Normal spirometric reference values for Omani children and adolescents

Objectives: Normal lung function has been shown to be population specific. The aim of this study was to derive normal reference spirometric values for Omani children and adolescents. Methodology: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), peak expiratory flow and forced mid-expiratory flow were measured in 837 healthy Omani school children aged 6-19 years. Multiple linear regression analysis was performed for each spirometric parameter against age, height and weight for boys and girls separately. Results: All measured spirometric parameters increased with age and height and were significantly higher in boys than girls. Height explained the maximum variance for all parameters. After accounting for height in the prediction equations, the contribution of age and weight was minimal. The expiratory ratio (FEV ₁%FVC) was independent of age and height and its mean values (± standard deviation) were slightly higher in girls (91.1 ± 6.1%) than boys (86.5 ± 7.1%; P<0.001). The predicted normal values of the subjects using the derived equations were between 5 and 10% lower than the respective values for subjects in Caucasian sample groups. Conclusion: The developed prediction equations can be used in clinical practice in Oman and can be considered for use in neighbouring Arab countries.