Department of Physiology, Ayub Medical College, Abbottabad,. Pakistan and Pulmonary Division, Department of Medicine,. University of Kentucky, Medical ...
Br. J. Dis. Chest (1987) 81, 35
SPIROMETRY AND FLOW-VOLUME CURVES IN HEALTHY, NORMAL PAKISTANIS M. AYUB, S. H. ZAIDI AND N. K. BURKI Department of Physiology, Ayub Medical College, Abbottabad, Pakistan and Pulmonary Division, Department of Medicine, University of Kentucky, Medical Center, Lexington, Kentucky, USA
Summary
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 6.5 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 (FEV,) 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 FEV, were slight so that, after the fourth decade, the FVC and FEV, values are very comparable between the European and Pakistani populations. Amongst Pakistani women, on the other hand, FVC and FEV, 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. INTRODUCTION Pulmonary function testing has become a routine part of the evaluation of patients in whom a diagnosis of pulmonary abnormality or disease is entertained. Spirometry offers the simplest test available for such evaluation, the recorded results in an individual being compared to an established standard range to determine whether the results fall within or outside the established range. Ethnic differences in the normal range of spirometric values Address for correspondence: N. K. Burki, MD, PhD, Pulmonary Division/Department of Medicine, Room MN.578, Medical Center, University of Kentucky, 800 Rose Street, Lexington, Kentucky 40536-0084, USA.
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have been described (l-3). Thus it is important that the ‘normal range’ in a given population be defined as accurately as possible so that the data are of use for both experimental and clinical studies. Furthermore, recent criteria (4) describing the techniques of measurement of spirometry have resulted in a reassessment of previously defined normal ranges in healthy non-smokers (5). Previous studies (2,6) have reported that spirometric values in normal Pakistani adults are lower than those in comparable ageand sex-matched European adults. The present study was undertaken for two purposes: to measure the range of spirometric values in a rigorously defined sample of the Pakistani population using current criteria for spirometric measurements, and simultaneously to measure maximum expiratory flow-volume relationships to establish the range of these parameters in the population and to provide additional insight into the possible effects of the decreased lung volumes on lung mechanics. Methods Spirometric measurements were made by standard techniques (4). The apparatus consisted of a mouthpiece attached to a pneumotachygraph (Messrs Dynasciences, Whittaker Corporation); the pressure across the pneumotachygraph screen was measured by means of a differential pressure strain gauge (Gould-Statham PM15E) and the resultant signal, proportional to airflow, was amplified and recorded on a 5 channel direct pen-writing recorder (Model 56, Gilson Medical Electronics, Inc.). The flow signal was electronically integrated to volume and recorded on the adjacent channel. A calibrated, 3-litre syringe was used to calibrate the volume and flow signalsfrom the pneumotachygraph; this was done several times during each testing day. All recordings were made at a paper speed of 25 mm/set. The ambient temperature and barometric pressure were recorded. Each subject was first instructed in the performance of a maximum expiratory effort after inhaling to total lung capacity; following this, at least three spirograms which met standard criteria of acceptability (4) were recorded in each subject. From these recordings, using standard measurement techniques including the use of ‘back extrapolation’ (4), the values of forced vital capacity (FVC), forced expiratory volume in 1 second (FEVi), and the ratio of FEVi to FVC (FEVJFVC, %) were calculated; values derived from the spirogram with the highest values for the sum of FVC and FEV,, converted to BTPS, were noted as the final values in each subject. From the simultaneously recorded flow and volume signals, the highest values for maximum expiratory flow (vpeak), and flow rates respectively, remain to be expired, when 75%, 50% and 25% of vital capacity $&75, timlmax50, i&MaxzS, were calculated. In each subject the age, height, and weight were recorded. Volunteer subjects, both male and female, between the agesof 18 years and 65 years were studied. None of the subjects had ever smoked cigarettes. Subjects with any history of allergies, cardiopulmonary or other systemic disease or abnormality, or with any symptoms of chronic or acute pulmonary disease such as cough or dyspnoea, were excluded from the study. In addition, pregnant women were excluded from the study. Studies were performed in two locations: in Northern Pakistan at Haripur (elevation above sea level: 600 m) and at Abbottabad (elevation 1120 m). The subjects were evenly divided between rural and urban dwellers; the general levels of chemical air pollution in these areas are very low. The data were analysed separately for men and women. Multiple linear regressions were constructed for each measured parameter in relation to age and height (7). In addition the standard error of the estimate (SEE) was calculated for each parameter based on the age and height (8). To test for the significance of the relative contributions of the relationship of each of the regressors to the multiple regression, partial correlation coefficients (7) were calculated. Analysis of differences between age groups amongst the various parameters was performed by Newman-Keuls one-way analysis of variance (7).
166.3 f7.0
42.47 k2.41 (n= 19)
154.0 t2.6
59.0 k5.8
All volumes
in BTPS.
155.7 k6.4
42.43 k2.39 (n=23)
(n=4)
156.9 k7.34
157.9 k6.15
32.85 k2.76 (n=33)
(n=20)
23.7 k3.32
Women
(n=6)
167.3 k4.50
170.5 k5.54
34.57 k2.87 (n=14)
57.0 f5.48
169.9 +7.47
Height (cm)
21.2 k2.93 (n=70)
Men
(years)
Age
61.0 k26.0
55.9 f9.0
56.2 t- 10.78
54.8 k10.0
61.3 k9.16
59.8 k9.5
61.6 29.35
61.66 k8.46
Weight (kg)
2.30 kO.65
2.44 kO.83
2.84 50.86
2.94 f0.72
3.89 k1.15
3.59 kO.66
4.08 21.04
1.81 kO.51
2.01 f0.61
2.44 f0.75
2.50 kO.55
3.01 kO.60
2.96 kO.55
3.21 f0.83
3.49 f0.72
(litres/sec)
4.07 kO.90
FEV,
(litres)
function
FVC
Table I. Pulmonary
10.16 k2.79
79.63 k12.46
5.13 k2.56 4.00 21.68 4.48 f1.48
85.50 k7.4 81.70 k7.45 83.10 k11.05
4.97 k1.59
8.61 k4.24
81.98 k5.84
88.97 k6.53
8.67 k3.28
9.08 k3.03
(litres/sec)
lipe,,
(mean *standard
78.70 f7.16
84.91 26.40
(%)
FEVJFVC
tests by age groups
4.15 k1.06
3.68 k1.46
4.39 k1.81
4.72 k1.55
8.39 k2.27
7.05 k3.67
6.98 k3.07
7.31 f2.57
deviation)
2.68 L1.06
2.53 -Cl.23
3.25 11.83
3.91 k1.35
5.35 f2.82
4.11 k1.62
3.87 a2.00
4.72 f1.97
(litres/sec)
r’,a* 50
1.05 f0.38
1.72 kO.44
1.25 f0.51
1.35 kO.58
1.39 f0.78
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Table II. Partial correlations Fvc
FEV,
Rim75
RllTmaX50
cnmax25
FEV,/FVC @)
0.04 0.42 NS
0.09
0.93 NS
0.01 0.10 NS
-0.275 -2.88 co.01
-0.270 -2.886
