saudi adults and to compare the derived equations with equations reported in selected population.

METHODS

Cross-sectional study of healthy nonsmoking men and women Saudi adults. The measured spirometric values were the forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1 ), peak expiratory flow (PEF) and forced mid-expiratory flow (FEF 25%-75%).

RESULTS

A total of 621 spirometric tests were done. The prediction equations were derived using the following formula: Predicted spirometric value = constant + (b1 × age) + (b2 × height (cm)), where b1 and b2 represent the regression coefficients for age and height, respectively. Variable Constant Age (years) Height (cm) Variable Constant Age (years) Height (cm) Males (n = 292) Females (n = 175) FVC -2.933 -0.018 0.046 FVC -3.470 -0.016 0.045 FEV1 -1.886 -0.019 0.036 FEV1 -2.482 -0.018 0.036 FEV1 /FVC (%) 98.41 -0.095 -0.068 FEV1 /FVC (%) 100.67 -0.142 -0.072 PEF 17.274 -1.243 3.471 PEF -226.648 -0.499 4.076 FEF25%-75% 0.100 -0.024 0.027 FEF25%-75% -1.337 -0.021 0.031 The means of the measured FVC and FEV1 were significantly lower than the predicted values derived by the American equations of -7.2% and -4.6% among males, respectively (P value < 0.00001), and -4.7%, and -5.26% among females, respectively (P value < 0.00001).

CONCLUSION

The reference spirometric values derived in our study were significantly lower than the predicted values derived by the American equations.

Pulmonary Function Studies of Healthy Non-smoking Male University Students of Kolkata, India - Revisited

BACKGROUND

Pulmonary function tests (PFTs) need to be revisited in light of rapid economic growth and industrial development. Questions have been raised about the validity of existing population-specific norms for predicting PFTs, and therefore, the present study aimed to determine the applicability of existing norms for PFTs in young healthy non-smoking male university students of Kolkata.

METHODS

PFTs were carried out for 87 non-smoking male university students who were randomly sampled from the University of Calcutta, Kolkata, India.

RESULTS

The PFTs data obtained in this study did not show a significant variation with that obtained in a previous study. Significant (P < 0.001) differences in the forced expiratory volume in 1 s (FEV1%) and peak expiratory flow rate (PEFR) between the two studies may be attributed to differences in the age and body height, which exhibited significant correlations with the vital capacity (VC), forced vital capacity (FVC), FEV1, FEV1%, and PEFR. Regression equations have been computed to predict PFTs parameters from age and body height.

CONCLUSION

Pulmonary function in the university students of Kolkata was found to have remained mostly unchanged in the last 24 years. The equations computed in this study are considered preferable owing to their substantially smaller standard error of estimate (SEE) than those proposed in the previous study.

Lung function in teenage Bangladeshi boys and girls

Data on forced vital capacity, forced expiratory volume in one second and peak expiratory flow rate were obtained in a group of 588 healthy and well-nourished (but not obese) Bangladeshi teenagers to establish normal values in this population. Bangladeshi girls in their early teens showed higher peak expiratory flow rates than boys of the same age but while this continued to rise in boys after the age of 15 years the peak expiratory flow rate in girls seemed to have attained its maximum values by that age. Correlations between sitting height and the lung function variables were found to be marginally greater than those with standing height. Prediction equations were calculated for each lung function variable with sitting and standing separately. Comparison of the results in our study with those reported from other ethnic groups indicate that Bangladeshi values are lower than those of Europeans, Jordanians or Chinese but not significantly different from those reported for Libyans. Since in practice, genetic, nutritional and environmental factors are not readily disentangled, norms for a given study population need to be derived from healthy subjects of similar background and ethnicity.

New regression equations for predicting peak expiratory flow in adults

An earlier study of peak expiratory flow (PEF) in normal adults contained too few men aged over 55 and women aged over 65 for the regression equations to be used for prediction in older people. A subsequent study was therefore carried out on an additional 23 men and 29 women aged 55 or over who were lifelong non-smokers and satisfied the same strict criteria of normality that had been used in the original study. The data from both studies were combined and a new model used to calculate equations for the regression of PEF on age and height in the two sexes. With this model predicted values could be derived for men and women aged between 15 and 85. These new equations gave predicted values in men and women aged less than 55 and 65, respectively, which were almost identical with those reported previously. The new regression equations for PEF enable values to be predicted for people aged 15-85 and so enhance the accuracy of testing in the elderly.

Ethnic variation in respiratory morbidity and lung function in childhood

In a population of 5689 primary schoolchildren there were few important differences between children of European (n = 5287), African (n = 198), and Indian origin (n = 204) in the prevalence of a history of past respiratory illnesses or current respiratory symptoms. The reported 12 month period prevalence of the symptom "ever wheezy" was 15%, 18%, and 17% respectively in the three ethnic groups (differences not significant). In a subsample of 973 European, 47 African, and 40 Indian children forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were significantly lower by 12% and 13% in Africans and by 8% and 9% in Indians than in Europeans after adjustment to the group mean height of 128 cm. No significant ethnic variation was found for forced mid expiratory flow, FEV1/FVC, or mean transit time. Since the lung function studies were performed on a sample from a large population with little variation in respiratory morbidity, the differences are likely to reflect human biological differences. Separate prediction equations need to be developed for the different ethnic groups in childhood.

Spirometry and flow-volume curves in healthy, normal Pakistanis

Previous studies have indicated that lung volumes in healthy, normal Pakistani adults are smaller than measurements reported in comparable healthy European populations; in order to confirm these findings and to examine the relationship of maximal expiratory flow rates to lung volumes, we studied 250 non-smoking healthy subjects (116 men and 114 women) between the ages of 18 and 65 years. The population sample was drawn from urban and rural areas of Pakistan, with low levels of air pollution. The results indicate that the forced vital capacity (FVC) and forced expired volume in 1 second (FEV1) were lower in the Pakistani population compared to European populations and North American populations of European descent. These data are in conformity with previous studies; however, in Pakistani men the effects of age on FVC and FEV1 were slight so that, after the fourth decade, the FVC and FEV1 values are very comparable between the European and Pakistani populations. Amongst Pakistani women, on the other hand, FVC and FEV1 remained lower than in their European counterparts throughout adult life. Maximal expiratory flow rates amongst the men did not correlate with age, and these values were very similar to those reported in age-matched European populations. In women, however, there was a significant correlation of maximal flow rates with age and height, and the maximal expiratory flows were decreased compared to European populations. These data indicate that in Pakistani men pulmonary mechanics may be different to their European counterparts, allowing for higher maximal expiratory flows at any given lung volume.

Ethnic differences in peak expiratory flow rate in Birmingham factory workers

Among 698 Birmingham factory workers, Asian men (n = 75) tended to have lower peak expiratory flow rates (PEFR) than black (n = 156) or white (n = 138) men when age, height and smoking habits were accounted for. This trend reached statistical significance in Asian females (n = 20), despite a small sample size. There were no significant differences in PEFR between blacks and whites of either sex.

Effects of temperature on Vitalograph spirometer readings

Spirometric variables were obtained from nine symptomless subjects, who performed forced expiratory manoeuvres with three Vitalograph spirometers at three different ambient temperatures (36.5 degrees C, 24.1 degrees C, and - 7.3 degrees C) over three days according to a Latin square design. Analysis of variance showed no significant difference between values at different ambient temperatures when measured at ATPS. Correction of the results to BTPS resulted in a significant difference in values at the three ambient temperatures for all measurements other than the Vmax25. The mean error introduced by conversion to BTPS varied from 7% (SD 5%) for the FVC at 24.1 degrees C to 30% (21%) for Vmax50 at - 7.3 degrees C. Possible explanations for these observations include the increasing compliance of the spirometer bellows with increasing temperature, relatively slow cooling of gases within the spirometer, and a combination of these effects. We conclude that there is no evidence that conversion to BTPS improves the accuracy of measurements made on a Vitalograph spirometer. Further studies on other spirometers are needed to see whether conversion to BTPS is always appropriate.

A survey of ventilatory capacity in Chinese subjects in Hong Kong

A survey of three indices of ventilatory capacity (forced expiratory volume in one second, FEV1; forced vital capacity, FVC; and peak expiratory flow rate, PEFR) was carried out on 3490 Chinese inhabitants of Hong Kong aged between 5 and 97 years. The results are compared with those of previous surveys of ventilatory capacity in a variety of ethnic groups. Our results confirm previous findings that the indices FEV1 and FVC are proportional to the square of the height of the subject, but we have found that PEFR is proportional to height itself. Using the indices FEV1/height2, and PEFR/height we have derived regression equations which may be used to predict normal values of the ventilatory indices for both adults and children. An interesting observation in this cross-sectional survey was that although all ventilatory indices were adversely affected by smoking, the rates of decline of these indices with age were not accelerated in smokers compared with non-smokers, in contrast to the findings of previous surveys on European populations.

Asthma in Asian immigrants

Adult Asian immigrants to the United Kingdom attending an asthma clinic have been compared with a control group of non-immigrant Caucasian asthmatic patients of similar age distribution. The Asian immigrants had a later age of onset of asthma than their non-immigrant controls. Comparison with studies of asthmatic patients in India suggests that this may be an intrinsic ethnic difference but an effect of migration in early adult life is not excluded. Despite a later age of onset, the frequency of positive skin prick tests to common allergens was similar in the immigrant and control groups and 71% of the Asians had positive reactions to the house dust mite. Most other clinical features, the variability of airways obstruction and the requirements for treatment showed no significant differences between the two groups.

Pulmonary function studies in healthy Pakistani adults

Predicted normal spirometric values have been shown to have significant geographical and ethnic variation. These variations are of epidemiological significance in determining the prevalence of disease and of clinical importance in measuring the effects on pulmonary function of various diseases. A total of 599 men were chosen from employees of a package manufacturer, a general hospital in Lahore, and a village in northern Pakistan; 94 students and staff of a women's college in Lahore were also studied. The forced vital capacity (FVC) was recorded from three satisfactory efforts, and the FVC, one second forced expiratory volume (FEV1), and maximal midexpiratory flow (MMF, or FEF25-75%) were calculated from the best FVC effort. The FVC and FEV1 in men were found to be similar to those of a group of emigrant Pakistanis and a north-western Indian population (Delhi) but higher than populations in south and eastern India. Pakistani women had values similar to those of women in northern India. None of the women smoked and, among Pakistani men, the smokers (285) averaged 6.7 pack years. While the FVC and FEV1 values did not differ between smokers and non-smokers, there was a significant difference in MMF (FEF25-75%) in the two groups. This latter finding corroborates studies on North American populations in which smokers generally have had a higher lifelong cigarette consumption. This confirms the MMF (FEF25-75%) to be a more sensitive test of subtle, asymptomatic changes in pulmonary function than the more widely used FVC and FEV1.

A computer system for processing data from routine pulmonary function tests

In larger pulmonary function laboratories there is a need for computerised techniques of data processing. A flexible computer system, which is used routinely, is described. The system processes data from a relatively large range of tests. Two types of output are produced--one for laboratory purposes, and one for return to the referring physician. The system adds an automatic interpretative report for each set of results. In developing the interpretative system it has been necessary to utilise a number of arbitrary definitions. The present terminology for reporting pulmonary function tests has limitations. The computer interpretation system affords the opportunity to take account of known interaction between measurements of function and different pathological states.

Lung function of healthy young men in India: contributory roles of genetic and environmental factors

The forced expiratory volume and vital capacity, the total lung capacity and sub-divisions and the lung transfer factor for carbon monoxide and its sub-divisions have been measured on 122 young men living near Delhi, including Servicemen from Gurkha, Rajput and south Indian regiments and civilians mainly from north India. The findings, standardized for age and stature and in the case of the transfer factor the smoking habits, the haemoglobin concentration and the tension of oxygen in the alveolar capillaries, have been compared with those for European and New Guinea men studied by similar methods and with data reported in the literature for other inhabitants of the Indian sub-continent. The lung function of the present Gurkha highlanders is superior to that of the Indian lowlanders and resembles that of both New Guinea highlanders living at an altitude of approximately 1800 m and men from Bhutan (altitude 3100 m). The Rajputs and other north Indians have slightly larger lungs than the men from south India; the lung function of the latter subjects resembles that of the New Guinea coastal dwellers. All these lowland subjects have lungs which are materially smaller than those of Europeans. The observed differences may be explained in terms of a genetic factor which contributes to the relatively large lung of people of European descent and an environmental factor, probably related to physical activity during childhood, which contributes to the superior lung function of hill people. The possible survival value in an inhospitable environment of large and permeable lungs may also have contributed to the difference, but the magnitude of this effect is probably small.