الفهرس 
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Abstract
Pulmonary function tests are the fundamental tool to evaluate the respiratory system of an individual and of all the tests, spirometer is by far the most common one used in the diagnosis, assessment and management of patients with different lung diseases. To make an assessment or interpretation of an observed value it is compared with a reference value, defined as ‘normal’ and is derived from a representative sample of healthy subjects. Unlike most other measurements in medicine where universally applicable normal ranges are available, lung function shows wide variations even in ‘normal’ not only due to technical factors related to equipment and procedures, but also due to biological and environmental factors. These include racial, ethnic, sex, anthropometric factors, socio-economic, geographical, climatic and nutritional conditions so that prediction equations developed in one set of population may not be applicable to a different set of population. The interpretation and categorization of spirometric results depend on comparison with reference values derived from ‘‘normal’’ populations.
The present study aimed to develop prediction equations for pulmonary function parameters in a sample of Egyptian people in Cairo governorate adult population and to compare them with the international reference figures used in our spirometric lab facilities.
This observational cross-sectional population-based study was carried out at Embaba Chest Hospital upon 610 normal healthy male and female subjects aged between 20 - 45 years. All subjects were subjected to history along with thorough clinical examination.
The data of the subjects; name, age, sex, height, weight and atmospheric temperature; were taken. Subjects underwent the spirometric test (using body box spirometry) in the sitting position and wearing a nose clip. Every subject attempted to perform manoeuvres. The manoeuvres were repeated until the subjects did it in a good performance. About 51% of the studied population were males.
Our study showed that weight and height were significantly higher among males. There was no significant relation between gender and age of participants. All spirometric measurements were significantly higher among males. Also, there was highly statistically significant negative correlation between age and weight with all the spirometric measurements and highly statistically significant positive correlation between height with all the spirometric measurements among the studied males.
In our study, there was highly statistically significant negative correlation between age (except FEV1/FVC) and weight with all the spirometric measurements and highly statistically significant positive correlation between height with all the spirometric measurements among the studied females. All the measured lung function variables correlated positively with height and negatively with age in males and females.
The prediction equation for each lung function value can be estimated using the following: Predicted lung function= (height x coefficient) – (age x coefficient) – (weight x coefficient) ± constant. Our study compared the mean predicted and present predicted values of lung function parameters of our subjects derived using our equations with the values for the same parameters derived using the selected prediction equations.
In female participants, FEF 25-75 ranged from 2.2619 to 3.1209 with mean 2.712 (± 0.19773). FEV1 ranged from 2.4355 to 3.2437 with mean 2.8648 (± 0.17228). FVC ranged from 3.135 to 3.8561 with mean 3.5131 (± 0.16387). FEV1/FVC ranged from 0.7788 to 0.8495 with mean 0.8169 (± 0.01473).
In male participants, FEF 25-75 ranged from 2.269 to 5.127 with mean 3.7591 (± 0.74313). FEV1 ranged from 3.1020 to 5.0192 with mean 4.0894 (± 0.49791). FVC ranged from 4.1262 to 5.3585 with mean 4.7432 (± 0.30956). FEV1/FVC ranged from 0.8109 to 0.984 with mean 0.872 (± 0.03277).
In our study, there was no significant difference between predicted FVC in the current study and the one recruited from US population, while the predicted FVC in the current study was significantly higher than the Omani and lower than the Jordanian studies among male participants.
There was no significant difference between predicted FEV1 in the current study and the one recruited from the Jordanian population, while the predicted FEV1 among males in the current study was significantly higher than the US and Omani populations.
There was no significant difference between predicted FEF 25-75 in the current study and the one recruited from the Jordanian population, but the predicted FEF 25-75 among males in the current study was significantly lower than the US and Omani populations.
There was no significant difference between predicted FVC in the current study and the one recruited from the Jordanian population, while the predicted FVC in the current study was significantly higher than the Omani and US studies among female participants.
There was no significant difference between predicted FEV1 in the current study and the one recruited from the US population, but the predicted FEV1 among females in the current study was significantly higher than the Omani and lower than the Jordanian populations.