Spirometric and flow standards for healthy adult non-smoking Sri Lankans belonging to the Sinhalese ethnic group.

The objective of this study was to establish reference norms for dynamic lung volumes and forced expiratory flows applicable to the Sinhalese ethnic group in Sri Lanka. Respiratory function tests were carried out on 367 female and 328 male healthy non-smoking Sinhalese adults of age range 17-65 years. Subjects included hospital and university staff, students of the Faculty of Medicine at Peradeniya and healthy relatives accompanying patients to outpatients clinics. An 8-litre rolling-seal spirometer was used in conjunction with a X-Y recorder. Forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1) reached a peak at 30 years in males and 23 years in females. All measurements except forced mid-expiratory flow (FEV25-75%) increased with increasing height. The flow-volume curve became progressively concave towards the volume axis with advancing age. Lung function measurements correlated best with age and height. Therefore prediction formulae were developed with these two measurements as the independent variables. Nomograms based on these formulae were constructed. When standardized for height and age, forced expiratory volumes were smaller than in Europeans, Negroes and Pakistanis, and were comparable to South Indian data. However, flows did not vary significantly from those of other ethnic groups. It can therefore be concluded that the Sinhalese have smaller lungs than Europeans and Negroes even after adjustment for differences in stature, but lung elastic recoil pressure and airway calibre (which are determinants of forced expiratory flows) appear to be similar to those of other ethnic groups.