Fig. 3.

Measured airway pressure (Paw, bold line) and its estimation (gray line) by the linear single-compartment model without (a) and with (b) the inclusion of the flow-dependent term in its constitutive equation. Single breaths produced by an anesthetized and paralyzed healthy patient are depicted. Patient was monitored during surgery and ventilated in pressure-controlled ventilation with a constant tidal volume of 8 ml/kg, endotracheal tube of 8 mm inner diameter, and zero end-expiratory pressure. Note that the inclusion of the flow-dependent parameter K₂ increased respiratory system elastance (Ers) by about 10%