Through the years, the professional practice of respiratory care has continually evolved to include management of critically ill patients. Although the functions and duties of respiratory care practitioners (RCPs) in this setting may vary across different institutions, it is widely recognised throughout the United States that RCPs contribute importantly to intensive care unit (ICU) outcomes. The American Association for Respiratory Care (AARC) has painstakingly established guidelines to more precisely define the role of RCPs in performing procedures in the ICU. Published studies demonstrate the added value of RCPs' collaboration in several ICU activities, including placement of arterial catheters, sampling of arterial blood gases, endotracheal intubation, and management of and weaning from mechanical ventilation. Other ICU activities in which RCPs participate include assisting with bronchoscopy, obtaining haemodynamic measurement, and indirect calorimetry and supporting specialised techniques such as extracorporeal membrane oxygenation (ECMO) and continuous veno-venous haemofiltration and/or haemodiafiltration (CVVH/CVVHD). Based on the demonstrated impact of RCPs and their technical and cognitive training, a continuing role expansion for RCPs in the ICU is expected.