The reference values of peak expiratory flow rate in Thailand children.

Background: Daily evaluation of peak expiratory flow rate (PEFR) is quite useful for monitoring and adjusting an asthmatic patient's treatment. Many factors including geography, ethnicity, socio-economic conditions, gender, and anthropometric play a role in lung function differences studies have found. The aim of this study is to present normal PEFR and to establish a PEFR equation for Thai children living in a suburban environment.

Methods: This study includes a cross-section of healthy children aged 6 to 18. It was conducted in Phitsanulok Province in the lower north of Thailand. The children were chosen to participate from five primary and secondary schools over the period from February 2014 to January 2015. The children were instructed on how to use the Wright peak flow meter (Clement Clarke International Ltd.). All of the participants performed PEFR 3 times and the highest value was recorded.

Results: A total of 2,000 students were initially examined; 80 students were excluded from the study. A total of 1,920 healthy children were recruited between the ages of 6 and18 years. Among them, 719 (37.4%) were males and 1,201 (62.6%) were females. The median age was 18 [12-18] years old, mean height, weight, body mass index (BMI) and PEFR were 155.98±14.99 cm, 51.38±16.95 kg, 20.62±4.79 kg/m and 339.31±113.55 L/min, respectively. PEFR has a linear relationship in regards age, weight, height and BMI. For males, age was the strongest factor associated with PEFR (r=0.838, P<0.001). Females had a highly significant correlation between height and PEFR (r=0.532, P<0.001). The regression equations are PEFR = (1.34 × height) + (1.41 × weight) + (16.56 × age) - 137.88 for males (R=0.751, P<0.001) and PEFR = (1.31 × height) + (0.94 × weight) + (7.30 × age) - 55.27 for females (R=0.507, P<0.001).

Conclusions: This research study has provided the normal range of PEFR for Thai children aged from 6 to 18 years in Phitsanulok. The data was obtained using the Wright peak flow meter. Height, weight, and age were the significant determiners of the PEFR for each sex in the regression equation.