In this book, the authors analyze the physical and rationale use of heliox gas mixtures in adult and pediatric patients, with a wide spectrum in acute respiratory (invasive and weaning mechanical ventilation) and chronic respiratory disorders (chronic obstructive pulmonary disease, asthma, neuromuscular, cystic fibrosis) where its usefulness has been well evaluated. In the chapters and sections, the authors describe the basic technology for elements in equipment and accessories, monitoring systems, and appropriate tools for safe clinical response evaluations during invasive mechanical ventilation and noninvasive ventilation and nasal high flow. Finally, a global summary and analysis based on clinical evidence and recommendations is provided.