Comparison of spirometric results obtained from the sitting and standing position in children participating in an epidemiological study

INTRODUCTION: It is recommended that spirometric testing in children be completed while sitting. Our experience indicates that children prefer standing during spirometry. AIM: We sought to compare spirometric results obtained from the sitting (SIP) and standing (STP) positions. MATERIAL AND METHODS: Two testing sessions were performed in random order (SIP vs. STP: 30–45 min apart) in 118 children (7–13 years), attending one, randomly selected, primary school (response rate: 92%). RESULTS: Acceptable quality was found in 77.9% of STP and 77.1% of SIP maneuvers. Higher values of spirometric variables on STP, compared to SIP, were obtained for forced vital capacity (FVC) (2.12 ±0.41 l vs. 2.11 ±0.39 l) and forced expiratory volume in 1 s (FEV(1)) (1.78 ±0.36 l vs. 1.77 ±0.35 l) but the differences were not statistically significant. Relative between-position differences (RBPD) ≤ 5% were found with the following frequencies: FVC: 56.4%, FEV(1): 69.2%, PEF: 21.7%, and FEF(25–75): 24.3%. Similar patterns were found for FEF(25), FEF(50), and FEF(75). Relative between-position differences were related to age in the case of FEV(1) (p = 0.005), FEF(25) (p = 0.02), and FEF(25–75) (p = 0.01) where older children had smaller RBPD. Forced vital capacity RBPD was lower (p = 0.01) in subjects with current wheeze; PEF RBPD were lower (p = 0.02) in children with asthma. CONCLUSIONS: In epidemiological studies, the position of spirometric testing does not affect the results of lung function assessment.