Preface “读万卷书不如行万里路” “First read plenty of books, then travel plenty of places” Confucius, 551–479 BC Thank you for picking up this ERS Practical Handbook of Invasive Mechanical Ventilation. In doing so you are probably interested in artificial ventilation in general, and “invasive ventilation” in particular, but you also appear interested in reading a medical book. The former is not surprising if you are a doctor or nurse treating patients in need of ventilatory support: artificial ventilation is the cornerstone of the treatment of acute respiratory failure. The interesting question is, why would you still read a medical book in 2020? Many people have unrestricted access to hundreds of medical journals online, in addition to a variety of apps, podcasts and online videos. All these “electronic” services provide an endless amount of useful, if not practical information, and such media undoubtedly will become even more important now artificial intelligence and machine learning have entered our profession. New sources of information are a fantastic achievement, which have not only increased, and continue to increase access to information, but have probably also improved patient care, and thus patient outcomes. However, with so much information at hand one may not see the wood for the trees. Indeed, during our daily rounds or when teaching trainees, we noticed that trainees were very aware of the most recently published RCTs on ventilatory support but frequently lacked a basic knowledge of ventilator modes, patient–ventilator interaction and ways to monitor invasively ventilated patients. For instance, we are all aware of the RCTs that have shown survival benefit when using a low versus a high VT in patients with ARDS. But does it matter whether a low VT is delivered in a controlled mode, in a partially supported mode, or maybe in an automated, artificial intelligence-driven mode? Is a low VT always protective? Does a low VT, maybe, affect patient–ventilator interactions, respiratory muscle function, or even haemodynamics? To answer these questions, a fundamental understanding of the basics of invasive ventilation is required. But there are several other topics to be discussed at the bedside. How should we act when hypoxaemia becomes refractory? When should we consider prone positioning and how does prone positioning improve outcome? What are the effects on ventilation/perfusion ratios? Is there still a role for inhalation