Simplify, simplify! Henry David Thoreau For writers of technical books, there can be no better piece of advice. Around the time of writing the first edition ? about a decade ago ? there were very few monographs on this s- ject: today, there are possibly no less than 20. Based on critical inputs, this edition stands thoroughly revamped. New chapters on ventilator waveforms, airway humidification, and aerosol therapy in the ICU now find a place. Novel software-based modes of ventilation have been included. Ventilator-associated pneumonia has been se- rated into a new chapter. Many new diagrams and algorithms have been added. As in the previous edition, considerable energy has been spent in presenting the material in a reader-friendly, conv- sational style. And as before, the book remains firmly rooted in physiology. My thanks are due to Madhu Reddy, Director of Universities Press ? formerly a professional associate and now a friend, P. Sudhir, my tireless Pulmonary Function Lab technician who found the time to type the bits and pieces of this manuscript in between patients, A. Sobha for superbly organizing my time, Grant Weston and Cate Rogers at Springer, London, Balasaraswathi Jayakumar at Spi, India for her tremendous support, and to Dr. C. Eshwar Prasad, who, for his words of advice, I should have thanked years ago. vii viii Preface to the Second Edition Above all, I thank my wife and daughters, for understanding.