Purpose of review: The aim of this review is to describe ventilator–patient interaction, employing the equation of motion and the curves obtained by the ventilator. Practitioners confronted with mechanically ventilated patients every day in intensive care units should be able to sort out from all data available from modern ventilators those relevant for choosing a correct ventilatory strategy for each patient.
Recent findings: Early determination of patient–ventilator asynchrony, air-leaks and variation in respiratory parameters is important during mechanical ventilation. A correct evaluation of data, for patient safety and tailored ventilatory strategy becomes mandatory when non-invasive ventilation by helmet or mask is applied.
Summary: The equation of motion is described and dynamic and static respiratory mechanics are analysed to highlight all those data that can influence decision-making in setting mechanical or assisted ventilation in invasively and non-invasively ventilated patients.