부산대학교 도서관

Introduction: Assessing preload reserve (PR) is important when managing cardiac surgery patients. Typically, a 10% change in cardiac output is used as a reference standard to gauge PR; how this change in cardiac output translates to common carotid artery (CCA) velocity is unknown. In this pilot study, we compared known changes in cardiopulmonary bypass (CPB) flow rate to those measured by a novel wireless, wearable Doppler ultrasound placed over the CCA.Methods: A sample of 14 adult patients undergoing elective CABG was studied. While on CPB, at least two changes in blood flow (one negative, one positive) were made. The corresponding change in CCA velocity was measured by a wearable continuous wave (CW) Doppler ultrasound patch. For each subject, CPB flow changes were determined from the displayed spectrogram by the peristaltic pulsation frequency and CCA velocity changes were calculated from the automated maximum velocity trace. 5-10s windows pre- and post-CPB speed changes were selected, with sufficient signal quality to determine both relative CPB flow and CCA velocity. A “dose-response” curve was fitted to the relative changes in flow and velocity for each subject, as shown in Fig. 1, and the CCA velocity change corresponding to a 10% change in CPB flow was calculated.Results: CPB flows ranged from 0.5-6.3L/min. Mean relative flow changes were -58 and 179%, corresponding to mean CCA velocity changes of -43 and 107%. A mean CCA velocity change of 14% was found to correspond to 10% CPB flow change, ranging from 1.5-27.8%.Conclusions: CCA velocity measured with the Doppler patch successfully tracked changes in CPB flow. A CCA velocity change of >14% suggests a >10% change in cardiac output. Although preliminary, these results provide another important parameter for predicting the response to preload using a novel, easy-to-use, wireless Doppler device.