A Comparative Study of the Peak Expiratory Flow Rate of Indian and Nepalese Young Adults in a Teaching Institute

As there is no signifi cant difference in the mean PEFR of Indian and Nepalese young adults, prediction equations made for Indian adults can be used to predict PEFR of Nepalese subjects. Therefore, an attempt has been made to formulate a regression equation from the combined Indian and Nepalese subjects. A stepwise, multiple, linear, regression analysis was performed for this purpose. The analysis showed that height is the best predictor for PEFR in the present study. The regression equation based on height for the combined Indian and Nepalese young adults is calculated as: PEFR = 5.687 × Height (cm) – 495.787. However, a stepwise, multiple, linear, regression equation with residual analysis for the best fi t model was performed to formulate prediction equation for PEFR and this showed a change of the earlier regression equation to PEFR = 5.930 × Height (cm) – 536.131.


INTRODUCTION
Pulmonary function tests using complete spirometry give quantifi able measures of the state of the respiratory system and positive information for the management of respiratory tract illness in clinical practice. However, the required instruments are relatively expensive. In contrast, the Peak Expiratory Flow Rate (PEFR) can be measured using relatively inexpensive Peak Flow Meters and are of value in identifying and assessing the degree of air fl ow limitations of individuals. 1 Many studies on PEFR in the general population have been carried out previously in India and abroad. 2-12 Only one published study was found on PEFR of Nepalese females with a smoking habit in Nepal. 13 No such study of normal Nepalese children and young adults was found. It is not possible to establish a national PEFR norm in a country for healthy men and women as the lung function varies with socio-economic, geographical, environmental and nutritional conditions. 14, 15 Nepal is a neighboring country of India and its socio-economic, geographical, environmental and nutritional conditions of the relation are quite similar with respect to India. So, an attempt has been made to evaluate the value of PEFR of healthy Nepalese adults and compare their value with healthy Indian counterparts to know whether Indian prediction equations for PEFR can be used for the Nepalese adult population or not.

MATERIAL AND METHODS
The present study is a cross-sectional study carried out on 123 non-smoking, healthy medical students of 18 to 20 years of age studying at the Manipal College of Medical Sciences (MCOMS) in Pokhara, Nepal. Students of basic sciences (1 st to 4 th semester) during the year 2005 to 2006 participated in the present study. A detailed medical history of the students was taken and clinical examination of individuals carried out by physicians to exclude any disease, mainly respiratory diseases. A healthy person was defi ned as one who did not have any systemic disease. 8 After medical tests, 123 healthy students were selected for the present study. Among the 123 students, 64 (28 Males, 36 Females) were Indians and 59 (32 Males, 27 Females) were Nepalese, by birth.
A verbal consent of all the 123 students was taken after they were explained the methods and a live of the study. A formal approval to conduct the study was taken from the MCOMS, Pokhara, Nepal. The necessary materials and instruments study were provided by the Department of Physiology of the MCOMS.
The age in completed year, standing height to the nearest centimeter without shoes and body weight in kilograms in minimum clothing were recorded for each subject at the Department of Physiology, MCOMS, Pokhara.

Peak Expiratory Flow Rate (PEFR)
PEFR was measured in the standing position with the 'standard range FERRARIS Pocket Peak Flow Meter' manufactured by FERRARIS Medical limited, London. 16, 17 The subjects were asked to relax before taking the PEFR measurement. The test procedure was explained to the subjects. After adequate rest, subjects were instructed to take a deep breath and exhale as forcefully as possible in once single blow into the instrument. During breathing out into the instrument the nose was closed by a nose clip. Three satisfactory readings were taken and the highest among the three was accepted. Close watch was made to ensure that a tight seal was maintained between the lips and the mouth piece. The PEFR was recorded nearest to Liter/ minutes. 18,19 The collected data was stored in a computer for analysis and Statistical Package for the Social Sciences (SPSS) version 10 was used for this purpose. The mean and the SD for all the selected variables and comparisons between Nepalese and Indians were performed by student t-test. A stepwise, multiple, linear, regression equation with residual analysis for best the fi t of the model was performed to formulate the prediction equation for PEFR from age and anthropometric data.

RESULTS
Comparisons of the physical characteristics including PEFR of the Indian and Nepalese young adults are shown in Table 1. Indian male young adults were found to have a PEFR of 490.4 (±49.85), whereas Nepalese male young adults were found to have 485.9 (±56.67). There is no statistical signifi cant difference between these two populations. On the other hand, the mean PEFR values of the Indian female young adults were found to be 386.0 (±48.31) L/min as compared to 365.2 (±55.43) of the Nepalese counterparts. Here too, there also no signifi cant difference between the two populations.
Comparisons of physical characteristics including PEFR of the male and female young adults of the Indian and Nepalese populations was done ( Table 2). Both Indian and Nepalese male students are found to have a signifi cantly higher PEFR value as compared to their female counterparts.
Stepwise, multiple, linear, regression analysis shows that height is the best predictor for PEFR ( Figure 1 and Table 3). The regression equation based on height for the combined subjects is: PEFR = 5.687 × Height (cm) -495.787.
The result of fi tting model of regression equation shown in Table 3 (full data) established that height was statistically signifi cant in predicting the PEFR. The overall fi tting model statistics for the signifi cance of regression model was found to be P<0.001. The residual plot of the predicted value of response variable vs. the standardized residual did not show any pattern and the residuals were randomly distributed around the mean value zero (0). However, there were six points which were large residuals (greater than or equal to 2 in absolute value). Therefore, we omitted these six outlines 20, 21 and re-estimated the regression model as seen in the results of Table 3 (reduced data, n, 117) that the proportion of explained variation (r 2 ) increased to 54% as compared to 45% (in full data; n, 123). On the other hand, the residual standard deviation (RSD) reduced to approximately 9% (RSD 57.158 to 48.310). So, as per residual analysis to fi t best model,

CONCLUSION
It can be concluded that as there is no signifi cant difference in the mean PEFR values of Indian and Nepalese healthy young adults in the present study, prediction equations made for Indian adults can be used to predict PEFR of Nepalese healthy adults. However, no attempt has been made to evaluate the suitability of the Indian prediction equation for Nepalese healthy young adults. So, further study is required to add more data on there fi ndings. However, we tried to make a prediction equation with combined Indian and Nepalese young adults to predict PEFR by multiple linear regression equation with residual analysis. From this analysis, it has been shown that height is the best predictor for the measurement of the PEFR of the present study.