Fig. 1

Measured and derived intra-breath oscillometry variables. The two parts of the respiratory impedance (Zrs), the resistance (Rrs) and the reactance (Xrs), are plotted in grey and red, respectively. Rrs reflects the sum of total airway and tissue resistances, whereas Xrs, which consists of elastic and inertial components, describes the ability to store energy and promote passive exhalation. A single patient’s Rrs and Xrs recordings are mapped against tidal volume and flow parameters. The arrows mark the direction of looping during a single breathing cycle. Positive flow indicates inspiration and negative flow indicates expiration. Plotting Rrs and Xrs against volume and flow permits insight into the intra-breath changes of airway mechanics in a detailed manner. To describe complex intra-breath changes in respiratory mechanics the following measured and derived variables were used:

ReE = end expiratory resistance; ReI = end inspiratory resistance; ΔR = difference between ReE and ReI; XeE = end expiratory reactance; XeI = end inspiratory reactance; ΔX = difference between XeE and XeI; AXV = area of Xrs vs V diagram; AXV’ = area of Xrs vs. V’ diagram;