Evaluation of Inhalation Rate Estimation Methods From Normal Korean Adults and Teenagers

Abstract

P-589 Introduction: Estimation of inhalation rate is essential for the assessment of uptake of airborne pollutants in population. Since heart rate (HR) and ventilation rate (VR) are closely correlated, inhalation rate is estimated from heart rate measurements over days. However, validity of estimating equation is widely varied, especially in adolescents and younger adults. This study was conducted to evaluate the methods of inhalation rate estimation for normal Korean adults and teenagers. Methods: We studied 51 (26 males and 25 females) volunteers of 15–47 years of age. Test protocol consisted of two phases of activity; resting phase, consisted of lying, sitting, and standing (15 minutes each); exercising phase, consisted of moderate (walking) and heavy (running) activity level, performed on a treadmill at 2 speed levels (slow and moderately fast, for 15 minutes each). HR and VR were simultaneously measured using gas analyzer at the last five minutes of each activity level. For the estimation equations fro VR from HR, equations derived from measurement of HR over all activity level in each individual and those derived from each age- and gender group, adjusted for anthropologic characteristics, were compared with actual VR measurements. Results: In resting phase, VR and HR were 7.0±1.4 L/min and 69.4±9.3 beat/s for lying, 7.4±1.7 L/min and 70.3±9.4 beat/s for sitting, and 8.5±2.1 L/min and 79.8±10.4 beat/s for standing. In exercising phase, VR and HR were 16.7±4.7 L/min and 90.9±11.7 beat/s for slowly walking, 20.1±5.0 L/min and 100.4±12.6 beat/s for moderately fast walking, 36.6±9.0 L/min and 137.6±18.2 beat/s for slowly running, and 45.9±12.3 L/min and 157.0±18.7 beat/s for moderately fast running. VR and HR had positive linear correlation with exercise intensity. VRs were significantly higher in males compared to females, but difference was not significant between age groups. When VR was estimated from equation by age group, gender, and activity level, adjusted for height and weight, R2 were between 0.84 and 0.94, lower at teenagers. When VR was estimated from HR equation of each individual for all the activity level, R2 were between 0.88 and 0.98. Discussion and Conclusion: VR and HR simultaneously increased according to the increase of activity level. HR was found to be feasible for use in studies on air pollution exposure assessment for the estimation of VR. For the estimation of inhalation rate from heart rate, equation derived from individual measurement had higher predictability compared to those derived from age-, gender- and activity level group.