Pulmonary function tests: normal values in non-smoking students and staff at the Aga Khan University, Karachi

To estimate normal values of peak expiratory flow rate (PEFR), forced expiratory volume in first second (FEV1), forced vital capacity (FVC) and ratio between FEV1/FVC among non-smoking staff and students at The Aga Khan University (AKU) Hospital, Karachi, and to study the effect of age, gender and body mass index (BMI) on these variables.

A cross-sectional study.

This study was conducted at the Multidisciplinary Laboratory (MDL) of AKUH, Karachi from May to November 2005.

Two hundred forty-one healthy never smokers were approached through non-probability convenient sampling among the staff and students of AKU and were screened through a questionnaire. Data from 200 subjects was used for analysis. Subjects were excluded if pregnant, body mass index (BMI) not ranging from 17-25, FEV1/FVC% less than 70 or with non-reproducible results. The mean values of FVC, FEV1, FEV1/FVC% and PEFR among males and females in different ages were compared by 't' test. Linear regression was applied to study the effect of age and BMI on the outcome variables.

Mean FVC, FEV1 and PEFR were found to be higher in males than the females in all the age groups, the difference in FVC was significantly higher in the age groups of less than 20 years and 20-29 years (2.09L, CI: 1.27-2.92) and (1.51L, CI: 1.29-1.73) respectively. The above spirometric values declined with age and increased with height. Increase in age by one year resulted in 0.051 L decline in FVC (CI: -0.056, -0.034) whereas increase in height by a centimeter improved the FVC by 0.044L (CI: 0.03, 0.056).

The mean FVC, FEV1 and PEFR were higher in males in each age group. Females had higher FEV1/FVC%. Height had positive linear relationship and age was inversely related whereas BMI was not significantly associated with these variables. In order to generalize these reference values, a larger study following the ATS criteria is needed.