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. 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).The Respiratory Tract in Pediatric Critical Illness and Injury.exe
