A system and method for monitoring the blood pressure of a patient that allows for a device sensor to be recalibrated according to atmospheric pressure without removing the device sensor from inside the patient. This permits quickly monitoring the blood pressure of a patient if a re-zero is needed. The invention has a blood pressure monitor (BPM) that obtains an atmospheric pressure observation. The atmospheric pressure observation is adjusted and stored to memory as a zero value. The zero value is retrieved to recalibrate the system and method if a device sensor has been disconnected from and reconnected to the same or a different BPM, the patient has been moved such that the surroundings have been altered to make it necessary to recalibrate according to atmospheric pressure, and/or the device sensor has been connected to a different patient care monitor.