Towards an algorithm for automatic accelerometer-based pulse presence detection during cardiopulmonary resuscitation.

Manual palpation is still the gold standard for assessment of pulse presence during cardiopulmonary resuscitation (CPR) for professional rescuers. However, this method is unreliable, time-consuming and subjective. Therefore, reliable, quick and objectified assessment of pulse presence in cardiac arrest situations to assist professional rescuers is still an unmet need. Accelerometers may present a promising sensor modality as pulse palpation technology for which pulse detection at the carotid artery has been demonstrated to be feasible. This study extends previous work by presenting an algorithm for automatic, accelerometer-based pulse presence detection at the carotid site during CPR. We show that accelerometers might be helpful in automated detection of pulse presence during CPR.

Pulse detection with a single accelerometer placed at the carotid artery: Performance in a real-life diagnostic test during acute hypotension.

Pulse detection via palpation is a basic and essential procedure in daily medical practice. We have been investigating the performance of a single accelerometer placed above the carotid artery, which is one of the recommended locations for manual palpation. A low-cost sensor attached by an adhesive measures accelerations due to carotid dilatations and whole body vibrations. A real-time demonstrator has been developed to classify 10 second- windows in "Pulse", "Motion" and "No Pulse" and to infer pulse rate. Data were obtained during a scheduled head-up tilt table test (HUTT). Our results show for a subgroup of 10 patients with acute hypotension a wide spread of "good" signal coverage ranging from as low as 37% up to 100%. Key factors compromising the performance in HUTT are motion artifacts, arrhythmias, sensor placement and sensor-skin coupling. In conclusion, pulse detection with a single accelerometer is sufficiently accurate, if good signal coverage can be achieved.

Feasibility of pulse presence and pulse strength assessment during head-up tilt table testing using an accelerometer located at the carotid artery.

Neurally mediated syncope (NMS) is a disorder of the autonomic regulation of postural tone, which is characterized by hypotension and/or bradycardia, resulting in cerebral hypo-perfusion and finally in a sudden loss of consciousness. Prediction of an impending NMS requires detection of pulse presence to derive heart rate (HR) as well as to assess the pulse strength (PS) related to systolic blood pressure (SBP) preferably from a single body location only. This paper analyses the basic feasibility of using a single accelerometer positioned above the common carotid artery to assess pulse strength and pulse rate towards NMS prediction. A physical model has been investigated to gain insights into expected signal morphologies and potential feature candidates vs. hemodynamic parameters such as SBP, pulse pressure (PP) and PR relevant for NMS detection. Model results are compared with first measurements obtained in a head-up tilt table test (HUTT) from a patient during impending syncope. We show that an accelerometer positioned at the carotid artery is a potential approach offering a valuable tool in syncope management.