Normal Predicted Value of Airway Resistance by Flow Interrupter Technique in Korean Primary School-Aged Children

ABSTRACT

PURPOSE: To get the normal predicted value of airway resistance in Korean primary school-aged children by using flow interrupter technique which is simple and easy enough to be applicable even to young children. METHODS: Among all the children of one primary school, we selected 964 (Male 469, Female 495). Excluded children were out of normal range in growth with Korean standard and/or history and/or symptom and sign of airway diseases. One medical doctor, well trained to the Microlab 4000 (Micromedical Co. England) educated the children before check and carried out all the procedure. Rint (Airway resistnace by interrupter technique) was checked 5 times. After exclusion of both highest and lowest values, we got the average of remaining 3 values as Rint (in both inspiratory and expiratory phases). We got mean, standard deviation, regression equation, correlation coefficient in every age, height group, weight group, and chest circumference group in both sex. RESULTS: 1) Age ranged from 6 to 11 years. 6-year-old boys' Rint were 0.56+/-0.15 kPa.l-1.s and 0.56+/-0.15 kPa.l-1.s in inspiratory and expiratory phase, respectively. They were 0.55+/-0.16 kPa.l-1.s and 0.55+/-0.18 kPa.l-1.s in girls. The Rint decreased as the children getting older. 2) Height ranged from 105 to 160 cm. Rint of boys from 111 to 115 cm in height were 0.54+/-0.11 kPa.l-1.s and 0.55+/-0.15 kPa.l-1.s in inspiratory and expiratory phase, respectively. They were 0.56+/-0.18 kPa.l-1.s and 0.56+/-0.19 kPa.l-1.s in girls. The Rint decreased as the children getting taller. 3) Weight ranged from 16 to 57 kg. Rint of boys from 16 to 18 kg in weight were 0.52+/-0.07 kPa.l-1.s and 0.59+/-0.07 kPa.l-1.s in inspiratory and expiratory phase, respectively. They were 0.47+/-0.15 kPa.l-1.s and 0.43+/-0.14 kPa.l-1.s in girls. The Rint decreased as the children getting heavier. 4) Chest circumference ranged from 50 to 85 cm. Rint of boys from 50 to 55 cm in chest circumference were 0.49+/-0.12 kPa.l-1.s and 0.46+/-0.13 kPa.l-1.s in inspiratory and expiratory phase, respectively. They were 0.53+/-0.16 kPa.l-1.s and 0.52+/-0.17 kPa.l-1.s in girls. The Rint decreased as the children's chest circumference increase. 5) We got regression equations and correlation coefficient by age, height, weight, and chest circumference in both boys and girls and in both inspiratory and expiratory phases. Correlation was best with height but correlation coefficient was less than 0.45. CONCLUSION: We got the normal predicted value of airway resistance by flow interrupter technique. It can be used in evaluating lung condition, progression of lung disease, and effectiveness of drugs in lung disease.