FEW WORDS ABOUT PROCEDURE
Body plethysmography allows to assess functional residual capacity (FRCpleth) and specific airway resistance (sRaw) as primary measures. In combination with deep expirations and inspirations, total lung capacity (TLC) and residual volume (RV) can be determined. Airway resistance (Raw) is calculated as the ratio of sRaw to FRCpleth. Raw is a measure of airway obstruction and indicates the alveolar pressure needed to establish a flow rate of 1 L s−1. In contrast, sRaw can be interpreted as the work to be performed by volume displacement to establish this flow rate. These measures represent different functional aspects and should both be considered.