Abstract
Thrombosis and restenosis after vascular reconstruction procedures may cause complications such as stroke, but a clinical means to continuously monitor vascular conditions is lacking. Conventional ultrasound probes are rigid, particularly for postoperative patients with fragile skin. Techniques based on photoplethysmography or thermal analysis provide only relative changes in flow volume and have a shallow detection depth. Here, we introduce a flexible Doppler ultrasound device for the continuous monitoring of the absolute velocity of blood flow in deeply embedded arteries based on the Doppler effect. The device is thin (1 mm), lightweight (0.75 g), and skin conforming. When the dual-beam Doppler method is used, the influence of the Doppler angle on the velocity measurement is avoided. Experimental studies on ultrasound phantoms and human subjects demonstrate accurate measurement of the flow velocity. The wearable Doppler device has the potential to enhance the quality of care of patients after reconstruction surgery.
Highlights
The variation in blood flow in time and space contains abundant information regarding a person’s cardiovascular situation
Long-term continuous monitoring of the blood flow velocity may be valuable in the diagnosis and prognosis of some vascular conditions [7, 8]
Ultrasonic measurements of blood flow velocity are based on the Doppler effect
Summary
The variation in blood flow in time and space contains abundant information regarding a person’s cardiovascular situation. Ischemic stroke occurs when an artery to the brain becomes blocked, which is partly caused by narrowing of the carotid artery (stenosis) and the formation of blood clots that can block the carotid artery (thrombosis) or can break off and travel to the brain through the bloodstream (embolism). Carotid endarterectomy is an accepted and effective procedure for preventing strokes due to carotid artery stenosis [9], but acute thrombosis may occur at the endarterectomy and clamping sites within 72 hours, causing postoperative stroke and increasing postoperative morbidity and mortality [10, 11]. To prevent thrombosis at the site of vessel anastomosis after replantation surgery, a common assessment is a physical exam of the capillary fill and skin color every hour [14, 15]. Patients can receive only a limited number of assessments when they are in the
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