The principal role of the respiratory system is to permit effi cient exchange of respiratory gases
(O2 and CO2) with the environment. The respiratory system is unique in that it is constantly
exposed to a barrage of foreign substances from both the internal environment (at any one point
in time, approximately one-half of the cardiac output is received by the lungs) and the external
environment (with each breath, the respiratory tract is exposed to pollens, viruses, bacteria,
smoke, etc). According to the Centers for Disease Control and Prevention, diseases of the respiratory
system were the seventh and eighth leading causes of deaths in children aged 1 to 19 years
in 2003 [1]. Dr. George A. Gregory, one of the founding fathers of pediatric critical care medicine,
once estimated that acute respiratory failure accounts for nearly 50% of all admissions to
the pediatric intensive care unit (PICU) [2]. Just as important are the many diseases that affect
the respiratory system that are not associated with acute respiratory failure, but nevertheless
constitute a major portion of the practice of pediatric critical care medicine, some of which
account for signifi cant morbidity and mortality [3]. Once again, we would like to dedicate this
textbook to our families and to the physicians and nurses who provide steadfast care every day
in pediatric intensive care units across the globe.