A portable patient monitor has an integrated mode in which it operates as a plug-in module for a multiparameter patient monitoring system (MPMS). The patient monitor also has a portable mode in which it operates separately from the MPMS as a battery-powered handheld or standalone instrument. The patient monitor has a sensor port that receives a signal indicative of physiological parameters as input to an internal processor. The patient monitor processes this sensor signal to derive patient measurements. In the portable mode, this information is provided on its display. In the integrated mode, the patient monitor provides patient measurements to the MPMS to be displayed on a MPMS monitor.