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 (FEV1) (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%, FEV1: 69.2%, PEF: 21.7%, and FEF25–75: 24.3%. Similar patterns were found for FEF25, FEF50, and FEF75. Relative between-position differences were related to age in the case of FEV1 (p = 0.005), FEF25 (p = 0.02), and FEF25–75 (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.