Enhancement of pulse contour analysis in the pulmonary artery by use of heart sounds

Pulse contour analysis (PCA) estimates cardiac stroke volume on a beat-to-beat basis from the systolic time interval of arterial blood pressure. Hence, identification of the ejection time intervals plays a crucial role. However, this is an intricate task when pulmonary artery pressure (PAP) measured with an implantable pressure sensing device is used. The feature marking the end of systole is rather indistinct and thus often not detectable in low-resolution signals. We therefore suggest using additional information from heart sounds, which are indicative of beginning and end of systole, respectively. The potential benefit of this approach was evaluated with data from an animal experiment. Blood pressure was recorded with a pressure transducer catheter and heart sounds with a prototype accelerometer. Using PAP only, 6.1% of all cycles were unusable for PCA. With additional use of heart sounds, however, a detection rate of 100.0% was achieved.