Fig. 5

Intra-breath changes of impedance values in one representative patient with OHS. The two parts of the respiratory impedance (Zrs), the resistance (Rrs) and the reactance (Xrs) are marked in grey and red, respectively. The Rrs and Xrs data are plotted against tidal volume and tidal flow parameters. The arrows mark the direction of looping during a single breathing cycle. With a stepwise elevation of CPAP, increasing expiratory Xrs values and decreasing AXV and AXV’ loop areas indicate the gradual release from tEFL. At CPAP 10 cmH₂O the tidal volume dependence of Xrs starts in the second half of expiration, and in this particular patient, the flow and volume dependence of Xrs was almost eliminated between CPAP 10 and 15 cmH₂O (marked with '*'). Small gradual intra-breath changes can be seen in Rrs. The CPAP level required to reduce the flow and volume dependence of Xrs was highly variable between patients (Figure S3)

Zrs = respiratory impedance; Rrs = respiratory resistance; Xrs = respiratory reactance;