A wearable carotid Doppler tracks changes in the descending aorta and stroke volume induced by end-inspiratory and end-expiratory occlusion: A pilot study

Background and AimsTo test the feasibility of a novel, wearable carotid Doppler ultrasound to track changes in cardiac output induced by end-inspiratory and end-expiratory occlusion tests. MethodsWe observed the pattern of Doppler change of the common carotid artery during a simulated end-inspiratory and expiratory occlusion test (sEIOT/sEEOT) in 10, nonventilated, healthy subjects. Simultaneously, we measured the Doppler signal of the descending aorta using duplex ultrasound (Xario, Toshiba Medical Systems) and stroke volume (SV) using noninvasive pulse contour analysis (Clearsight, Edwards Lifesciences, Irvine, California). ResultsDuring sEIOT, SV, maximum velocity time integral (VTI) of the descending aorta, and common carotid fell by 25.7% (P =.0131), 26.1% (P <.0001), and 18.5% (P <.0001), respectively. During sEEOT, SV, maximum VTI of the descending aorta, and common carotid rose by: 41.3% (P =.0051), 28.3% (P <.0001), and 41.6% (P <.0001), respectively. There was good correlation between change in aortic VTI and carotid VTI (r(2) =0.79); SV and aortic VTI (r(2) =0.82), and SV and carotid VTI (r(2) =0.95).The coefficient of variation of the VTI measured by the Doppler patch was roughly 60% less than that of the duplex system. ConclusionsThe pattern of SV change induced by a sEIOT/sEEOT in nonmechanically ventilated volunteers is reflected in the common carotid artery and descending aorta. The VTI variability of the Doppler patch was less than that of the traditional, duplex Doppler.