In vivo characterization of ultrasonic transducers for the detection of airway occlusion in Sleep Disordered Breathing

Abstract

Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS) is the most common form of Sleep Disordered Breathing (SDB) and it is estimated to affect approximately 15% of US adult population. Various methods have been proposed for the development of inexpensive screening methods to detect SDB to reduce the need for costly nocturnal polysomnography (NPSG). In this paper, a description of the ultrasonic transducer design and characterization is presented, followed by the results of a full night sleep study. The findings show a significant difference in the temporal features extracted from the received ultrasonic waveform during apneic breathing, compared to the hyperventilation that follows. Therefore, the findings indicate the feasibility of developing an ultrasonic detection device for low cost diagnosis of SDB.

Upper airway occlusion detection using a novel ultrasound technique

“…The design, fabrication, and in vivo characterization of the sensor arrays used in this study were reported in [8]. The design of the transducers followed an optimization process.…”

“…The smaller this angle is, the higher the transducer's directivity [9]. The design considerations for the receiver transducers are similar to those for the transmitter [8]. However, in order to achieve maximum reception, these transducers need to be designed with a wider beam width to allow for normal and oblique incidence of the received ultrasonic waveform, to account for the curvature of the neck.…”

“…The thickness of the PZT crystal is 0.58mm, for f=3MHz. The divergence half angle, θ R , is 3.5° [8][9]. This is the angle that the main lobe is enclosed in.…”

“…Constraints for the transducer design included the heterogeneity of the neck anatomical media, the neck curvature, and the location of the site of the occlusion [8]. Fig.…”

“…We have reported in [7] and [8] the results of in vitro and in vivo characterization of ultrasonic sensors for the detection of occlusion in an upper airway, and have presented preliminary results on temporal features extracted from the ultrasonic waves.…”