DIURNAL VARIATION OF PEAK EXPIRATORY FLOW RATE IN HEALTHY YOUNG ADULTS

Background: Peak expiratory flow rate is an indicator of respiratory capacity and bronchial responsiveness which can be useful in diagnosing respiratory diseases. However, a circadian rhythm has been observed in its values. The aim of this study was to determine the diurnal variation of peak expiratory flow rate in healthy young adults. Methods: A total of 160 subjects of age 18-24 years were studied in this cross-sectional study done on students of Manipal College of Medical Sciences between March to September 2021. Subjects were asked to record their peak expiratory flow rates five times a day using Mini-Wright peak flow meter after adequate training. Diurnal variability was expressed as amplitude percent mean and standard deviation percent mean. Data analysis was done in SPSS version 25 by Kruskal Wallis test and Mann Whitney U test. Results: Lowest mean peak expiratory flow rate (L/min) was observed in morning in both males (564.21 ±  57.10) and females (320.68 ± 17.05) with progressive rise throughout the day thus reaching highest value in evening (males: 583.16 ± 64.45; females: 349.13 ± 36.32). Statistically significant (<0.005) difference in mean peak expiratory flow rate at different time intervals was found in the overall population. Diurnal variation calculated as amplitude percent mean and standard deviation percent mean was found to be significantly higher in females than males (<0.005). Conclusions: Significant diurnal variation of peak expiratory flow rate was seen in healthy young adults.