Noninvasive mechanical ventilation has managed to establish itself as the treatment option for a wide variety of causes of acute and chronic respiratory failure in different settings in hospital and home noninvasive mechanical ventilation. In the last decades, we have discovered its positive effects on gas exchange and symptoms such as dyspnea control, widely contrasted against endotracheal intubation. However, although this wide range of beneficial effects have been described, pathophysiology, diagnosis, prevention and treatment of noninvasive mechanical complications could not be forgotten for a correct application as they clearly affect patient outcome and mortality. Nowadays, there is a scarce number of publications analyzing noninvasive mechanical ventilation complications and this book is the first dedicated to its analysis. This book brings together a broad multidisciplinary vision of common and unusual complications, thus it serves as the original and essential scientific published reference on noninvasive mechanical ventilation complications. The present book has been structured to offer through its sections and chapters an exhaustive and in-depth analysis of noninvasive mechanical ventilation complications, mechanisms, direct or indirect factors determinants, key recommendations for the early diagnosis and treatment for most frequent applications from multidisciplinary perspective. Finally, we analyze noninvasive mechanical ventilation complications and how they impact in short- and long-term complications and mortality. The book concludes analyzing evidence in diagnosis, prevention and treatment. We believe that the readers of this book will find in it an essential reference for a correct application of noninvasive mechanical ventilation, and thus be able to improve results and prognosis. Only the precise knowledge of complications of noninvasive mechanical ventilation will allow us to achieve a proper application to success.