An implantable or other ambulatory medical apparatus comprising: a posture sensing circuit configured to provide a time varying electrical posture signal representative of posture of a subject; a physiologic sensing circuit configured to sense one or more time varying physiologic signals, wherein the physiologic signal includes physiologic information of the subject; and a processor circuit, communicatively coupled to the posture sensing circuit and the physiologic sensing circuit, wherein the processor circuit includes: a posture calculation circuit configured to: obtain posture data for a specified time duration and to determine a posture of the subject using the posture data obtained using the posture signal; and determine when the posture of the subject is steady state during at least one time period during the specified time duration; and a measurement circuit configured to: derive a physiologic measurement using physiologic data extracted from the physiologic signal during at least one time period when posture is determined to be steady state; and to provide the physiologic measurement to at least one of a user or process in association with the determined steady state posture, characterised in that the physiological sensing circuit includes a heart sound sensor and in that the physiologic measurement includes a measurement of a heart sound parameter which may indicate a change in status of heart failure of the patient. a posture sensing circuit configured to provide a time varying electrical posture signal representative of posture of a subject; a physiologic sensing circuit configured to sense one or more time varying physiologic signals, wherein the physiologic signal includes physiologic information of the subject; and a processor circuit, communicatively coupled to the posture sensing circuit and the physiologic sensing circuit, wherein the processor circuit includes: a posture calculation circuit configured to: obtain posture data for a specified time duration and to determine a posture of the subject using the posture data obtained using the posture signal; and determine when the posture of the subject is steady state during at least one time period during the specified time duration; and a measurement circuit configured to: derive a physiologic measurement using physiologic data extracted from the physiologic signal during at least one time period when posture is determined to be steady state; and to provide the physiologic measurement to at least one of a user or process in association with the determined steady state posture, characterised in that the physiological sensing circuit includes a heart sound sensor and in that the physiologic measurement includes a measurement of a heart sound parameter which may indicate a change in status of heart failure of the patient. a posture calculation circuit configured to: obtain posture data for a specified time duration and to determine a posture of the subject using the posture data obtained using the posture signal; and determine when the posture of the subject is steady state during at least one time period during the specified time duration; and a measurement circuit configured to: derive a physiologic measurement using physiologic data extracted from the physiologic signal during at least one time period when posture is determined to be steady state; and to provide the physiologic measurement to at least one of a user or process in association with the determined steady state posture, characterised in that the physiological sensing circuit includes a heart sound sensor and in that the physiologic measurement includes a measurement of a heart sound parameter which may indicate a change in status of heart failure of the patient. obtain posture data for a specified time duration and to determine a posture of the subject using the posture data obtained using the posture signal; and determine when the posture of the subject is steady state during at least one time period during the specified time duration; and a measurement circuit configured to: derive a physiologic measurement using physiologic data extracted from the physiologic signal during at least one time period when posture is determined to be steady state; and to provide the physiologic measurement to at least one of a user or process in association with the determined steady state posture, characterised in that the physiological sensing circuit includes a heart sound sensor and in that the physiologic measurement includes a measurement of a heart sound parameter which may indicate a change in status of heart failure of the patient.