Ultrasound patch for detecting fluid flow

An ultrasound patch includes one or more transmit and receive piezoelectric transducer elements. In some embodiments, the transducer elements are positioned on a ramp on a patient pad of the patch that is configured to fit within an anatomic space between the trachea and the sternocleidomastoid muscle to orient the transducer elements toward a carotid artery. In some embodiments, a flexible phased array transducer includes a number of pillar piezoelectric elements joined by a flexible adhesive with metal electrodes deposited thereon. The phased array transducer is mounted to a flexible circuit board that allows the transducer to bend and conform to a subject's anatomy.