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 FEF_25–75: 24.3%. Similar patterns were found for FEF₂₅, FEF₅₀, and FEF₇₅. Relative between-position differences was related to age in the case of FEV₁ (p = 0.005), FEF₂₅ (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.