The implications of intensive care unit capacity strain for the care of critically ill patients

Every intensive care unit (ICU) has an inherent “capacity” or “ability to provide high-quality care for everyone who is or could become a patient in that ICU on a given day”. As with any operation, an ICU’s capacity is not without bounds. ICU capacity has been likened to a balloon – able to stretch to a point to accommodate more patients or higher acuity, but when capacity is exceeded, the balloon pops or care deteriorates. However, it is also possible that ICUs operate like motors – rather than exhibiting markedly different performance at an inflection point of demand, their efficiency may change as a continuous function of the demands placed on them. In this perspective, we discuss the evidence regarding what contributes to ICU capacity strain, identify key knowledge gaps in the field, and consider the implications for future research and patient care.