Patent ID: 8903491

Claim:
An implantable medical device, comprising: a controller programmed to control the delivery of pacing pulses in accordance with a programmed pacing mode; a minute ventilation sensor interfaced to the controller; an activity level sensor interfaced to the controller for measuring a parameter related to a patient's level of physical activity; wherein the controller is programmed to construct a historical record of activity level versus minute ventilation, referred to as a minute ventilation response profile; wherein the controller is further programmed to monitor a patient's cardiopulmonary functional status by computing a minute ventilation response slope from the minute ventilation response profile, defined as the ratio of an incremental change in minute ventilation to an incremental change in measured activity level, and compare the minute ventilation response slope to a specified limit value; and, wherein the controller is further programmed to update the minute ventilation response profile by averaging a currently measured minute ventilation over an N second interval and associating the averaged minute ventilation with an activity level corresponding to an average of a currently measured activity level over the N second interval, wherein the minute ventilation response profile is updated only if activity level measurements taken over the N second interval meet a predefined stability criterion that involves a comparison of a statistic of the activity level measurements with a limit value.