Techniques and devices that support or restore a patient's breathing, circulation or core physiology in an emergency or a critically ill state, rather than a technique whose primary purpose is anesthesia, pain relief or routine airway placement. This includes cardiac arrest and circulatory resuscitation (cardiopulmonary resuscitation, extracorporeal cardiopulmonary resuscitation, cardioversion, defibrillation, resuscitative endovascular balloon occlusion of the aorta, selective aortic arch perfusion, emergency preservation and resuscitation, heroic measure, early warning system), mechanical and extracorporeal circulatory and respiratory support (cardiopulmonary bypass, extracorporeal membrane oxygenation, extracorporeal carbon dioxide removal, mechanical ventilation, artificial ventilation, positive end-expiratory pressure), oxygen and gas delivery and thermal life-support techniques (oxygen therapy, hyperbaric oxygen therapy, medical gas therapy, demand valve oxygen therapy, targeted temperature management, therapeutic hypothermia), and vascular access and fluid resuscitation (fluid replacement, intraosseous infusion, central venous catheterization, arterial line, pulmonary artery catheterization, peripherally inserted central catheter, chest tube). A device or technique whose primary purpose is securing the airway passage itself, delivering anesthesia or sedation, or preparing a patient before a procedure is grouped elsewhere even when it is also used during a resuscitation.