M. Amjad Hameed ( Department of Physiology, Army Medical College, Rawalpindi. )
Saadat Ali Khan ( Department of Physiology, Army Medical College, Rawalpindi. )
Aftab Ahmed ( PMRC Research Centre, Army Medical College, Rawalpindi. )
Pulmonary function tests were studied in 519 healthy children (263 boys and 256 girls) from various schools of Rawalpindi and Karachi.
FVC, FEV1, MVV and PEFR were measured in all. FVC and FEV1 showed fairly constant increase from 5-12 years age, more variable in 13-15 years and constant in boys after 15 years while it declined in girls. Mean of FEV1/FVC ratio was 78.19% ± 2.4 in boys and 78. 14% ± 3.4 in girls. In younger age group (5-10 years), the mean was 76.04% ± 2.67 for boys and 76.45% ± 3.52 for girls while in older age group (11-16 years), it was 80.44% ± 2.41 and 79.55% ± 4.06 respectively. Both groups showed increased tendency with age, more significant in boys.
Multiple linear regression equation and correlation coefficient for age, weight and height were drawn. The results showed boys and taller subjects higher values for all parameters. Present values approximate to those of Western countries but are significantly higher (P < 0.01) than that of Indian children (JPMA 37: 318, 1987).
Respiratory tract in children is probably most often affected by the disease than any other system of the body. The studies of lung function in infants and children are important to describe the normal growth and development of respiratory system and to understand the physiological abnormalities that occur in disease state1. With the proliferation of equipment the lung function testing by the physicians in their private offices or in general pediatric clinics has become popular, with little standardization of testing procedures and little consensus as to “normal” or “abnormal” test values. Anthropometric measurements affect the results of lung function tests in children2-5.
To assess pulmonary function, measurements of forced vital capacity (PVC), forced expiratory volume for first, second (FEV1), maximum ventilatory volume (MW), and Peak expiratory flow rate (PEFR) are done in common practice. Decades have passed since the introduction of these pulmonary function tests; spectacular increase in their use testifies that most physicians are convinced of their value. Data of last six decades on the pulmonary function in children are available to help clinicians assess the related problems. 6-7 Most of the values reported in literature pertain to the Western world and only few studies have been carried óut in Pakistani children.
Lack of normal values for children from a particular population may jeopardise the clinical value of such data as it must be derived specifically from a sampling of that population. The purpose of this study was to analyse data obtained from healthy Pakistani subjects and to establish specific normal values.
PATIENTS AND METHODS
Five hundred and nineteen healthy children (263 boys and 256 girls) between the age of 5 to 16 years were selected from primary and secondary schools in Rawalpindi and Karachi area. Most of the children belonged to the middle socioeconomic group. Data were recorded for sex, age, height and weight.
The criteria for healthy status were: No present acute or past chronic disease of respiratory system, no major respiratory disease, i.e., congenital anomalies, destructive type of pneumonia or thoracic surgery in the past. No systemic disease which directly or indirectly was known to influence the respiratory system. No more than incidental smoking experience and no history of upper respiratory tract infection during the previous three weeks.
Testing consisted of measurements of PVC, FEV1, MVV and PEFR in the standing position with a nose clip on by means of Digital Pulmometer (Kinetics) and mini Wright’s Peak Flowmeter. Both instruments were standardized and adequate training was given to the participants about their use. Three test values were obtained for all these tests and the mean of the three was recorded for further analysis. The ambient temperature during testing at all locations ranged between 22°C to 28°C. The values were subse quently computed for standard barometric pressure and temperature.
Indices of lung function were analysed and the results expressed as mean values with standard deviation. Correlation coefficients and various parameters were calculated with the height of the subjects. Multiple regression equation was drawn to find regression relationship of lung function on age, height and weight, separately for boys and girls. Comparison of low age group and high age group was made by using student’s “t” test.
In the present study, reference standards of pulmonary function in healthy Pak1stani children were determined Proper instructions to first, second and third grade school children (5 to 9 years of age) resulted in meaningful and reproducible FVC maneuvers in over 95% of the subjects. The number of attempts a child should be asked to make to provide 3 acceptable values is important8. A balance is needed to allow for learning effect and yet not reach the stage where child tires or becomes bored9. In this group of children where pretest training was given most of the children achieved their maximal values in the first recording. However in order to have better stability of measurement mean values were used to safeguard occasional erroneous measurements.10
Pulmonary function in normal healthy Pakistani children is closely related to growth and development (Table II, III). The growth of lung function from ages 5 to 16 years can best be described in curvilinear fashion (Figure la 1). This confirms observations of previous workers. 7,11,12
The correlation between the lung indices and height, weight and age were striking (Table. W). In younger age (5 to 12 years) the differences between bbys and girls were minor and the volume and indices of flow increased uniformly with height, which affords a better index of body size than does age13. At adolescence, the rate of pulmonary development increases and marked differences between boys and girls were noted. This conforms to present findings (Figure 1, la). In boys, pulmonary function peaks at approximately age 15 years. While female subjects attain their! maximum pulmonary function at approximately age 15 years then decrease with increasing age. These figures are slightly on lower side compared to Dickman and associates, may be because our study group range was 5 to 15 years while they studied upto 18 years.
The FEV,/FVC in normal subject was impressively stable regardless of age, sex or height. Mean values were 78.20% ± 2.4 for boys and 78.14% ± 3.4 for girls. Means for boys and girls were 76.04% ± 2.67 and 76.45% ± 3.52 respectively in low age group (5 to 10 years) while it was 80.44% ± 2.41 forboysand79.55%±4.06 forgirls in high age group (11 to 16 years). Although these values were quite stable in their own group but were significantly (P<0.0000l) different from those observed by other workers11,13,14 However in view of the standard deviations observed in all these studies, the practical clinical conclusion is that a ratio of FEV1 to FVC less than 70% is abnormal for any age, sex or height.
To assess pulmonary function of a particular adult the observer usually refers to nomogram of linear regression curve. In children, however, these two methods cannot be used because other factors, i.e., weight and growth spurt, not represented in such computations have an important role. Multiple linear regression formulae are thus better expressions. The regression relationship determined presently, Table VII for boys and Table VIII for girls, could be reliably applied to Pakistani children belonging to any age, height and weight groups.
In figure 2 and 3 we compared the FVC and FEy, values of Pakistani children with those of European, white North American and Indian children as reported by other workers5,11,13,15,17 The data suggest that these values for Pakistani children are in conformity with those of Euiopean, white North American but are significantly higher (P< 0.01) than those of Indian children. This disparity may be due to selection of the subjects from the two major cities of the country where socio.economic conditions of the people are better than in the remote places.
In conclusion our findings provide baseline data for lung function indices in healthy Pakistani children and we support the need to establish similar normal values in men and women in any previously untested ethnic or geographical group before decisions are made about the prevalence of dysfunction relating to disease.
The writers wish to thank the teachers and local administration of the schools for making the students available to participate in this study. We also acknowledge the efforts of Mr. Aftab Qazi for providing help and guidance in cons¬truction of various statistical figures, Mr. Muhammad Irtiza Khan and Mr. M. Yaqoob for typing the manuscript.
The study was supported by PMRC Research Centre, Army Medical College, Rawal¬pindi.
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