Cardiopulmonary functional status assessment via metabolic response detection by implantable cardiac device
First Claim
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1. 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.
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Abstract
An implantable cardiac device is configured and programmed to assess a patient'"'"'s cardiopulmonary function by evaluating the patient'"'"'s minute ventilation response. Such evaluation may be performed by computing a minute ventilation response slope, defined as the ratio of an incremental change in minute ventilation to an incremental change in measured activity level. The minute ventilation response slope may then be compared with a normal range to assess the patient'"'"'s functional status.
109 Citations
20 Claims
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1. An implantable medical device, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for operating an implantable medical device, comprising:
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programming a controller to deliver pacing pulses in accordance with a programmed pacing mode; wherein the controller is interfaced to a minute ventilation sensor that measures a patient'"'"'s minute ventilation and to an activity level sensor that measures a parameter related to a patient'"'"'s level of physical activity; programming the controller to; construct a historical record of activity level versus minute ventilation, referred to as a minute ventilation response profile; 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 comparing the minute ventilation response slope to a specified limit value; and
,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. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification