The intensive care unit (ICU) is a hospital department where critical patients are monitored and healed: the sensors used to check their vital conditions produce a huge amount of data that can be exploited to predict outcome about their future conditions. In this work mortality prediction is performed using data recorded from more than 9000 patients in different hospitals of the Capital Region of Denmark from 2009 and 2016. Since the high number of physiological variables acquired in the ICU a study of which variables subset provides more information is carried on, taking into account the number of patients who have that subset of physiological variables monitored.