According to the recent literature, approximately 250,000 deaths occur annually in U.S. hospitals resulting from medical error, making it the 3rd leading cause of death. One of the most commonly used devices in hospitals is the Patient Monitor (PM), a device which constantly monitors the vital signs of the patient. This paper reports on a review of the scientific literature on the usability of PMs in critical care. A detailed analysis of the data reveals that: (i) PMs are undergoing a slow, but continuous process of evolution with new advances focusing on enhancing the interaction between the caregivers and the PM, (ii) the usability of PMs is beginning to receive particular attention as usability is now considered to be strongly associated with patient safety. The data from this study will be used to carry out further investigations into the usability of PMs and to inform the design of future PMs.