This book analyses and describes the whole spectrum of technical elements related with non-invasive mechanical ventilators technologies, ventilator modes and complementary technologies for correct interpretation and clinical indications. With the aim of addressing different topics, authors have presented in each chapter and section a rigorous summary of non-invasive mechanical ventilators principles and technologies, as well as clinical indications in order to understand lung function. Moreover, this book also offers a comprehensive examination of how mechanical ventilators interact, for example, in case of asynchrony (diagnosis/treatment), and other tools. The patient-mechanical ventilator interactions sections have been planned from a physiological basis, as they include physical description of the ventilator elements and the non-invasive algorithms that allow adequate patient-ventilator interaction. We describe the correct interpretation and monitoring of positive pressure, airflow and volume waveforms, leakages impact and analysis and interface options and technology (facial mask, nasal mask and other new interface). From a practical point of view, authors describe non-invasive mechanical ventilators device selection, indications and evaluation in different clinical conditions, acute and chronic setting from hospital (emergency/critical care/anesthesiology/pneumology) and from home non-invasive mechanical ventilation. We consider this to be an original and exhaustive book crucial and practical for the correct understanding of mechanical ventilators principles of technology and science of non-invasive mechanical ventilation.