A user interface system provides patient medical parameter data for trend indicative display covering a time period comprising user selectable acquisition time intervals. An acquisition processor acquires, from a patient monitoring device, data representing a patient parameter comprising a plurality of data values at a corresponding plurality of different times within multiple user selectable patient parameter acquisition intervals of a time period. A generator generates data representing a first image showing a trend indicative display of the patient parameter covering a time period comprising user selectable acquisition time intervals and including a first number of data points in an individual acquisition time interval. The generator generates data representing an image window comprising an expansion of the individual acquisition time interval and including a second number of data points greater than the first number, in response to user command. The generator updates the individual acquisition time interval of the first image with at least one data point selected from the expanded individual acquisition time interval window to replace the first number of data points, in response to user command.