A novel, hands-free ultrasound patch for continuous monitoring of quantitative Doppler in the carotid artery

Abstract

Quantitative Doppler ultrasound of the carotid artery has been proposed as an instantaneous surrogate for monitoring rapid changes in left ventricular output. Tracking immediate changes in the arterial Doppler spectrogram has value in acute care settings such as the emergency department, operating room and critical care units. We report a novel, hands-free, continuous-wave Doppler ultrasound patch that adheres to the neck and tracks Doppler blood flow metrics in the common carotid artery using an automated algorithm. String and blood-mimicking test objects demonstrated that changes in velocity were accurately measured using both manually and automatically traced Doppler velocity waveforms. In a small usability study with 22 volunteer users (17 clinical, 5 lay), all users were able to locate the carotid Doppler signal on a volunteer subject, and, in a subsequent survey, agreed that the device was easy to use. To illustrate potential clinical applications of the device, the Doppler ultrasound patch was used on a healthy volunteer undergoing a passive leg raise (PLR) as well as on a congestive heart failure patient at resting baseline. The wearable carotid Doppler patch holds promise because of its ease-of-use, velocity measurement accuracy, and ability to continuously record Doppler spectrograms over many cardiac and respiratory cycles.

The Doppler shock index measured by a wearable ultrasound patch accurately detects moderate‐to‐severe central hypovolemia during lower body negative pressure

“…Fourth, the Doppler angle of insonation employed by the ultrasound patch is estimated to be 60°. In vitro, we have shown that this estimation introduces a clinically small, fixed error into the VTI calculation that is mitigated when the VTI is referenced to its baseline value 19 . Because the ultrasound patch is adhered to the neck, the angle of insonation remains relatively constant throughout the study and small, absolute velocity error is accounted for.…”

“…In vitro, we have shown that this estimation introduces a clinically small, fixed error into the VTI calculation that is mitigated when the VTI is referenced to its baseline value. 19 Because the ultrasound patch is adhered to the neck, the angle of insonation remains relatively constant throughout the study and small, absolute velocity error is accounted for. Importantly, however, should the carotid artery move relative to the adhered transducer face (eg, significant head and neck movement), erroneous VTI change is introduced.…”

“…Importantly, however, should the carotid artery move relative to the adhered transducer face (eg, significant head and neck movement), erroneous VTI change is introduced. 19 Finally, we did not account for differences between the internal and external carotid arteries. Although others have found that blood flow in the internal carotid artery tracks changes in SV, 20 the congruence between internal and common carotid artery blood flow in the face of changing cardiac output is an avenue of future study.…”

“…Because the ultrasound patch is adhered to the neck, the angle of insonation remains relatively constant throughout the study and small, absolute velocity error is accounted for. Importantly, however, should the carotid artery move relative to the adhered transducer face (eg, significant head and neck movement), erroneous VTI change is introduced 19 . Finally, we did not account for differences between the internal and external carotid arteries.…”

Inferring the Frank–Starling Curve From Simultaneous Venous and Arterial Doppler: Measurements From a Wireless, Wearable Ultrasound Patch

“…as neck position does not change during the maneuver (34). Also, the device averages cardiac cycles over many seconds which attenuates handheld sampling variability (30,31).…”