Al-Riyami BM, Al-Rawas OA, Hassan MO. Normal spirometric reference values for Omani children and adolescents. Respirology 2004, 9, 387–391.

Subjects
The study was conducted in primary, intermediate and secondary schools in the village of Al-Khod, which is near the University Hospital. This new village is inhabited by Omanis from all the regions of Oman. Typically, schools had many classes of the same grade and only one or two classes from each grade were randomly selected so as to include at least 15 children in each year for each sex. An Arabic version of the European Respiratory Health Survey Questionnaire was used to identify children with respiratory problems and smokers. Students aged 12 years and older completed their own questionnaires and they were asked about smoking, whereas the parents or guardians of the younger children were requested to complete the questionnaires. Written consent was obtained from the parents through school authorities.

Measurements
Anthropometric measurements of standing height without shoes (to the nearest cm) and weight in school uniform (to the nearest kg) were taken. Manual height and weight scales were used and were calibrated daily. Age was taken as the number of complete years from birth to the date of the study. All measurements were performed indoors between 08.00 and 13.00 hours, where the temperature was between 22 and 26 °C. Spirometry was performed using the same portable spirometer (Compaq, Buckingham, UK) and all measurements were carried out by two trained technicians, in accordance with the American Thoracic Society guidelines. Children were instructed on the technique of the manoeuvres in small groups and the instructions were reinforced to each child individually before the test. The spirometer was checked for leaks and calibrated at the start of the day, and then recalibrated after every six subjects. Tests were performed with subjects in a sitting position.
For measurements of vital capacity (VC), children were asked to take in a maximum breath and, with their nose clipped, to blow out through the mouth into the spirometer at a steady rate to their maximum expiration. For measurements of FVC they were taught a similar inspiratory manoeuvre and were asked to blow out as fast as possible and for as long as possible. The value for FEV₁ was obtained from the FVC manoeuvre. A minimum of three to a maximum of five trials were performed for each manoeuvre. Peak expiratory flow (PEF) and forced mid-expiratory flow (FEF_25-75%) were automatically determined by the spirometer. FEV₁ as a percentage of FVC (FEV₁%FVC) was also calculated.
At the end of each day, all spirograms were assessed for technical acceptability using standard objective criteria (smooth and continuous curve; apparent maximal effort; good start; and no evidence of false start, excessive hesitation, coughing, early termination, leaks or obstructed mouthpiece). The FVC and FEV₁ values from the best two tracings had to be within 5% of each other. The largest values from acceptable tests were reported for each parameter (FVC, FEV₁, PEF and FEF_25-75%). A total of 1123 children (527 boys) with completed questionnaires were allowed to perform spirometry and those who met exclusion criteria were excluded from the analysis. The exclusion criteria were a current or past history of asthma or chronic respiratory illness, recent upper respiratory tract infection (within the past month), any personal history of smoking, age below 6 years or above 19 years and unacceptable spirometric technique.

Note

More data are available on adults, but as these have not yet been published (a manuscript is being being peer reviewed as of now) no specific information will be disclosed about these. Suffice it to say that Omani people are shorter that those in Europe and the USA (see table below), and that the level of FEV₁ and FVC is definitely lower than in Europe, but FEV₁/FVC is definitely comparable.