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Session: Poster Session 1 (Even numbers)
Session starts: Thursday 26 January, 16:00
Presentation starts: 16:00

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Esmée de Boer (Eindhoven University of Technology)
Catarina Dinis Fernandes (Eindhoven University of Technology)
Danihel van Neerven (Maastricht Universitair Medisch Centrum+)
Christoph Pennings (Maastricht Universitair Medisch Centrum+)
Rohan Joshi (Philips Reseach)
Sabina Manzari (Philips Research)
Sergei Shulepov (Philips Research)
Luuk van Knippenberg (Eindhoven University of Technology)
John van Rooij (Philips Research)
Arthur Bouwman (Catharina Ziekenhuis Eindhoven)
Massimo Mischi (Eindhoven University of Technology)

Abstract:
Hemodynamic monitoring is of utmost importance when treating critically ill patients. Currently used hemodynamic techniques are invasive, such as the transpulmonary thermodilution approach for cardiac output estimation, and their use brings the risk of catheter-related complications. Over the last two decades, carotid artery ultrasound (US) has been investigated as a non-invasive modality for hemodynamic monitoring, including cardiac output estimation. Traditionally, carotid flow measurements are performed with the US probe oriented parallel to the vessel. Assuming a circular cross-section of the vessel and a parabolic flow profile, the probe should be properly positioned along the mid-axis to obtain an accurate blood flow calculation. However, obtaining and maintaining this mid-axis parallel view is difficult, and literature describes that operator experience may impact the reliability of carotid flow measurements. Another way of assessing the cross-section of the carotid artery is by rotating and tilting the probe, a view that is easier to visualize and assess for sonographers. Preliminary research on velocity measurements showed that the rotated and tilted view was more robust to motion and less operator-dependent than the parallel view. To evaluate these findings in a clinical setting, we performed measurements with a parallel and rotated and tilted probe orientation intending to investigate the operator-dependency and diameter estimates. Transverse measurements were also obtained and used as a reference. Carotid Doppler measurements of 25 adult cardiac surgery patients were performed with the probe oriented parallel, transverse, and rotated and tilted. The US recordings were analyzed with previously developed algorithms, optimized for each probe orientation, resulting in a median diameter estimation per 30s measurement. Preliminary results of the first 9 patients show that diameter estimations from the three views are comparable: median diameter estimates [IQR] are 6.27 [5.67-7.25]mm, 6.74 [6.33-7.13]mm, and 6.33 [5.98-7.69]mm for the parallel, transverse, and rotated and tilted views, respectively. Visual data inspection confirmed comparable within-patient estimates in all except two patients, in whom artifacts caused by probe movement were found in the US recordings. Normality was checked using the Shapiro-Wilks test and a one-way ANOVA confirmed that the diameter estimates from the different views were not significantly different. Future analysis comprises expansion of the current results and investigating inter- and intra-operator reliability of the different views.